Ergonomics : Design, Integration and Implementation [1 ed.] 9781608767717, 9781606923276

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Copyright © 2008. Nova Science Publishers, Incorporated. All rights reserved. Ergonomics : Design, Integration and Implementation, edited by Bram N. Brinkerhoff, Nova Science Publishers, Incorporated, 2008. ProQuest Ebook Central,

Copyright © 2008. Nova Science Publishers, Incorporated. All rights reserved. Ergonomics : Design, Integration and Implementation, edited by Bram N. Brinkerhoff, Nova Science Publishers, Incorporated, 2008. ProQuest Ebook Central,

ERGONOMICS: DESIGN, INTEGRATION AND IMPLEMENTATION

Copyright © 2008. Nova Science Publishers, Incorporated. All rights reserved.

No part of this digital document may be reproduced, stored in a retrieval system or transmitted in any form or by any means. The publisher has taken reasonable care in the preparation of this digital document, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained herein. This digital document is sold with the clear understanding that the publisher is not engaged in rendering legal, medical or any other professional services.

Ergonomics : Design, Integration and Implementation, edited by Bram N. Brinkerhoff, Nova Science Publishers, Incorporated, 2008. ProQuest Ebook Central,

Copyright © 2008. Nova Science Publishers, Incorporated. All rights reserved. Ergonomics : Design, Integration and Implementation, edited by Bram N. Brinkerhoff, Nova Science Publishers, Incorporated, 2008. ProQuest Ebook Central,

ERGONOMICS: DESIGN, INTEGRATION AND IMPLEMENTATION

BRAM N. BRINKERHOFF

Copyright © 2008. Nova Science Publishers, Incorporated. All rights reserved.

EDITOR

Nova Science Publishers, Inc. New York

Ergonomics : Design, Integration and Implementation, edited by Bram N. Brinkerhoff, Nova Science Publishers, Incorporated, 2008. ProQuest Ebook Central,

Copyright © 2009 by Nova Science Publishers, Inc. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. For permission to use material from this book please contact us: Telephone 631-231-7269; Fax 631-231-8175 Web Site: http://www.novapublishers.com NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers’ use of, or reliance upon, this material. Any parts of this book based on government reports are so indicated and copyright is claimed for those parts to the extent applicable to compilations of such works. Independent verification should be sought for any data, advice or recommendations contained in this book. In addition, no responsibility is assumed by the publisher for any injury and/or damage to persons or property arising from any methods, products, instructions, ideas or otherwise contained in this publication. This publication is designed to provide accurate and authoritative information with regard to the subject matter covered herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS.

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LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA Ergonomics : design, integration and implementation / [edited by] Bram N. Brinkerhoff. p. cm. Includes index. ISBN 978-1-60876-771-7 (E-Book) 1. Health facilities--Design and construction. 2. Human engineering. I. Brinkerhoff, Bram N. RA967.E74 2009 725'.51--dc22 2008055489

Published by Nova Science Publishers, Inc.    New York

Ergonomics : Design, Integration and Implementation, edited by Bram N. Brinkerhoff, Nova Science Publishers, Incorporated, 2008. ProQuest Ebook Central,

CONTENTS Preface

vii

Copyright © 2008. Nova Science Publishers, Incorporated. All rights reserved.

Research and Review Studies Chapter 1

Acoustic Design of Enclosed Spaces Paulo Henrique Trombetta Zannin, Carolina Reich Marcon Passero and David Queiroz de Sant`Ana

Chapter 2

Reliability of Shoulder Functional Measures in Assessing Physical Capacity of Individuals With Chronic Neck/Shoulder Pain Karen Lomond, Evelyne Boulay, Charlene Leduc-Poitras and Julie Côté

Chapter 3

Ergonomics in the Operating Room – An Overview L. S. G. L. Wauben, A. Albayrak and R. H. M. Goossens

Chapter 4

Integration of Ergonomic Design with Finite Element Analysis and Structural Optimization Technology: Ergonomics in Aluminum Beverage Containers Koetsu Yamazaki, Jing Han, Sadao Nishiyama and Ryoichi Itoh

1

53

79

119

Chapter 5

Ergonomics in the Operating Room: Design Framework A. Albayrak, L. S. G. L. Wauben and R. H. M. Goossens

147

Chapter 6

Ergonomic Considerations for the Radiological Workspace P. M. A. van Ooijen and A. W. G. van Ooijen

179

Chapter 7

Current Ergonomic Issues in Radiology Xiao Hui Wang, Walter F. Good, Makoto Omodani, J. Ken Leader, Bin Zheng

205

Short Communications A

The Need for Research on Ergonomics in Bariatric Patient Handling Traci Galinsky, Stephen Hudock and Jessica M.K. Streit

223

B

Preventing Musculoskeletal Injuries in the Construction Industry Sang D. Choi and Lisa Hudson

235

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vi

Contents

C

Ergonomics and epidemiology in evidence based health prevention Olaf C. Jensen

D

Foot Movements for Foot Controls: What We Know and What We Do Not Know Annie W. Y. Ng and Alan H. S. Chan

255

Biomechanics as a Tool in Ergonomics: Demonstration for Back Posture, Balance and Mechanical Work in Expert/Novice Handlers Micheline Gagnon

265

E

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Index

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245

273

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PREFACE Ergonomics is the science of designing the job, equipment, and workplace to fit the worker. Ergonomics is widely used by industrial companies to design tasks and work areas to maximize the efficiency and quality of their employees' work. The field is also called human engineering and human factors engineering. This book presents new and significant research in the field. Good acoustics is a crucial element in verbal communication and in the learning process, and is therefore vital for all societies whose development is knowledge-based. An overview of room acoustics in enclosed spaces is given, as well as alternative techniques for measuring parameters. An overview of ergonomics in the operating room (OR) based on scientific research is given as well. In addition, brief attention is paid to the environmental ergonomics dealing with the OR environment, lighting, temperature and airflow. The introduction of new technologies into the practice of radiology is causing a major shift in the operating paradigms of radiology departments, and along with this, a need to reconsider the relevant ergonomic issues. The ergonomics of the radiological workspace are explored, and different input devices are studied and tested within the radiological workspace, many of which originated from either graphical design or the gaming applications. Construction remains one of the largest industries in the United States. Recent research literature on ergonomic issues in the construction industry are reviewed, as well as how to prevent work-related musculoskeletal injuries. Finally, ergonomics and epidemiology in bariatric patient handling and in evidence based health prevention are discussed in this book. In particular, interventions needed to prevent overexertion in patient handling are described. The ergonomics that can contribute to the common development of public health and occupational preventive methods are also looked at. In addition, two recent foot movement studies for foot controls are reviewed, in order to facilitate designers to create more user-friendly foot controls in the ergonomic workplace. Biomechanics as a tool in ergonomics is discussed, with demonstrations for back posture, balance and mechanical work in expert/novice handlers. Chapter 1 - A large number of modern building spaces around the world can be treated as enclosed spaces, e.g., schools (classrooms), functional offices, churches, theatres, conference rooms, etc. Human development depends strongly on verbal communication. Good acoustics is crucial for effective verbal communication and in the learning process, and is therefore essential for all societies whose development is knowledge-based. Acoustic comfort is an ever more pressing need due to the increasing levels of noise pollution, especially in medium-

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Bram N. Brinkerhoff

sized towns and large cities. This chapter offers an overview of room acoustics in enclosed spaces. Techniques for the measurement of parameters that characterize room acoustics are presented and discussed, such as reverberation time, clarity, definition, and speech transmission index. One alternative for the measurements is computational simulation. This alternative is presented through real case studies in classrooms, churches, and offices. The advantages and disadvantages of each of these approaches are discussed, as are technical standards in different countries. Chapter 2 - Timely return to work (RTW) is often identified as one of the priority goals of occupational health professionals. One of the primary determinants of RTW in workers with neck-shoulder pain symptoms is the degree of functional limitation. Thus, the capacity to reliably assess workers’ functional capacity as they prepare to RTW is of paramount importance. The purpose of this study was to assess the reliability of shoulder functional measurements taken from participants with chronic neck/shoulder pain and to correlate pain and disability levels on functional outcome measures. Chapter 3 - When a person becomes ill different stages have to be completed before he or she is ‘cured’: visits to general practitioner (GP), visits to specialist, possibly medication and therapy, admission into hospital, possibly surgery, release from hospital, checkups with the specialist or GP, etc. During surgery several people are involved: anesthetists, surgeons, residents and nurses. Within the sub stage surgery three phases are present: pre-operative, intra-operative and post-operative phase. This chapter focuses on the intra-operative phase of surgery only, mainly concentrating on the surgical team and scrub nurses. The chapter provides an overview of the ergonomics in the operating room (OR) based on the scientific research. Due to the growing variety of technical machines, products and increasing safety awareness, many ergonomic (Human Factor) specializations have evolved. One of them is the ergonomics of the OR. Within this specialization the discipline Industrial Design Engineering entails inventing, producing and using tools, focusing on the human aspects of the product design: ‘creating products people love to use’. In relation to medical product development and medical product evaluation this means that the OR and its products should be adapted to staff working in the OR, instead of adapting the workers to the OR environment. The three main domains of specialization of ergonomics are related to the sensorial, cognitive and physical ergonomics. Within all these domains problems are encountered using the currently available products. For the sensorial domain, factors such as perceiving surgical images, displays, haptics, and the use of foot pedals were discussed. Examples within the cognitive domain are: indirect vision, behavior, training of technical and non-technical skills, protocols, checks and checklist and time-out procedures. For the physical ergonomics the apparatus and instrument used in the OR (e.g. operating table, foot pedals, monitor, etc) play a role. In addition, brief attention will be paid to the environmental ergonomics dealing with the OR environment, lighting, temperature and airflow. All domains have to be taken into account when designing and evaluating products, however their focus will shift. Chapter 4 - This chapter describes integration of ergonomic design with Finite Element Analysis (FEA) and structural optimization technology, and its applications to aluminum beverage containers including cans and bottles. Ergonomic design examples of the containers considering human emotional feelings are introduced. To satisfy human visual and tactile

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Preface

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sensation, various specific metal printing and sheet embossing techniques are used to change appearance in different temperature environments, surface conditions and shape of containers. FEA is then introduced into the ergonomic design to evaluate the human feeling numerically and objectively. In a design example of the beverage can end (the lid of can), experiments and FEA of vertically indenting the fingertip pulp by a probe and the tab of the can end are conducted to observe force responses and to study feelings in the fingertip. A numerical simulation of the finger lifting the tab to open the can is also performed, and discomfort in the fingertip is evaluated numerically to present the finger accessibility of the tab. A comparison of finger accessibility between two kinds of tab ring shapes show that the tab that has a larger contact area with the finger is better. Structural optimization technology based on FEA is also integrated into the ergonomic design to achieve the best solution. In the design example of beverage bottles used to serve hot drinks in winter, FEA of the tactile sensation of heat is performed to numerically evaluate the touch sensation of the finger when holding the hot bottle. Numerical simulations of the embossing process are also performed to evaluate the formability of various rib-shape designs. Using multi-objective and multi-disciplinary optimization techniques, the optimum design is then carried out considering the hot touch sensation as well as the metal sheet formability Chapter 5 - Healthcare is one of the most dynamic and expanding areas in the world. This introduces a multi-disciplinary approach to deal with, on one side the technology-driven trends and on the other side the social-economic consequences on the healthcare system. Regardless of the field of application, in healthcare the human plays a central role. Healthcare is practiced by humans to cure, care and prevent other humans from illness. Beside healthcare, there is another field in which humans also plays a central role, namely ergonomics. ‘Ergonomics (or human factors) is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance’. Because care, cure and prevention are human-centered, ergonomics plays an important role in healthcare. On this perspective, it is not surprising that knowledge in the field of ergonomics has significant contributions to the improvement of the healthcare sector. Application of ergonomics in healthcare is not only based on a fundamental and theoretical framework of ergonomics as a science, but also other aspects such as legislations, methodology and communication define the precondition of the design space. As a result, highly skilled engineers in this field are needed who are capable of translating practical needs of the healthcare sector into products specially designed for low-tech as well as high-tech medical applications. First, the engineer and the medical specialist have to speak the same language. This can be improved by using the ‘Participatory Design’ as a methodology during the design process. Participatory Design actively involves the user into the design process, leading to a designed product that meets the user’s specific needs. The design process is based on ‘trial-and-error’ whereby the emphasis is on doing feasibility studies with a prototype in practice. The feedback from the user is then used to improve the product. In the faculty Industrial Design Engineering at Delft University of Technology this approach is integrated and applied in education and design projects. This chapter discusses three cases of the application of this method regarding three domains of ergonomics. In the first case the emphasize lies on the sensorial domain; the

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design of an abdominal wall tension measurement device. The second case shows how the ergonomics of minimally invasive surgery can be improved by means of an integrated surgical suite, within the cognitive domain. Finally, within the physical domain the design of a curved instrument for minimally invasive surgery to improve the surgeon’s body postures will be illustrated. Chapter 6 - With the digitalisation of the radiology department, the workspace of the radiologist moved from the dark room with walls covered with lightboxes to an office workplace equipped with a multi-monitor workstation. Besides the basic workstation required for examining the images, many peripherals are added to this workspace for interaction and digital dictation. A default workspace can be equipped with a keyboard, mouse, foot controls and digital speech microphone. However, other peripherals such as dedicated keyboards (e.g. for mammography) or a special mouse can be added. All these changes that were introduced with the transition from lightbox to workstation greatly changed the way a radiologist works. Therefore, the ergonomics of the radiological workspace has gained interest in recent years and studies have been performed to evaluate and enhance the ergonomic conditions of this workspace. Furthermore, different input devices are studied and tested within the radiological workspace many of which originate from either graphical design or the gaming applications. Chapter 7 - Historically radiographic displays consisted of x-ray projections recorded on film and viewed by mounting the film on a lightbox. Once films were interpreted by a radiologist, they were manually filed in vast film libraries where they were maintained in anticipation of possibly being needed for comparison purposes at a later date. Other than adjusting acquisition parameters for optimal film exposure and controlling the brightness of the lightbox and the level of ambient lighting, radiologists had little control over the how images were viewed. Furthermore, because of the effort required to retrieve films from libraries, radiologists needed to wait on prior studies to be retrieved and often, previous films could not be provided in time to have an impact on the interpretation process. Over the past couple of decades radiology has moved toward digital acquisition, storage and display of image data, as well as a shift from the acquisition of 2-D projection images to the acquisition of large 3-D digital datasets, each of which can be equivalent to hundreds of individual images. Also, it has become customary to have a considerable amount of computer processing power between the acquisition process and the final display, and to provide radiologists with computerized control of the display. Thus, the opportunity for radiologists to interact with these processes, and the potential complexity of these interactions, have greatly increased. At the same time, because of the larger volume of image data when anatomical information is represented as a 3-D volume as opposed to a 2-D projection image, the workload on radiologists has increased dramatically. To take advantage of the opportunities provided by computerized methods, while increasing the efficiency of the overall practice of radiology, ergonomic considerations have become a topic of considerable interest to radiologists. This has included efforts to streamline user interface designs for radiographic workstations; to incorporate viewing methods such as stereographic display, that take advantage of innate human capabilities; and, to employ computerized methods such as computer aided diagnosis to assist with certain mundane tasks that are amenable to computerized analysis. The ultimate radiology workstation will likely be a system in which radiologists wear a head-mounted display and use their head motion to

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control roam and zoom within a 3-D image space, though there will be a long evolutionary process to get such a system adopted within radiology. Short Communication A - Healthcare workers who routinely lift and move patients, such as nurses and nursing aides, have a higher risk of musculoskeletal injuries than workers in most other occupations. Recently-documented rates of injury due to overexertion in hospital and extended care nursing personnel were 70.5 and 138.3 per 10,000 workers, respectively. By comparison, the average rate of work-related overexertion injuries for all U.S. industries is 30.8 per 10,000 workers (Bureau of Labor Statistics -- BLS, 2006). For several years, overexertion injury rates for healthcare workers have ranged from two to five times the national rate for all industries, and have exceeded rates in other strenuous occupations such as construction and mining (BLS, 1994-2006). Whereas rates of work-related injuries in most other occupations have been decreasing during the past decade, rates of musculoskeletal injuries in nursing personnel are epidemic (Owen, 1999) and have continued to increase (Fragala and Bailey, 2003). Short Communication B - Construction remains one of the largest industries in the United States, historically constituting about 10 percent of the nation’s gross national product and employing some 10 million workers. For years the construction sector has been associated with increased rates of work-related musculoskeletal disorders (WMSDs). According to the National Occupational Research Agenda, conservative estimates of the economic burden imposed by WMSDs in the United States are between $45 and $54 billion annually. Thus, this study reviews the recent research literature on ergonomic issues in the construction industry and how to prevent work-related musculoskeletal injuries. Available research on ergonomics and construction is examined, and practical solutions to help reduce risk of repetitive stress injury in common construction tasks are provided. Understanding the jobspecific risks and hazards in construction projects could help identify training and intervention requirements to meet the challenges facing construction workers in the field. Short Communication C - According to the definitions, ergonomics is a natural part of the health and safety activity but it has its own research methods and causal models. Public health, occupational and clinical medicines are closely related to epidemiology and differ from ergonomics by using a disease model with a wide web of causal factors. Evidence based medicine, mainly based on epidemiology, was established to improve the quality of the pharmacological treatments based on randomised controlled clinical trials. Later, evidence based medicine was extended to non-pharmacological public health trials, but the same success of health effects from the clinical trials could not be obtained. It is argued that the ergonomics design, Integration and Implementation can be strengthened by adapting the epidemiological methods and causal models. The ergonomics can then contribute to a common development of public health and occupational preventive methods. One important aspect is whether the randomised controlled study design should still be held as first priority for the evaluation of large scale health interventions, or the use of descriptive studies are the most useful. Randomised intervention trials are probably most useful for patients or for persons with pre-conditions of diseases like pre-hypertension and pre-diabetes and for the most vulnerable parts of the populations. Short Communication D - There has been an increasing number of applications of foot controls in the human machine interfaces. Examples include stage lighting foot switch systems, foot operated computer mice, and medical foot-operated controls. This paper presents a review summarizing the current state of knowledge about foot movements. The

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review covers previous studies on foot-tapping between pedals with a model of movement time, the determination of task conditions for ballistic, visually controlled, and non-visually foot-tapping, and foot response time from a resting position to a target pedal. Two recent foot movement studies conducted by the authors were also discussed. Such a review would facilitate designers to create more user-friendly foot controls and is helpful in formulating research plans and methodologies for further studies on foot movement. Short Communication E - The challenge for instructors is to detect unsafe practices and reinforce safer ones. Some examples illustrate here how biomechanics may help reaching these objectives. Six expert manual handlers from a transport industry were compared with five novices as they displaced loads in similar laboratory conditions while being filmed with 2 cameras positioned at a right angle. A previous ergonomic analysis of these data had emphasized footwork, load tilts/handgrips and posture as differential elements between experts and novices; separate biomechanical studies had shown the safety potential of these elements, especially for symmetry of back posture, balance and mechanical work. In the present study, the data were reanalyzed for biomechanics by combining visual inspection and a subjective evaluation based on biomechanical principles, a simpler approach applicable to instructors. One particularly difficult task was chosen for illustration, i.e. lowering from an important height (shoulders level to ground). When compared to the novices, the following elements characterized the experts: 1) symmetry of back posture involved the use of diagonal handgrips, the maintenance of both hands and both shoulders at the same heights during load transfer and the maintenance of the transverse axes of pelvis/shoulders parallel (no torsion), the load facing the trunk; 2) optimization of body balance involved the keeping of both feet in contact with the ground at take-off and deposit, displacements using short steps and the rapid lowering of load by the extension of elbows and finally, 3) minimization of mechanical work involved the adoption of handgrips that allowed the tilting of load, hence limiting knee flexion at take-off and deposit and limiting elbow flexion during transfer. This approach remains simple for application and may help instructors for evaluating the safety practices in workers. Comparisons of experts/novices strategies based on biomechanical principles appear an interesting tool for the training of workers to safe handling.

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Chapter 1

ACOUSTIC DESIGN OF ENCLOSED SPACES Paulo Henrique Trombetta Zannin∗, Carolina Reich Marcon Passero and David Queiroz de Sant`Ana Federal University of Paraná, Centro Politécnico, Curitiba, Paraná, Brazil LAAICA – Laboratory of Environmental and Industrial Acoustics and Acoustic Comfort

ABSTRACT

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A large number of modern building spaces around the world can be treated as enclosed spaces, e.g., schools (classrooms), functional offices, churches, theatres, conference rooms, etc. Human development depends strongly on verbal communication. Good acoustics is crucial for effective verbal communication and in the learning process, and is therefore essential for all societies whose development is knowledge-based. Acoustic comfort is an ever more pressing need due to the increasing levels of noise pollution, especially in medium-sized towns and large cities. This chapter offers an overview of room acoustics in enclosed spaces. Techniques for the measurement of parameters that characterize room acoustics are presented and discussed, such as reverberation time, clarity, definition, and speech transmission index. One alternative for the measurements is computational simulation. This alternative is presented through real case studies in classrooms, churches, and offices. The advantages and disadvantages of each of these approaches are discussed, as are technical standards in different countries.

1. INTRODUCTION This chapter presents a study of the acoustic quality of classrooms, open plan offices and churches. The acoustic quality of these places is examined in the light of the results of in situ measurements and of computational simulations. Education is as essential in today’s societies as it was in the past. The most formal education takes place in classrooms, where learning involves intensive verbal communication between teachers and students and among students. Although today’s world is a digital one, it ∗

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Paulo Henrique Trombetta Zannin, Carolina Reich Marcon Passero et al.

is in the classroom that effective contact takes place between those who have something to teach and those who want to learn. Nothing can supplant this relationship, so this communication must be efficient. In order for this communication to be efficient, and the study environment adequate for information exchange, several acoustical parameters must be evaluated. Some of these parameters are: reverberation time, noise levels inside and outside the classroms, sound insulation of doors and windows, speech transmission index, etc (Lubman, 2001). Many aspects that have appeared with the evolution of the modern era have contributed to deteriorate the acoustic environment of classrooms (Loro, 2003; Ferreira, 2004; Zwirtes, 2006). One of the reasons for the existence of problems of acoustic comfort nowadays in classrooms, resulting in learning impairment, is the simple lack of an adequate project. Sometimes there is a project, but it hasn't been developed with the refinement and quality actually available with the current tools of acoustics measurement equipment and softwares for simulation and data analysis. Seep et al. (2002) stated that the best way to solve acoustic problems is to avoid them in the design phase. This chapter will cover an overview of some of these tools. The subject of acoustic comfort (ambient noise, sound insulation, reverberation time, speech intelligibility, auralization, acoustic materials) in the classrooms of primary and secondary schools and universities has been the focus of several studies around the world (Sala and Viljanen 1995, Ercoli and Azzurro 2001, Hodgson 2001, Karabiber and Vallet 2003, Shield and Dockrell 2004, Hodgson 2004, Hagen et al. 2004, Krüger and Zannin 2004, Yang and Hodgson 2005, Kennedy et al. 2006, Yang and Hodgson 2006, Hodgson and Scherebnyj 2006, Yang and Hodgson 2007, Zannin and Marcon 2007, Astolfi and Pellerey 2008, Zannin et.al. 2008, Zannin and Zwirtes 2009). Another focus of studies has been the perception of noise by students and teachers, and the influence of noise on those people (Evans and Maxwell 2000, Lercher 2003, Shield and Dockrell 2003, Dockrell and Shield 2004). With regard to the work environment, the issue of acoustic quality can be divided into two major sectors: the industrial and the commercial environments. These sectors, in turn, are divided into various subsectors according to their activities, each of them having specific environmental needs. Noise in the industrial environment has been exhaustively studied and controlled, since extremely high noise levels are generated and workers exposed continually to these sound pressure levels tend to present serious occupational disorders such as acquired deafness. Although the sound levels in commercial and services environments are relatively lower, the acoustic ambiance of functional offices must be examined (Cordeiro, 1996). Environments with noise levels below those found in industrial environments, the technical and administrative offices of industry, banks and other commercial sectors should be acoustically conditioned to offer their users a healthy and comfortable work environment. In terms of spatial organization, offices can be divided into two categories: closed or conventional offices, and open plan offices. According to Durval et al. (2002), open plan offices have been popular among design professionals since the 1960s, in response to the need for communication and the search for intense productivity. Duffy (1980) stated that the characteristics of offices designed according to this concept have large open spaces, with a work environment arranged freely rather than in straight geometric lines. Although this type of office arrangement is advantageous for its users in terms of fast exchange of information

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Acoustic Design of Enclosed Spaces

3

and productivity gains, it is disadvantageous in terms of physical comfort, privacy and the ability to concentrate. Correct acoustic treatment of the environment is therefore necessary. Nijs et al. (2002) point out that the need for acoustic planning in such offices is increasing because designers come up ever more frequently with architecturally open ambiances. The absence of high partitions and doors facilitates viewing of the entire space, information exchange among users, access to departments, and increases the flexibility of the layout. In contrast, however, it magnifies the sound interference among work stations, leading to poor intelligibility and lack of speech privacy in these spaces (Nogueira, 2002). According to Yoon and Loftness (2002), lack of privacy is considered the greatest factor of dissatisfaction among the occupants of open plan offices. The obstacles created by the elimination of partitions and walls up to the ceiling, which are responsible for a large part of the acoustic insulation in work environments, may lead to dissatisfaction in the workplace. Duffy (1980) claimed that the main purpose of planning work environments is to enhance the workers’ productivity. Durval et al. (2002) point out that open plan offices accommodate a greater density of occupants than do conventional offices. Studies have shown that the larger the worker’s space the more satisfied he is with his work environment, and that the fewer people in the same space, the greater the satisfaction. These same authors emphasize that the optimal density of workers in an office can be determined by the activity carried out there. In small and mediumsized companies, a variety of activities are often carried out in open plan offices without a proper spatial organization for each task. Studies of open plan offices have revealed that the noise in these environments can be stressful and demotivating (Evans and Johnson 2000), leading to high levels of distraction and low levels of privacy (Hedge 1982). A subjective analysis of questionnaires found that speech is the sound source causing the greatest disturbance in open plan offices (Hongisto et al. 2004). The most distracting conversations come from the closest work stations. Speech privacy between work stations should therefore be as good as possible, but it is typically lower than the privacy found in closed plan offices. Even so, a measure of privacy can be attained through the selection of certain components. An open plan office is rendered acoustically adequate through the interaction of elements such as the ceiling, wall finish, furniture, ventilation system, heating and air-conditioning, and the sound masking system (ASTM 2002). The idea of studying the acoustics of churches and other places of worship is fascinating simply because these places play an important role in societies all around the world. This is exemplified by the major role churches, mosques and synagogues have played in the construction of the history of civilization. Churches have a very distinctive type of architecture and although they are built as places for praying, they play several roles, serving as meeting venues for communities that have no other public spaces for such purposes. They are also often used as large community halls for instrumental and choir musical events (Cirillo and Martellotta 2006). The acoustic requirements of churches are often difficult to satisfy. These buildings must display two characteristics, namely: 1) they must meet the requirements of an auditorium for speeches, and 2) they must be suitable concert halls. In Catholic churches, from the standpoint of acoustics, the replacement of Latin by local languages to conduct the liturgical service, as proposed by the Second Vatican Council (1965), meant a greater demand for speech intelligibility. At the same time, the choir singing resulting from the active participation of the congregation meant the church halls had to be adapted for music (Cirillo and Martellotta 2006).

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Due to the acoustic complexity of these buildings, this theme has attracted the attention of several researchers around the world (Carvalho 1995, 1999, Galindo et al. 1999, 2000, Desarnaulds 2002, Cirillo and Martellotta 2002, 2003, 2005, 2006). However, there is still a paucity of information about this type of hall when compared with information about concert halls and auditoria.

2. ACOUSTIC DEFINITIONS – PARAMETERS USED TO CHARACTERIZE THE ACOUSTICS OF ENCLOSED SPACES When a sound is emitted in free field, part of its energy follows a path unimpeded by obstacles until it reaches a receiver. This part is called direct sound. Without reflections, once the emission ceases, the decay of sound energy is immediate. When a sound is emitted in an enclosed space, the energy that reaches a receiver is divided into two parts, the first corresponding to the direct sound and the second to the energy reflected by its surfaces. The reflections prolong the energy decay time, which depends on the acoustic properties of the materials that make up the surfaces of the room, especially their properties of absorption and diffusion. The perception of sounds in rooms is strongly influenced by the behavior of the reflections and of the sound energy distribution through the environment. The acoustic assessment of a room seeks the correct description of these perceptions. Researches based on different approaches of subjective impressions have been widely employed to characterize the acoustics of rooms (Schroeder et al. 1974, Hojan and Pösselt 1990, Bradley and Soulodre 1995), but they require intensive material effort. On the other hand, an objectively measurable group of parameters can be correlated and applied to each subjective sensation, according to a standardized scientific method ISO 3382-1, 2006 (Cirillo and Martellotta 2006).

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2.1. Subjective Attributes of Sound Fields in Enclosed Spaces A listener, trained or not, can recognize and quantify many attributes of the sound field in a room, providing important data for its evaluation (Yamaguchi 1972, Jeong and Fricke 2000, Sato and Sakai 2002). Among the subjective attributes, the one most easily perceived is reverberation. Reverberation can be understood as the sensation of persistence of sound after the sudden interruption of a sound source, followed by a sufficiently long pause. The reverberation is inversely proportional to the absorption of sound energy by the surfaces. A reverberating room is commonly qualified as a “live” room. A slight reverberation represents a high absorption of the sound energy by the surfaces and corresponds, subjectively, to a socalled “dead” room (Eyring 1930) in which direct sound predominates, which is little reinforced by reflections. The human ear is sensitive to a frequency range that varies from approximately 20 to 20,000 Hz. This sensitivity is not homogeneous for all the frequency ranges. The properties of sound absorption and diffusion of the materials that make up the surfaces of rooms behave similarly. The predominance of certain frequencies over others is responsible for the subjective sensation of the tonal balance and the sound is called bright when there is a

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predominance of high frequencies (Bostwick 1930) and warm when low frequencies predominate. In the latter case, intelligibility may be impaired due to the human ear’s lesser sensitivity to low-pitched sounds (Everest 2001). Another easily identifiable attribute is loudness. According to Fletcher and Munson (1933), loudness is associated with the sense of magnitude with which a sound is perceived. The loudness, or sound level, is an attribute that depends on the characteristics of the sound source, the loudness and the sound absorption of the place. Compared to a soloist, a group of violinists produces a higher sound level (Cirillo and Martellotta 2006). In live rooms, i.e., highly reverberant ones, the sound level is also perceived as being more intense than in dead rooms or in the open air. Similarly, the size of the room influences perception, causing the sound loudness in small rooms to seem higher than in large rooms. Also important is the subjective attribute called clarity. Clarity can be understood as the degree to which distinct sounds (musical notes or speech phonemes) are perceived separately. This attribute depends strongly on the characteristics of the music and the skills of the speaker, but it is also intrinsically connected to the acoustic characteristics of rooms (Beranek 1996, Bradley et al. 1999, Galindo et al. 1999), especially to the reverberation time and the balance between the initial energy, direct sound and first reflections and the energy contained in the reverberating field. The interactions between the first reflections and the reverberating tail can give the listener two sensations regarding his spatial perception of the sound. These two subjective attributes, recently incorporated into the acoustic assessment of rooms, are called Apparent Source Width (ASW) and Listener Envelopment (LEV). ASW is strongly influenced by the first reflections and correlates the visual and auditory impressions of source size (Cirillo and Martellotta, 2006). LEV, which is described as the sensation of envelopment or immersion in the sound environment, is produced by the reverberating part of sound when the listener receives reflections from every direction (Beranek 1996).

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2.2. Objective and Metric Parameters for Room Acoustics Subjective approaches are important tools for the description of sound fields in rooms. Again, note that subjective sensations can be correlated to several objectively measurable parameters. These parameters are measured by recording the sound energy decay in the room. After an excitation signal the reflections increase in number and decrease in intensity. According to Cirillo and Martellotta (2006), when plotted on a graph of energy (Y axis) as a function of time (X axis), the sound displays a decay whose behavior is similar to a linear function (see Figure 1). The decay curve can be analyzed as though it were divided into three parts: direct sound, early sound and reverberating sound. Direct sound is the first sound, the part of the energy that reaches the listener directly and that appears as a vertical line in the left portion of the graph. “... The term early sound encompasses the direct sound plus all the reflections that reach a listener’s ears in the first 80 milliseconds (msec) after the arrival of the direct sound…” (Beranek, 2004).

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Figure 1. Decay curve.

Figure 2. Impulse response of a room.

Decay curves are obtained by two methods: 1) by direct recording of the pressure levels immediately subsequent to the interruption of a continuous excitation of the room’s air volume by a wideband frequency sound signal, called the Interrupted Noise Method, or 2)

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through the reverse quadratic integration of an impulse signal (a bursting balloon, a pistol shot), known as the Integrated Impulse Response Method. An impulse response is recorded as a graph of the sound pressure level – at a given measured point – as a function of time, resulting from the excitation of a room by a Dirac delta function (see Figure 2). Although a real Dirac delta function cannot be created and irradiated in practice, one can use sufficiently efficient approximations such as frequency sweep signals, maximum length sequences (MLS) or sound signals that allow for later mathematical processing (ISO 3382-1, 2006).

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“The representation of the sequence of direct sound, early, and late reflections, each one with its intensity following an impulse sound (such as a hand clap, a pistol shot, or something similar) is known as echogram or impulse response and is the starting point of any objective evaluation of the acoustic properties of a room” (Cirillo and Martellotta, 2006).

2.2.1. Reverberation Time An important parameter affecting the acoustic quality of rooms is the reverberation time (RT). It is important for the RT to be suitable for the purpose of the room. The subjective sensation of reverberation is related with amount of reflection of sound in a room. The objective parameter to describe the reverberation is Reverberation Time (RT). Introduced by room acoustics pioneer Wallace Clement Sabine of Harvard University, this concept is defined as the time, in seconds, necessary for the sound level in a room to decay by 60 dB starting from the interruption of a continuous sound. Since a decay of 60 dB is often difficult to record because of the influence of ambient noise on the reverberating tail, the Reverberation Time is extrapolated from the first 20 dB of decay measured from the reduction of 5 dB below the initial sound-pressure level down to 25 dB below that level. This metric is represented by the letter T followed by the index corresponding to the measured interval, T20. T30 is calculated likewise, by recording a longer interval (-5 dB to -35 dB), which is more commonly utilized (ISO 3382-1, 2006). The Reverberation Time (RT) is determined for the frequency ranges normally used in room acoustics, in octave-band frequencies of 125 Hz to 4000 Hz. The RT will also be differentiated in the various frequencies. In cases where speech predominates, it is common to evaluate the RT in the frequency bands of 500, 1000 and 2000 (Jenisch et al., 2002). The RT of a room can also be expressed by a single value corresponding to the arithmetic mean of the 500 Hz, 1000 Hz and 2000 Hz bands. In live rooms and in rooms where conditions of sound diffusion prevail, the RT can be estimated based on Sabine’s theory, whereby the inverse ratio between the reverberation time and the sound absorption of surfaces is observed, as expressed by equation (1):

RT = 0.161

V [s] A

(1)

where: V is the room’s volume in m³; A is the room’s total sound absorption in m2:

A = S1α1 + S 2α 2 + S3α 3 + ....S nα n , where S n is the area of the different materials that make up the room, and αn is the sound absorption coefficient of those materials.

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According to Fasold and Veres (2003), the condition for the application of Sabine’s equation is that the room’s mean sound absorption coefficient is up to α room = 0.3 (live rooms). On the other hand, Eyring’s equation is used for rooms where

α room is greater than

0.3 (dead rooms), i.e., with high absorption. In 1930, Carl Eyring proposed a modification of Sabine’s formula. This modification would be suitable for rooms with high absorption, “dead” rooms, with α higher than 0.5. Eyring claims that Sabine’s formula is not valid for rooms with considerable absorption and that it should be used for “live” rooms. Eyring’s formula is based on free propagation between reflections characterized by a diffuse sound field (Neubauer and Kostek 2001). Eyring’s formula is as follows:

RT =

0,163.V − S . ln(1 − α )

(2)

where: RT is the reverberation time; V is the room’s volume in m3; S is the total area of the room’s surfaces in m2; ln is the Napierian logarithm; α is the mean absorption coefficient of all the materials: α = 1 ∑ S i .α i , where Si is the area of each surface that makes up the room S i and αi is the sound absorption coefficient of those materials. Another formula for calculating the RT is the Arau-Puchades formula. This formula, which should be used for rooms with asymmetric distribution of sound absorption, assumes that reverberation decay is a hyperbolic process. This decay is the superposition of three contributions: initial decay, first and second linear portion of the decay, and third linear portion of the decay (Neubauer and Kostek 2001). For rectangular rooms, Arau-Puchades define an absorption coefficient based on Eyring’s model for each surface parallel to the three axes of x, y and z spatial coordinates (Ducourneau and Planeau 2003). Arau-Puchades in 1988 proposed the following formula for calculating the RT (Neubauer and Kostek 2001):

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Sx

⎡ ⎤S 0,163V RT = ⎢ ⎥ ⎣ − S . ln(1 − α x ) + 4mV ⎦

Sy

⎤S ⎡ 0,163V .⎢ ⎥ ⎢⎣ − S . ln(1 − α y ) + 4mV ⎥⎦

Sz

⎡ ⎤S 0,163V .⎢ ⎥ ⎣ − S . ln(1 − α z ) + 4mV ⎦

(3)

where: the first portion corresponds to the absorption of the materials located parallel to the x axis (floor and ceiling), the second parallel to the y axis (side walls), and the third parallel to the z axis (front and end walls); V is the room’s volume in m³; ln is the Napierian logarithm; α x is the area-weighted arithmetical mean of the energetic absorption coefficients of the floor

S x1 and ceiling S x 2 surfaces and S x = S x1 + S x 2 , α x = (α x1 S x1 + α x 2 S x 2 ) / S x ; α y and

α z are the arithmetical mean of energetic absorption coefficients of the side walls, and front and end walls, respectively; S is the sum of the area of all the materials that make up the room; S x , S y and S z are the sum of all the areas of the materials parallel to the

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x , y and z axes, respectively; 4mV corresponds to the acoustic absorption of airborne sound,

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where V is the volume of the room and m is the airborne sound absorption coefficient, expressed in Sabins per meter. The value of m is a function of relative air humidity. For relative humidity of 40 to 60%, Mehta et al. (1999) present the following m values: at the frequency of 2000 Hz, 4000 Hz and 8000 Hz, the corresponding values of m are 0.009, 0.025 and 0.080 Sabin/m, respectively. Another parameter adopted for the objective evaluation of reverberation is the Early Decay Time (EDT). The EDT indicates the time required for the sound level to decay by 10 dB after the interruption of the room’s excitation signal multiplied by six. The estimated time for the 10 dB drop is approximately one sixth of the RT (60 dB) and, according to Beranek (2004), the correction factor allows for a direct comparison of the two reverberation descriptors. The EDT values are particularly affected by changes in the geometry of rooms. The 10 dB interval is very strongly influenced by the first reflections, which makes the EDT highly sensitive to the relative positions between the source and the receiver, when compared with the RT (Cirillo and Martellotta 2006). The EDT indicates the influence of direct sound on the perceived reverberation, which is why it seems to be a more effective reverberation descriptor than the RT for more detailed diagnoses (Beranek 2004). Moreover, it is simple to measure and does not require additional equipment.

2.2.2. Clarity and Definition Subjectively, clarity can be understood as the degree to which distinct sounds are perceived separately (Beranek 1996). The stronger the influence of direct sound, on the receiver the greater the clarity. Clarity is at its highest in free field, and in enclosed spaces it declines as the reverberating tail increases. Combined with direct sound, the early reflections impress the auditory system and produce a natural sound reinforcement effect. “...The time interval in which an early reflection is also a ‘useful’ reflection varies according to the nature of the sound. For music it is assumed to be 80 ms, while for speech it is 50 ms. Outside this interval reflections are considered ‘detrimental’ to clarity, but they nonetheless contribute to creating a sense of room sound for the listener and to blending sounds together. This means that a reasonable compromise must be found between these opposing needs.” (Cirillo and Martellota 2006). There are two objective criteria of clarity, which are calculated based on early-to-late sound energy ratios (ELR). In speech, the German term Deutlichkeit (D50) (ISO/IDS 33821:2006) - definition - is the ratio of sound energy, direct and reflected, contained in the first 50 ms of the decay curve and the total energy of the sound impulse. The reflections that reach the receiver within the first 50 ms of the decay curve contribute to increase the definition of speech (Cavanaugh and Wilkes 1999). D50 is expressed as a percentage and is calculated separately for each frequency band from 125 Hz to 4000 Hz. Definition is expressed by the following equation:

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Paulo Henrique Trombetta Zannin, Carolina Reich Marcon Passero et al. 0 , 05

D50 =

∫p

2

(t )dt

0 ∞

∫p

(4) 2

(t )dt

0

2

where: p (t ) is the quadratic response of the sound pulse. For music, clarity is calculated taking as the interval the first 80 ms of the decay curve. The Clarity (C80) parameter is the ratio, expressed in decibels (dB), of the sound energy contained in the first 80 ms of the impulse response to the remaining energy (Bradley 1986). Clarity is calculated for each octave-band frequency from 125 Hz to 4000 Hz, according to the following equation: 0 , 08

C80 = 10 log

∫p

2

∫p

2

(t )dt

0 ∞

dB

(5)

(t )dt

0 , 08

2

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where: p (t ) is the quadratic response of the sound pulse.

2.2.3. Speech Inteligibility – Speech Transmission Index – STI Speech consists of a succession of sounds varying rapidly at every instant in intensity and frequency (French and Steinberg 1947). According to Steinberg (1929), speech sound waves are characterized by three magnitudes: amplitude, frequency, and phase, all of which are essential for the correct recognition of sounds by the listener. With regard to the human voice, research has demonstrated that, in terms of normal vocal effort, the frequency of 500 Hz predominates for both men and women (Harris 1998). The average equivalent sound pressure level for this effort is 58 dB(A) for men and 55 dB(A) for women. The predominant sound levels and frequencies are 88 dB(A) and 1250 Hz for men and 82 dB(A) and 1250 to 1600 Hz for women, considering a high vocal effort. These levels may vary according to the speaker and the ambient conditions, background noise and reverberation. Most people with normal hearing can communicate reasonably well if the voice level is 7 to 11 dB above the ambient sound level (Harris 1998). Distortions in speech usually occur if there are relative changes in one or more of the magnitudes that characterize the process of sound wave transmission from the speaker to the listener (Steinberg 1929). Makrinenko (1994) states that speech intelligibility is determined by acoustic characteristics, such as the level of the speech signal, the level of background noise, reverberation time, and the pattern of sound reflections. Therefore, good intelligibility is determined by the high level of speech, low level of noise, shorter reverberation time and brief reflection pattern without a marked lag of early reflections. According to Knudsen (1929), the optimal sound level for understanding speech is 70 dB, but the equivalent sound level at a distance of 1 meter from the speaker is usually 50 to 65 dB(A) for conversation at a normal voice level (Harris 1998).

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French and Steinberg (1947) stated that a person tends to adjust his voice to the intensity in which he hears it. Hence, speech intensity also depends on the intensity of undesirable sounds, such as the ambient noise where the speaker is located. According to Knudsen (1929), noise interferes in hearing speech, producing the so-called masking effect, so hearing depends on the intensity of noise rather than on that of speech. Steinberg (1929) continued by stating that the principal effect of noise on the interpretation of speech sounds is intimately associated with masking, i.e., the difficulty to understand or hear those sounds. Reverberation and the distance between the speaker and the listener also interfere in communication (Steinberg 1929). In a study involving auditoriums of 5,500 to 8,500 square meters, Knudsen (1929) found that the intelligibility of speech declined on average 6% at each increment of one second in the reverberation time. With regard to the sound distortions caused by resonance, sounds that have important frequencies in the resonance region undergo distortions. On the other hand, resonance attenuates or reduces the level of sounds that have important frequencies outside the resonance region (Steinberg 1929). Thus, using as an example an auditorium for purposes of speech, according to Knudsen (1929), ideally, it is small and noiseless and its surfaces are covered with perfectly absorbent material, because in a small room the speaker is close to the listener, so his voice can be heard at a suitable intensity. Moreover, there is no interference from noise, reverberation or delayed reflections (Knudsen 1929). Although the objective of acoustic design in auditoriums is to maximize the intelligibility of speech, the opposite occurs in spaces destined for offices (Mehta et al. 1999). In those places, the design is aimed at achieving the lowest possible intelligibility, so that a speaker at one work station will not be understood by his coworker at the neighboring work station. According to Mehta et al. (1999) and Long (2006), low speech intelligibility implies high speech privacy. Cavanaugh et al. (1962) emphasize the importance of speech privacy in buildings, stating that although there is indeed a relation between disturbance and sound pressure level for certain sounds such as air-conditioning and traffic noise, the disturbance produced by sounds that involve information such as intrusive speech (background speech, i.e., the speech of other occupants of the environment other than that of the main speaker) is determined by intelligibility. Chigot (2007) contends that the concept of speech privacy involves the level of speech disturbance between two individuals who are not talking to each other. According to Schlittmeier et al. (2007), office workers often complain about noise, particularly from background speech, such as conversations between coworkers or the noise of other people talking on the telephone. Therefore, the reduction of background speech intelligibility is considered a solution to this problem. The intelligibility of this speech is destroyed when the speech peaks are submerged in background noise (Cavanaugh et al. 1962). Egan (1988) maintains that speech privacy in open or closed plans depends on the signal to noise ratio between intrusive speech (signal) and the background sound level (noise). Hence, in office environments where privacy is extremely important, a suitable signal to noise ratio must be achieved (Long 2006). The level of speech intrusion is to a large extent determined by the speaker’s vocal effort and the reduction of sound between closed rooms or between work stations in open plans (Egan 1988). In addition to speech intrusion, speech privacy will be determined by the ambient background noise level. Egan (1988), states that occupants of rooms with very low background noise levels have serious problems with speech intrusion compared with occupants of rooms with adequate masking noise. Therefore, according to the author, if the

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signal to noise ratio between intrusion speech and background noise is -10 dB, i.e., if the speech of coworkers is 10 dB below the background noise, there is 100% satisfaction with respect to privacy. On the other hand, if the signal to noise ratio is +5 dB, i.e., if the speech of coworkers is 5 dB above the background noise, there is total dissatisfaction. Table 1, adapted from Long (2006), presents the signal to noise ratio and the subjective impressions of speech intelligibility and privacy. Table 1 indicates that to achieve very good intelligibility, the speech level must be higher than the background noise. On the other hand, for privacy at a confidential level, speech must be at least 12 dB below the background noise. However, Cavanaugh et al. (1962) assert that the degree of speech privacy required by the occupant of a room depends on his activity. To exemplify, let us consider the case of an engineer or a technician. During most of his work day, his desire for speech isolation is defined by his desire for a reduction of distractions, which can be called “normal privacy”. However, were this worker summoned to his supervisor’s office to discuss salary issues or personal problems, the need for speech isolation would be different. There would be not only the desire for a lower level of distractions but also the desire to be sure his coworkers cannot hear his conversation. According to Cavanaugh et al. (1962), this type of privacy is called “confidential”. This difference in intelligibility requirements usually implies the need for a reduction of 6 dB in the signal to noise ratio. Schlittmeier et al. (2007) conducted an experiment to verify the interference of background speech intelligibility in the following basic cognitive functions: 1) short term verbal memory, 2) maintenance of attention, and 3) verbal and logical reasoning. The authors found that the performance of these cognitive functions is significantly dependent on a combination of the reduction of the level and of the intelligibility of sound, and that a reduction solely of the sound level is insufficient. The data garnered in this study indicated the need to reduce the intelligibility of background speech to allow for better cognitive performance, since its reduction leads to improved task performance compared with work conditions involving highly intelligible background speech (Schlittmeier et al. 2007). Speech intelligibility and privacy can be measured subjectively by means of an articulation test. In this test, the speaker utters various speech sounds and a listener writes down the sounds he hears. The sounds heard by the listener are compared with the spoken sounds, indicating the percentage of sounds that were correctly recognized. This percentage, which is called articulation, is taken as a measure of the ability to recognize speech sounds (Steinberg 1929). Table 1. Signal to noise ratio and speech intelligibility and privacy, adapted from Long (2006) Objective Evaluation Signal to Noise Ratio in (dB) Higher than 0 -3 -6 -9 -12

Subjective Evaluation Intelligibility/Privacy Very good/None Good/Poor Weak/Transitory Poor/Normal Very poor/Confidential

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Knudsen (1929) adds that the percentage of articulation means the percentage of typical speech sounds that can be heard correctly by a listener. The percentage of articulation depends on the speech level reaching the ears of the listener (Steinberg 1929), which, in turn, is associated with the size of the room, the characteristics of reverberation, the quantity of undesirable sound, and the shape of the room (Knudsen 1929). Steeneken and Houtgast (1980) contend that assessment by means of articulation tests offers the considerable advantage of evaluating the influence of the direction of the speaker in relation to the listener. Nonetheless, there are major disadvantages, such as the need for a large number of trained listeners and speakers and little information about the type of signal decay. With regard to objective characterization, according to Hongisto et al. (2004) there are two principal ways to calculate speech intelligibility. The first is the audiological method described by the ANSI S3.5 standard of 1997, which generates the speech intelligibility index, SII, or the articulation index, AI. The second is the method of modulation transfer function, MTF, specified by the IEC 60268-16 (IEC, 2003) standard, which generates the speech transmission index, STI. French and Steinberg (1947) presented a formulation of data garnered from studies that express the intelligibility of speech. These studies and this formulation were developed at Bell Telephone Laboratories over many years. According to the authors, the intelligibility of received speech sounds is related to a magnitude called articulation index. The articulation index, AI, is a weighted fraction that represents, in certain noise conditions, the effective portion of the normal speech signal which is intelligible to the listener (Kryter 1962). Table 2, adapted from Long (2006), presents the relation between the objective values of the Articulation Index, AI, and the subjective impressions of speech intelligibility and privacy. The AI is computed by acoustic measures or estimates, in the ear of a listener, of the speech spectrum and the effective masking of any noise that is present (Kryter 1962). According to Steeneken and Houtgast (1980), the AI method is particularly suitable for channels with frequency-domain distortions, such as interference noise and limits of band passage, but is not applicable when nonlinear distortions (peaks) or time-domain distortions (reverberation and echoes) are involved. Kryter (1962) stated that AI values should be corrected because speech intelligibility tests are influenced by a great many situations of distortions and stresses imposed through the speech signal during its transmission. These factors are: masking of constant noise, masking by variable noise, distortions in speech signal frequency and amplitude, reverberation, vocal effort, and visual signals (lips and facial expressions). Table 2. Relation between the values of the Articulation Index AI and speech intelligibility and privacy, adapted from Long (2006) Objective Evaluation Articulation Index – AI Higher than 0.4 0.3 0.2 0.1 Lower than 0.05

Subjective Evaluation Intelligibility/Privacy Very good/None Good/Poor Weak/Transitory Poor/Normal Very poor/Confidential

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Kryter (1962) developed graphs and charts for correcting AI values according to variations in these factors. Despite such corrections, however, the author asserts that no single AI value can be specified as a criterion of acceptable communication, because efficiency in communication is the result of the message to be transmitted and the proficiency of the speakers and listeners involved. Hence, the level of performance that should be required of a given system is undoubtedly dependent on the factors whose importance can be evaluated only by the users of the communication system. Houtgast and Steeneken (1973) suggested that the relation between the sound of the speaker’s speech and the sound perceived by the listener can be described by a filter characteristic, effectively through the sound emitted by the speaker. In the case of mitigation of the sound level, the filter is essentially in low frequency. This characteristic, called the Modulation Transfer Function, MTF, was studied by Houtgast and Steeneken (1973) to quantify the intelligibility of speech in enclosed spaces. The result was that the values reached by the MTF are strongly correlated with evaluations made by subjective tests. The MTF is a procedure initially used to assess the performance of optical systems (Houtgast and Steeneken 1985). When the MTF is applied in the transmission of sound in rooms, the analyses can be done by a temporary sinusoid of the modulated test signal. The reduction of the modulation depth as a function of the modulation frequency constitutes the temporal MTF (Houtgast and Steeneken 1985). Based on earlier studies using the MTF applied to acoustics and the AI method, Steeneken and Houtgast (1980) proposed a physical method for measuring the quality of speech transmission channels. Essentially, the method represents an extension of the concepts of the articulation index, AI. The initial concept of the study conducted by Houtgast and Steeneken (1973), based on the modulation transfer function, MTF, of a transmission channel, was adapted to allow for the identification of nonlinear distortions (peaks), as well as timedomain distortions (reverberation, echoes). The resulting index was the Speech Transmission Index, STI, which, when compared to subjective results, presented a standard deviation of only 5% (Steeneken and Houtgast 1980). The IEC 60268-16 (IEC 2003) standard defines the STI as the “physical quantity that represents the quality of speech transmission in relation to its intelligibility”. This standard characterizes the STI as an objective measure, based on the weight of the contribution of a number of frequency bands within the frequency range of speech signals, and these contributions are adjusted by the effective signal to noise ratio. According to Harris (1998), the STI is similar to the articulation index, AI, but it has a more general application because it considers the effects of reverberation time and noise in the determination of speech intelligibility. Kang (2002) adds that an important characteristic of the STI is that the effects of reverberation, of ambient noise, and the contribution of the direction of the source, which are normally treated separately, are combined naturally in a single index. Ronsse (2006) claims that the STI is the most efficient objective measure for the determination of speech intelligibility, which became popular with the advent of the high speed measurement techniques and the easy portability of measuring equipment. According to Steeneken and Houtgast (1980), the determination of the STI consists of two steps: 1) measurement of the Modulation Transfer Function (MTF) for seven octave bands, and 2) calculation of the STI by the MTFs. For each octave band, the decay of the test signal is measured by the reduction of the modulation index to 14 modulated frequencies.

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The STI method described in attachment A of the IEC 60268-16 (IEC 2003) standard is based on the determination of the modulation transfer function for 98 points of data, obtained for 14 modulation frequencies in 1/3 octave intervals of 0.64 Hz to 12.5 Hz and for seven octave bands with the central frequency between 125 Hz and 8 kHz (IEC 60268-16, IEC 2003). This procedure offers a selective measure of the rhythmic and octave band fluctuation of the signal to noise ratio after transmission of the noise (Steeneken and Houtgast 1980). There is a simplification of the STI method, called RASTI, which reduces the number of octave bands. The analysis is restricted to just two octave bands with central frequencies of 500 Hz and 2 kHz, and only 4 and 5 modulation frequencies, respectively, in these bands (IEC 60268- 16, IEC 2003). According to Houtgast and Steeneken (1985), measures obtained by the RASTI method showed a good correlation with data obtained from subjective articulation tests in several languages. Ronsse (2006) tooks STI measurements in auditoriums using acoustic software that generates and captures sound in the room to be analyzed. In this study, the rooms were first classified subjectively as having good, regular, poor or very poor speech intelligibility, based on the author’s observations of the rooms’ architectural features. Comparing the subjective values against the measured STI values, Ronsse (2006) concluded the following: 1) the auditoriums classified as good and regular did not show differentiated STI values, which varied from 0.64 to 0.75; 2) the auditoriums classified subjectively as poor had an STI of approximately 0.55; and 3) the auditorium classified as having very poor intelligibility showed an STI of 0.44.

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3. MEASURING INSTRUMENTS AND TECHNIQUES The objective evaluation of the acoustic quality of a room consists of measuring objective parameters correlated to the listener’s subjective perception. This work concentrated on the evaluation of the descriptor parameters of reverberation and clarity: 1) Reverberation Time, 2) Early Decay Time (EDT), 3) Clarity in 80 ms (C80), 4) Definition in 50 ms (D50), and 5) Speech Transmission Index (STI). The methods and equipment for measuring these parameters meet the specifications of the ISO/DIS 3382-1:2006 standard, reviewed edition of ISO 3382:1997, and the IEC 6026816 (IEC 2003) standard. The use of the international ISO 3382 standard for acoustic measurements of rooms produces an enormous volume of information. These data cover a set of objective evaluation parameters for six octave bands (from 125 Hz to 4000 Hz) and follow a combination of position points of the sound source and receiver set, taking into account the size of the room, its capacity (number of seat) and state of occupation. A room with 1000 seats, for instance, should have a combination of at least 3 positions for the sound source and 8 for the microphone. Such a large volume of information must be condensed, for important information is often not immediately perceived. The use of averages to diagnose the room as a whole seems to be the simplest way to treat these data. The average values can be obtained by arithmetic means. The averages can be calculated for each frequency band at the same point, or between points distributed around the room, to describe the room or portions of it as having similar characteristics. The use of average

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values, however, requires some care. For Bradley (2005), although average values provide an image of the room as a whole, it is advisable to draw up graphs of the measured values as a function of the distance between the source and the receiver for this type of evaluation. The frequency averages can be defined by taking the values in octave bands in pairs (125 and 250 Hz; 500 and 1000 Hz; 2000 and 4000 Hz), in three groups, to present values corresponding to low, intermediate and high frequencies. Two complications in this procedure occur at 4000 Hz, as Barron (2005) explains. The first refers to air absorption while the second is inherent to 400 mm diameter dodecahedron loudspeakers (used as omnidirectional sound sources), which become directional at 4000 Hz. As for spatial averages, their representativeness is questionable for some objective metrics. When a metric varies little spatially, it is appropriate to use average values. When the variation through the room is significant, the average value can only be taken for a small part of the audience in the proximities of the measured point. The average says little or almost nothing about the dispersal of the values obtained. The calculation of the average of the measured frequency values is appropriate, but using the spatial averages to obtaining a single value for the room is little representative of the room’s characteristics, except for the reverberation time (Barron 2005). In measurements, the sound excitation of the room’s air volume should be done with the source preferably placed in the same position in which the sound is emitted in the real working condition. The distribution of receiving points should be as uniform as possible around the audience in order to cover all the areas of interest (ISO 3382-1, 2006). The source should be as omnidirectional as possible and should be positioned at a height of 1.5 meters from the floor, and the microphones at 1.2 meters, which corresponds to the average height of the ears of a seated listener. The sound signals for recording the decay curve should be sine sweeps or pseudo-random noise that ensure coverage of the 125 Hz to 4000 Hz range in octave bands or of the 100 Hz to 5000 Hz range in one-third octave bands. To measure the STI, the IEC 60268-16 (IEC 2003) standard specifies that a test signal should be transmitted by a sound source situated in the position of the speaker to a microphone placed in the listener’s position. The important characteristics for the sound source are physical size, direction, position and sound pressure level. According to Müller (2007), to obtain a realistic result when measuring the STI, the loudspeaker employed to inject the excitation signal into the room should have a direction very similar to that of a person; otherwise, the levels of reflections reaching the receiver will be unrealistic. Brüel and Kjaer (2003) state that the methods most commonly used for measuring the STI are Noise Modulation and Impulse Response. The Noise Modulation method is a direct method, whereby a source produces a basic excitation signal composed of 7 (125 to 8000 Hz in octave bands) by 14 (0.63 to 1.25 Hz in one-third octave bands) central frequencies, resulting in a total of 98 sound signals, filtered and 100% modulated (Brüel and Kjaer, 2003). A receiver captures the signal in the position of the listener and a measurement is taken of the reduction in the modulation, MTF, for each octave band and frequency modulation. In this method, the source and the receiver are independent and separate, which is advantageous for long measured distances. However, due to the excitation signal utilized, it takes a long time to obtain results during the measurement, i.e., about thirty seconds. During this time, the background noise may vary and the receiver may interpret this change erroneously as a modulation signal and estimate the intelligibility of the voice at values below the signal to

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noise ratio. If the impulse response method is employed, the measurement will take less time than by the previous method, i.e., about 5 seconds, which is why the latter method yields more reliable data (Brüel and Kjaer 2003). When the measurements have been completed, they should be compared with reference values to assess the acoustic quality of the room. These values are obtained in laboratory tests or in extensive field research about a given type of architectural space. Bradley (2005) recommends comparing the measurements with values obtained in similar and well known rooms, arguing that optimal normalized values have not yet been established.

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Figure 3. BK 4296 omnidirectional dodecahedron sound source.

Figure 4. BK 2260 sound analyzer.

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To measure the reverberation time of a space there must be a sound source and a system for measuring the decay of sound pressure levels as soon as the source is turned off. The RT can be measured by the Interrupted Noise Method (ISO 3382) or the Impulsive Noise Method (ISO 3382). Measurements by the Interrupted Noise Method are done by exciting the room with a pink noise and calculating the RT based on the room’s response to the excitation. We used a two-channel BK 2260 modular real-time sound analyzer, which sends a sound signal to a BK 2716 power amplifier coupled to a BK 4296 omnidirectional dodecahedron sound source. The sound is captured by a microphone connected to the BK 2260 analyzer, which automatically calculates the reverberation time in each frequency of the spectrum of interest. The number of measuring points in each room can be defined according to the room’s volume and geometry. The specifications for this type of measurement are established by the ISO 3382 standard. In general, measurements are taken at three different points in each room. Three readings are taken at each point. In the laboratory, the measurements can then be transferred to a computer using Brüel and Kjaer Qualifier 7830 software, which calculates the mean reverberation time and the respective standard deviation for each frequency. Measuring the RT by the impulse response is similar to the previous method, but the room’s response is given by the impulse response. Similarly to the previous measurement, the room is excited with a sound signal, in this case a sweep type signal. The difference lies in the way this signal is captured, transformed into an impulse and the RT calculated from the decay of this impulse. This measurement method is less affected by background noise than the former one (Fasold and Veres 2003). According to Chigot (2007), there are limitations in the use of the reverberation time for the acoustic assessment of open plan offices. Variations in measured reverberation times are a well known problem: measurements taken in the same room may present different results, and the same applies to various measurements taken in the same position in the room. These results are attributed to the fact that acoustic measurement schemes in enclosed spaces were originally created based on a cubic geometry, with good dispersal of the sound energy (diffusion). However, they seem to be unsuitable for special acoustic conditions in open plan offices with a nondiffuse sound field, complex geometry, multiplicity of receivers and sources and complex sound propagation. Chigot (2007) also emphasizes that, for a more complete evaluation of their acoustic characteristics, open plan offices should be evaluated based on parameters other than reverberation time. Version 3.1 of the Dirac software package (Brüel and Kjaer 2003) was used in the case studies described in this chapter to measure the reverberation, clarity C80, definition D50, and Speech Transmission Index STI. This software uses the impulse response technique to measure the room’s acoustic parameters. The equipment required for taking measurements with this software consists of: 1) an omnidirectional source (distributes the sound around the room); 2) sound amplifier (connects the source to the audio interface); 3) audio interface (connects the sound amplifier to the mobile computer); 4) sound level meter (receives the room’s response); and 5) a mobile computer with Dirac 3.1 software (generates the noise, receives the response from the sound level meter, analyzes and stores the data) (Brüel and Kjaer 2003). To measure the STI requires the use of a frequency equalizer and a mouth simulator. The directivity of a mouth simulator, which is similar to that of a human mouth, is relevant for speech intelligibility. A high quality loudspeaker with a diameter not exceeding 100 mm serves this purpose. Figure 5 depicts the Brüel and Kjaer BK 4227 mouth simulator.

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Figure 5. BK 4227 Mouth Simulator.

The schematic diagram in Figure 6 illustrates the set-up for measuring the Reverberation Time (RT), Early Decay Time (EDT), Clarity in 80 ms (C80) and Definition in 50 ms (D50). The equipment for measuring the Speech Transmission Index, STI, should be set up as shown in the diagram of Figure 7.

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Figure 6. Set-up for measuring the Reverberation Time (RT), Early Decay Time (EDT), Clarity (C80) and Definition (D50).

Figure 7. Set-up for measuring the Speech Transmission Index, STI.

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4. ACOUSTIC SIMULATION In the acoustics of enclosed spaces, the development of prediction techniques is still quite recent. The first efforts in this area began in the early 20th century with the works of Wallace Clement Sabine. Until that time, the acoustic quality of a room was achieved by trial and error. In the following decades, several techniques were developed to investigate acoustic solutions, including the use of small scale physical models. Scale models were widely used to test concert hall designs. Despite their efficiency, however, they have gradually been set aside as computer programs become increasingly reliable. The advantages of digital models go far beyond material testing flexibility and financial cost reductions. Even so, computer models are still far from a faithful resolution of reality. “The simplifications necessary to be able to carry out calculations in a reasonable time still leave us with an imperfect picture, but as technical sophistication and computing ability increase, the models are improving.” (Long, 2006)

Most computer programs for the acoustic simulation of rooms use the classical methods of geometric ray tracing and specular images of the source. Combinations of these two methods, the so-called hybrid methods, are the basis of the most successful models currently in use. The ray tracing method uses a large number of particles that are emitted from a source into every direction, describing an energy ray. On their trajectory, the particles reach the surfaces of the room and are reflected specularly (Snell’s law). At each reflection, part of the energy is absorbed according to the sound absorption coefficient of the surface reached. The acoustic parameters are calculated when a ray reaches a receiver point or passes by that point. So what is the minimum number of rays needed for these calculations to be made? For Rindel (2000), the probability of a ray reaching a surface of area S after an interval of time t is greater if the surface in question is larger than the area of the wavefront. The minimum number of rays is calculated by the following expression:

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N≥

8πc3 2 t S

(6)

where: N is the number of rays; c is the speed of airborne sound (340m/s); t is the time; and S is the area of a surface of the room. A large number of rays are required for a normal room. For a surface of ten square meters, for instance, and a time of 600 ms, approximately 100,000 rays should be used. A number of this order of magnitude implies an undesirable increase in processing time. Recent developments in ray tracing models have produced good results in enhancing the precision and reducing calculation times. Farina’s (1995) pyramidal model replaces ray tracing with cones, allowing for perfect coverage of the spherical surface of the source and avoiding the superposition of surfaces. In ray tracing, specular reflection produces good results for low frequencies. Vorländer (1995) emphasizes that the ray tracing method allows not only the effects of sound absorption to be calculated but also sound diffusion to be treated, resulting in better reproduction of surfaces.

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The image source method is based on the construction of an image of the sound source through mirroring, by a plane normal to the ray positioned at the point of incidence of this ray on a surface of the room. For Allen and Berkeley (1978), the mirror method is especially efficient for small and simple rooms. They add that the best results are achieved when the focus of the evaluation falls on specific positions, i.e., on a defined pair of points (source and receiver). Obtaining images in a room of this type is quite simple and the calculation very fast when compared with the ray tracing method. The parameters are calculated each time a direct or reflected ray intercepts a receiver. According to the volume of a simple room, Rindel (2000) calculates the approximate number of reflections that intercept a receiver and that are statistically applicable to the most complex geometries, using the following mathematical expression:

N refl =

4πc 3 3 t 3V

(7)

where: N refl is the number of reflections; c is the speed of the airborne sound (340m/s); t is time; and V is the volume of the room. If the room has a complex geometry, the possible number of images grows exponentially at each reflection, rendering computational processing unfeasible. The possible number of images as a function of the number of surfaces and the order of reflection is proposed by Rindel (2000) as expressed in the equation below,

N source = 1 + (

[

]

n ) (n − 1)i − 1 ≈ (n − 1)i n−2

(8)

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where: N source is the number of image sources; n is the number of surfaces; and i is the order of reflection. The hybrid methods were developed by combining the potentialities of the two classical geometric methods, i.e., the speed of the image source method and the possibilities of sound diffusion treatment of the ray tracing method. The image source geometric method has the disadvantage of producing a huge number of possible images of which only a small part will be effectively used. Vorländer (1989) presents a hybrid method for applications restricted to purely specular reflection. The central idea behind this method is to test the visibility of the source by inverse ray-tracing – from a receiver – to determine which images, among the possible ones, are usable. This testing reduces the calculation time when various receivers are processed simultaneously. Naylor (1992, apud Rindel 2000) developed a fairly efficient method called secondary source, which has been used satisfactorily in the ODEON computer program. In this method, a secondary source is generated at the point of collision each time a ray is reflected by a surface. This new source irradiates energy, equivalent to the reflected energy, into a hemisphere in front of it with intensity proportional to the cosine of the angle obtained between the normal surface and the vector traveling from the secondary source toward the

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receiver. The first reflections are ensured by a visibility test, which allows for the convenient treatment of large and complex rooms and a small number of rays. The acoustic properties of construction materials are characterized based only on the sound absorption coefficient, α, measured in a reverberating chamber (ASTM C423-07, 2007). To quote Mommertz (2000): “For room-acoustic calculations according to Sabine’s reverberation theory, this frequency-dependent quantity is often sufficient. However, in using more sophisticated prediction methods (e.g., ray-tracing), an appropriate description of the scattering properties is important”. The directional distribution properties of materials will hereinafter be referred to as sound diffusion properties. Sound diffusion varies according to the angle of incidence of the sound upon the surface. Dealing with a large set of data can be little productive, so reducing this set of values to a single coefficient can be very useful for purposes of acoustic prediction. Thus, like the sound absorption coefficient, diffusion was quantified into a single value, called the diffusion coefficient, which can be defined as the ratio between the non-specularly reflected sound energy to the total reflected energy. This coefficient does not include any information about the directionality of the diffused energy. In the methods of acoustic prediction of rooms, the directional distribution of energy, albeit not physically exact, can be expressed by Lambert’s cosine law if the diffusion coefficient is known (Vorländer and Mommertz 2000). The determination of sound diffusion coefficients and their application has been the object of various recent studies (Mommertz 2000; Vorländer and Mommertz 2000; Jeon et al. 2004; Zeng et al. 2006). The prediction of acoustic parameters is a useful tool in the design phase of buildings. The STI parameter, for instance, can be calculated as a function of the acoustic and geometric characteristics of an enclosed space and is therefore a design tool (Houtgast and Steeneken 1985). The STI of a room can be predicted in the design phase by a statistical method and by sound ray-tracing simulation. According to Houtgast and Steeneken (1985), the prediction of the STI by sound ray tracing takes into account factors existing in the room that are not considered when the STI is obtained by a statistical method. These factors are, for example, the proportion between the dimensions of the room (height x length x width), the distribution of absorption, and the specific shape of the room. Ronsse (2006) draws attention to the fact that, in order to reach similar STI values in measured and simulated data, the characteristics of the loudspeaker used in the computer simulations must be the same as those of the loudspeaker used in the measurements. Moreover, the source and receiver must be located at the same points in the measurements and the simulations (Ronsse 2006), because the STI is strongly influenced by the listener’s position in relation to the speaker (Houtgast and Steeneken 1985).

5. TECHNICAL STANDARDS AND VALUES RECOMMENDED FOR ACOUSTIC PARAMETERS The reference values suggested by the ISO/DIS 3382-1:2006 standard are listed in Table 3, below, and are valid for non-occupied concert halls and multi-purpose halls with volumes of up to 25,000 m3. The values in this table reflect measurements taken in a single position.

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Table 3. Proposed values based on the listener’s subjective impression. Adapted from the ISO/DIS 3382-1:2006 standard

Subjective aspect

Acoustic Parameters (Objective Descriptor)

Reverberation

Early Decay Time, EDT, in s Reverberation Time, RT, in s

Clarity

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*

Clarity, C80, in dB Deutlichkeit, D50, in %

Single number frequency averaging Hz

Typical Values

500 to 1000

1.0 to 3.0

500 to 1000

1.0 to 3.0*

500 to 1000

-5 to + 5

500 to 1000

30 to 70

According to Cirillo and Martellotta (2006).

With regard to enclosed spaces, various acoustic standards (national and international) present reference values for the RT that should be observed in the design of a room, with the RT conditioned to the purpose for which a given room is designed. Brazil has a national standard for room acoustics, the NBR 12179 (1992) standard, which establishes criteria for the acoustic treatment of enclosed spaces. The establishment of optimal RT values is determined according to the type of use and the volume of the room for a frequency of 500 Hz. The standard that specifies RTs for enclosed spaces (furnished and unoccupied) does not specifically mention classrooms, but presents the curve for the optimal reverberation time at a frequency of 500 Hz for conference rooms, which can be used to evaluate classrooms because of the similar use of the latter for speech transmission. In the case of Catholic churches, the RT values vary from ~0.8 s to ~2.4 s for halls with volumes varying from 30 m3 to 30,000 m3. Germany, Japan, the UK and the US have specific technical standards for evaluating the RT of classrooms. In Japan (Fukuchi and Ueno 2004), RT values represent the average in 2octave bands including 500 Hz and 1000 Hz, and RT is measured in the furnished and unfurnished classroom. In the United Kingdom, the Building Bulletin BB-93 (2003) indicates that RT is given in terms of the maximum mid-frequency reverberation time, Tmf, the average RT in the 500 Hz, 1000 Hz and 2000 Hz octave bands, and RT should be measured in the unfurnished classroom, and not in the furnished one. In the USA (ANSI S12.60, 2002), RT is given as the maximum RT for midband frequencies of 500 Hz, 1000 Hz and 2000 Hz, and RT is measured in the furnished and unfurnished classroom. In Germany, the DIN E 18041 (Hohmann et al. 2004) standard establishes that RT values represent the average in 2-octave bands including 500 Hz and 1000 Hz, and RT is measured in the furnished and unfurnished classroom. The DIN E 18041 also specifies that, for occupied rooms, 0.2 s should be subtracted from the RT values listed in Table 4. With regard to the ideal reverberation time in open plan offices, Chigot (2007) presents reference values for the RT contained in the national standards of Norway, Finland, Sweden and Australia/New Zealand. The ideal reverberation times established by those standards are valid for open plan offices with volumes above 300 m³. According to Chigot, the Norwegian

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standard NS 8175 of 2005 establishes optimal RT values of 0.6 to 0.8 seconds for the frequencies of 125 to 2000 Hz. Table 4. Recommended Reverberation Time, RT, for Classrooms Country

Brazil

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Germany

Reverberation Time, RT, of Classrooms (s) V = Volume in m3 RT of 0.5 to 0.6; 120

≤ V ≤ 300 m3

RT of 0.8 to 1.0; V up to 250 m3 RT of 0.9 to 1.1; V up to 500 m3 RT of 1.1 to 1.2; V up to 750 m3

Japan

RT = 0.6; V ~ 200 m3 RT = 0.7; V ~ 300 m3

United Kingdom (UK)

RT = Tmf+ < 0.6 RT = Tmf++< 0.8 + Primary schools; ++Secondary schools

United Stated of America (USA)

RT = 0.6; V < 283 m3 RT = 0.7; 283 m3 < V ≤ 566 m3

In contrast, the ideal values according to the Finnish standard SFS 5907 of 2004 for furnished rooms are much lower, i.e., 0.25 to 0.65 seconds for frequencies of 250 to 4000 Hz. However, the latter standard allows a greater tolerance for the frequency of 250 Hz, for which it considers RT values of 0.05 to 0.85 seconds as ideal. The Swedish standard SS 025268 of 2001 establishes a single value of 0.4 seconds for the frequencies of 250 to 4000 Hz, with a tolerance of more than 20% only for the RT at a frequency of 125 Hz. For the Australian and New Zealand standard AS/NZS 2107 of 2000, the optimal RT values for open plan offices are 0.4 to 0.6 seconds at the frequencies of 500 and 1000 Hz. The values specified by these standards are for furnished rooms without occupants (Chigot 2007). The German code VDI 2569/1990 – Schallschutz und Akustische Gestaltung im Büro (German Engineering Federation – Noise control and acoustic treatment in offices) recommends an average reverberation time of RT ≤ 0.5 for large offices (Jenisch et al. 2002). The French standard NF S31-080, published in 2006, specified RT values according to the desired performance level (Chigot 2007). For a normal performance, it recommends reverberation times of up to 1.2 s (RT ≤ 1.2s), and for efficient performance, RT ≤ 1.0 s. If high performance is required, the RT should not exceed 0.8 s. The values recommended by the French standard are for rooms with volumes exceeding 250 m³ (Chigot 2007). To each subjective impression of speech intelligibility, the IEC60268-16 (IEC, 2003) standard associates an objective value measured for the STI. Thus: 1) STI values of 0.00 to 0.30 correspond to bad subjective impressions; 2) 0.30 to 0.45 represent poor subjective impressions; 3) values of 0.45 to 0.60 are equated with fair subjective impressions; 4) 0.60 to 0.75 represent good subjective impressions; and 5) 0.75 to 1.00 correspond to excellent subjective impressions. For the specific case of offices, considering adjacent work stations,

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reference values are given by Hongisto et al. (2004), who correlates the STI values with speech intelligibility and privacy. Table 5. Recommendations for STI between adjacent work stations in open plan offices. Adapted from Hongisto et al. (2004) Objective Evaluation (STI) 0.00-0.05

Subjective Impression (Speech Intelligibility /Privacy) Very bad/Confidential

0.05-0.20

Bad/Good

0.20-0.40 0.40-0.60 0.60-0.75

Poor/Resonable Fair/ Poor Good/Very poor

0.75-1.00

Excellent/None

Architectural arrangements found in offices for speech intelligibility and privacy Two closed offices with excellent insulation between them Two closed offices with normal insulation between them Work stations in a very noisy open plan office Desks in a well designed open plan office Desks in a reasonably well designed open plan office Desks in an open plan office with no acoustic design

6. ACOUSTIC EVALUATION OF ROOMS Acoustic evaluations were done in buildings of different shapes and functions. These buildings functioned as schools, offices and a church. In terms of shape, school buildings have similar measures of height, length and width. Office buildings, on the other hand, have much lower height measurements in proportion to width and length. Churches have similar length and height measures, but much smaller widths. Four classrooms were evaluated, each with a volume of up to 300 m³, the volume of the church was about 1500 m³, and the open plan office of this study had a volume of approximately 2500 m³.

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6.1. Assessment of Acoustic Parameters in Classrooms The classrooms assessed in this study are typical in Brazil, designed to meet the needs of the public school system. The classrooms evaluated were elementary school and university classrooms. Measurements were taken of the reverberation time in these rooms. Computational simulations were also conducted in the university classrooms to obtain the acoustic parameter of Speech Transmission Index. The classrooms depicted in Figure 8, model 1, were built in the 1970 and have a volume of about 139 m3 and can accommodate up to forty students. These rooms have wooden ceilings, flooring of parquet tiles without sealing glued onto a concrete underlayment, and the walls are finished with mortar and paint. The chairs and desks have metal frames with chair seats and backs and desk tops of Formica-covered plywood.

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The model 2 classroom shown in Figure 9 is another typical example of school classrooms in Brazil’s public school system. This model has a volume of 156 m3 and a capacity for up to forty students. In this model of classroom, of more recent design and construction after 2000, the floor is made of ceramic tiles and the walls are mortared and painted. The desks and chairs are of the same type as the ones in model 1.

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Figure 8. Floor plan of the model 1 classroom.

Figure 9. Floor plan of the model 2 classroom.

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Table 6. Reverberation times measured in Model 1 and 2 classrooms

Frequency (Hz)

Reverberation Times (s) Model 1 classroom (V = 139 m3)

Model 2 classroom (V = 156 m3)

125

1.3

3.3

250

1.1

2.7

500

1.1

2.1

1000

1.1

2.0

2000

1.0

1.9

4000

0.8

1.6

The reverberation times measured in these two types of classrooms with similar volumes, 139 and 156 m3, are listed in Table 6. An observation of this table indicated that the Model 2 classroom has very high reverberations times, thus failing to meet any of the technical standards listed in Table 4, which gives the recommended RT in various countries. Table 7 presents the values of the sound absorption coefficient for the ceiling and the floor of classroom models 1 and 2. As can be seen clearly, model 1 – with its wooden ceiling and parquet flooring – presents RT values more in line with the technical standards presented in this chapter. The acoustic treatment of ceiling and floor is extremely important in the acoustic conditioning of a classroom. These surfaces are usually the largest areas available for receiving the necessary acoustic materials for an RT suitable for the function of the space. The available area of the side walls for receiving acoustic absorbent materials is compromised because inevitably they have some kind of opening, windows and/or doors. Table 7. Sound absorption coefficients for floors and ceilings of model 1 and 2 classrooms

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Materials

Sound Absorption Coefficient ( α ) Frequency (Hz) 125

250

500

1000

2000

4000

Glued Parquet*

0.04

0.04

0.06

0.12

0.10

0.17

Ceramic tiles**

0.01

0.01

0.02

0.02

0.03

0.03

Mortar plastered and painted ceiling ***

0.02

0.02

0.02

0.02

0.03

0.03

Painted wooden ceiling***

0.04

0.04

0.03

0.03

0.03

0.03

*

Taken from Bobran 1995; ** Taken from Hohmann et al. 2004; *** Taken from Costa 2003.

The measured RT values indicate that the teaching and learning activities in the model 2 classrooms may be strongly compromised. Spaces with high reverberation times make

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concentration difficult and tend to induce tiredness more rapidly in both students and teachers. Reverberating environments force teachers to increase their vocal effort. A subjective evaluation of teachers working in model 1 and 2 classrooms revealed that 21% of the interviewed teachers (out of a total of 71) have had to take a leave of absence from teaching due to noise-related problems, the main reason being vocal fatigue (Zwirtes and Zannin, unpublished data). Zannin and Marcon (2007) evaluated teachers working in model 2 classrooms and, in response to the question: “How does noise affect you?” were told that the teachers’ routine professional activities are strongly affected by noise, which reduces their ability to concentrate and forces them to speak more and more loudly. One must also consider the presence of students with hearing impairment and/or concentration difficulties. For such students, classrooms with inadequate RT will give rise to even greater learning problems. Table 7 presents the absorption coefficients of floor and ceiling materials that are used in model 1 and 2 classrooms. The RT in a classroom is influenced by the state of occupation. Figure 10, adapted from Loro (2003), shows the three situations evaluated in the model 2 classrooms: 1) classroom without occupants; 2) classroom with 50% of occupants, i.e., 20 students; and 3) classroom with 100% of occupants, i.e., 40 students.

Figure 10. Influence of the rate of occupation of the classroom on the reverberation time. Adapted from Loro (2003).

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The influence of the state of occupation of the room on the RT is evident. However, even with total occupation, the classroom presents a reasonable acoustic quality when one compares the measured values to those of the technical standards listed here (Table 4). It should be kept in mind that the RT values listed in Table 4 are considered for furnished and unoccupied rooms, except for the British standard, BB93, which establishes RT values for unfurnished and unoccupied rooms. Figure 11 (Model 3) and Figure 12 (Model 4) present models of classrooms in the Federal University of Paraná. The classroom in Figure 11 dates back to the 1970s, while the one in Figure 12 was built after 2000.

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Figure 11. Model 3 classroom.

Figure 12. Model 4 classroom.

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Paulo Henrique Trombetta Zannin, Carolina Reich Marcon Passero et al. Table 8. Reverberation times measured in the Model 3 and 4 classrooms Reverberation Times (s) Frequency (Hz)

Model 3 classroom (V= 294.7 m3)

Model 4 classroom (V= 277.5 m3)

125

1.0

3.6

250

0.7

3.7

500

0.7

2.7

1000

0.6

2.6

2000

0.6

2.2

4000

0.5

1.7

The acoustic quality of these classrooms was assessed by measuring the reverberation time and predicting the Speech Transmission Index (STI) by computational simulation (ODEON 7.01, ODEON A/S.). The Model 3 classroom built in the 70`s (Figure 11) was designed as an auditorium. The floor of this room is wooden, as are the desks and chairs. The ceiling is lined with an acoustic material of wood fiber and the walls are mortared and painted. The room has a volume of 294.7 m³. Model 4, built after 2000 (Figure 12) has a volume of 277.5 m³. The desks and chairs have metal frames and tops, seats and backs of Formica-covered plywood. The walls are brick finished in mortar and painted, and the ceiling is an unpainted concrete slab. Table 9 lists the sound absorption coefficients of the floor and ceiling materials of the classroom models 3 and 4. The acoustic quality of the Model 3 classroom can be considered very good, as indicated by the measured reverberation times. The Model 4 classroom, however, presented excessively high reverberation times for a classroom. The better acoustic condition of Model 3 is due to the greater sound absorption promoted by the finishing materials used, especially for the floor and ceiling (see Table 9). Table 9. Absorption coefficients for the ceiling and floor of Model 3 and 4 classrooms

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Materials

*

Sound Absorption Coefficient ( α ) Frequency (Hz) 125 250 500 1000 2000 4000

Glued parquet floor*

0.04

0.04

0.06

0.12

0.10

0.17

PVC floor**

0.01

0.02

0.01

0.03

0.05

0.05

Wood fiber ceiling***

0.25

0.49

0.69

0.78

0.61

0.48

Mortar plastered and painted ceiling****

0.02

0.02

0.02

0.02

0.03

0.03

Taken from Bobran 1995; ** Taken from Hohmann et al. 2004; 1988; **** Taken from Costa 2003.

***

Taken from Knudsen and Harris

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In addition to the reverberation time measurements, computational predictions of the speech transmission index (STI) were made for Models 3 and 4. This prediction was made using a sound source and a network of receivers. The background noise was disregarded, and only the rooms’ architectural characteristics were considered. The results of these simulations are depicted in the figures below.

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Figure 13. Prediction of the speech transmission index (STI) in the Model 3 classroom.

Figure 14. Prediction of the speech transmission index (STI) in the Model 4 classroom.

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Paulo Henrique Trombetta Zannin, Carolina Reich Marcon Passero et al.

In Figures 13 and 14, the teardrop-shaped point (S) represents the sound source, and the tip of this teardrop indicates the direction of the source. In the two figures, the red area represents the area where the teacher spends most of the time: near the blackboard. A comparison of the figures clearly shows the difference in speech intelligibility of the two classrooms. In the Model 3 classroom, at most of the desks, the intelligibility lies within the range of 0.65 to 0.75, which the IEC 60268-16 (IEC, 2003) standard considers good intelligibility. However, at most of the desks in the Model 4 classroom, the intelligibility varied from 0.50 to 0.60, which the IEC 60268-16 (IEC, 2003) considers only regular. A comparison of the STI and RT values measured in the two classrooms showed a strong correlation between these parameters. Comparing the results obtained for Model 3 and 4 classrooms indicated that, from the standpoint of reverberation, the acoustics of the Model 3 classroom led to better conditions of intelligibility. It should be noted that the STI values presented here did not consider ambient noise, since the room was considered unoccupied. If this noise were introduced into the predictions, there would be a significant reduction in the STI values. Therefore, although occupation favors the acoustic condition, reducing the reverberation time (Figure 10), it reduces speech intelligibility by increasing the room’s sound levels.

6.2. Assessment of Acoustic Parameters in Open Plan Offices

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Open plan offices have become widely popular in several countries since the 1960s. This form of organizing the work place emerged from the need for communication, the intensive quest for productivity and for a space-saving arrangement, which ended up becoming universal. An acoustic assessment was made of an open plan office with about 150 workers. In terms of size, the office has an area of 1015 m2 and a volume of 2690m3.

Figure 15. General view of the open plan office of this study.

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The office was assessed in two situations: 1) the previous situation: brick walls, ceramic tile floor, desks and dividers of plywood finished with laminate surfacing, upholstered chairs and ceiling of gypsum board; and 2) after implementation of the acoustic conditioning project, in which the original gypsum ceiling was replaced with glass wool. The absorption coefficient of the two materials, gypsum board and glass wool, are shown in the table below. The work stations are separated by small dividers of variable heights, the highest of which is one meter above floor level. Table 10. Sound absorption coefficient of the ceiling in the open plan office in situation 1 – gypsum board, and 2 – glass wool Materials Gypsum board* Glass wool (25mm) covered in micro-perforated PVC**

Sound Absorption Coefficient ( α ) Frequency (Hz) 125 250 500 1000 2000 4000 0.29 0.10 0.05 0.04 0.07 0.09 0.08

0.43

0.79

1.02

0.82

0.58

Taken from Long 2006; ** Taken from Isover 2008.

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*

This office was acoustically evaluated based on measurements and computer simulations. The sound pressure level and reverberation time in the office were measured in situation 1, with gypsum ceiling, and situation 2, with glass wool ceiling. The speech transmission index (STI) was measured and simulated only in situation 2. In situation 2, the sound pressure level was computationally simulated. The simulated parameters of sound pressure level and STI considered a point source and receivers distributed in a grid. The sound pressure level measurements were taken during normal working hours. The parameter measured was the A-weighted equivalent continuous sound level (LAeq). For the office in situation 1, the LAeq resulting from a spatial average of points distributed around the room, was 66 dB. In contrast, the office in situation 2 showed an average LAeq of 61 dB, which is substantially lower than the level found in situation 1. In addition to the physical measurements, computer simulations were made of the sound pressure level in situation 2 in order to observe the behavior of the sound emitted by a source simulating a speaker. In Figure 16, the teardrop-shaped point (S) represents a sound source (mouth simulator), and the tip of the teardrop indicates the direction of the source. This source is similar to a speaker, with a sound pressure level of 67 dB, calibrated at a distance of one meter. In this figure, note that the adjacent work stations receive the direct sound emitted by the speaker. This level is between 60 and 70 dB(A). At non-adjacent work stations, however, the sound pressure level drops to values of 50 to 60 dB(A), reaching approximately 45 dB(A) in the acoustic shadow produced by the columns. Only at work stations fairly distant from the source or behind the wall, the area at the right-hand side of the figure, do the levels decline to values below 40 dB(A). It should be noted that these levels are produced by only one source. However, in this open plan space, there may be up to 150 speakers, assuming all the workers are speaking at the same time. As for the reverberation time, acoustic measurements were taken in situations 1 and 2 (Table 11). Table 11 clearly shows a reduction in the reverberation time of the office after the gypsum ceiling (situation 1) was replaced with fiberglass (situation 2). Fiberglass has a much higher absorption coefficient than gypsum board, especially at frequencies of 500 and 1000

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Paulo Henrique Trombetta Zannin, Carolina Reich Marcon Passero et al.

Hz. This increase in absorption was clearly characterized by the reverberation times attained in the two situations in this open plan office.

Figure 16. Simulation of the sound pressure level emitted by a speaker (mouth simulator) in the open plan office.

Table 11. Reverberation time measured in the open plan office

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Frequency (Hz)

Reverberation Time (s) Situation 1

Situation 2

125

1.16

0.68

250

1.20

0.60

500

1.25

0.49

1000

1.31

0.58

2000

1.29

0.65

4000

1.24

0.75

Figure 17 depicts the sound absorption of each material in the office in situation 2. Note the higher absorption at medium and high frequencies in this figure, which is due to the fiberglass. At low frequencies, on the other hand, the larger absorption area is a result of the material of the desks: plywood. The measured RTs were compared with the standards presented by Chigot (2007) and Jenisch et al. (2002). The office in situation 1 is considered adequate only by the French standard (NF S31-080) and at the frequency of 250 Hz, provided a normal performance is expected of its occupants. In this case, according to the standard, the limit value is 1.20s.

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Figure 17. Area of sound absorption of the various materials in the office.

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In situation 2, on the other hand, the office showed the following values. 1) The measured RTs fell within the standards of Australia and New Zealand (AS/NZS 2107) and of France (NF S31-080), considering a high performance in the location. 2) The measured RTs failed to meet the standards of Norway (NS 8175) only at the frequency of 500 Hz and of Finland (SFS 5907) only at 4000 Hz. 3) Even after acoustic treatment, the RT still remained above the values recommended by the Swedish (SS 025268) and German (VDI 2569) standards. Figure 18 illustrates the position of the source and the receivers to measure the STI in situation 2. The tip of the teardrop, which represents the source in this figure, indicates its direction.

Figure 18. Position of the source and the receivers to measure the STI.

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In STI measurements, the distance and orientation of the source in relation to the receiver strongly affect the result. Therefore, the value found should always be related to its location. The STI values measured with and without ambient noise are listed in Table 12. An analysis of the STI values in Table 12 reveals a considerable difference between the values measured with and without ambient noise. The sound pressure level of the human voice at a distance of one meter is 67 dB(A) and the average ambient noise in this office is 61 dB(A). Therefore, the speech transmission index is strongly reduced when the measurement includes the ambient noise. Table 12. Measured speech transmission index, 1) not considering, and 2) considering ambient noise. Values with correspondence to the subjective scale described in the IEC 60268-16 (IEC, 2003) standard

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Point

Speech Transmission Index (STI) Without ambient noise

With ambient noise

1

0.90 – excellent

0.48 – regular

2

0.76 – excellent

0.28 – bad

3

0.81 – excellent

0.32 – poor

4

0.85 – excellent

0.37 – poor

5

0.81 – excellent

0.37 – poor

6

0.69 – good

0.22 – bad

7

0.74 – good

0.28 – bad

8

0.74 – good

0.28 – bad

9

0.48 – regular

0.08 – bad

10

0.55 – regular

0.08 – bad

Figure 19. Points of STI measurements and their respective values (considering ambient noise).

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The STI values varied significantly according to the position of the receiver (Figure 19). The highest STI value in the real situation, i.e., considering the ambient noise, was 0.48 (point 1, Figure 19). This value is compatible with intelligibility rated as regular by the IEC 6026816 (IEC, 2003) standard. Therefore, in this office, a speaker communicates relatively well with a listener at the workstation immediately in front of him. Observing Figure 20, one can see that points 3 and 5, which show STI values of 0.32 and 0.37, respectively, also represent listeners located at work stations adjacent to the source.

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Figure 20. Signal to noise ratio in the measurement of STI at point 1.

Figure 21. Signal to noise ratio in the measurement of STI at point 9.

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However, they are not in front of the source, so they present a poor intelligibility index according to the IEC 60268-16 (IEC, 2003) standard. Points 2 and 4 are practically equidistant from the source, but point 2 presented a much lower STI (0.28) than point 4 (0.37). This may be explained by the presence of barriers between point 2 and the source, which do not exist between point 4 and the source. The two points farthest from the source presented the same STI values, i.e., 0.08, although one of them was in front of the source and the other behind it. This case illustrates the lesser influence of the direction of the source at points farther away from it. The STI value is related to the signal to noise ratio at the measured point. Figure 20 depicts the signal to noise ratio at point 1, where the STI was 0.48 (Figure 19), the highest measured STI. Figure 21 shows the signal to noise ratio at point 9, where the STI was 0.08, the lowest STI measured in the room.At point 1, the signal to noise ratio varied from approximately -15 to 5 dB according to the frequency, while at point 9 this ratio varied from 5 to -25 dB. In other words, the ambient noise at point 9 was higher than the sound of the sound source at all the frequencies. The STI was computer simulated by means of a source and receivers arranged in a 0.50 x 0.50 meter grid to cover the entire area of the office. Figure 22 gives a magnified view of the area around the sound source (S). The simulated STI indicates excellent intelligibility only very close to the source, at the speaker’s own work station (Figure 23). At the adjacent work station in front of the speaker, the intelligibility is fairly reduced, i.e., approximately 0.5 (Figure 23, green area). The pale blue area, with an intelligibility of approximately 0.35, reaches the other works stations adjacent to the speaker. The remaining work stations, however, fall within the dark blue area which represents intelligibility below 0.2 According to Hongisto et al. (2004), an STI of less than 0.2 represents a bad intelligibility and, in offices, indicates good speech privacy. A careful look at the simulated STI of the entire office area in Figure 23 indicates the reduction in speech intelligibility caused by obstacles between the source and the receiver. In this particular case, the work stations situated along the line of acoustic influence of the structural columns present very reduced speech intelligibility.

Figure 22. Simulation of the STI with receivers arranged in a grid, area around the source.

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Figure 23. Simulation of the STI with receivers arranged in a grid, total area of the office.

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6.3. Assessment of Acoustic Parameters in Churches The objective assessment of the acoustic quality of a room consists of measuring objective parameters correlated with the listener’s subjective perceptions. Due to the characteristics inherent to church activities, the analysis concentrated on evaluating the parameters: 1) Reverberation Time (RT), 2) Clarity (C80), and 3) Deutlichkeit (D50) (Meyer, 2003; ISO/DIS 3382-1:2006). These parameters were evaluated by means of in situ measurements taken in an empty church and by computer simulations. In the simulations, an evaluation was made of the influence of the full occupation of the church on the descriptor parameters of the room’s acoustic conditioning. The difficulty of making acoustic evaluations of churches lies in the burdensome work of surveying their architectural characteristics, which is fundamental for instrumenting computer simulations, and in the large number of measurements required to characterize the acoustics of these geometrically very complex spaces as correctly as possible. Another difficulty is the fact that, in general, the values of reference for acoustic parameters, such as RT, C80 and D50, reported in the international literature are specific for concert halls or multiuse halls. The international ISO 3382-1:2006 standard presents a range of values typical for the C80 and D50 of concert and multiuse halls with volumes of up to 25,000 m3. In a recent publication about church acoustics, Cirillo and Martellota (2006) added the typical range of RT values for the same types of enclosed spaces described in the ISO 3382-1:2006 standard (see Table 3). The building studied, the Igreja da Ordem Terceira de São Francisco das Chagas (Church of the Third Order of Saint Francis of the Wounds), is an example of Brazilian colonial architecture. This church was built in 1737 and is the oldest one in the city of Curitiba. Its original name was Igreja de Nossa Senhora do Terço (Church of Our Lady of the Rosary).

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Figure 24. Igreja da Ordem III de São Francisco das Chagas – exterior frontal view.

The church housed a Franciscan convent and was the parish church of the Polish immigrants. On the occasion of the visit of Dom Pedro II to Curitiba, the church underwent a process of restoration. In 1951 it became a Votive Temple of Perpetual Worship of the Sainted Sacrament. The edifice was declared a Historical Heritage of Paraná in 1966, and today houses the Archdiocesan Museum of Sacred Art (Figure 24). The interior of the church is characterized by a single nave, with small apertures providing little natural lighting. The stone walls are very thick and are finished in mortar and painted. The walls are undecorated, for the church’s art work is concentrated on the altar and in the paintings of the nave’s ceiling (Figure 25). The main nave is separated from the presbytery by a passage 3.6 m wide and 5.7 m high. This passage divides the church into two parts, approximately in the middle of its longitudinal axis. The presbytery is narrower, measuring 6 m in width, and has an area of 84 m2. The nave is 8.3 m wide by 17.6 m long, making a total of 146.3 m2. The furniture in the nave is limited to plain wooden pews, while the presbytery contains individual wooden chairs finished in velvet upholstery. The wooden ceiling of the presbytery is arched and suspended by a truss structure while the ceiling of the nave is of concrete finished with stucco. The floor of the entire church is parquet on a concrete underlayment. The church has a choir with a finely carved wooden balustrade. The technical details of the architectural design and the dimensions of the church are given in Table 13. The measurements were taken with the sound source positions in the presbytery, on the axis of symmetry of the nave. In order to ensure that the spatial distribution of the measurements was as uniform as possible (ISO 3382-1:2006), the measuring microphone (receiver) was positioned at different points inside the church.

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Figure 25. Igreja da Ordem III de São Francisco das Chagas – interior view of the nave.

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Table 13. Dimensions of the Ordem III de São Francisco das Chagas Church Architectural characteristics

Dimensions (SI units)

Maximum width – including side chapels

8.3

Maximum length – from the main entrance to the altar

32.6

Maximum height – from the floor to the highest point of the arched ceiling

8.0

Height at the altar – from the floor of the altar to the highest point of the arched ceiling

7.6

Total volume

1658.20

Total floor area

232.2

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Figure 26. Measured points – Ordem III de São Francisco das Chagas Church.

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These points were arranged on a rectangular grid and the distance of the microphone from the sound source is expressed as a function of its longitudinal coordinate, making a total of ten receiving points distributed through the church. Two points were measured in the presbytery and eight in the nave. The measurements were repeated twice at each point, making a total of 20 measurements (Figure 26). The reverberation time (RT) was measured for the six octave bands, from 125 Hz to 4000 Hz, and the spatial average was calculated for each octave band. The average values of the measurements are listed in Table 14. The church has an almost uniform reverberation response at all the frequency bands. This minor variation in RT facilitates the implementation of electric-electronic reinforcement systems – sound amplification systems (Shankland and Shankland 1971). The measured data were compared against the values recommended for Catholic churches by the Brazilian NBR 12179:1992 standard, which lists reference RT values only for the frequency of 500 Hz as a function of volume. For churches with a volume of 1500 m3, this standard recommends an RT of 1.6 s. As can be seen, therefore, the measured RTs far exceed the recommended values. Table 14. Spatial average of the measured reverberation times Reverberation Times in octave bands Frequency (Hz)

125

250

500

1000

2000

4000

Reverberation Times (s)

2.2

2.3

2.4

2.4

2.2

1.9

Hohmann et al. (2004) propose RT values of 2 – 3 s for churches, at the frequency of 500 Hz. It should be noted that these values are presented independently of the volumes of the churches. Cirillo and Martellota (2006) present average RT values of 1 to 3 s at frequencies of

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500 and 1000 Hz. However, they point out that the enclosed spaces considered are not actually churches but concert halls and multiuse rooms of up to 25000 m3. Considering these approaches, the church evaluated here can be considered to present an adequate RT. To characterize the room in terms of its quality for musical reproduction, the Clarity (C80) was measured. The mean value at the frequencies of 500 and 1000 Hz, obtained for the C80, was four negative decibels, -4 dB (Table 15). When compared against the typical range of values presented by the ISO 3382-1:2006 standard, the average can be seen to fall within the range of values of the normalized interval, i.e., -5 dB to + 5 dB. Again, it should be noted that the values suggested by the ISO 3382-1:2006 standard are not specific for churches, but for concert halls and multiuse rooms with volumes of up to 25000 m3. Deutlichkeit (D50), the parameter that characterizes speech quality in enclosed spaces, was measured in this church and the results are listed in Table 16. The average value at the frequencies of 500 and 1000 Hz is below the typical range of values presented by the ISO 3382-1:2006 standard, i.e., 30 – 70%. Similarly, as pointed out earlier for the C80 parameter, the ISO 3382-1:2006 standard does not present specific values for churches, but for concert halls and multiuse rooms with volumes of up to 25000 m3. Churches are built to receive large numbers of people, so the influence of the occupation of their enclosed spaces on their acoustic parameters cannot be disregarded. The occupation of areas destined for the audience significantly increases the sound absorption of rooms. However, it is difficult to take acoustic measurements in the presence of audiences. The mathematical correction of acoustic parameters under the influence of occupation has proved effective as an auxiliary tool in the process of evaluating the acoustic quality of concert halls (Hidaka, Nishihara and Beranek 2001). The possibilities of acoustic predictions provided by computer models are a low cost an operationally easy alternative compared with physical scale models. Based on statistically tested digital models, the influence of occupation on the acoustic characteristics of a room can be predicted with satisfactory precision. Current software programs are also powerful design support tools. The ODEON 7.01 application package (ODEON A/S, 2005) was used for the acoustic predictions of the room with total occupation of the seating area. Table 15. Measured Clarity values

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Frequency (Hz) Clarity C80 (dB)

C80 values averaged over frequencies 125 250 500 1000 -3.45

2000

-4.00

4000 -1.93

Table 16. Measured Deutlichkeit values D50 values averaged over frequencies Frequency (Hz) Deutlichkeit D50 (%)

125

250 20

500

1000 21

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4000 29

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Figure 27. Reverberation Time (RT) measured in the unoccupied room and predicted for the condition of complete occupation of the seats.

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The prediction of seat occupation indicated a reduction of the reverberation time in the order of 1 second, at intermediary frequencies of 500 Hz and 1000 Hz, in relation to the simulated values with the unoccupied room (Figure 27). The RT is approximately 1.5 s at most of the points investigated. Only with all the seats occupied would this room meet the values recommended by the Brazilian standard (NBR 12179, 1992). However, this standard specifies ideal values of RT only for unoccupied rooms. Unlike the RT, clarity is an attribute highly sensitive to the relative position between the receiver and the sound source. Clarity tends to diminish as this distance increases. Its variation is very significant around the room. The variation of C80 directly reflects the influence of direct sound in the composition of the energy levels in the first 80 milliseconds of the decay curve.

Figure 28. Clarity (C80) measured in the unoccupied room and predicted for the condition of complete occupation of the seats.

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When occupied, the room showed a gain in the order of 3 dB in the C80 in relation to the values obtained with the unoccupied room. This gain was found to occur at the points located in the nave (Figure 28). The influence of occupation on C80 was found to be greater at the points farthest from the sound source. In those positions, the amount of energy supplied by direct sound and by the early reflections is naturally lower due to the distance from the source. This justifies the abrupt drop in C80 values between points 1, 2 and the other points (see Figure 26). The concentration of energy of the early sound in relation to the reverberating tail is essential to clarity. The increase of absorption as the reverberating tail decreases ensures an energy balance that is proportionally favorable to clarity. The gain in sound absorption provided by seat occupation increased the C80 values, causing them to fall within the typical range of values recommended by the ISO 3382-1:2006 standard (see Table 3). Similarly to the C80, the Deutlichkeit, D50, also benefited from the increased sound absorption provided by occupation (See Figure 29). Nevertheless, even with a 15% increase in relation to the values obtained with the unoccupied room, the values of D50 with occupation remained below 30% at all the receiving points in the nave (See Table 3). The predictions of Deutlichkeit (D50) for the two points in the presbytery closest to the source yielded values of 30% and 45%, which are compatible with the typical interval for the average of the frequencies of 500 Hz and 1000 Hz (ISO 3382-1:2006). It can also be stated that the descriptors of clarity indicate two different acoustic conditions for the room. The presbytery showed good clarity for both speech and music, while the results for the nave suggest that the clarity of the space is poor. The fluctuation of the values of clarity parameters in churches is attributed mainly to the effect of distance between the source and receivers and the complex paths of sound reflection and diffusion, which alter the early reflections typical of the spatial features of this type of edifice (Carvalho 1995).

Figure 29. Deutlichkeit (D50) measured in the unoccupied room and predicted for the condition of complete occupation of the seats.

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CONCLUSION Acoustic comfort is an ever more pressing need due to the increasing levels of noise pollution that prevail especially in medium-sized towns and large cities. The pursuit of acoustic comfort in spaces where humans engage in their activities, be they educational (e.g., in classrooms), work-related (in functional offices) or cultural (in churches), has been studied exhaustively in recent decades, as attested by the large body of research listed in the references. The sheer number of these studies derives from the ever growing need for improved communication between people. The numerous researches in this field are also a consequence of the technological evolution of measuring devices and simulation software tools, which allow for the study of a wide range of parameters that describe the acoustic quality of enclosed spaces. The acoustics of enclosed spaces should be seen especially as a function of the activities conducted inside them and the pursuit of their acoustic comfort should take into account their particularities. The concept of acoustic conditioning of an enclosed space cannot be treated in an absolute way as good or bad, but always correlated to its use or function. The findings presented here indicate that the parameters of reverberation time, RT, and speech transmission index, STI, are excellent acoustic descriptors to characterize a classroom acoustically. The technical standards of different countries specify ideal RT values as a function of the volume of classrooms. In the specific case of STI, this is an excellent parameter to describe the intelligibility of speech in an enclosed space, providing a better characterization than that of the Speech Intelligibility Index, SII, the Articulation Index, AI, and the Speech Intelligibility Level, SIL (Lazarus et al. 2007). For classrooms, it is recommended that the STI be as high as possible throughout their entire area, thus ensuring the listeners’ good perception of speech. In the case of open plan offices, the results indicate that RT and the STI are good descriptors of the acoustic quality of these spaces. In terms of RT, several countries have optimum standards for the acoustic conditioning of open offices. Unlike classrooms, where the STI should be as high as possible, the STI in open offices should be precisely the opposite. Low STI values ensure greater speech privacy and a lower source of distractions in the work environment. Churches differ acoustically from classrooms and open plan offices, for they should offer a compromise between the quality of speech and of musical reproduction, which are acoustically opposite requirements. The difficulty of making acoustic evaluations of churches is the fact that, in general, the values of reference for acoustic parameters reported in the international literature are specific for concert halls or multiuse halls. Among the various acoustic descriptors, evaluations were made of the reverberation time, RT, the C80 for musical quality, and the D50 for speech quality. These parameters should be as uniform as possible throughout the room and should not be lower than 30% for D50, and fall within the interval of -5 to +5 dB for C80. With regard to the acoustic assessment approaches described in this chapter, computational simulations have proved to be a good tool to aid the processes of evaluation and design of improvements aimed at acoustic comfort in enclosed spaces. Simulations are an alternative to measurements, since the latter require great operational effort. However, measurements are indispensable to calibrate the computational model.

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Chapter 2

RELIABILITY OF SHOULDER FUNCTIONAL MEASURES IN ASSESSING PHYSICAL CAPACITY OF INDIVIDUALS WITH CHRONIC NECK/SHOULDER PAIN Karen Lomond*, Evelyne Boulay†, Charlene Leduc-Poitras‡, and Julie Côté#, CRIR Research Centre, Jewish Rehabilitation Hospital site, McGill University, Montreal, Canada

ABSTRACT

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Timely return to work (RTW) is often identified as one of the priority goals of occupational health professionals. One of the primary determinants of RTW in workers with neck-shoulder pain symptoms is the degree of functional limitation. Thus, the capacity to reliably assess workers’ functional capacity as they prepare to RTW is of paramount importance. The purpose of this study was to assess the reliability of shoulder functional measurements taken from participants with chronic neck/shoulder pain and to correlate pain and disability levels on functional outcome measures.

Methods Sixteen participants with neck/shoulder pain (pain intensity ≥ 3/10 for at least 3 months within the past year) were recruited to perform a functional assessment protocol in two sessions. During each, they completed the Shoulder Pain and Disability Index (SPADI) and the Neck Disability Index (NDI). Shoulder function was assessed using the BTE simulator II *

[email protected] [email protected] ‡ [email protected] # [email protected] †

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system (BTE-Tech, Baltimore, USA). Tasks included flexion and abduction active range of motion (ROM), maximal voluntary pushing effort (MVPE), and cumulative power output (PO) in a dynamic pushing/pulling task. Subjects rated their pain on a 10-point numeric rating scale (NRS) intermittently throughout the protocol. Differences between sessions were assessed via paired t-tests and between-session reliability was assessed by Intra-Class Correlation co-efficient (ICC). Additionally, minimal detectable change (MDC) was calculated. Results: While there were no significant differences in participants’ pain scores between sessions, all functional measures increased from session 1 to session 2. Shoulder flexion and abduction ROM were highly reliable (0.94 and 0.92, respectively), as were MVPE (ICC = 0.86); however, the PO task demonstrated poor reliability (ICC = 0.52). There were no significant correlations between pain and functional scores during session 1; however, there was some significant correlation between abduction ROM and both NDI and NRS after the PO task during session 2.

Conclusions Overall, it appears that the BTE has some promise in reliably assessing shoulder function in individuals with chronic neck/shoulder pain in particular for ROM tasks. While the static protocol (i.e. MVPE) may be useful in distinguishing between individuals with large differences in function, the dynamic protocol (i.e. PO) demonstrated only poor to moderate reliability. With some modifications the BTE may be a useful tool in assessing shoulder function in individuals with chronic neck/shoulder pain.

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INTRODUCTION Work-related musculoskeletal disorders (WMSD) affect a wide variety of individuals in various occupations [1], accounting for a significant portion of workers compensation claims, lost time, and health care costs [2]. WMSD most often affect upper limb structures (e.g. hands, elbows, shoulders and neck), with neck and shoulder disorders accounting for 25 % of WMSD in Canada in 2003 [3]. While most WMSD are rooted in more minor soft tissue aches and pains and can be treated adequately with rest or task reorganization to eliminate offending movements [4], when left untreated or without adequate recovery time they can become chronic conditions. The primary consequences of these conditions are moderate to severe pain and discomfort, combined with substantial declines in physical functioning [4, 5]. In turn, this often leads to interruptions in activities of daily living, lost time from work, and oftentimes costly compensation claims. Although literature has identified some risk factors for neck/shoulder pain related to both neck and shoulder function, most studies that have investigated this condition agree that in clinical practice, pain complaints generally affect both structures; thus, the etiology of neckshoulder pain is thought to revolve around one common mechanism which is not fully understood [6]. Recent reviews have shown evidence of a relationship between neck-shoulder pain and both physical and psychosocial workplace factors [7, 8]. Physical risk factors include: posture, static loading of muscles, vibrations, and the frequency, force and duration

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of repetitive movements; whereas, psychosocial factors include: job control, psychological demand, and stress [9]. In particular, working postures that include overhead work or the use of the arms at or above shoulder height (e.g. carpentry, manufacturing, etc.) are known to induce fatigue and demonstrate a high incidence of neck and/or shoulder pain and injury [1014]. These tasks tend to combine prolonged static contraction of the shoulder and neck muscles (particularly the upper trapezius), repetitive movements, and, in some cases, forceful exertions, all of which have been identified as risk factors for neck-shoulder WMSD[1]. The complex nature, common occurrences, and high costs associated with chronic workrelated musculoskeletal pain has necessitated the assignment of specialists and/or teams to manage cases of WMSD, with the goal of minimizing lost time and ensuring safe and prompt return to work (RTW) [15]. Much work has been dedicated to describing the complexities of RTW, in particular in workers with low back pain [e.g. 16, 17-19]; from this, there is no doubt that the evaluation of an individual’s ability to perform their work tasks is an integral part of this process [2, 17, 18]. To date a variety of assessment tools have been developed to facilitate this process, resulting in the design of functional capacity evaluations (FCE). FCE are groups of standardized clinical tests that are aimed at qualifying a patient’s ability to safely perform work-related activities by relating their evaluated performance with actual job task requirements [17]. When an injured worker’s performance does not meet minimum job requirements or if there is no job to return to, the results of the FCE can also be used to guide vocational rehabilitation and job placement [17]. Beyond these clinical implications, the timeconsuming nature of FCE renders them as expensive as advanced diagnostic procedures and their outcomes are often used to inform decisions regarding employment status (e.g. benefit suspension or claim closure); consequently their outcomes have important financial implications for patients, employers, insurers, and society[17, 20] . As such, the ability of the FCE to accurately and reliably measure the desired performance outcomes and allow direct relation of these outcomes to valid real-world situations is essential [21, 22]. The broad category of FCE includes a variety of assessments that cover many working tasks and situations; overviews of these are presented in two review papers [21, 22]. In short, FCE can: focus on an individual’s self-perception of task performance, rely on observations from skilled clinicians, require special equipment, focus specifically on certain tasks (e.g. lifting) or cover a wide variety of physical demands. However, there is limited evidence of reliability or validity in most of the assessments on the market today [21, 22]. One tool that is available to measure functional capacity and that is relatively well-known by practitioners is the Baltimore Therapeutic Equipment Work Simulator II (BTE) (BTETech©, Baltimore, MD). The BTE has been the focus of numerous papers, including several investigations of its reliability and validity. Generally, this instrument demonstrates good testretest reliability in the static mode; however, only a limited number of the BTE’s 22 attachments have been tested [23-26]. To date, strong evidence of reliability exists only for static grip strength and wrist flexion strength (e.g. r = 0.91 and 0.98 [27]; ICC = 0.98 [26]). Investigations into dynamic protocols have yielded more variable results. For instance, Kennedy & Bhambhani [28] compared oxygen uptake (VO2) and heart rate during simulated and real upper extremity MMH tasks at three work intensities in healthy men and found strong correlations (r = .74-.87 and r = .59-.78, respectively). Both Kennedy [28] and Wilke [29] noted significantly lower metabolic responses during simulated tasks on the BTE, compared to real tasks, in healthy men performing MMH task of varying intensities and

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cardiac patients performing a series of job and home activities (e.g. hammering, vacuuming, etc), respectively. Similarly, more recent work by Ting and colleagues [30] noted a significantly lower VO2 and heart rate values during a simulated lifting task performed by healthy males than in an actual lifting task. The authors suggest that this discrepancy in physiological requirements between real and simulated tasks may contribute to overestimate the endurance measured using the BTE, suggesting that clinicians use caution when making decisions based on patients’ functional capacity measured using such simulated tasks [28, 30]. Additionally, several authors have designed protocols applying constant force to attachments in the dynamic mode and noted large variability in outcomes measures, raising concerns as to BTE’s reliability in the this mode [23-25, 30-32]. While some of the studies described above have contributed to establishing construct validity of BTE protocols, it appears that its face and content validity are more implicitly assumed, as only a brief overview of the physical demands covered by the BTE exist [33]. Concurrent validity has been assessed by several authors comparing the BTE #162 (grip strength) tool to the Jamar © dynamometer with positive results [e.g. 34]. While grip strength is a frequently accepted measure of gross muscle strength and upper extremity function in the rehabilitation measure setting [34], it does not necessarily represent an individual’s ability to perform work tasks safely with the entire upper limb. Despite the lack of evidence-based data to support the use of the BTE, one of its main advantages is that it affords practitioners the opportunity to simulate actual job tasks in a more controlled environment so as to obtain objective outcome measures. In turn, outcome measures can be related to some job performance requirements. This possibility to objectively assess specific characteristics of work task performance may be essential as it allows practitioners to target the high-risk and/or most demanding aspects of a particular job or task (e.g. in the case of neck/shoulder pain tasks at or above shoulder height). As such, the BTE has become quite popular as a means of assessing patient functional abilities in performing manual materials handling (MMH) tasks (e.g. lifting/lowering, pushing/pulling) [28, 30, 3538]. Currently, there exist substantial data on “normal” or “safe” values for many common MMH tasks in the literature [e.g. 39, 40-42]; these data are imperative to guide the design of safe work environments and can assist practitioners in accurately identifying task requirements. However, the influence of pain and injury on both the ability to perform the movement task and how these tasks are coordinated is beyond this scope. For instance, pain’s influence on movement has long been recognized as adverse; however, recently the concept of pain has been expanded to include pain as a dimension of the disorder or injury, rather than simply a consequence of the disorder. In particular, much work has been devoted to quantifying and describing movement strategies in both healthy and injured workers, in order to understand injury mechanisms and inform decisions in rehabilitation and RTW [e.g. 43]. From this work evidence of fundamental differences in movement strategies between symptomatic and asymptomatic individuals has begun to emerge [e.g. 44]. For instance, studies have shown that the presence of pain in a variety of forms, whether experimentally induced [e.g. 45], musculoskeletal [e.g. 19] or stemming from systemic disease [e.g. cancer 46, or HIV 47] , can dramatically alter some aspects of movement outcomes such as overall movement speed. Moreover, closer examination of muscle activity in the presence of pain has revealed higher signal amplitude and duration in affected muscles [48] and delayed onset or complete inhibition in deep synergistic muscles [49]. In addition, it appears that the presence

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of localized pain also plays a role in altering whole body movement strategies in multi-joints tasks [45, 50]. Taken together, these studies clearly point to the importance of developing tools to assess work tasks in individuals with pain not only in terms of traditional outcome measures (e.g. isometric force production) but that will also allow the measurement of other, more complex indicators of performance (e.g. movement speed, power output, muscle recruitment, movement reorganization, etc). As a whole, the reviewed literature leads us to the conclusion that it is imperative that practitioners involved in a RTW context are able to understand and evaluate the potential effects of pain on functional outcome measures. To date, the BTE has demonstrated some success in differentiating between patient groups (i.e. clinical and healthy populations) [51]; however, it appears unable to distinguish between groups with similar pathologies (e.g. fibromyalgia and rheumatoid arthritis [52]). While this lends some support to the use of BTE in functional capacity evaluations, the reliability of BTE measures in individuals with chronic musculoskeletal pain patients remains unknown. This may constitute a part of the key to allowing a more precise and accurate interpretation of functional outcome measures in workers with pain, As such, this chapter describes a study that was undertaken with the goal of developing an assessment protocol to quantify key functional outcomes relevant to common workplace movements and likely affected in individuals with chronic neck/shoulder pain. We also sought to study the association between these outcome measures and pain and disability measures. Finally, the test- re-test reliability of functional outcome measures has been assessed between testing sessions. Where possible, results have also been compared to similar measures in the literature.

METHODS

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Participants Sixteen individuals (mean age ± SD = 40.1 ± 12.1 years; 7 males, 9 females) reporting chronic neck/shoulder pain signed informed consent forms approved by the Research Ethics Board of the Centre for Interdisciplinary Research in Rehabilitation (CRIR) of Greater Montreal. Inclusion in the study required that participants be diagnosed with chronic neck and/or shoulder pain that interfered with their work and/ or activities of daily living. Pain level inclusion criteria were both expressed in intensity (i.e. greater than 3 on an 11-point numeric rating scale (NRS), where 0 = no pain and 10 = worst imaginable pain) and duration (i.e. longer than 3 months) and were verified in a telephone interview. Additionally, all participants had to have sought medical attention (e.g. family physician, physiatrist, physical therapist, etc.) for their pain during the last twelve months. Participants were excluded if they had a concomitant medical condition, other than that of the neck-shoulder, which could have interfered with the performance of the experimental tasks or render them contraindicated. Participants were also excluded if they: were diagnosed with shoulder capsulitis or paralysis of the dominant arm; received a pain-relieving steroids injection or supra-ulnar nerve block during the month preceding their participation; suffered from head or neck trauma or a concussion in the previous six months; or, were involved in litigation with regard to their

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injury. Additionally, participants were asked to avoid beginning any new exercise or treatment programs during their participation in this study.

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Experimental Protocol Participants performed a series of functional tests with their injured arm on two separate days, following the same experimental sequence. Testing sessions were scheduled a minimum of 48 hours apart in order to allow participants time to recover from any muscle soreness and fatigue from the initial session. Within this limitation, time between testing sessions was kept as minimal as possible, as much as participants’ schedules allowed. Prior to each of the two experimental sessions, they were asked to subjectively rate their neck and shoulder pain and disability on the Shoulder Pain and Disability Index (SPADI) and Neck Disability Index (NDI). The SPADI is comprised of five questions to assess the level of pain felt in the shoulder during everyday tasks (e.g. “What is the severity of your pain when you touch the back of your neck using your injured arm?”) and eight questions to assess the level of disability consequent from the shoulder pain symptoms (e.g. “How much difficulty do you have pulling something from your back pocket with the injured arm?”) [53], and has demonstrated reliability and validity in assessing these constructs [54, 55]. Participants indicated the level of shoulder pain or the degree of shoulder disability elicited in each of the thirteen situations on a visual-analog scale. The NDI follows a similar format rating the impact of neck pain and disability on activities of daily life and has also demonstrated high reliability and validity in patients with neck pain [56]. Additionally, participants were asked to periodically rate their pain (in the neck/shoulder region) throughout the protocol on an 11point NRS, which is commonly used to asses pain in a variety of populations [e.g. 57]. This measure was assessed at baseline, after completing the above questionnaires, and twice during the functional protocol. The shoulder functional assessment protocol featured here utilizes the BTE Work Simulator II, which features some 22 attachments and three primary testing modes (static, dynamic, and endurance) and a protocol devoted solely to lifting [21, 22]. The BTE has been commercially available, in varying forms, since 1979 and is marketed as a tool to assess and treat upper extremity function in a rehabilitation context. The unit consists of a software based controller interface, a position adjustable exercise head that includes an electromagnetically activated resistance control, and a set of interchangeable attachments that can be used to simulate a wide variety of working tasks. The height, orientation, and resistance (clockwise or counterclockwise) at the exercise head can be independently adjusted based on task requirements. Once configured with the appropriate tool, BTE can record a variety of functional outcome measures (e.g. peak force, time, and cumulative power output) at a sampling frequency of approximately 10 Hz. The unit has three primary testing modes: static, dynamic, and endurance. The static mode locks the exercise head in a chosen position for isometric exertions, recording maximum force output. The dynamic mode allows the clinician to define the resistance at the exercise head while the patient performs repeated movements and records cumulative power output over a given time period. The endurance protocol allows the clinician to define the resistance at the exercise head and the cadence of movement being performed and computes the cumulative power output over five second

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increments. The task continues at the specified cadence until the power output drops below a pre-defined level, with total work, angular distance, and time recorded as outcome measures. The outcome measures assessed during the experimental protocol were shoulder range of motion (ROM) in both flexion and abduction, as these are commonly impeded in cases of chronic neck/shoulder pain [58], peak force, and cumulative power output accumulated over 10s during a pushing/pulling task in a horizontal plane at shoulder level. These tasks, in particular pushing, are common in industries where MMH is required [41] and are associated with onset of neck/shoulder pain [59, 60]. Moreover, repetitive arm tasks performed at or above shoulder level have been associated with increased risk of neck/shoulder injuries [13]. This protocol was performed using a custom-modified version of the large crank handle (#802) attachment, where the existing multi-position crank handle was replaced with a 23 inch long section of 1¼ inch box steel. This modified crank handle had a 3/8 inch wide and 11 inches long channel cut through its center, which allowed the original adapter from the #802 tool to be attached. The far end of the tool was fitted with a round (1¼ inch diameter) handle placed parallel to the exercise head to allow for force application during the various tasks and a removable Velcro strap to secure participants’ limbs during ROM trials (Figure 1). This modification provided a stronger attachment and also allowed a greater range of adjustment along its length. For all tasks, participants were seated in a chair which was secured to the floor and allowed their upper trunk to be secured to the backrest via adjustable straps. Forthcoming sections will discuss the experimental protocols for each task in the order which they were tested: flexion ROM, abduction ROM, maximal voluntary pushing effort (MVPEP, and cumulative power output (PO). ROM trials were performed first as they pilot testing revealed that they did not cause increased pain perception in participants, while the more demanding trials (MVPE and PO) were performed afterward and with longer rest periods between trials.

Flexion and Abduction ROM Shoulder flexion ROM was assessed with participants seated such that the axis of flexion rotation, that is through the head of the humerus at the acromion process of the scapula, of the glenohumeral joint was aligned perpendicularly with the BTE’s axis of rotation at the center of the exercise head (Figure 1). Their arm was strapped to the attachment such that it was aligned along the lateral, longitudinal midline of the humerus in line with the lateral epicondyle and secured using a Velcro strap. Initially, the arm rested at the participants’ side, parallel to the body. Participants were instructed to “rotate their arm as far up and back as comfortably possible”, and then return to their starting position. To assess shoulder ROM in abduction, participants sat with their backs to the BTE. The axis of abduction rotation of the glenohumeral joint was defined at the anterior portion of the acromion process of the scapula, aligned through the center of the head of the humerus, of the glenohumeral joint was aligned perpendicularly with the BTE’s axis of rotation at the center of the exercise head (Figure 2). Their arm was strapped to the attachment such that it was aligned along the posterior, longitudinal midline of the humerus in line with the olecranon process and secured using a Velcro strap. From the same starting position as the flexion ROM, instructions were: “raise the arm to the side as high as comfortably possible” and then return to the starting position. For both shoulder ROM tasks, participants completed three consecutive trials, with 10s between trials and 2 min between tasks.

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Figure 1. Shoulder range of motion in flexion

Figure 2. Shoulder range of motion in abduction

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Mvpe Next, subjects performed trials of maximal voluntary pushing effort (MVPE).The BTE exercise head was placed such that it was perpendicular to the floor, with the attachment locked at shoulder height and aligned with the midsagittal line (Figure 3). Participants’ trunks were secured to the chair’ backrest via adjustable straps as they were instructed to grip the handle of the attachment with their injured arm in a power grip, such that their wrist was in a neutral position, the elbow was flexed 120°, and the shoulder was abducted and flexed 90°. A mesh barrier was attached to the face of the unit, directly under participants’ elbow to ensure that movements were limited to the horizontal plane at shoulder level (Figure 3). Participants were instructed to keep their elbow above the barrier and push forward on the attachment (i.e. elbow extension) as hard as possible, following verbal encouragement from the researcher. Each effort lasted approximately five seconds, using a ramp-up, hold, and ramp-down sequence. Three trials were performed, with at least two minutes of rest between trials. The peak force (in N) of these three trials was defined as MVPE for the remainder of the protocol. Immediately following the final MVPE trial, participants indicated their pain level on the NRS.

Figure 3. Maximal voluntary pushing effort

PO Following approximately five minutes of rest, participants performed a dynamic pushing and pulling task in which cumulative power output (PO) was recorded over a 10s sample. The BTE unit remained in the same configuration as in the MVPE task; however, the exercise head was unlocked and set to rotate in the transverse plane, with a resistance equal to 50% of MVPE in both the clockwise and counter-clockwise rotations (Figure 4). Participants were instructed to “push and pull the handle back and forth as fast as comfortably possible for 10

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seconds”, while receiving verbal encouragement from the researcher. Participants completed three of these trials with two minutes of rest between each; immediately following the third trial, they were asked to again rate their pain on the NRS.

Figure 4. Power output task. Note: arrow indicates directions of motion.

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DATA ANALYSIS Throughout the protocol, rotation of the exercise head, peak force, and cumulative power output were obtained from the BTE software after the ROM, MVPE and PO trials, respectively. Shoulder ROM in flexion and abduction were measured as the mean difference in the maximum and minimum angular positions of the exercise head over three trials. For each subject, the peak MVPE and PO values across the three trials were retained for further analyses. In addition to these functional measures, baseline neck/shoulder pain and disability (i.e. SPADI and NDI) and pain levels during the protocol (i.e. NRS pain scale) were also assessed in each of two sessions. Descriptive statistics (mean ± SD) were calculated for each outcome measure on each session and were compared using paired t-tests with p values > 0.05 considered significant. Test-retest reliability of all outcome measures was assessed by Intra-class correlation coefficients (ICC). The model ICC(2, 1) was used to assess reliability of outcome measures with a single value per session (i.e. peak MVPE, cumulative PO, and pain scores), while the model ICC(2, k) was used to assess outcome measures with scores averaged over multiple trials (i.e. flexion and abduction ROM) [61]. The ICC is considered preferable to correlation coefficients as a reliability index as it provides a single value for variance estimates that reflect errors within the measurement and true differences in the data set [61]. However, since many previous reliability studies using the BTE reported only correlation coefficients [e.g.

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27, 28], Spearman ranked order correlation coefficients were also calculated to facilitate comparisons. Standard error of the measurement (SEM) values were calculated as estimates of the error associated for each outcome. SEMs also serve to indicate the range of scores that can be expected from test to test of the same individual; values were calculated using the following equation [62]:

SEM = SD • 1 − ICC where SD represents the mean of the standard deviations of each measure on session one and session two and ICC is the intra-class correlation coefficient between session one and session two. SEM was also used to calculate the minimal detectable change for the 90th percentile confidence interval (MDC90), as follows[63]:

MDC90 = SEM • 2 • ( z score)90 where z score90 is the z score associated with the 90th percentile confidence interval (i.e. z = 1.65) [63] and SEM is the previously described standard error of the measurement. MDC90 is a measure that reflects the minimum amount of change in a measurement that is not likely to be due to chance variation in the measurement; since the MDC90 is highly dependent on the size of the reliability correlation, instruments with poor stability across repeated tests will have sizable MDC90 values [64]. Strengths of reliability measures were interpreted using Portney and Watkins’ classification scheme [61] (Table 1). Most statistical analyses were performed using Statistica 7.0 software (Statsoft, Inc., Tulsa, OK), while ICC values were calculated using a website recognized by the scientific research community (http://sip.medizin.uniulm.de/informatik/projekte/Odds/icc.html).

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Table 1. Interpretation of measures of reliability (Adapted from Portney & Watkins, 2000) Measure of Reliability Correlation Coefficient (r)

Intra-class Correlation Coefficient (ICC)

Range of Values

Interpretation of Values

0.00-0.25 0.26-0.50 0.51-0.75 > 0.75 ≥ 0.90

Little or no relationship Poor to fair Moderate to good Good to excellent Required for clinical application to ensure valid interpretation of findings

≤ 0.75 > 0.75 ≥ 0.90

Poor to moderate reliability Good reliability Required for clinical application to ensure valid interpretation of findings

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RESULTS At screening, participants reported pain ranging in intensity form 3 to 7.5 (mean 5.2 ± 1.5) on the NRS for durations ranging from 1 to 15 years (mean 4.4 ± 3.5). Individual patient demographics are reported in At the time of the initial testing session all patients were participating in their usual daily activities, including work or school. Table 2. At the time of the initial testing session all patients were participating in their usual daily activities, including work or school.

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Table 2. Participant demographic data (D – Dominant, ND – Non-Dominant)

Participant

Gender

Injury Location

Injured Side

Age (years)

Pain Intensity (0-10)

Pain Duration (years)

P01 P02 P03 P04 P05 P06 P07 P08 P09 P10 P11 P12 P13 P14 P15 P16

M M F M F F F M M F M F F F M F

Shoulder Shoulder Neck and Shoulder Shoulder Shoulder Neck and Shoulder Shoulder Shoulder Neck and Shoulder Neck Neck and Shoulder Shoulder Shoulder Shoulder Neck and Shoulder Neck and Shoulder

D D D D D D ND ND ND D ND D ND D D D Mean (SD)

55 40 56 28 25 52 53 23 22 38 48 52 34 33 34 49 39.1 (11.8)

7.5 4.0 4.5 4.5 5.0 7.0 3.5 4.0 7.5 7.0 5.0 5.0 4.0 3.0 5.0 6.5 5.2 (1.5)

7.0 2.5 4.0 1.0 5.0 5.0 5.0 3.0 1.0 5.0 15.0 1.0 5.0 2.0 7.0 1.5 4.4 (3.5)

Testing sessions were an average of 9.5 (± 7.1) days apart. Individual participant peak and mean functional outcome measure scores are presented in Table 3, while group mean values for each measure during each testing session are presented in Table 4. Participants reported similar shoulder pain and function on the SPADI scale on each session (30.0 ± 13.4 and 27.7 ± 11.5 %, respectively); however, NDI scores decreased from 23.0% to 18.7% from the first to the second session (p = 0.030). While there were no significant differences in individual NRS pain scores at any point in the testing protocol between testing sessions, all shoulder functional measures increased significantly between sessions (p = 0.018, 0.003, 0.029, and 0.046 for flexion ROM, abduction ROM, MVPE, and PO, respectively).

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Table 3. Comparison of individual participant peak and mean functional measures between testing sessions ROM Flexion (°) Session P01 P02 P03 P04 P05 P06 P07 P08 P09 P10 P11 P12 P13 P14

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P15 P16

Peak

ROM Abduction (°)

MVPE (N)

PO (W)

Mean (SD)

Peak

Mean (SD)

Peak

Mean (SD)

Peak

Mean (SD)

1

229.7

222.0 (9.7)

192.2

183.5 ± 8.0

277.8

277.4 ± 0.56

53.9

42.7 ± 10.4

2

230.8

224.6 ± 5.4

202.1

201.2 ± 1.1

217.8

213.8 ± 5.6

0.7

0.6 ± 0.1

1

150.7

142.5 ± 7.3

137.7

133.4 ±3.9

54.7

53.1 ± 2.6

8.5

7.6 ± 1.2

2

189.7

186.6 ± 4.6

145.6

138.9 ± 7.8

88.7

84.6 ± 5.7

39.2

33.0 ± 5.7

1

93.6

89.5 ± 3.7

28.8

27.1 ± 1.6

8.5

6.1 ± 2.0

35.0

32.7 ± 2.2 21.7 ± 9.7

2

86.4

80.7 ± 5.2

68.8

66.0 ± 3.9

74.0

59.1 ± 13.1

30.4

1

181.8

177.1 ± 4.3

66.4

62.0 ± 4.0

103.6

99.0 ± 5.0.

15.0

9.3 ± 5.2

2

174.6

167.5 ± 8.8

126.9

122.7 ± 3.7

242.0

232.5 ± 9.1

190.7

153.3 ± 41.3

1

162.5

157.4 ± 6.5

154.3

150.2 ± 3.8

208.6

202.4 ± 5.7

12.2

11.4 ± 0.7

2

178.9

171.2 ± 6.7

171.2

168.3 ± 4.5

271.4

235.9 ± 33.3

15.1

13.5 ± 1.5

1

170.3

157.4 ± 14.8

125.6

123.9 ± 1.4

170.7

121.1 ± 54.3

30.6

29.3 ± 1.2

2

184.9

181.1 ± 4.1

195.3

188.4 ± 6.5

217.8

202.0 ± 13.8

9.0

8.5 ± 0.6

1

175.1

173.8 ± 1.4

175.1

167.2 ± 7.2

96.6

82.6 ± 12.6

45.6

41.3 ± 5.1

2

194.4

186.0 ± 8.7

177.1

170.3 ± 6.1

133.5

114.8 ± 19.1

12.0

11.1 ± 1.0

1

165.8

160.4 ± 5.1

137.2

134.5 ± 2.4

239.2

237.2 ± 3.0

38.0

36.7 ± 1.7

2

166.7

162.6 ± 3.6

149.4

144.8 ± 5.0

257.5

241.2 ± 16.4

26.9

23.4 ± 4.7

1 2 1

179.6 194.4 239.9

163.0 ± 15.0 193.4 ± 1.1 228.8 ± 10.3

181.8 205.9 165.6

177.7 ± 3.7 202.6 ± 3.0 159.9 ± 8.2

74.0 76.2 13.5

71.4 ± 4.1 69.7 ± 5.8 11.4 ± 1.8

16.7 28.7 11.5

15.1 ± 1.9 27.2 ± 1.8 10.3 ± 2.1

2

210.1

208.0 ± 1.8

147.1

136.6 ± 9.2

88.8

87.8 ± 1.5

58.8

46.6 ± 12.4

1

182.2

176.1 ± 5.4

151.9

147.9 ± 4.2

36.5

34.2 ± 2.2

58.5

32.7 ± 25.5

2

196.2

191.3 ±6.4

185.4

180.7 ± 5.7

20.5

16.5 ± 3.6

44.3

35.2 ± 9.3

1

218.2

210.1 ± 9.4

150.1

148.3 ± 1.7

24.3

23.8 ± 0.5

170.9

159.2 ± 14.8

2

222.7

217.1 ± 6.1

186.3

181.3 ± 5.2

12.0

10.4 ± 1.4

47.2

41.8 ± 6.0

1

113.2

112.8 ± 0.4

93.1

87.4 ± 5.0

9.0

8.9 ± 0.17

50.9

46.7 ± 7.0

2

159.5

154.3 ± 6.9

145.8

139.7 ± 6.7

22.5

18.3 ± 3.8

56.2

49.7 ± 9.9

1

178.6

175.5 ± 3.0

195.7

194.4 ± 1.4

17.6

12.7 ± 4.3

23.4

21.5 ± 1.7

2

187.4

184.9 ± 2.2

195.3

190.8 ± 4.7

79.4

75.3 ± 3.6

12.0

11.4 ± 0.8

1

204.3

200.7 ± 3.4

204.3

203.5 ± 1.3

55.8

49.5 ± 10.7

17.7

15.1 ± 3.8

2

211.9

207.3 ± 4.6

211.3

207.0 ± 3.7

51.7

43.5 ± 7.1

37.2

35.8 ± 2.0

1

226.3

223.5 ± 3.9

196.4

42.2

25.1 ± 15.0

26.9

25.3 ± 1.5

2

247.7

240.0 ± 7.5

218.9

187.6 ± 8.2 201.7 ± 14.9

32.8

31.3 ± 1.4

20.6

18.0 ± 3.3

Test-retest reliability between sessions ranged from fair to high for the measures tested (Table 5). Correlation coefficients (r) of both pain and shoulder functional measures between testing sessions were significant (p < 0.05), ranging from moderate to high, with the exception of the PO task. Both questionnaire measures were highly correlated (r = 0.78 and 0.80 for SPADI and NDI, respectively) and demonstrated high ICC values (0.74 and 0.85, for SPADI and NDI, respectively). Mean SEM and MDC90 values were 5.6 ± 2.1% and 13.0 ± 4.9%, for the SPADI and NDI, respectively.

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Karen Lomond, Evelyne Boulay, Charlene Leduc-Poitras et al. Table 4. Comparison of group mean outcome measures between testing sessions 1

SPADI (%) NDI (%) Baseline MVPE PO Flexion ROM (°) Abduction ROM (°) MVPE (N) PO (W)

Questionnaires

NRS Pain Scores

BTE Functional Measures

Session One 30.0 ± 13.4 23.0 ± 13.7 3.0 ± 1.9 4.1 ± 2.2 4.1 ± 2.2 173.2 ± 38.7 143.5 ± 50.2 89.5 ± 87.5 34.4 ± 44.2

Session Two 27.7 ± 11.5 18.7 ± 12.5 2.3 ± 2.3 3.5 ± 2.3 4.2 ± 2.3 184.8 ± 36.1 165.4 ± 38.2 117.9 ± 92.0 45.7 ± 37.9

p-value 0.328 0.03* 0.086 0.280 0.838 0.018* 0.003* 0.029* 0.046*

NRS pain scores taken at the same point in the protocol were slightly more variable, with only moderate correlations between sessions, ranging from r = 0.57 to 0.61. Overall, NRS Pain scale data sampled throughout the testing protocol had only a moderate correlation, with a mean ICC of 0.59 ± .0.11, ranging from 0.52 to 0.72; however, baseline scores did reach high correlation (0.72). Mean SEM was low at 1.3 ± 0.3 points, ranging from 1.0 to 1.5 on a scale of 0 to 10. Similarly, mean MDC90 values were 3.1 ± 0.7 points, ranging from 2.3 to 3.5 points on a 0 to 10 scale. NRS pain scale ratings taken at baseline, also demonstrated the lowest SEM and MDC90 values. Table 5. Test-retest reliability of outcome measures 2 Spearman r

SEM

MDC90

0.74 0.85

6.9 5.3

16.1 12.3

0.72

1.0

2.3

0.54 0.52

1.5 1.5

3.5 3.5

0.94 0.92

1.4 1.4

3.3 3.3

0.86 0.52

33.3 28.4

77.8 66.2

Questionnaires

NRS Pain Scores

MVPE PO

0.57*

Flexion ROM (°) Abduction ROM (°)

0.79* 0.73* 0.81* 0.37

Baseline

BTE Measures

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ICC

0.78* 0.80* 0.61*

SPADI % NDI %

Functional

MVPE (N) PO (W)

0.61*

Finally, BTE functional measures were highly correlated for both measures of ROM and MVPE, ranging from r = 0.73 to 0.81, but PO demonstrated a low correlation (r = 0.37). These measures appear to demonstrate high test-retest reliability, ICC ranging from 0.86 to 0.94; however, again values for the PO portion of the protocol are only moderately reliable with an ICC of 0.52. Similarly, mean SEM and MDC90 values reported were 16.1 ± 17.1 and 37.6 ± 39.9, respectively. However, closer examination reveals that SEM and MDC90 values decrease during the ROM tasks, as opposed to the MVPE and PO tasks.

1 2

* p < 0.05 * p < 0.05

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Reliability of Shoulder Functional Measures …

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Spearman correlations between pain and functional measures within each session are presented in and Table 7. While there is little to poor correlation between the pain and functional outcome measures during session one, there is some significant correlation between the abduction ROM and both the NDI and NRS after the PO during session two, albeit moderate. Table 6. Spearman correlations between measures during session one 3

Session One BTE Functional Measures

PO (W) Flexion ROM (°) Abduction ROM (°) MVPE (N)

Questionnaires SPADI NDI % % 0.05 0.03 0.39 0.09 0.19 0.22 0.25 -0.09

NRS Pain Scores Baseline

MVPE

PO

0.14 -0.05 0.26 -0.14

0.06 0.22 0.21 -0.12

-0.07 0.08 0.04 -0.22

Table 7. Spearman correlations between measures during session two 4 Questionnaires Session Two

BTE Functional Measures

PO (W) Flexion ROM (°) Abduction ROM (°) MVPE (N)

SPADI % -0.12 0.46 0.43 -0.33

NDI % 0.24 0.41 0.52* -0.08

NRS Pain Scores Baseline 0.15 0.01 0.11 0.03

MVPE 0.35 0.26 0.31 0.06

PO 0.15 0.39 0.54* -0.08

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DISCUSSION The primary purpose of this chapter was to describe an assessment protocol that quantifies upper limb pain and functional outcomes relevant to chronic neck/shoulder pain and common workplace movements. Such a protocol could be used by clinicians to assess patient functional capacity and ultimately help guide safe and swift RTW [2]. In order for this or any functional assessment to be useful to practitioners it must demonstrate properties of validity (in particular predictive validity) and reliability [18]. To date, recent reviews indicate that there is limited evidence of validity and reliability in commercially available functional assessments sufficient for clinical or legal purposes [21, 22]. Of those assessments reported in the literature, the BTE was established as one of the most researched instruments, with protocols demonstrating moderate to good criterion validity under various circumstances [21]. Innes and Straker [21] define moderate criterion validity when: “statistical evidence suggests that there is some similarity between test and criterion measure” with a correlation coefficient r > 0.50. Several BTE attachments have demonstrated this level of evidence when comparing the simulated task to actual work demands [e.g. 28, 29]; however, to date, there are no studies 3 4

* p < 0.05 * p < 0.05

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Karen Lomond, Evelyne Boulay, Charlene Leduc-Poitras et al.

specifically addressing using the BTE to measure shoulder function. Forthcoming sections will compare functional BTE measures from this protocol to existing data and discuss the reliability of the functional measures recorded and the potential influence of pain on these measures.

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INTER-SESSION COMPARISON OF FUNCTIONAL MEASURES: ROM All functional measures increased significantly from session one to session two, though the clinical significance of these increases varies as a function of the task. For instance, shoulder ROM measures increased by averages of 11.6º and 21.9º in flexion and abduction, respectively. Since both of these increases are greater than SEM and MDC90 (1.4º and 3.3º, respectively for both measures), these increases are beyond those inherent to the instrument or chance variation and likely reflect an actual functional change. This is in contrast to other studies that have reported strong correlations and no significant differences in functional measures between testing sessions in chronic pain patients [e.g. 65, 66, 67]. The mean time between testing sessions was rather long (12 days), which might have impacted participants’ pain or functional status. While there were no significant differences between individual NRS pain and SPADI scores between sessions, NDI scores decreased significantly between sessions, which may indicate improved neck function from session one to session two. Similarly, within session data revealed a moderate but significant tendency for NDI and post-PO NRS scores to correlate with abduction ROM during session two. However, the difference between mean NDI scores between sessions was only 4.3% which is well under the MDC90 calculated here (12.3%). This value is of a similar magnitude to the MDC90 reported by the questionnaire’s authors (10.0 %) [56] and indicates that changes in NDI scores of this dataset less than 12.3% are likely to be the result of chance variation in measurement [64]. Both ROM measures demonstrate good to excellent reliability between testing sessions (r = 0.79 and 0.73, for flexion and abduction, respectively) and ICCs strong enough (i.e. > 0.90) to ensure clinically valid interpretations of findings. However, the significant differences between testing sessions indicate that these values may be influenced by other factors such as habituation from the previous visit. For instance, familiarity with the protocol and testing environment may have reduced patients’ fear of the movement task, which has been shown to have positive effects on function [68]. While, this construct was not measured here, the appearance of moderate correlations between abduction ROM and some pain and disability measures during the second visit may indicate a relation between these values.

VALIDITY OF SHOULDER ROM MEASURES Despite the apparent robustness of these data, there are some discrepancies with absolute ROM values obtained from the BTE and those reported with more traditional goniometric methods. Shoulder ROM in flexion and abduction in this protocol were 179° ± 35° and 154° ± 37° (mean of both sessions), respectively. These values are greater than those reported in

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Reliability of Shoulder Functional Measures …

69

studies of shoulder pathology, which ranged from 82° to 143° and 90° to 135° for flexion and abduction, respectively ( Table 8) [69-71]. In addition to standard goniometers, Hayes and colleagues [70] also found similar shoulder flexion ROM using visual estimation and still photography techniques. The discrepancies between the values obtained on the BTE and these other measures are likely largely due to the number and age of participants tested and differences in their pathologies (e.g. acute/sub-acute, as opposed to chronic). Two of the papers cited above present either a single case or a group of only nine participants and the mean age of these participants is substantially older than those tested here (60 and 64 ± 14.7 years, respectively) [69, 70]. In fact, differences in performance are likely accounted for in age alone, as there is clear evidence of decreased shoulder ROM in all directions as a function of age [72]. Rudiger et al. [71] presented a large sample size (n = 158) of patients whose ROM was measured immediately prior to surgical consultation. Demographic information was not provided for this study, but the pre-operative status of the patients suggests that their functional status is likely more impaired than participants in this study, who have experienced chronic pain.

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Table 8. Shoulder ROM (degrees) in flexion and abduction, as measured by a variety of devices in multiple studies (mean ± standard deviation, where reported) n

Side

Measurement Device

ROM Flexion (°)

ROM Abduction (°)

Greene & Wolf (1989)

20

Dominant

Goniometer

155.8 ± 1.4

167.6 ± 1.81

Constant & Murley (1987)

Injured Noninjured

105

90

1

Goniometer

180

180

143 ± 21 135 ± 26 128 ± 28

135 ± 33 129 ± 35 131 ± 35

Hayes et al. (2001)

9

Injured

Visual Estimation Goniometer Still Photography

Rudiger et al. (2008) Sabari et al. (1998)

158

Injured

Goniometer

82

102

30

NonInjured

Goniometer

157.8 ± 14.89

156.23 ± 16.91

Data from this study are closer in magnitude to those reported in uninjured shoulders, ranging from 156° to 180° for both flexion and abduction [69, 73, 74]; however our data appear more variable (SD 35° and 37°, respectively) than that of healthy subjects. This may be related to the seated position used in the protocol, as most goniometric protocols suggest measuring shoulder flexion ROM in the supine position to minimize scapular movement [e.g. 75]. The chair used for our task had straps to secure the upper trunk to the backrest; however it may have still allowed participants some scapular movement which may have extended their flexion ROM. As a whole, it appears that the shoulder ROM protocol described here is sufficiently reliable for clinical practice and yields data of a similar magnitude to those obtained using the validated instruments described above; however, care should be taken to further restrict scapular movement if isolation of glenohumeral range of motion is desired. There is some indication that pain and disability measures (particularly in the neck) may influence patient performance, but these may be mediated by other psychosocial factors (e.g. fear of pain,

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Karen Lomond, Evelyne Boulay, Charlene Leduc-Poitras et al.

catastrophizing, etc.) between testing sessions. Further investigation is warranted into these psychosocial factors to investigate the degree to which they impact ROM of the shoulder.

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INTER-SESSION COMPARISON OF FUNCTIONAL MEASURES: MVPE AND PO Our results indicate that as with ROM measures, both MVPE and PO measures also increased significantly between testing sessions (by 28.4 N and 11.3 W, respectively); however, unlike ROM measures, these increases were less than the SEM or MDC90 values (33.3 N or 77.8 N; 28.4 W or 66.2 W for MVPE and PO, respectively). Therefore, despite their statistical significance these increases are within less than the inherent errors in the measurement and therefore cannot necessarily be considered clinically significant. While these large SEM values indicate substantial variability between the two test sessions, the MVPE measure appears to offer some evidence test-retest reliability; with between session correlation coefficient (0.73) rating moderate to good, and the ICC reliability index (0.86) rating good to excellent. However, these values still fall short of the reliability indices required for valid interpretation of clinical findings (i.e. r ≥ 0.90 or ICC ≥ 0.90). Measures on the PO task proved unreliable, with ratings of poor and moderate for the correlation coefficient and ICC, respectively. This is consistent with previous test-retest data from the BTE using various FCE protocols. The static testing mode of the BTE, used during the MVPE protocol, has demonstrated good to excellent reliability in several studies, using a variety of attachments, including the standard version of the 802 attachment [24, 25, 27]. However, some of these studies calculated only the correlation coefficient to assess reliability, rather than the preferred ICC value, and did not present information on the SEM of their respective protocols [24, 25, 27, 28]. With regard to the dynamic portion of the protocol, concern has previously been raised regarding the efficacy of the BTE between testing sessions in the dynamic mode [23-25, 32]. Results were similar in this study, as the PO task consistently demonstrated the poorest testretest properties (r = 0.37; ICC = 0.52). In particular, a series of studies using a timed weight drop test identified large variations in resistance between individual dynamic trials [23, 31, 32], which would likely contribute to the poor test-retest reliability properties in this mode. Fess [24, 25] offers some insight into this issue by identifying two distinct phases within the dynamic mode: the pre-inertia phase and the rotational stage. The pre-inertia stage is equivalent to the first 6º to 20º of rotation of each movement arc, where if the applied force is not sufficient to overcome rotational inertia the BTE does not always accurately record the torque data, thus leading to variable results between similar trials. The rotational stage, where rotation is greater than 20º per movement arc, appears more stable; however, Fess [24, 25] did refer to occasional “surges” occurring in this stage that increased recorded values 30 to 50%. Additionally, as the MVPE was used to determine an adequately challenging resistance for the PO task, it was always completed immediately prior. Despite the five minute rest period allowed between these sets of trials, it is possible that participants’ increased pain perception during the MVPE task may have influenced their performance of the PO task. However, since there were no significant differences in pain scores after the MVPE or PO

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Reliability of Shoulder Functional Measures …

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tasks, any influence of residual pain perception appears to be consistent across testing sessions. Taken together, it appears that both our MVPE and PO tasks are somewhat variable, each requiring large changes to truly establish a functional change among clinical populations. Correlation coefficients for the MVPE task suggest that it may be possible to reliably distinguish between the most affected workers and healthy workers; however, large SEM and MDC90 values indicate that the measure may not be stable enough to distinguish between injured workers or track the progression of their symptoms. The reliability of the PO task may be compromised by variable resistance applied at the exercise head during the BTE’s dynamic protocol. As such, any attempts to evaluate patients’ functional capacity should only include dynamic protocols when these fluctuations in resistance pose no threat to the patient and should include multiple dynamic tasks to ensure an accurate reflection of their true functional capacity [23, 30, 32, 35]. Additionally, careful monitoring of patient’s pain levels and adequate recovery time is essential to determine the patients’ true functional potential.

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VALIDITY OF STATIC AND DYNAMIC SHOULDER FUNCTION MEASURES Of interest in this protocol were measures of shoulder function related to pushing and pulling performance as nearly half of all MMH tasks involve these movements [76] and there seems to exist a strong dose-response relationship between these tasks and incidence of shoulder injury [60]. However, due to the specific movement chosen here to measure static and dynamic shoulder function, our results cannot be directly compared to others in the literature. Several authors have also attempted to reproduce shoulder tasks specific to certain job requirements [77, 78] and in doing so have created similar movements to the pushing/pulling tasks presented here. Since these movements involve similar muscle groups it is not surprising that peak forces applied in these tasks are similar in magnitude to those recorded here. For instance, Andrews and colleagues [77] simulated a hose insertion task, common in automobile manufacturing, using a tri-axial load cell, obtaining mean peak forces in the forward pushing position of 75.5 ± 22.4 N. While this is less than in the current study (i.e. mean MVPE for both sessions = 104 N ± 90 N), the study only included female participants; when male participants are excluded from our results, they are more comparable (mean 84.6 ± 82.8 N). Herring and Hallbeck [78] examined maximal push and pull forces generated while performing a simulated manual gear shift task as a function of gear shift location. The furthest and highest position was similar to those used in our MPVE task and generated a mean push force of 161.9 ± 33.1 N. Again this study included only female participants, yet the values are greater than those obtained in the current study. This study only examined healthy university students, which likely accounts for their stronger performance; however, the design of the task was slightly different than our MVPE with the pushing surface (i.e. gear shift) closer to the trunk (allowing increased elbow flexion) and six inches to the right of the subjects. While these types of maximal exertions tend to be useful in assessing function in healthy individuals, their usefulness in assessing injured populations is not well documented. In fact, a recent review has demonstrated that measures of maximal function must be interpreted

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Karen Lomond, Evelyne Boulay, Charlene Leduc-Poitras et al.

cautiously as they depend heavily on participant effort, which is difficult to measure [79]. Chronic pain patients tend to systematically overestimate the magnitude of pain intensity and unpleasantness in more challenging movements [19, 44]; that is, they appear less inclined to push their performance to maximal levels due to neuromuscular inhibition, fear of re-injury, or other psychological factors [68, 80]. Thus, a more pertinent measure of functional status of the shoulder may be a sub-maximal dynamic task, such as the PO task presented here. However, although our PO task was performed with sub-maximal resistance (50% MVPE), this value was still relative to the ability to produce voluntary force and the sincerity of effort during the MVPE task. Clearly, the question of how to test the strength of pathological populations whose mechanical ability to produce a maximal effort may be impaired by their pain perceptions remains to be elucidated. While comparable data from a similar dynamic pushing/pulling task is not readily available, other papers have directly compared simulated and real tasks and assessed consistency of work demands between the two [e.g. 28, 29, 35]. Generally, these have demonstrated moderate validity, with the BTE underestimating physiological requirements (i.e. V02 and heart rate) when actual and BTE-simulated tasks compared [28, 29]. Similarly, Bhambhani and colleagues [35] noted that despite moderate to good correlation (r = 0.62 to 0.82) between three tasks on the BTE (i.e. wheel turn, simulated sawing, and overhead reach), the common variance between tasks was low (r2 = 38 to 67%). Practically, these results suggest that clinicians using the BTE for functional evaluation should include as many simulated working tasks as needed to ensure a comprehensive evaluation that is representative to the overall nature of work tasks performed by the injured worker.

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CONCLUSION Overall, it appears that the BTE has some promise in reliably assessing shoulder function in individuals with chronic neck/shoulder pain. In particular ROM values showed high reliability coefficients and small variance measures; however, it may benefit further from increased stabilization of the scapula to isolate pure glenohumeral motion. Despite the robust reliability coefficients, there is some evidence that ROM measures (particularly in abduction) may be related to pain and disability levels, particularly of the neck, during the testing session. While this remains a subject for further investigation, clinicians should be aware of the potential impact of pain on outcome measure and should document pain and disability measures during each testing session. The simulated pushing and pulling tasks demonstrated more variable results and consequently, may be less reliable. As with previous investigations tasks performed in the static mode (i.e. MVPE) appeared more reliable than those in the dynamic mode (i.e. PO), suggesting that such static functional assessments may be useful in distinguishing between individuals with large differences in function (i.e. healthy vs. injured). The dynamic protocol presented here demonstrated consistently poor to moderate reliability, which may be attributed to fluctuations in resistance. As such, it should only be used in FCE with caution and included as one of several dynamic tasks in a protocol to ensure the most accurate representation of patients’ functional capacity.

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Taken together this does not imply that the BTE is without merit in FCE. Its flexibility of task design and objective, quantitative data regarding of patients’ abilities are a vital component of accurate functional assessment. Careful design and application of testing protocols (e.g. close monitoring of pain status, multiple dynamic trials, etc) should allow clinicians to overcome many of the limitations identified here.

ACKNOWLEDGMENTS Supported by grants from Canadian Foundation for Innovation (CFI), Institut de recherché Robert-Sauvé en santé et en sécurité du travail (IRSST), National Sciences and Engineering Research Council of Canada (NSERC).

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healthy men. American Journal of Occupational Therapy. 2001 Mar-Apr; 55(2):18490. Dunipace KR. Reliability of the bte work simulator dynamic mode. Journal of Hand Therapy. 1995; 8(1):42-3. Cetinok EM, Renfro RR, Coleman EF. A pilot study of the reliability of the dynamic mode of one bte work simulator. Journal of Hand Therapy. 1995; 8(3):199-205. Lechner D, Roth D, Straaton K. Functional capacity evaluation in work disability. Work. 1991; 1(3):37-47. Beaton DE, O'Driscoll SW, Richards RR. Grip strength testing using the bte work simulator and the jamar dynamometer: A comparative study. Baltimore therapeutic equipment. Journal of Hand Surgery. 1995 Mar; 20(2):293-8. Bhambhani Y, Esmail S, Brintnell S. The baltimore therapeutic equipment work simulator: Biomechanical and physiological norms for three attachments in healthy men. American Journal of Occupational Therapy. 1994 Jan; 48(1):19-25. Esmail S, Bhambhani Y, Brintnell S. Gender differences in work performance on the baltimore therapeutic equipment work simulator. American Journal of Occupational Therapy. 1995 May; 49(5):405-11. Lee GK, Chan CC, Hui-Chan CW. Consistency of performance on the functional capacity assessment: Static strength and dynamic endurance. American Journal of Physical Medicine and Rehabilitation. 2001 Mar; 80(3):189-95. Lee GK, Chan CC, Hui-Chan CW. Work profile and functional capacity of formwork carpenters at construction sites. Disability Rehabilitation. 2001 Jan 15; 23(1):9-14. Snook SH, Ciriello VM. The design of manual handling tasks: Revised tables of maximum acceptable weights and forces. Ergonomics. 1991 Sep; 34(9):1197-213. Snook SH, Irvine CH, Bass SF. Maximum weights and work loads acceptable to male industrial workers. A study of lifting, lowering, pushing, pulling, carrying, and walking tasks. American Industrial Hygiene Association Journal. 1970 Sep-Oct; 31(5):579-86. Ciriello VM, McGorry RW, Martin SE, Bezverkhny IB. Maximum acceptable forces of dynamic pushing: Comparison of two techniques. Ergonomics. 1999 Jan; 42(1):32-9. Ciriello VM, Snook SH, Hughes GJ. Further studies of psychophysically determined maximum acceptable weights and forces. Human Factors. 1993 Mar; 35(1):175-86. Simmonds MJ. Measuring and managing pain and performance. Manual Therapy. 2006; 11:175-9. Simmonds M, Goubert L, Moseley G, Verbunt J, editors. Moving with pain. 11th World Congress on Pain; 2006; Sydney, Australia. IASP Press, Seattle WA. Madeleine P, Lundager B, Voigt M, Arendt-Nielsen L. Shoulder muscle co-ordination during chronic and acute experimental neck-shoulder pain. An occupational pain study. European Journal of Applied Physiology & Occupational Physiology. 1999; 79(2):127. Simmonds MJ. Physical function in patients with cancer: Psychometric characteristics and clinical usefulness of a physical performance test battery. Journal of Pain Symptom Management. 2002; 24(4):404-14. Simmonds MJ, Novy D, Sandoval R. The differential influence of pain and fatigue on physical performance and health status in ambulatory patients with human immunodeficiency virus. Clinical Journal of Pain. 2005; 21:200-6. Simmonds MJ. Measuring and managing pain and performance. Manual Therapy. 2006; 11:175-9.

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[49] Veiersted KB, Westgaard RH, Andersen P. Pattern of muscle activity during stereotyped work and its relation to muscle pain. International Archives of Occupational and Environmental Health. 1990; 62 31-41. [50] Cote JN, Raymond D, Mathieu PA, Feldman AG, Levin MF. Differences in multi-joint kinematic patterns of repetitive hammering in healthy, fatigued and shoulder-injured individuals. Clinical Biomechanics 2005; 20(6):581-90. [51] Cote JN, Raymond D, Mathieu PA, Feldman AG, Levin MF. Differences in multi-joint kinematic patterns of repetitive hammering in healthy, fatigued and shoulder-injured individuals. Clinical Biomechanics. 2005; 20(6):581-90. [52] Beaton DE, Dumont A, MacKay M, Richards R. Steindler and pectoralis major flexorplasty: A comparitive analysis. Journal of Hand Surgery. 1995; 20A(5):747-56. [53] Roach KE, Budiman-mak E, Sonsiridej N, Lertatanakul Y. Development of a shoulder pain and disability index. Arthritis Care & Research. 1991; 4:143-9. [54] Beaton DE, Richards RR. Assessing the reliability and responsiveness of 5 shoulder questionnaires. Journal of Shoulder and Elbow Surgery. 1998; 7:565-72. [55] MacDermid JC, Solomon P, Prkachin K. The shoulder pain and disability index demonstrates factor, construct and longitudnal validity. BMC Musculoskeletal Disorders. 2006; 7(1):1:12. [56] Vernon H, Mior S. The neck disability index: A study of reliability and validity. Journal of Manipulative and Physiological Therapeutics. 1991; 14(7):409-15. [57] Lundeberg T, Lund I, Dahlin L, Borg E, Gustafsson C, Sandin L, et al. Reliability and responsiveness of three different pain assessments. 2001; 33(6):279-83. [58] Donovan P, Paulos L. Common injuries of the shoulder: Diagnosis and treatment. The Western Journal of Medicine. 1995; 163(4):351-9. [59] Hoozemans MJ, van der Beek AJ, Fring-Dresen MH, van der Woude LH, van Dijk FJ. Low-back and shoulder complaints among workers with pushing and pulling tasks. Scandinavian Journal of Work, Environment, and Health. 2002 Oct; 28(5):293-303. [60] Hoozemans MJ, van der Beek AJ, Frings-Dresen MH, van der Woude LH, van Dijk FJ. Pushing and pulling in association with low back and shoulder complaints. Occupational and Environmental Medicine. 2002 Oct; 59(10):696-702. [61] Portney L, Watkins M. Statistical measures of reliability. Foundations of clinical research: Applications to practice. 2nd ed. New Jersey: Prentice Hall; 2000. p. 557-86. [62] Portney L, Watkins M. Foundations of clinical research: Applications to practice. 2nd ed. New Jersey: Prentice Hall; (2000). [63] Stratford P. Getting more from the literature: Estimating the standard error of measurement from reliability studies Physiotherapy Canada. 2004; 56:27-30. [64] Haley S, Fragala-Pinkham M. Interpreting change scores of tests and measures used in physical therapy. Physical Therapy. 2006; 86(5):735-43. [65] Andersen LL, Kjaer M, Andersen CH, Hansen PB, Zebis MK, Hansen K, et al. Muscle activation during selected strength exercises in women with chronic neck muscle pain. Phys Ther. 2008 Mar 13. [66] Cagnie B, Cools A, De Loose V, Cambier D, Danneels L. Differences in isometric neck muscle strength between healthy controls and women with chronic neck pain: The use of a reliable measurement. Archives of Physical Medicine and Rehabilitation. 2007; 88:1441-5.

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[67] Mannion AF, Taimela S, Müntener M, Dvorak J. Active therapy for chronic low back pain: Part 1. Effects on back muscle activation, fatigability, and strength. Spine. 2001; 26(8):897. [68] Vlaeyen JW, Kole-Snijders AM, Boeren RG, van Eek H. Fear of movement/(re)injury in chronic low back pain and its relation to behavioural performance. Pain. 1995 Sep; 62(3):363-72. [69] Constant C, Murley A. A clinical measure of functional assessment of the shoulder. Clinical Orthopaedics and Related Research. 1987; 214:160-4. [70] Hayes K, Walton JR, Szomor ZL, Murrell GA. Reliability of five methods for assessing shoulder range of motion. Australian Journal of Physiotherapy. 2001; 47:289-94. [71] Rudiger HA, Fuchs B, von Campe A, Gerber C. Measurements of shoulder mobility by patient and surgeon correlate poorly: A prospective study. Journal of Shoulder and Elbow Surgery. 2008 Mar-Apr; 17(2):255-60. [72] Barnes CJ, Van Steyn SJ, Fischer RA. The effects of age, sex, and shoulder dominance on range of motion of the shoulder. Journal of Shoulder and Elbow Surgery. 2001; 10(3):242-6. [73] Greene BL, Wolf SL. Upper extremity joint movement: Comparison of two measurement devices. Archives of Physical Medicine and Rehabilitation. 1989 Apr; 70(4):288-90. [74] Sabari J, Maltzev I, Lubarsky D, Liszkay E, Homel P. Goniometric assessment of shoulder range of motion: Comparison of testing in supine and sitting positions. Archives of Physical Medicine and Rehabilitation. 1998; 79:647-51. [75] Palmer KT, Smedley J. Work relatedness of chronic neck pain with physical findings--a systematic review. Scandinavian Journal of Work, Environment, and Health. 2007 Jun; 33(3):165-91. [76] Brace T. The dynamics of pushing and pulling in the workplace: Assessing and treating the problem. American Association of Occupational Health Nurses Journal. 2005 May; 53(5):224-9. [77] Andrews D, Potvin J, Calder I, Cort J, Agnew M, Stephens A. Acceptable peak forces and impulses during manual hose insertions in the automobile industry. International Journal of Industrial Ergonomics. 2008; 38:193-201. [78] Herring S, Hallbeck S. The effects of distance and height on maximal isometric push and pull strength with reference to manual transmission truck drivers. International Journal of Industrial Ergonomics. 2007; 37:685-96. [79] Flores L, Gatchel RJ, Polatin PB. Objectification of functional improvement after nonoperative care. Spine. 1997 Jul 15; 22(14):1622-33. [80] Hirsch G, Beach G, Cooke C, Menard M, Locke S. Relationship between performance on lumbar dynamometry and waddell score in a population with low-back pain. Spine. 1991 Sep; 16(9):1039-43.

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Chapter 3

ERGONOMICS IN THE OPERATING ROOM – AN OVERVIEW L. S. G. L. Wauben∗, A. Albayrak and R. H. M. Goossens Delft University of Technology, Faculty of Industrial Design Engineering Landbergstraat 15, 2628 CE Delft, the Netherlands

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ABSTRACT When a person becomes ill different stages have to be completed before he or she is ‘cured’: visits to general practitioner (GP), visits to specialist, possibly medication and therapy, admission into hospital, possibly surgery, release from hospital, checkups with the specialist or GP, etc. During surgery several people are involved: anesthetists, surgeons, residents and nurses. Within the sub stage surgery three phases are present: preoperative, intra-operative and post-operative phase. This chapter focuses on the intraoperative phase of surgery only, mainly concentrating on the surgical team and scrub nurses. The chapter provides an overview of the ergonomics in the operating room (OR) based on the scientific research. Due to the growing variety of technical machines, products and increasing safety awareness, many ergonomic (Human Factor) specializations have evolved. One of them is the ergonomics of the OR. Within this specialization the discipline Industrial Design Engineering entails inventing, producing and using tools, focusing on the human aspects of the product design: ‘creating products people love to use’. In relation to medical product development and medical product evaluation this means that the OR and its products should be adapted to staff working in the OR, instead of adapting the workers to the OR environment. The three main domains of specialization of ergonomics are related to the sensorial, cognitive and physical ergonomics. Within all these domains problems are encountered using the currently available products. For the sensorial domain, factors such as perceiving surgical images, displays, haptics, and the use of foot pedals were discussed. Examples within the cognitive domain are: indirect vision, behavior, training of technical and non-technical skills, protocols, checks and checklist and time-out procedures. For the physical ergonomics the apparatus and instrument used in the OR (e.g. operating table, foot pedals, monitor, etc) play a role. In addition, brief attention will be paid to the ∗

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L. S. G. L. Wauben, A. Albayrak and R. H. M. Goossens environmental ergonomics dealing with the OR environment, lighting, temperature and airflow. All domains have to be taken into account when designing and evaluating products, however their focus will shift.

INTRODUCTION When a person becomes ill different stages have to be passed through before he or she is ‘treated’: visiting the general practitioner (GP) and specialist, possibly medication and therapy, admission into hospital, possibly surgery, release from hospital, checkups with the specialist or GP, etc (Figure 1). This chapter focuses on the stage surgery.

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Figure 1. Stages of cure.

Figure 2. Surgical phase.

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Surgery involves activities between humans (e.g. anesthetists, surgeons, residents and nurses) and machines aiming to cure the patient. Surgery can be divided into three phases: pre-operative, intra-operative and post-operative phase. This chapter will focus on the intraoperative phase of surgery only, mainly concentrating on the surgeons and scrub nurses (Figure 2). Human performance is not error free, the best performance that is reasonable is within the ALARP region where the risk is As Low As Reasonable Possible [28]. As a consequence, errors occur. An error is defined as: ‘the failure of a planned action to be completed as intended, or the use of a wrong plan to achieve an aim’ [50]. Errors may or may not have consequences. When errors have consequences these are called adverse events, and if no consequences these are called near-misses (close call) or a no-harm events [29]. The latter types occur 300 to 400 times more than adverse events, and although not harmful for the patient in the end these series of errors that accumulated within the system over time eventually cross a threshold and result in an adverse event. [29; 83]. Currently, most of the errors in healthcare are related to surgical procedures [55; 75; 101]. The increased advanced high technology in the operating room (OR), which makes the OR a more complex and high-risk environment, and the increased complexity of the surgical procedures contribute to the medical errors rates [101]. However, these rates have to be limited in order to improve patient safety. Therefore, both the (unpredictable) surgical environment and the human-product activities have to be controlled [28; 101]. Several error classification systems are described in literature. However, the classification by Bogner (2003) matches the approach of our faculty of Industrial Design Engineering of the Delft University of Technology best. Here errors are seen as a behavior being the result of the interaction of the person and its environment [16]. The environment consists of several conditions shown in Figure 3. Changes in any part of the system impacts the other systems in a reverse ripple effect. Within the frame of the ‘artichoke model’, error rates can be influenced by or related to several factors (Table 1). Table 1 shows that during surgery both errors associated with the motor control of instruments as well as procedural errors can be made [53].

Figure 3. Systems approach: Artichoke model. (adapted from Bogner 2003)

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L. S. G. L. Wauben, A. Albayrak and R. H. M. Goossens Table 1. Errors influenced by or related to [26; 27; 29; 47; 50; 55; 72; 73; 75; 83; 86; 89; 97; 116] Provider (surgeon) ƒ Inattention ƒ Stress ƒ Lack of experience or training of the staff ƒ Bad performance ƒ Wrong diagnoses ƒ Failed reaction on results of monitoring and testing Ambient ƒ Noise (80-85dB instead of 45dB) ƒ Prevailing external circumstances ƒ Equipment failure ƒ Stage of the surgery ƒ Complexity of surgery ƒ Inadequate information technology for staff

Social ƒ Failure of communication, decision making and situational awareness skills ƒ Inadequate teamwork ƒ Mental stress (leads to fatigue) Organization ƒ Time pressure ƒ Overwork Legal/ regulatory / cultural / reimbursement ƒ Poor Leadership ƒ Unclear protocols, briefings and procedures ƒ Nontransparent culture ƒ Lack of quality assurance measures ƒ Lack of evidence-based practice ƒ Inadequate system for detection of poor performance

Physical ƒ Unsuitable OR ergonomics ƒ Sleep deprivation ƒ Circadian rhythms

One of the factors contributing to patient safety is ergonomics. Improvement of ergonomics leads to less stress, less strain, and reduces fatigue, which prevents injuries to the surgical team and enhances their performance, thus lowering error rates [73; 81]. This chapter gives an overview of ergonomics in general, in surgery, and ergonomics in the OR. The different aspects and their problems will be discussed.

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ERGONOMICS IN GENERAL The study of ergonomics, also called human factors, is a rather young discipline in science. The word ergonomics originates from the Greek words ‘ergon’ (labor) and ‘nomos’ (law), and therefore the main research focus of the discipline is to study the laws of human labor. Although the word was first used in a book in 1857, it lasted till the Second World War before the importance of ergonomics was recognized [9]. At that time it became more and more important to systematically improve the tools and tasks of the soldiers to reduce fatigue, reduce errors and in that way increase the achievements. During the first years the focus of ergonomics was on industrial labor [9]. Research was mainly conducted on inefficiency of human labor and how this was influenced by the use of machines (it is therefore that even nowadays sometimes the term man-machine-interaction

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instead of ergonomics is used), and also tools and also organizational aspects of labor were improved. At those days the majority of the labor was based on physical effort, and therefore the risk on physical complaints because of poor ergonomic conditions was immense. To cure this situation machines, workplaces and organization of labor were adapted to human capacities. Soon after this first period the attention in ergonomics shifted from curative to preventive ergonomics and incorporated knowledge of as well technical as medical disciplines. The applied knowledge that had started with application of knowledge from physiology, psychology and mechanical engineering, soon also incorporated disciplines like anatomy, sensory perceptions, biomechanics, movements sciences, cybernetics and informatics. And because also physical labor became less and less important a shift was noticeable towards the optimization of information exchange between the user and the products that he uses at home, at work, during leisure and traveling [9]. Ergonomics studies and seeks to minimize risk factors between human beings and the tasks and environment that occupy them [57]. The International Ergonomics Association defines the discipline of ergonomics and the ergonomist as follows [114]: .

‘Ergonomics (or human factors) is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance’. ‘Ergonomists contribute to the design and evaluation of tasks, jobs, products, environments and systems in order to make them compatible with the needs, abilities and limitations of people’.

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The science of ergonomics is still regarded as a rather recent discipline, just 60 years as a formal body of knowledge [57]. In cooperation with the enormous and still growing variation in products that are used nowadays, a lot of knowledge needs to be developed in close cooperation between both human and technical sciences. This implies that nowadays many new specializations of ergonomics can be found. It also means that a lot of uncertainty is met when ergonomics is applied to a new field at the frontiers of knowledge, like in nowadays surgery.

Ergonomics in Product Design The product designer must offer new solutions by means of products to new or existing problems. The designer will use all the available knowledge to do this in an optimal way, and often the use of ergonomics will be part of that too. In that case the aim of product ergonomics is to provide data of human capacities and methods to apply these as an integral part of a design process in order to guarantee efficient, safe and comfortable use of the products [33]. Therefore in product design these three aspects are the most important aims of the application of ergonomics.

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Importance of Ergonomics The importance of ergonomics becomes obvious realizing that new products and environments are developed continuously and that the guidelines are to be used by designers are partly based on scientific data of ergonomic studies. To introduce a new product design without the use of these findings can create (health) risks and inefficiency in processes. Especially in activities that demand a long, intense and complex interaction with products, as in the OR, ergonomics has to play a major role, especially in the light of safety.

Ergonomics in the Operating Room When a focus is put on the ergonomics of the OR, the product designers should ‘adapt the environment to the team instead of asking adaptation from the team-members to their environment’ [40; 105]. This focus means that as well as the physical ergonomic aspects should be studied, as the interaction of the surgeon and his team with each other, and the over 100 products that surround them. Of those products some are very low tech and easy to learn, but others are very complex and require days and sometimes weeks of practice before these can be used in a safe way.

Domains of Specialization

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The classic way to define domains in ergonomics is to define clusters along the different human capacities when interacting with products. These activities take place in the physical and mental domain, and require transformation of information from physical to mental via the senses. Therefore, physical, sensorial and cognitive ergonomics is a good basis to be used as a first step towards understanding the interaction in the OR (Figure 4).

Figure 4. Domains in ergonomics.

Sensorial Ergonomics The sensorial ergonomics focuses on the human senses and human perception and factors influencing these. Problems occur when there are difficulties getting the necessary information from the environment. On the product side this includes products that support the senses and perception, such as visual displays (monitors), but also tactile displays (force feedback in the handle) and auditory displays (beeps and alarms in the OR) [40].

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Cognitive (Perceptional) Ergonomics The cognitive ergonomics studies the throughput and storage of information. Problems occur when the offered information is difficult to interpret. Products that support this domain in ergonomics can be schemes of structures, mnemonic devices (memory aids), software to control a process and training devices. Physical Ergonomics The physical ergonomics studies the functions of the human musculoskeletal system, such as body shapes and postures, and measures movements and applied forces. An example is that problems occur when the position of the surgeon differs from the ergonomically optimal position. This can lead to irritations or injuries. On the product side, this covers products that support the body (e.g. chairs), tools (especially their handles) and special outfits [40].

SURGERY This section describes the people in the OR, the two main surgery types and the OR environment during surgery.

People in the Operating Room

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During surgery several persons are involved, all with their own profession, tasks and responsibilities. Although both sexes represent the medical staff, from this point forward they are referred to as ‘he’.

Figure 5. People in the operating room.

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Patient The main person during the surgical procedure is the patient, who has no active role. When the patient enters the OR the anesthetist will bring him under complete, regional or local anesthesia. After that, the nurses and assistant place him in the correct position, which differs for each surgery. The patient is covered with sterile sheets except for the part that will be operated on. This part is cleaned thoroughly. Surgeon The surgeon, also called operator, leads and is responsible for the surgery. Usually the surgeon is specialized in a specific discipline (e.g. gynecology, orthopedics, general surgery, cardio, etc.). Assistant / Resident / Intern The assisting surgeon can be another surgeon or resident. A resident is a graduated medical student, who attends and assists during surgeries for a period of time (at least five years in the Netherlands). After this period he becomes a surgeon and can lead the surgeries himself. The resident learns his profession from the surgeon based on an apprenticeship model, e.g. by watching, assisting and performing surgeries under supervision of the surgeon [74]. Sometimes an intern is present. He is a medical student, without a full license to practice medicine unsupervised. Scrub Nurse The scrub nurse hands over the instruments to the operator, in the sterile field (see Figure 9), during the surgery. He has followed a special education and knows the functions and usage of all the instruments required for surgery and when these are needed. He also prepares the patient and the OR before surgery.

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Circulating Nurse The circulating nurse is also a surgical nurse and has followed the same education as the scrub nurse, or is still following it. The circulating nurse performs all actions in the nonsterile area. He hands over the materials and instruments to the scrub nurse. Anesthetist and Nurse Anesthetist The anesthetist is a specialist, who is responsible for monitoring the patient and administering anesthetics, drugs, fluids and blood. He also monitors the heart rate, oxygen level and the patient’s temperature. He is not always present during the whole surgery, because in some hospitals he takes care of more patients at one time. In his absence, the nurse anesthetist takes care of the patient. Remaining Persons Depending on the procedure several additional persons are present, such as perfusionist, radiology staff, pathology staff, researchers and guests.

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Types of Surgery At present there are mainly four types of surgery (Table 2): conventional open surgery, hand-assisted surgery, small incision surgery and minimally invasive surgery (MIS). This chapter will focus on open surgery and MIS. Table 2. Taxonomy of abdominal surgical techniques [88] Direct visual observation

Indirect visual observation via the endoscope Hand assisted (laparoscopic) surgery

Direct manipulation

Open surgery

Indirect manipulation via instruments

Small incision surgery (small incision by which the operating field can be seen)

(small incision makes it possible for the hand to touch the operating field)

Minimally Invasive Surgery (MIS)

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Conventional Open Surgery During open surgery a large incision in the patient’s body gains direct access to the tissue and organs. The surgeons can feel temperature, shape, structure and consistency of the tissue and can touch the organs in a natural way by means of his gloved hands [89; 110]. Besides this ‘natural’ haptic feedback, the surgeon has direct vision on the operating field and his movements are less restricted than during Minimally Invasive Surgery [89]. In addition relative simple and intuitive instruments are used [89]. Minimally Invasive Surgery (MIS) MIS, also called endoscopy or keyhole surgery, is performed trough small incisions in the skin or through the natural openings of the human body. The first laparoscopic procedure (MIS in the abdomen) was performed by a general surgeon Philippe Mouret in France in 1987 [30; 63]. This breakthrough changed modern surgery rapidly and definitely and now laparoscopy is a popular technique. Already in 1999 in the United States, 47% of the general procedures were performed by means of laparoscopy [52]. Nowadays, the laparoscopic gallbladder removal has become the golden standard for the surgical management of gallstone disease and is performed in more than 95% of the cases [30; 59; 63]. Over the last two decades MIS has become popular due to the advantages for the patient compared to open surgery, such as less exposure to surgical and cosmetic trauma, less pain after surgery, shorter recovery time, better cosmetic results and less liability for contamination due to small incisions [30; 81; 97]. However, there are also disadvantages, partly because the OR layout and apparatus and equipment did not chance accordingly (Table 3).

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L. S. G. L. Wauben, A. Albayrak and R. H. M. Goossens Table 3. Problems and challenges of MIS [2; 26; 48; 63; 81; 82; 89; 97; 108; 111] ƒ ƒ ƒ ƒ ƒ ƒ ƒ

Higher operating complexity Longer operative time Longer turnover time More facilities, instruments, equipment More disturbances More people in the OR More training

ƒ ƒ ƒ ƒ ƒ

Higher medical costs of surgery Less tasks for the scrub nurse Surgeons more dependant on surgical team More technology demanding and dependant Poor ergonomics

MIS Procedure During the open approach of a laparoscopic procedure first the abdomen will be inflated with carbon dioxide gas by means of an insufflator. This creates more space in the abdomen and provides a good view of the internal organs. Then a trocar is inserted (Figure 6). In order to look inside the patient’s body an endoscope is used (Figure 7). The endoscope is an optic with a system of lenses and a light source. The endoscope is mounted onto a camera, which projects the image of the abdomen on a monitor screen. Finally, at least two additional trocar ports are placed for the insertion of long, thin instruments used to manipulate the tissue inside the abdomen (Figure 8).

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Figure 6. Trocars.

Figure 7. Endoscope.

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Figure 8. Laparoscopic procedure.

The Operating Room Environment The OR can be divided into three working areas (Figure 9):

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1. The sterile field, within the operating area, is mainly around the operating table, which is mostly placed in the center of the room underneath a clean airflow (laminar flow). This is the working area of the surgeon, assistant and scrub nurse. The field is sterile from waist up to the surgical team’s breast. 2. The anesthetic area is at the patient’s head, which is the working area of the anesthetist and nurse anesthetist. This area is usually separated from the sterile area with a drape. The equipment, such as anesthetic, airway, monitoring, registration, and safety equipment, are placed here. 3. The non-sterile field includes the remaining part of the OR, in which all other team members work.

Figure 9. Operating room during a minimally invasive procedure.

Lighting Many ORs do not have daylight [66]. Therefore, artificial lights are present in the OR: 1) environmental lights, which are used for lighting the whole OR and mainly the anesthetic area, and 2) surgical lights to illuminate specific areas in the operating field. Neon lighting and halogen lights mounted in the ceiling produce the environmental lights. Based on the Dutch basic quality regulations from the board of ‘Hospital facilities’ the nominal illuminance in the OR produced by the environmental lights should be approximately 1000 lux. It is expected that each surgery requires its own lighting conditions. The quality and intensity of lighting on the operating field are the main visual ergonomic considerations [9].

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A recent study showed that most of the hazards related to surgical lighting are due to insufficient illumination of the operating field, especially during dangerous situations [66].

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Temperature and Air Condition Both ambient temperature and air condition are important in the OR, as inadequate values could lead to bacteria growth, patient’s hypothermia, discomfort amongst the team members, and airborne infection risk (via inhalation or settling on a susceptible area) for all people in the OR [23; 34]. The ambient temperature is kept low (20-23ºC) primarily for the team’s comfort. However a study of Matern and Koneczny (2007) showed that 18% of the participating surgeons experience the ambient temperature as too cold, 25% too warm and only 31% as comfortable [66]. In order to prevent infections and contamination, high-quality ventilation, heating and air conditioning system are present in the OR to guarantee and control the quality and airflow as the airborne route is the most important and consistent route of contamination of the patient’s skin at the wound site (98% of bacteria in the patient’s wounds after surgery came directly or indirectly from the air)[23]. The features of the OR airflow system for health protection are: ventilation, air distribution, room pressurization and filtration. The higher the ventilation, the lower the concentration of airborne contaminant, which includes bacteria and anesthetic gas [23]. Although there are design standards for proper air-conditioning and ventilation schemes for ORs, it still can be a complex issue. One of the major sources of airborne contamination is the surgical team, their surgical gowns and their level of conversation [24; 51]. However, equipment, such as surgical lights, also contribute to the contamination risk due to obstruction of the airflow [24]. Crowding ORs were originally designed for open surgical procedures and its lay-out has changed little over the last 100 years [4; 38]. The introduction of MIS procedures in the OR has led to the proliferation of monitors, insufflators, camera control units, light sources, cables, cords, tubing, insufflators, foot controls, documentation devices and other equipment, mostly placed on wheeled instrument towers. These towers have to be wheeled into position, or even into the OR, and equipment has to individually placed and connected. In addition, extra personnel are needed. In total, this requires 10% more floor space compared to open surgery [2]. As the ORs were not designed to accommodate all these new technologies, their space is overwhelmed [4]. Adding connecting the cables, cords and tubing creates potential mechanical, electrical, biological and occupational hazards to the patient and the surgical team [9]. Also it leads to inefficiency on the OR use, longer operative times, longer turnover times and greater wear and tear of the mobile equipment. [2; 48; 111].

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ERGONOMICS IN THE OPERATING ROOM With the introduction and widespread acceptance of MIS, ergonomics has acquired increased importance [57]. The division of ergonomics into physical, cognitive and sensorial is also applicable during both open surgery and MIS. This section will describe the major ergonomic problems encountered during surgery (Figure 10).

Figure 10. Overview ergonomics during surgery.

Sensorial Ergonomics

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As most of the sensorial problems are seen during MIS, this section focuses on MIS procedures.

Vision During MIS, the surgeon has indirect vision, and indirect control, on the internal organs. The image of the internal organs captured by the endoscope and camera is projected on a monitor, and therefore limiting the visual feedback [110]. This is a disadvantage for the surgeon, because the normal 3D vision is replaced by a 2D image, which makes accurate spatial orientation and the ensuring maneuvers very difficult [38; 65]. The surgeon’s perception and performance is affected and errors can occur due to misinterpretation and/ or false perceptual information of the video images rather than errors in skill, knowledge or judgment [90; 106]. Another disadvantage working with an image displayed on a screen is that this image is not aligned with the operating field. Therefore coordination problems during movements can occur. The lens of the endoscope sometimes becomes unclear due soiling of the lens (e.g. fog, smoke, blood). This requires extra cleaning and could lead to a longer operative time because the endoscope has to be retracted, cleaned (mostly with warm saline solution) and reintroduced in the trocar each time. It occurs 0-10 times per procedure and is considered annoying [84]. Other factors influencing the view are: unintentional movements of the endoscope by an in-experienced camera assistant [38], obstruction of the sight on the monitor by other persons or equipment, and inadequate angle of incidence on the monitor (causes mainly problems with flat screens).

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Haptics Haptics are the combination of tactile perception (through the skin receptors, sensing pressure, vibration, and texture) and kinesthetic perception (through muscle, tendons and joints sensing position, movement and forces)[110]. Lack of good haptics endangers patient safety, e.g. instruments could damage tissue or organs by grasping too hard [96; 103]. The instruments used during MIS reduce haptic feedback considerably [32; 110]. The tactile feedback is eight times lower than of bare fingers [32]. Several other factors also interfere the haptic perception [89; 110]: 1. Friction between the trocar and the instrument shaft [26; 89]. 2. Resistance of the abdominal wall during a lever movement. 3. Scaling and mirroring tip forces, ranging from 0.2 to 4.5 times the force generated by instrument tissue contact. 4. The instrument’s mechanism differs per instrument. ƒ ƒ ƒ

Distortion and loss of force transmission, up to 50% [8]. Not a constant force transmission, uncertainty about the grasp force exerted on the surgeon’s hand when using the same operating force. Lower mechanical efficiency than open instruments [8; 10].

5. High velocity of translation movements, big angle of tilt and an inefficient-accurate mechanical mechanism causes reduced haptic sensation. Although some product solutions are available, still the instruments do no have full haptic feedback comparable to open surgery.

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Foot Pedals During surgery, mostly foot pedals are used to operate devices for coagulation, suction and irrigation [105]. Diathermy is used to separate tissue and small vessels. There are two methods (each with two speeds) to reach this transformation of tissue: High Frequency electro surgery (HF) and Ultrasonic Dissection (UD), which uses ultrasonic vibrations. The pedal placement of the UD is opposite from the placement for HF (Figure 11). Both types can be used during a procedure. The foot pedals cause sensorial problems [64; 67; 100; 105]: ƒ

ƒ

The surgeon has no direct view of the pedals, because these are on the floor under the operating table, which is covered with sterile sheets in weak light (especially during MIS). The pedals get lost and this increases the risk of hitting the wrong pedal, which is annoying and potentially dangerous for the patient. The pedals can move unintentionally farther under the operating table, so that the surgeon loses contact with the pedal and has to look down to restore the right position of the foot.

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Figure 11. Pedal placement for diathermy.

Cognitive (Perceptional) Ergonomics

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During surgery the surgeon has to execute a primary and a secondary task (Figure 12). However, the surgeon only has a limited amount of mental workload [21]. In addition, parallel tasks require attention to several things and time pressure and stress makes completing several tasks even more difficult [21; 92]. Therefore product design, instruments and training should reduce the mental workload required to maintain acceptable performance levels in the primary surgical task. Design features should be included that reduce the amount of time the surgeon must hold information in working memory prior to its use, and reduce the non-essential, error-prone mental operations that surgeons must perform [21].

Figure 12. Simplified procedure during surgery (adapted from Carswell 2005).

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Indirect Vision In contrast to open surgery, in which the surgeon has a direct view on the operating field, during MIS there is no direct vision, no realistic view of the operating field. This can cause cognitive problems, such as [3; 18; 38; 43; 87; 89; 107; 108]: 1. 2. 3. 4. 5. 6. 7.

High concentration levels of the surgical team are required. Interpretation of the 2D image of a 3D environment. The view is magnified (which also can be an advantage). Limited, small field of view. Insufficient resolution. Insufficient light. Disturbed hand-eye coordination due to: ƒ ƒ ƒ ƒ

Loss of depth perception. Misallocation of the visual and motor axis. Disorientation instruments (fulcrum effect): mirroring and scaling of the actions. Endoscope is controlled by camera assistant.

8. Movement and rotation of the endoscope due to inexperience, or loss of concentration of the camera assistant.

Miscellaneous The foot pedals also cause cognitive problems [64; 67; 100; 105]: ƒ ƒ ƒ

The left and right pedals are identical and the surgeon has to look down to see which pedal he is pushing. Restoring contact with the appropriate pedal interrupts the surgeon’s concentration. The interpretation of the pedals’ function and use is not intuitive.

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Changing instruments and repositioning within the abdomen also poses a safety risk to the patient, because it disrupts the flow of the procedure, which can break the surgeon’s concentration [67; 69]. In addition, the indirect control over the position and orientation of the endoscope could lead to disorientation and misinterpretation of the position of the target organs [38].

Behavior A model to describe human behavior is the model of Rasmussen. In this model three different levels can be distinguished: skill-, rule-, and knowledge based behavior. Skill based behavior is the human behavior that takes place without conscious control. The task execution is highly automated and is based on fast selection of motor programs, which control the appropriate muscles. Many tasks in surgery are a sequence of skilled acts (e.g. suturing). During skill-based behavior the sensory information is seen as continuous signals. This behavior can be trained by means of a training in for instance a surgical simulator, pelvitrainer and animal models [109]. During MIS the surgeon’s skills are hampered, because of the reduction of haptics and the absence of extended kinesthetics, which is needed to achieve motor skills. These motor skills are also hampered by the

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limitations of the instruments (reduced degrees of freedom) and the missing eye-hand coordination and have to be learnt by intensive training to perform a successful surgical procedure [89]. Factors that improve skill-based behavior are active or passive feedback of the instrument’s forces and increasing the number of degrees of freedom (DOF) comparable to the functions available during open surgery [89].

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Figure 13. Three level behavior model (adapted from Rasmussen 1983).

During rule-based behavior task execution is controlled by stored rules or procedures, which have been derived from previous cases, other people’s expertise and instructions. Examples of rule-based behavior during surgery are the procedural steps and the recognition of anatomy and pathology. During rule-based behavior the information is seen as discrete signs, which serve to trigger or activate a stored rule. This behavior can be trained and improved by means of lectures, textbooks, video instructions, integration of per- and preoperative information and better logistics [89; 109]. During MIS the rule-based behavior can be improved by means of improving the dept perception (e.g. improving pictorial information, parallax and visuomotor cues) and enabling the surgeon to control the endoscope himself [89]. In unfamiliar, new situations and unexpected events human behavior is knowledge based. During this behavior, which cannot be automated, the aim is explicitly formulated, based on the analysis of the overall aim [89]. Then the best strategy is selected, by means of mental processing and the appropriate actions are taken. At this level the information is perceived as symbols, referring to chunks of conceptual information. During MIS the four major knowledge-based behavior activities are [89]: ƒ ƒ ƒ ƒ

Transformation of the coordinate system of the endoscope and the instruments. 3D reconstruction and the remembrance of 2D CT and MRI pictures. Interpretation of pre-operative images in relation to the endoscope’s image. Interventions needed during unexpected events.

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Knowledge based behavior can be trained during actual procedures in the OR or via living animal models outside the OR [109]. During MIS, solutions such as augmented reality and a 3D endoscope could take away a lot of mental burden, leaving the surgeon the cognitive data processing capacity for the real task [89].

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Training of Technical Skills Technical skills, which involve knowledge of anatomy and pathology, dexterity, handeye coordination, technical proficiency, etc is essential to surgical training [29; 74; 85]. In order to perform MIS the surgeon needs highly developed motor skills [63; 67]. In the past motor skills for open surgery were learned in the OR directly on the patient, by means of the apprenticeship model. However, although this method is effective it may be inefficient, costly, and may endanger patient safety [85]. Also, this method could not accommodate the new skills required for MIS [1]. Therefore, basic (and also intermediate) MIS skills are also being trained before-the-job in addition to on-the-job, replacing the actual patient by bench models, Augmented Reality simulators and Virtual Reality simulators [57; 85]. Advantages of the simulated environments are that objective assessment and direct feedback during training can be given to the trainee, these are safe, reproducible, readily available, offer unlimited practice and require no supervision [17; 74; 85]. In this way novice surgeons can progress along the early part of the learning curve before entering the OR and improve their performance in the OR [1; 85]. However, simulation programs are to be seen as an adjunct to traditional methods of training, and not as an alternative [1]. Non-Technical Skills The surgical team is a dynamic multi-disciplinary team, consisting of staff and trainees [46; 60; 94]. To perform safe surgery, the surgical team has to depend on their technical and non-technical skills [74; 116]. Non-technical skills are the important cognitive and interpersonal skills (such as communication, situational awareness, teamwork, decisionmaking, etc.) of experienced professionals, which are a supplement to the technical skills [95]. Literature shows that many underlying causes of errors originate from non-technical aspects rather than a lack of technical expertise [29; 47; 72; 86; 116]. This is comparable to other high-risk industries such as aviation, where 70% of commercial flight accidents are caused due to communication failures among the crewmembers, rather than technical malfunctioning of the airplane [47; 58]. Wrong side, wrong procedure, wrong person and wrong doses of medication are some examples that contribute to the inadvertent patient harm. These and other medical errors are partly caused due to malfunctioning of the surgical team and errors in teamwork, leadership, decision-making, situational awareness and communication [47; 58; 61; 86; 116]. The information transfer between the surgical team members differs from case to case and team to team; information transfer is non-standardized, non-inclusive and poorly integrated in the OR procedures [6; 58; 60]. In addition, the performance in the OR is relatively non-standardized compared to other high-risk industries [42; 60]. Non-technical skills are increasingly recognized in literature and it is stated that improving these skills could reduce the number of errors during surgery and therefore improve patient safety [6; 45; 46; 47; 58; 72; 86; 95; 116]. Ergonomics could support these non-technical skills with several solutions. Figure 14 provides some examples.

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Figure 14. Ergonomics solutions for supporting non-technical skills.

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Protocols, Checks and Checklist Protocols A protocol is a formal set of guidelines usually consisting of actions to be performed, leading to a specific end result [104]. Consequently, the availability of a uniform, standardized protocol such as those used in other technical high-risk fields (e.g., aviation, nuclear industry, oil industry) would be advantageous for patient safety [31; 55]. As discussed before, patient safety also depends on effective teamwork. An uniform standardized protocol could contribute to the shared understanding of the roles of the entire surgical team, their tasks, and objectives throughout the surgical process as well as enhancing surgical education and training. Furthermore, owing to the fast growth of MIS techniques accompanied by the increased use of more complex apparatus and instruments, technicians are no longer a supplier of equipment but represent an important source of information [2; 25; 38; 101]. Because technical principles from industry play a substantial role in improving medical treatment, a major point of interest is the implementation and integration of technical quality systems in health care [104]. Present surgical protocols differ too much to be transferable, which if tried would lead to a lack of clarity [104]. Although the influence of the lack of a uniform standardized protocol has not been determined scientifically for surgery, in the sense of a greater incidence of poor outcome, this lack of standardization in general and its influence has been proven in other high-risk industries. Already in health care, several associations use protocols and guidelines for clinical decision-making, for facilitating relevant training of the surgical team, and as support for maintaining professional standards in daily practice [55; 112; 113; 115]. One of the merits of standardizing the surgical process in general and individual protocols in particular, is improved communication among members of the surgical team and between physicians and technicians by avoiding confusion with regard to the procedure’s technical details (tasks and direction). Furthermore, ‘man–machine’ interaction (communication between team members and the instruments and apparatus) can also be improved by using these protocols. Standardization also forms the basis for further use of the

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information and communication technology necessary for digitizing patient data, such as the use of the electronic medical record and the digital operative notes. In addition, one standardized protocol, in combination with increasing surgical experience, can lead to a lower conversion rate during a laparoscopic cholecystectomy [41]. An additional advantage of a protocol is the detailed definition of actions, step by step, serving as a checklist comparable to those used in aviation. Also, without checking each action, the protocol diminishes the possibility of skipping important actions such as control of port-site bleeding after trocar removal during MIS [31; 49; 55]. By including equipment in the standardized protocol, a thorough pre-operative setup can be established, thereby reducing the total operative time (no waiting for missing equipment) [101]. Warnings, instructions, and additional explanations during critical stages during the procedure could contribute to the completeness of the standardized protocol.

Checks The quality of the apparatus and equipment is of great importance for performing a thorough and safe surgery. This is especially the case with MIS where the surgery cannot be performed when the equipment is malfunctioning [22; 25]. A surgery should not be started before the equipment (endoscope, fiber optic cables, light source, camera system, monitor, electrosurgical equipment, insufflator, instrument set, etc) is checked and found to be safe. The surgeon, who is in charge of the surgery, is responsible to start with this equipment. Besides checking the equipment, some other factors have to be checked as well [70]: ƒ

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ƒ ƒ

Control of surgical skill, acquaintance with basic techniques and measure at regular intervals. Control of technology, keeping abreast of the latest technology. Control of surgical technique, following surgical techniques (protocols).

Checklist In aviation, checklists are the basis for procedural standardization and are employed during critical situations. By using the conscious crosschecking, the checklist is executed, involving two or three crewmembers. The checks act both to ensure proper functioning of the individual performance as well as the plane’s performance [31; 44]. Checklists can also be used during the pre-operative, intra-operative and the postoperative phase of surgery to check, for instance, the presence of the required equipment, the ergonomic setup, the establishment of the ‘Critical View of Safety’ during laparoscopic cholecystectomy, the number of equipment on the instrument table after surgery, etc. The checklist can be used to safeguard the quality of a surgical procedure. In addition, due to the use of a checklist, the surgical team is aware of the status of their actions, the status of the instruments and the surgery [101].

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Briefing / Time Out

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A way to improve patient safety, by reducing the number of incidents/errors during the intra-operative process, and improve teamwork and communication in the OR is a briefing before surgery. This briefing, also called ‘time out procedure’, enables the team members to get a shared mental model of the situation, cross check important steps, check the availability and safety of instruments, avoid surprises and positively affect how the team works together [29; 58; 61; 86; 101]. Now, there is a considerable discrepancy in perception on teamwork between the team members. Where physicians rate the teamwork as high, nurses perceive teamwork as mediocre [62; 91]. The Joint Commission on Accreditation of Health Care Organizations developed a first version of a standardized time out procedure in 2004. They introduced the Universal Protocol to prevent wrong site, wrong procedure and wrong person surgery [62]. Additional steps can be added to complete the verification (Figure 15). The different colors in Figure 15 represent the different team members asking a question. This way, task and responsibilities are added to the time-out, which can also improve active communication and teamwork. The time-out is conducted in a ‘fail-safe’ mode, i.e. the procedure is not started until any questions or concerns are resolved.

Figure 15. TOPplus: Time Out and Debriefing (designed by LSGL Wauben & CM Dekker-van Doorn).

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Also a debriefing (after surgery) contributes to patient safety. This procedure takes only a few minutes during which the surgery is discussed and evaluated: ‘what went well’, ‘what were the challenges’, ‘what to do differently’ [29; 58; 61; 86]. The purpose is to summarize the incidents, interventions, and actions taken and evaluate the structured communication during the intra-operative phase of the procedure.

PHYSICAL ERGONOMICS A lot of research is focused on improving instruments and devices on ergonomic aspects (e.g. preventing damage to the staff’s health and preventing complications for the patient). The aim of the equipment is to enhance the work of the surgical team [7; 56]. However, this is not always the case in the OR environment. Both open surgery as well as MIS cause physical problems for the surgical team members. This is partly caused by products used in the OR. The following section emphasizes on the operating table, monitor, instruments, foot pedals and on the surgeon’s posture.

Operating Table

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The operating table (Figure 16) supports the patient during surgery. The table can be adjusted in height and can also be rotated. Because currently available operating table were designed for open surgery the height range is not adequate for MIS, mostly too high [15; 68; 99; 105]. Most surgeons prefer the table to be lowered more in relation to the currently available operating tables [105]. The table height (= distance from the table top to the floor) depends on different factors [68], such as the surgeon’s stature, angle of the elbow joint, handle type of the instruments used, working angle of the instrument in the patient’s body wall, and height of the patient’s (inflated) body wall. Industrial ergonomic design recommendations state a working height of 5 cm below elbow height, with an acceptable range of 12.5 cm below to 2.5 cm above elbow height for normal working circumstances. However, these recommendations are not sufficient for MIS, because of the great length of the endoscopic instruments [15].

Figure 16. Operating table.

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Figure 17 shows the optimal height range of the operating table during open en MIS. For open surgery the height should range from 73 to 122 cm. Present operating tables meet this range [4]. The optimum table height for MIS is lower than for open surgery, ranging from 29 - 69 cm to 122 cm above floor level [15; 64; 68; 97]. The highest position should be maintained because the table and patient are raised to close the trocar sites. Footstools (Figure 18) can be used to level the surgical team and patient, but the standing surface is small and the stools mostly have only one height, which is often not sufficient for the different body lengths. Additional drawbacks are that the stool limits the freedom of movement of the team members, leading to static postures, (Figure 19) and foot pedals are difficult to be placed on [64].

Figure 17. Optimum table height during open en MIS.

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Insufficient adjustment of the table height causes a decrease of freedom and can therefore lead to extreme positions of the upper limb joints and can cause physical discomfort in the surgeon’s upper arms, neck and shoulders [13; 15; 98; 105].

Figure 18. Footstools.

Figure 19. Standing on a stool.

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Static effort should be prevented because it restricts the blood flow to the muscles, leading to the condition of ‘muscular fatigue’. In the short term, mounting discomfort may distract the surgeon from his task, leading to an increased error rate, reduced output and accidents, which can be dangerous for the patient. In the long-term pathological changes in the muscles soft tissue take over, which causes physical injury [80]. The lifting mechanism of the operating table also restricts the standing area (Figure 16). This limits the team members to move their feet freely and causes a static posture. Summarized, the physical problems caused by the operating table are: • • • • •

Extreme abduction of the arms due to the height. Ulnar deviation of the wrist due to the height. Raised shoulders due to the height. Abduction of the upper body due to the width. Static body position due to the presence of the table foot (and possible footstools).

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Monitor Placement and Height During MIS, the view of internal organs and tissue is projected on a monitor. There are different types of monitors; flat screens (LCD’s and plasma), regular CRT (Cathode Ray Tube) monitors or projection of the image on a screen [20]. The CRT monitors are mostly used, 80% versus 19% flat screen and 1% projection screens. [4; 105]. Nevertheless, flat screen and HDTV (High-resolution Digital Television) are introduced in the OR. Flat screens have some disadvantages such as less brightness, lower resolution, limited color fidelity and a smaller viewing angle, but the visual quality of flat screens is improving very fast [19]. Advantages of a flat screen are its thinness, lower weight, higher contrast and the possibility to place the monitor in the surgeon’s line of sight. Furthermore, in a comparative study on two display systems, 92% of the subjects preferred the use of flat screens [98]. Advantages of HDTV are higher brightness and more detailed picture compared to CRT monitors. However, its price and the incompatibility between standard and HDTV formats (making it necessary to replace all OR video systems) is a major disadvantages [90]. Most of the monitors are currently placed on an instrument tower (71%), versus 19% on a moveable arm with height adjustment and 10% on a moveable arm without height adjustment (Figure 20) [4; 105]. The instrument tower restricts an adequate position and height of the monitor. Besides the sensorial and cognitive ergonomic disadvantages, the monitors used during MIS also cause physical problem. As already discussed, the image display and the operating field are not the same. During the placing of the trocars, the surgeon has a higher frequency of neck flexions, because the operating field is not aligned with the monitor. This can cause physical discomfort [76]. During the actual surgery, the position of the monitor is fixed and therefore the surgeon has significantly fewer lateral neck flexion movements compared to open surgery, because he only has to look straight in front, leading to a static neck posture. [76]. An advantage of using a video camera and monitor is that the muscle strain and fatigue resulting in a lower frequency of back pain for the surgeon is considerably reduced. Furthermore, the monitor offers the opportunity for the complete surgical team to participate visually, which improves attention and training possibilities [65].

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Figure 20. Monitor on an instrument tower.

The monitor position and height influences the surgical team’s posture and can cause physical discomfort in the neck [105]. To prevent neck torsion, fatigue, musculoskeletal disorders and psychological discomfort, the monitor should be placed at an ergonomic position. There are different guidelines for the placement of the monitor at an ergonomic position. These all suggest that monitors should be placed straight in front of the viewer, but these differ on the height placement: •

•

Placing the monitor so that the posture is neutral: this means without torsion of the back and neck and with the head slightly flexed at an angle of 15 – 45º to the horizontal, shown in Figure 21 [33; 65; 93; 97; 98; 102]. Placing the monitor at the level of the manipulation workspace (hands), permitting gazing-down viewing, and alignment of the visual and motor axis. This way the visual signals correspond with instrument manipulations, similar to the situation during conventional open surgery. This makes orientation easier in the operating field in case difficult movements have to be performed or technical problems occur. It also reduces the task time and the number of errors. [65; 77]

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Figure 21. Ergonomic viewing angle (adapted from Pheasant 1996) .

When several monitors are used, these should be placed in such a position that they do not obstruct the view of the other team members. Summarized, the physical problems caused by the monitor position and monitor height are: • • • • •

Static body position. Extension of the neck. Torsion of the neck. Flexion of the neck. Abduction of the upper body to look about the assistant / surgeon.

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Instruments During MIS, four instrument groups are used besides the endoscope [98]: 1) instruments for the active manipulation of tissue: graspers, dissectors, and scissors, 2) instruments for electro surgery, 3) instruments for suction and irrigation, and 4) instruments for automatically suturing tissue (e.g. staplers). The instruments cause several physical problems: • •

Only a limited degrees of freedom (DOF): only five DOF during MIS in contrast to seven DOF in open surgery [38; 89]. Due to the length of the instruments and the fixed insertion point, the surgeon has to use large envelopes of motion to direct the instrument to the desired location within the patient. During these non-ergonomic motions the upper limb position is awkward and can lead to increased muscle fatigue and degradation of performance [8; 35; 67; 78; 93]

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•

•

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Changing instruments and repositioning within the abdomen are cumbersome and time-consuming tasks, because of the need to introduce the instruments through the trocar [67; 69]. Mainly the difference in efficiency of force transmission from handle to tip, require that the surgeon has to exert substantially higher muscle forces using MIS instruments compared to open instruments. The MIS instruments also require significantly greater peak and total muscle effort of the surgeon’s forearm and thumb, leading to additional fatigue. Surgeons experience more awkward wrist movements during MIS (wrist supination, ulnar and radial deviations) [8; 12; 35; 76; 93].

Handles The handle is the interface between the surgeon and instrument. The instruments’ handles have been designed with a single size for all surgeons and for multitasks. The contact surfaces, that are relatively narrow, the handles’ shapes (Figure 22) and the movements do not correspond with anatomic features of the surgeon’s hand. As a result there is often a mismatch between the instrument-hand interface. The nature of the handle and its associated activation mechanism has an influence on joint movements, muscle recruitment, and muscle fatigue in the upper arm. In turn, these factors impact on the surgeon’s comfort level, the execution speed, and the quality of task performance. Excessive pressure on sensitive areas of the palm and fingers can cause temporary nerve injuries. [8; 10; 35; 36; 97; 98]

Figure 22. Schematic overview of types of handles: A) Angled ring handle, B) In-line handle, double action hinged, C) In-line handle, single action hinged, D) Angled handle, lever manipulated (vertical), E) Angled handle, lever manipulated (horizontal).

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Summarized, the physical problems caused by the instruments are: • • • •

Large envelopes of motion of the arms. Extreme movements of the wrist (ulnar deviation, flexion, extension and supination). Compression of the nerves of the hand. Rotation and abduction of the upper body in order to control the instruments.

Foot Pedals Besides the sensorial and cognitive problems the foot pedals also cause physical problems [105]. There are several problems with the foot pedals [64; 67; 100; 105]:

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• •

During the procedure, the surgeon keeps one foot flexed above the pedals and loads the body weight on the other foot, to prevent losing contact with the right pedal. This is physically exacting and demands a high concentration level, which could lead to physical discomfort. The pedals obstruct the surgeon’s freedom of movement. It is difficult to switch the surgeon’s side of the patient during surgery. The circulating nurse has to move the pedals across the operating table.

Due to these problems, many surgeons would like to control the diathermy in another way (e.g. hand-control, voice control, infrared navigation, device in shoe) [100; 105]. Summarized the physical problems caused by the foot pedals are: • • •

Flexion of the foot. Discomfort in legs and feet. Presence causes static body position.

PHYSICAL DISCOMFORT

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Maintaining good posture, and limiting physical discomfort, is absolutely essential for good surgical performance and outcome [57]. Physical discomfort occurs when the team members’ positions and movements differ from the ergonomically optimal positions. These positions should be within the neutral zones of the joint excursions (Figure 23)[97]. Also static postures should be avoided. Small pauses and posture changes can prevent physical complaints in the short term and damage in the long term. During the pauses, the muscles can relax and the blood flow can be restored, oxygen can be transported to the muscles and waste products be transported away. These pauses also allow the joint to be lubricated again.

Figure 23. Neutral zones of the joint excursions [97].

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Open Procedures

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During open surgery the surgeon stands and sometimes sits in different postures all the time (Figure 24). He is constantly looking at the operating field at different angles, standing one foot or the other and / or leaning against the operating table. Occasionally, the operating field is too far away from the edge of the table, therefore the surgeon has to lean over or on the patient [5]. Also when the operating field is perpendicular to the edge of the table, the surgeon has to rotate and lean against the table or patient. The surgeon’s posture is characterized by a head-bent and back-bent posture [5; 13]. Occasionally substantial forces on tissue have to be exerted, influencing the body posture [9]. The assistant has to stand in awkward positions. Flexion of the neck and abduction of the upper body occur almost all the time. However, prolonged and repetitive use of muscle groups should be avoided, because it could lead to several injuries, such as carpal tunnel syndrome, repetitive strain injury, and cumulative trauma disorder [81].

Figure 24. Postures during open surgery.

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The line of vision can also be obstructed by other team members hands or bodies, leading to back and neck torsion and flexion to allow clear vision of the operating field [39]. Although the duration of extreme postures is only short, the team members have to maintain their postures for long periods of time, which results in physical complaints, such as pain in lower back and neck, and stiffness of shoulders [37; 54; 71].

During MIS

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Most factors causing physical discomfort during MIS were already discussed in previous paragraphs: height of the operating table, position and height of the monitors, use of instruments and the use of the foot pedals. However, there are more factors contributing to physical discomfort, which will be discussed in this section. The surgeon’s body posture during MIS differs from the posture during open surgery (Figure 25). The surgeons have a higher frequency of internal rotations of the shoulder during MIS than during open surgery and tend to hold their trunk very still with fewer abductions of the upper body while concentrating on the monitor [76]. Surgeons and scrub nurses exhibit repeated static postures characterized by the head bent forward (54% of the time) and the back twisted and bent (27% of the time) which they see as ‘distinctly harmful’ postures [5; 9; 13].

Figure 25. Postures during MIS.

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Additional discomfort with potential risks for musculoskeletal injury and muscular fatigue are pain and stiffness in neck, back, shoulders, eyestrain, wrist flexion and extension [10; 38; 76; 79; 105]. One of the injuries is the so-called ‘laparoscopist’s thumb’ in which the nerves of the thumb and thenar are damaged [14; 102]. The position in Figure 26 is considered ideal for the MIS surgeon [67]. The arm is slightly abducted, retroverted, and rotated inward at shoulder level. The elbows are bent at about 90–120º, the wrists are slightly extended and the hands are completely relaxed. In this position the most force can be applied. The head is slightly flexed with an angle between 15– 45º, or even better, different head postures between these angles [64].

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Figure 26. Ideal posture for MIS surgeon.

Whenever possible, MIS surgeons should strive to place their instruments and trocars at a position that minimizes extreme horizontal or vertical displacement of their hands away from a resting position of comfort [11].

AWARENESS There are many products and even specially designed OR’s available on the market to reduce physical discomfort, such as several kinds of footstools, chairs and crutches, body supports, arm supports, equipment and monitors on ceiling-mounted booms and voice controlled devices, [5; 78]. However, although most members of the surgical team state that ergonomics in the OR are important, only few are aware of ergonomic guidelines concerning placing of the equipment and apparatus and of ergonomically correct postures [105]. This

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unawareness of ergonomic guidelines is a major problem that poses a tough position for the ergonomics in the OR. This leads to that most of the time, equipment is used in its initial position, and although possible, it is not adjusted according to the ergonomic guidelines for better comfort. A first step is to improve the awareness. Only then ergonomically designed product can be used to its full benefit. Figure 27 gives an example of ergonomics guidelines for MIS.

Figure 27. Ergonomic guidelines for MIS (designed by LSGL Wauben).

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CONCLUSION Ergonomics is aimed to adapt the environment and its products to its users. The overview in this chapter shows that there is a gap between this aim and reality in the OR. In general the classical ergonomic domains are: sensorial, cognitive and physical. All these domains need to be addressed in the design of products and processes, however the focus can be different in each case. When looking into the field of ergonomics in the OR most scientific research and product development is conducted within physical ergonomics. With the discipline OR ergonomics maturing, more difficult problems are researched. Within the domain of physical ergonomics effort is put into restoring the originally enjoyed level of surgical movement in the OR environment. However, this OR environment is changing drastically, from ORs designed for open procedures solely, to specially designed surgical suites focusing on MIS and / or robotic surgery. More and more technology is incorporated in the OR, making it a more complex and high-risk environment, comparable to environments as aviation, oil and nuclear industry. Therefore, when designing products and processes, valuable lessons can be learned and applied from these industries.

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As a result a new domain is added, the environmental ergonomics. Factors as climate, lighting, color, and noise level, etc. contribute to both the well being of the medical staff and patient. In hospitals ‘healing environments’ are introduced to make the patient less nervous and stressed. These environments are quit, have natural daylight, fresh air, use of color and convenient logistics are introduced. In the OR, equipment is hanging on booms, reducing the amount of cables and wiring, special surgical lights based on Light Emitting Diode (LED) technology are introduced producing a more natural light color, etc. Surgery as a discipline has a proud history of science and tradition, with changes being gradual and usually with consensus. However, surgical procedures are also evolving fast to more and more complex procedures. Future research, product development and redesign will focus on these more complex surgical procedures, which require even more advanced technology. These advanced technologies should be harnessed to optimize surgical practice by rethinking and re-applying technology that currently exist in a manner that is more systematic and better managed, and a reconsideration of who should be applying these technologies for the practice of the surgery of the 21st century. Still MIS causes ergonomic problems, leading to higher complication rates and considerable frustration for some surgeons. Still some surgeons have great difficulty to learn these skills or are unable to learn these. Ergonomics should strive to facilitate to learn and finally perform MIS. Performing MIS procedure should be as intuitive as performing open surgery. In order to do so, within MIS several areas will be researched and developed: robotics, 3D vision, haptic instrument feedback, information systems, realistic training possibilities, etc. New surgical approaches as NOTES (Natural Orifice Translumenal Endoscopic Surgery) are entering the OR. This new type of surgical procedure is currently being studied at research hospitals and facilities around the world, aiming to reduce scaring and recovery time of the patient. New technologies, instruments and equipment have to be designed or redesigned, not only on the physical aspects but also on sensorial and cognitive aspects, making products become intelligent partners of the surgical team. Also the introduction of more computers, displays, digital video equipment, storage capacity, realistic data collection, 3D motion analysis, augmented reality, etc. in the OR causes a shift from physical to more sensorial and cognitive ergonomics. The latter two domains will be merged, finally leading to two domains: the physical and informational domain. The shift to informational ergonomics, focusing more on process and procedures is expected to be similar as the shift that took place in Industry in the early 60-ties. Because of the complexity of future products and processes, design teams have to be multi-disciplinary, consisting of technicians, ergonomists, physiologists, philosophers, medical staff, jurists, software designers, hardware designers, user interface specialist, endusers, etc. They all have to be included and participate in the whole design cycle: from first hunch until prototyping. At the faculty of Industrial Design Engineering at Delft University of Technology we apply this method called ‘Participatory Design’. The chapter ‘Ergonomics in the Operating Room: Design Framework’ will elaborate on this methodology and give some examples. Besides the medical professionals, industry should also be involved to speed up the time to market of products. In the end, ergonomics should make sure that the advances in technology are to facilitate surgery and not to complicate it, because at the sharp end of these technologies lie patients whose well being is the first priority.

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[72] Mishra, A., Catchpole, K., Dale, T., and McCulloch, P. (2008). The influence of nontechnical performance on technical outcome in laparoscopic cholecystectomy. Surgical Endoscopy, 22(1), 68-73. [73] Moorthy, K., Munz, Y., Dosis, A., Bann, S., and Darzi, A. (2003). The effect of stressinducing conditions on the performance of a laparoscopic task. Surgical Endoscopy, 17, 1481-1484. [74] Moorthy, K., Munz, Y., Sarker, S. K., and Darzi, A. (2003). Objective assessment of technical skills in surgery. British Medical Journal, 327, 1032-1037. [75] Moorthy, K., Munz, Y., Undre, S., and Darzi, A. (2004). Objective evaluation of the effect of noise on the performance of a complex laparoscopic task. Surgery, 136, 25-30. [76] Nguyen, N. T., Ho, H. S., Smith, W. D., Philippsb, C., Lewis, C., Verab, R. M. D., et al. (2001). An ergonomic evaluation of surgeons’ axial skeletal and upper extremity movements during laparoscopic and open surgery. The American Journal of Surgery, 182, 720-724. [77] Omar, A. M., Wade, N. J., Brown, S. I., and Cuschieri, A. (2005). Assessing the benefits of ‘‘gaze-down’’ display location in complex tasks. Surgical Endoscopy, 19, 105-108. [78] Patil, P. V., Hanna, G. B., Frank, T. G., and Cuschieri, A. (2005). Effect of fixation of shoulder and elbow joint movement on the precision of laparoscopic instrument manipulations. Surgical Endoscopy, 19, 366-368. [79] Person, J. G., Hodgson, A. J., and Nagy, A. G. (2001). Automated high-frequency posture sampling for ergonomic assessment of laparoscopic surgery. Surgical Endoscopy, 15, 997-1003. [80] Pheasant, S. (1996). Bodyspace; anthropometry, ergonomics and the design of work (Second ed.): Taylor and Francis, London. [81] Reyes, D. A., Tang, B., and Cuschieri, A. (2006). Minimal access surgery (MAS)related surgeon morbidity syndromes. Surgical Endoscopy, 20(1), 1-13. [82] Satava, R. (2004). Disruptive visions. Surgical Endoscopy, 18, 1297-1298. [83] Satava, R. M. (2004). Disruptive visions: a robot is not a machine...Systems integration for surgeons. Surgical Endoscopy, 18, 617-620. [84] Schoofs, J., and Gossot, D. (2004). A neglected but frustrating ergonomic issue: The thoracoscopic trocar. Minimally Invasive Therapy and Allied Technology, 13(3), 133137. [85] Scott, D. J., Bergen, P. C., Rege, R. V., Laycock, R., Tesfay, S. T., Valentine, R. J., et al. (2000). Laparoscopic Training on Bench Models: Better and More Cost Effective than Operating Room Experience? Journal of American College of Surgeons, 191(3), 272-283. [86] Sexton, J. B., Makary, M. A., Tersigni, A. R., Pryor, D., Hendrich, A., Thomas, E. J., et al. (2006). Teamwork in the operating room: frontline perspectives among hospitals and operating room personnel. Anesthesiology, 105(5), 877-884. [87] Shah, J., Buckley, D., Frisby, J., and Darzi, A. (2003). Depth cue reliance in surgeons and medical students. Surgical Endoscopy, 17(1472-1474). [88] Sjoerdma. (1998). Surgeons at work, time and actions of the laparoscopic surgical process. Delft University of Technology, Delft.

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[89] Stassen, H. G., Dankelman, J., Grimbergen, C. A., and Meijer, D. W. (2001). Manmachine aspects of minimally invasive surgery. Annual Reviews in Control, 25, 111122. [90] Szold, A. (2005). Seeing is believing: visualization systems in endoscopic surgery (video, HDTV, stereoscopy, and beyond). Surgical Endoscopy, 19(5), 730-733. [91] The Joint Commision. (2003). Universal Protocol For Preventing Wrong Site, Wrong Procedure, Wrong Person Surgery. Retrieved May 26, 2008, from http://www.jointcommission.org/NR/rdonlyres/E3C600EB-043B-4E86-B04E-CA4A89 AD5433/0/universal_protocol.pdf [92] Traverso, L. W., Koo, K. P., Hargrave, K., Unger, S. W., Roush, T. S., Swanstrom, L. L., et al. (1997). Standardizing laparoscopic procedure time and determining the effect of patient age/gender and presence or absence of surgical residents during operation. Surgical Endoscopy, 11, 226-229. [93] Uhrich, M. L., Underwood, R. A., Standeven, J. W., Soper, N. J., and Engsberg, J. R. (2002). Assessment of fatigue, monitor placement, and surgical experience during simulated laparoscopic surgery. Surgical Endoscopy, 16, 635-639. [94] Undre, S., Sevdalis, N., Healey, A. N., Darzi, S. A., and Vincent, C. A. (2006). Teamwork in the operating theatre: cohesion or confusion? Journal of Evaluation in Clinical Practice, 12(2), 182-189. [95] University of Aberdeen. (2006). The Non-technical Skills for Surgeons (NOTSS). System Handbook v1.2: University of Aberdeen. [96] Van der Voort, M., Heijnsdijk, E. A. M., and Gouma, D. J. (2004). Bowel injury as a complication of laparoscopy. British Journal of Surgery, 91, 1253-1258. [97] Van Veelen, M. A. (2003). Human-Product Interaction in Minimally Invasive Surgery: A Design Vision for Innovative Products. Delft University of Technology, Delft. [98] Van Veelen, M. A., Jakimowicz, J. J., Goossens, R. H. M., Meijer, D. W., and Bussmann, J. B. J. (2002). Evaluation of the usability of two types of image display systems, during laparoscopy. Surgical Endoscopy, 16, 674-678. [99] van Veelen, M. A., Kazemier, G., Koopman, J., Goossens, R. H., and Meijer, D. W. (2002). Assessment of the ergonomically optimal operating surface height for laparoscopic surgery. Journal of Laparoendoscopic & Advanced Surgical Techniques, 12(1), 47-52. [100] van Veelen, M. A., Snijders, C. J., van Leeuwen, E., Goossens, R. H., and Kazemier, G. (2003). Improvement of foot pedals used during surgery based on new ergonomic guidelines. Surgical Endoscopy, 17(7), 1086-1091. [101] Verdaasdonk, E. G., Stassen, L. P., van der Elst, M., Karsten, T. M., and Dankelman, J. (2007). Problems with technical equipment during laparoscopic surgery. An observational study. Surgical Endoscopy, 21(2), 275-279. [102] Vereczkei, A., Feussner, H., Negele, T., Fritzsche, F., Seitz, T., Bubb, H., et al. (2004). Ergonomic assessment of the static stress confronted by surgeons during laparoscopic cholecystectomy. Surgical Endoscopy, 18, 1118-1122. [103] Wagner, C. R., Stylopoulos, N., and Howe, R. D. (2002, March 24-25). The Role Of Force Feedback in Surgery: Analysis of Blunt Dissection. Paper presented at the Haptic Interfaces for Virtual Environment and Teleoperator Systems, Orlando.

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[104] Wauben, L. S., Goossens, R. H., van Eijk, D. J., and Lange, J. F. (2008). Evaluation of protocol uniformity concerning laparoscopic cholecystectomy in the Netherlands. World Journal of Surgery, 32(4), 613-620. [105] Wauben, L. S. G. L., Van Veelen, M. A., Gossot, D., and Goossens, R. H. M. (2006). Application of ergonomic guidelines during Minimally Invasive Surgery: A questionnaire amongst 284 surgeons. Surgical Endoscopy, 20(8), 1268–1274. [106] Way, L. W., Stewart, L., Gantert, W., Liu, K., Lee, C. M., Whang, K., et al. (2003). Causes and prevention of laparoscopic bile duct injuries: analysis of 252 cases from a human factors and cognitive psychology perspective. Annals of Surgery, 237(4), 460469. [107] Wentink, M. (2003). Hand-eye coordination in MIS: Theory, Surgical practice and Training. Delft University of Technology, Delft. [108] Wentink, M., Jakimowicz, J. J., Vos, L. M., Meijer, D. W., and Wieringa, P. A. (2002). Quantitative evaluation of three advanced laparoscopic viewing technologies: A stereo endoscope, an image projection display, and a TFT display. Surgical Endoscopy, 16, 1237-1241. [109] Wentink, M., Stassen, L. P. S., Alwayn, I., Hosman, R. J. A. W., and Stassen, H. G. (2003). Rasmussen’s model of human behavior in laparoscopy training. Surgical Endoscopy, 17, 1241-1246. [110] Westebring-van der Putten, E. P., Goossens, R. H., Jakimowicz, J. J., and Dankelman, J. (2008). Haptics in minimally invasive surgery--a review. Minimally Invasive Therapy and Allied Technology, 17(1), 3-16. [111] Wong, J. C., Yau, K. K., Chung, C. C., Siu, W. T., and Li, M. K. (2006). Endo-Lap OR: an innovative "minimally invasive operating room" design. Surgical Endoscopy, 20(8), 1252-1256. [112] www.acc.org/. American College of Cardiology. Retrieved 6 September 2007. [113] www.guideline.gov/. National Guideline Clearinghouse. Retrieved 6 September 2007. [114] www.iea.cc. The International Ergonomics Association. Retrieved 27 May 2008, 2008. [115] www.sages.org/publications.html#guide. Society of American Gastrointestinal and Endoscopic Surgeons. Retrieved 6 September 2007, 2007. [116] Yule, S., Flin, R., Paterson-Brown, S., and Maran, N. (2006). Non-technical skills for surgeons in the operating room: a review of the literature. Surgery, 139(2), 140-149.

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Chapter 4

INTEGRATION OF ERGONOMIC DESIGN WITH FINITE ELEMENT ANALYSIS AND STRUCTURAL OPTIMIZATION TECHNOLOGY: ERGONOMICS IN ALUMINUM BEVERAGE CONTAINERS Koetsu Yamazaki1, Jing Han2, Sadao Nishiyama3 and Ryoichi Itoh2 1

Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan 2 Universal Can Corporation, 1500 Suganuma, Oyama, Sunto, Shizuoka 410-1392, Japan 3 Universal Can Corporation, Koishikawa 1-4-1, Bunkyo, Tokyo 112-8525, Japan

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ABSTRACT This chapter describes integration of ergonomic design with Finite Element Analysis (FEA) and structural optimization technology, and its applications to aluminum beverage containers including cans and bottles. Ergonomic design examples of the containers considering human emotional feelings are introduced. To satisfy human visual and tactile sensation, various specific metal printing and sheet embossing techniques are used to change appearance in different temperature environments, surface conditions and shape of containers. FEA is then introduced into the ergonomic design to evaluate the human feeling numerically and objectively. In a design example of the beverage can end (the lid of can), experiments and FEA of vertically indenting the fingertip pulp by a probe and the tab of the can end are conducted to observe force responses and to study feelings in the fingertip. A numerical simulation of the finger lifting the tab to open the can is also performed, and discomfort in the fingertip is evaluated numerically to present the finger accessibility of the tab. A comparison of finger accessibility between two kinds of tab ring shapes show that the tab that has a larger contact area with the finger is better.

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Koetsu Yamazaki, Jing Han, Sadao Nishiyama et al. Structural optimization technology based on FEA is also integrated into the ergonomic design to achieve the best solution. In the design example of beverage bottles used to serve hot drinks in winter, FEA of the tactile sensation of heat is performed to numerically evaluate the touch sensation of the finger when holding the hot bottle. Numerical simulations of the embossing process are also performed to evaluate the formability of various rib-shape designs. Using multi-objective and multi-disciplinary optimization techniques, the optimum design is then carried out considering the hot touch sensation as well as the metal sheet formability

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1. INTRODUCTION We need beverages in daily life, and beverages need containers from which we can drink and sealed containers for keeping the products fresh and safe during transportation from the beverage-filling plants to our hands. Most containers are made of metal, plastic, glass and paper. Containers made of metals including aluminum and steel have many advantages, such as long shelf life, high strength, and good productivity in can-making plants as well as beverage-filling plants. Aluminum containers are especially lightweight and have high recycle-ability; therefore, they are cost effective and environment-friendly [Nishiyama, 2002]. Two-piece aluminum beverage cans with a Stay-on-tab (SOT) end, as shown in Fig. 1(a), have been developed over more than 30 years and are very familiar to consumers as popular containers for beer and soft drinks [Nishiyama, 2001]. Two-piece aluminum beverage bottles with a screw cap, as shown in Fig. 1(b), were introduced to the Japanese market in 2000 to meet the new drinking custom of consumers because the bottles can be resealed [Ueno, 2003]. Cans are produced by deep drawing and ironing thin aluminum sheets, while bottles are produced by necking and screw-forming the open end of the can body; hence, they are more cost effective and lighter than other kinds of metal bottles, such as those produced by the impact extrusion process. Structural optimization methods based on finite element analysis (FEA) have been applied to search for optimum shapes and dimensions of aluminum beverage cans and bottles [Han et al., 2004, 2005; Yamazaki et al., 2007a]. Light-weight design has been implemented for the can end (the lid of the can) subject to strength constraints [Yamazaki et al., 2007a]. To effectively optimize a design problem with many design variables in complex geometrical relations, the design variable progressive optimization method has been proposed and applied to optimize the bottom of two-piece aluminum beverage bottles [Han et al., 2005]. As crushable beverage cans, cylindrical shells have been triangulated and optimized so that they can be more easily crushed to save space during the used can recycling process [Han et al., 2004]. The beverage container must not only protect its contents but also capture the consumers’ attention. Functions, performance and price of products are not the only factors to effect customers’ decisions in purchasing products, so beverage companies also expect containers to serve as a marketing tool to gain a potentially enormous advantage. With the improvement in the quality of human life, it is also becoming necessary to design containers for universal use based on ergonomic evaluation that considers psychological, physiological and anatomical effects.

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(a) Two-piece cans with a SOT end

(b) Two-piece bottles with a screw cap

Figure 1. Selected aluminum beverage containers on the market.

To gather data for determining consumers’ preference, a survey of trained panelists or consumers is usually carried out using trial products. The semantic differential method [Iwashita, 1983] and factor analysis [Shiba, 1979; Gorsuch, 1983] are typical techniques used in questionnaires. Kansei Engineering was initially proposed by a Japanese researcher and is now used internationally by designers as a design methodology [Nagamachi et al., 1974; Nagamachi, 1995, 2000]. While in the product-designing stage before making many types of trial products, a numerical simulation using the finite element method is a cost- and time-

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effective tool used to predict whether or not design requirements will be satisfied, and whether or not a particular design will be preferred by consumers. In this chapter, ergonomic design examples of containers considering human emotional feelings are introduced. To satisfy human visual and tactile sensation, various specific metal printing and sheet-embossing techniques are used to change looks in different temperature environments, surface condition and shape of containers. FEA is then introduced into the ergonomic design to evaluate the human feeling numerically and objectively. In the design example of the beverage can end, experiments on and FEA of vertically indenting the fingertip pulp with a probe and the tab of the can end are conducted to observe force responses and to study sensations in the fingertip. A numerical simulation of finger lifting the tab to open the can is also performed, and discomfort in the fingertip is evaluated numerically to determine the finger accessibility of the tab. A comparison of finger accessibility between two types of tab ring shape design shows that the tab that has a larger contact area with the finger is better. Structural optimization technology based on FEA is also integrated into the ergonomic design to achieve the best solution. In the design example of beverage bottles serving hot (about 60°C) liquids in winter, the FEA of tactile sensation of heat is performed to evaluate numerically the sensation of the finger when holding the hot bottle. The numerical simulations of the embossing process are also performed to evaluate the formability of various rib-shape designs. Using multi-objective and multi-disciplinary optimization techniques, the optimum design is then carried out considering the hot touch sensation as well as the metal sheet formability.

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2. ERGONOMICS IN ALUMINUM BEVERAGE CONTAINERS With functional performances of products being satisfied, ergonomic designs are expected to increase the comfort level of consumers. Samples in Figs. 2–6 are commercial products on the canned/bottled beverage market. Metal decorating technology is utilized to make containers enjoyable and catch the customers’ eye more easily. For example, the beverage bottle in Fig. 2 shows different looks under different temperature. When the bottle is cooled down in a refrigerator, the picture on the bottle shows a boy under water with many fishes swimming around him, as shown in Fig. 2(a). When the bottle returns to room temperature, the picture shows the boy out of water with a captured octopus, as shown in Fig. 2(b). Specific paint can also create various surface conditions of the container; hence, various touch feelings. For example, the can in Fig. 3 has a dry and smooth surface, while the can in Fig.4 has a smooth alternating rough surface. The metal sheet embossing technology has also been used in making innovative and consumer-friendly containers. The can in Fig. 5(a) is embossed with ice features to match the cool image of its content. Equipments for necking and screw-forming processes of the two-piece bottle also can emboss simultaneously and efficiently the bottle to give various looks as shown in Fig. 5(b). Consumers in a dark environment or blind persons can easily identify the canned or bottled beverage by touching and feeling containers.

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(b) Room temperature

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Figure 2. A bottle shows different looks under different temperatures.

Figure 3. A can painted with a dry and smooth surface.

To complete a drinking action, we grasp and open containers by our hands, and make drinks flow into our mouth. Effects of the bottle opening size on drinking feelings are investigated by surveying 120 subjects in order to improve the comfort level of consumers when drinking tea and carbonated beverage directly from the bottle opening. Questionnaires using three kinds of bottles with opening diameters (outside diameter of the screw part) of 28, 33 and 38 mm shown that the 33-mm opening is best for Japanese adult consumers with no matter the type of drinks, gender and the mouth size [Yamazaki et. al., 2007b]. Another

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questionnaire shown that when we drink beverage of strong aroma such as coffee, the 38-mm opening is better for the aroma float out quickly, so we can also enjoy the aroma immediately after the cap is removed (Fig. 6).

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Figure 4. A bottle painted with a smooth alternating rough surface.

(a) Two-piece can

(b) Two-piece bottle

Figure 5. Beverage containers featuring 360-degree embossing.

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(b) Opening diameter = 38 mm

Figure 6. Bottles of different opening size.

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Computer Aided Design and Computer Aided Engineering (CAD/CAE) have been applied in developing beverage cans to save development time and cost. Fig. 7(a) shows two design examples of embossed can and shaped can that are designed for easy holding, and Fig. 7(b) illustrates the stress distribution and deformation under an axial load to confirm that the strength requirement of the can is satisfied.

(a) Design examples of embossed and shaped cans (b) Deforming simulations under an axial load

Figure 7. CAD/CAE applied in developing beverage containers.

3. INTEGRATION WITH FINITE ELEMENT ANALYSIS The physical, cognitive and emotional comfort of the consumers should be considered to create an optimal human-product interaction. Survey of consumers or trained panelists is a

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popular way to evaluate a product ergonomically. Measurement of changes in physiological signals of human subjects, such as blood pressure, muscular load and fatigue and so on, is performed frequently, when using trial products. However, in the product designing processes, we need some objective, measurable laboratory standards, which can be linked to subjective perceptions of comfort, to predict whether or not a particular design will be felt comfortable by the consumers. As an example of integration of FEA into ergonomics, development of the can end is illustrated [Han et al., 2008]. Functional issues of the can end (Fig.8), such as the seal-ability and end open-ability have been almost solved, while human-friendly ease-of-use and comfort are expected in the development of containers. The finger accessibility is used to evaluate whether it is easy to insert a fingertip into the gap between the tab ring and finger deboss of the can end, and whether it is painful or uncomfortable to pull up the tab ring. The more easily the fingertip can be inserted and the ring can be pulled up, the better the finger accessibility is evaluated. To improve finger accessibility, various methods have been developed. For example, deepening the finger-deboss, curving up the ring, or applying scores to the panel under the tab so that the tab may float up a little when the can is filled with beverages and pressured [Yoshida and Yoshizawa, 1996]. All of these methods are trying to enlarge the gap between the tab ring and the finger-deboss to allow a fingertip to go into the gap easily and consequently to improve finger accessibility. Since there are limitations of these methods, such as a clearance restriction between the tab and the top edge of the seaming wall, the geometrical shapes of the tab ring need to be investigated.

Nose Panel Rivet Finger deboss

Ring

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Figure 8. An SOT end.

On the other hand, the fingertip is a most sensitive and important part of the human body for obtaining information by touching an objective and controlling manipulation. Experimental results show that the fingertip is almost incompressible for a point indentor, with the highest change in volume occurring at the largest depth of indentation [Srinivasan et al., 1992]. A study has reported that few statistically significant Pearson correlations has been found among the relationships of pulp parameters (such as, pulp displacement and stiffness) with fingertip dimensions, gender, and subject age [Serina et al., 1997]. FEAs have been performed to predict surface deformations of the fingertip [Srinivasan and Dandekar, 1996], and geometric and structural models of the fingertip pulps supported by experimental data, have been developed to predict the force–displacement and force–contact area responses of the human fingertip during contact with a flat, rigid surface [Serina et al., 1998]. Experiments

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that present stimuli with spherically curved surfaces to the fingertip pulps of human subjects have been performed, and it is observed that an increase in curvature (with no change in contact force) results in a sharper and higher response profile as well as an increase in perceived contact force [Goodwin and Wheat, 1992]. Perception of surface pressure applied to the fingers has been investigated experimentally, and the pressure level at which human subjects perceive a pain has been measured as the pain pressure threshold [Brennum et al., 1989; Fransson-Hall and Kilbom, 1993; Johansson et al., 1999]. Statistical analysis showed that the average pain pressure threshold of males is higher than that of females. Moreover, the surface shape design method that took the tactile sensation into consideration has been proposed, and the surface temperature has been used to present warmness of the surface [Suzuki and Nishihara, 2004].

3.1 Experiments on Indenting Human Finger Pulp

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To observe the relation between the pain and the force-displacement curves when a load is applied to the fingertip pulp, a tension–compression tester has been used for the experiments on indenting finger pulp to enable dynamic real-time measurements to track the finger pulp thickness changes and force changes over a very short period. As shown in Fig. 9(a), the index finger is laid on the table of the tester and then an indentor is moved down at a constant velocity v to indent the finger pulp at the center in width direction and at a distance L from the fingertip in longitudinal direction. A computer records automatically the force applied to the finger and the displacement of the indentor every 0.05 s. To avoid any injury to the subjects, an upper limit of the force Pmax or an upper limit of the displacement Hmax of the indentor is set in advance. When the force reaches the upper limit Pmax or the displacement reaches Hmax, the indentor is stopped for 60 s and then unloaded to its initial position. Participants have been allowed to relax until the fingertip regained its undeformed shape for the next indentation. The mean age of subjects is 38 years, with a range of 28 to 56 years. The initial width and thickness T0 of the finger pulp at various distances L from the tip has been measured for each subject prior to the experiment with the finger being free from any external loads.

(a) Indenting fingertip

(b) Hemispherical probe

(c) Tab of can end

Figure 9. Experimental setup of indenting fingertip

In order to determine the deforming property of the finger pulp and to experience the feeling of pain, experiments on finger pulp indentation at L = 8 mm by an aluminum probe with a hemisphere tip 3.68 mm in diameter (Fig. 9(b)) have been performed. Fig. 10 shows the force changes with time and the displacement of the probe at velocities of v = 1 mm/min as an example of measurement results. The force–time relation plotted in Fig. 10(a) shows

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that when keeping the probe unmoving after it reaches the upper limit Hmax, the indentation depths in the finger does not change while the force decreases with time. This is the so-called stress relaxation due to the viscoelastic property of human fingers. A typical force– displacement curve, as shown in Fig. 10(b), may be simplified as a combination of Part 1, Part 2 and Part 3 as shown in Fig. 10(c). The upper transverse axis represents the fingertip thickness Tf, calculated as Tf = T0 - H, where H is the indentation depth, i.e., the displacement of the indentor. It has been observed that the finger thickness decreases almost linearly at Part 1. The rate of thickness decrease reduces at Part 2, and the thickness decreases almost linearly again but at an even lower rate of decrease at Part 3. It is considered that when the deformation of soft tissue approaches its limit, the force required to deform the soft tissue becomes higher and higher. The experimental results agree with those in the literature [Serina et al., 1997].

Load(N)

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2 Unloading

0

0

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200 300 Indenting time (sec)

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(a) Relation between indenting time and load.

Load(N)

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Stop moving

4

Loading

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Unloading 0 0.0

1.5 3.0 4.5 Indenting depth (m m )

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(b) Relation between indenting depth and load.

Force V.S finger thickness change Finger thickness, Tf Part 3 DiscomfortÆ Pain

Load

Part 1 Touch

Part 2 Pressure

Displacement of indenter, H

Force V.S displacement (c) Diagram of feelings in fingertip

Figure 10. Experimental observations of indenting fingertip.

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Concerning the influence of the individual differences and the indenting velocity of the probe, the experimental results of HS1 (Subject 1, in 30 s, female), HS2 (30 s, male) and HS3 (50 s, male) are compared in Fig. 11, when v = 1 and 4 mm/min. Comparison of the results shows that the gradient of Part 3 in the force–displacement plot does not change much even though the finger dimensions are different from person to person. The experimental results agree with those in the literature [Serina et al., 1997]. Fig. 11 also shows that the gradient of Part 3 in the force–displacement plot does not change much even though the indenting velocity changes. However, the slower the velocity, the later the Part 2 rises. It is because that if the velocity is lower, the indenting time becomes longer, hence, the resistance of the fingertip becomes smaller due to stress relaxation in the soft tissue.

v = 4 mm/min HS1 v = 1 mm/min HS1

10

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HS2

HS3

HS2

HS3

6 4 2 0

0

50

100 150 Time (Sec)

200

250

(a) Relation between indenting time and load. 10

v = 4 mm/min HS1 v = 1 mm/min HS1

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Load (N)

8

HS2

HS3

HS2

HS3

6 4 2 0

0

1

2 3 Indenting depth (mm)

4

5

(b) Relation between indenting depth and load.

Figure 11. Observations of individual differences.

All participants have been asked to report their feeling in their fingertips during the indentation. The common feeling changed as follows: they felt a touch at Part 1 of the force–

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displacement curve, then feel a pressure and their pulse at Part 2, finally feel discomfort followed by a pain in the fingertip at Part 3. The discomfort and pain in the finger increased as the force or the indentation depth increased. If the total load is the same, the narrower the contact area, the deeper the indentation depth becomes, i.e., the thinner the fingertip becomes, hence, the greater the discomfort and pain. In the numerical analysis of finger accessibility of the tab described later, only Part 3 is necessary to be taken into account because we focus on only the feeling of discomfort and pain in the fingertip when pulling up the tab to open the beverage can. Therefore, it is judged that the fingertip model can be simplified as an elastic model with a constant value of Young’s modulus.

3.2 Experiments and FEA of Fingertip Indentation by Tabs To construct a finite element model of human fingertip for numerical analyses of finger accessibility, the experiments and the FEA of the tab indenting the finger pulp vertically at L = 2 mm have been performed and compared. A tab with the convex ring, as illustrated in Fig. 9(c), has been tested. The tab is fixed in a cylindrical resin so that they can be fixed to the tester to indent vertically the index fingertip pulp of human subjects. Fig. 12 shows the forcedisplacement curve as an example of the experimental results. 0

6

Displacement (mm) 1

2

6

FEM

4

4

2

2

0

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0

1

2

Displacement (mm)

3

Load (N)

Load (N)

Round Tab Experimental result

0

Figure 12. Comparison between simulation results and experimental ones.

Fig. 13(a) shows the schematic diagram of the distal part of human fingertip [Netter, 2004]. The fingertip has been simplified as an elastic model with two kinds of mechanical properties, the bone and the soft tissue. Figs. 13(b) and (c) show the vertical cross-section, transverse cross-section and the whole model of the three-dimensional finite element model of the finger. The mechanical properties of bone and soft tissue of index fingertip model has been assumed as: Young’s modulus E = 17 GPa, 5MPa, Poisson’s ratio ν = 0.3, 0.45, respectively [Wu et al., 2002; Fung, 1981]. The model has been descritized into eight-node solid elements. The tab ring has been assumed to be a rigid body in the finger indenting simulation. The finite element code, MSC.MARC has been utilized to perform the numerical analyses of the tab indenting vertically the finger pulp, as shown in Fig. 14.

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(a) Schematic diagram of finger cross-sections [Netter, 2004]. Soft tissue 5mm

Bone

(b) Cross-sections

(c) Finite element model.

Figure 13. Model of distal part of human finger.

Tab

Fingertip Figure 14. Analysis model of indenting finger by a tab.

Copyright © 2008. Nova Science Publishers, Incorporated. All rights reserved.

Experimental results and numerical analysis results are compared in Fig. 12. The upper transverse axis represents the displacement at the indentation position obtained by numerical analyses, while the lower transverse axis represents the displacement measured in the experiments. Comparing the analysis results with the experiment results, it is clear that the last part of the force–displacement curves agree very well with each other. Therefore, it can be concluded that the finite element model of the finger can be used by finger accessibility analysis to evaluate discomfort numerically in the fingertip.

3.3 Design of Can End Considering Finger Accessibility Fig. 15 shows the standard opening method of the beverage can with an SOT end [Reynolds Metals Company, 1984]. There are four steps; the first step is to pull up the tab ring using the index finger while pressing the tab nose with the thumb. The second step is to pull the tab completely forward and the third step is to push the tab back down. The can is ready for drinking when the tab stays on the can as shown in the last step. In the first step, pressing the tab nose by the thumb can make the tab ring rise up a little naturally and can prevent the tab ring slipping down the surface of the index finger pulp so that the finger can be easily inserted into the space under the tab ring. Although there are various postures for

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opening the beverage can by consumers, as illustrated in Fig. 16, the common points are the tab ring and fingertip. To evaluate the feeling of the pain (or discomfort) in the finger when pulling up the tab ring, a FEA model has been developed as shown in Fig. 17. Assuming the deformations of tabs and the finger models are symmetrical to the central vertical plane, numerical analyses on 1/2 finite element model has been performed. All freedoms of the nodes on the circular edge of the rivet part of the tab have been fixed. The edge nodes of the bone elements on the tip of the finger model have been enforced to move 0.5mm forward and then move up and forward to simulate the process of a fingertip pulling up the tab as illustrate in Fig.18. The maximum value of the contact normal stress of the finger model when pulling up the tab has been used to represent the pain (discomfort) in the finger. The smaller the contact stress is, the less pain (discomfort) the finger experiences and the better the finger accessibility of the tab has been evaluated. The material model used for the aluminum tab is assumed as an elasto-plastic von Mises material with isotropic hardening. The Young’s modulus E = 70 GPa, Poisson’s ratio ν = 0.33 and yielding stress σ = 260 MPa have been assumed. The tab model has been descritized into four-node shell elements with 0.33mm thickness.

(a) Step 1

(b) Step 2

(c) Step 3

(d) Step 4

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Figure 15. Procedures for opening SOT ends.

Figure 16. Various postures for opening ends.

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Figure 17. Analysis model of finger accessibility.

(a) Press tab nose

(b) Insert Finger

(c) Lift Tab

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Figure 18. Model of finger accessibility.

In order to investigate the effect of the geometric shape of the tab ring, two kinds of shape designs, i.e., the convex ring (Model 1) and the concave ring (Model 2), have been modeled as shown in Fig. 19. The concave ring is designed to match the shape of finger pulp. The length of the symmetric central lines and the symmetric central cross-sections of two tab models are the same. Fig. 20 shows the deformation of the fingertip pulp and the contact normal stress distribution of finger model when the tab models are pulled up 2.5 mm. It is obvious that the stress concentration occurs at the part in contact with the central part of the convex ring. When the displacement of the ring center (H1) reaches 2.5 mm, the finger can be inserted more and the tab can be re-held for easy opening. The difficulty evaluated is the socalled can openability rather than finger accessibility when H1 is larger than 2.5 mm, so the simulation results before H1 reaches 2.5mm has been observed. The maximum value of the contact normal stress, the contact areas, and the maximum value of the equivalent elastic strain of the finger have been compared in Fig. 21 for two tab models when H1 = 2.5 mm. In the case of the tab with a concave ring, the contact area between the finger and the ring is larger and the maximum value of the contact normal stress and equivalent strain are smaller. It is considered that if a larger area shares the load required for pulling up the tab, the contact normal stress and equivalent strain may become lower. Hence, discomfort in the finger may decrease more. Therefore, it is concluded that the finger accessibility of the tab with a larger contact area with finger is better. The finger accessibility of the tab with a concave ring is better than that of the tab with a convex ring.

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(a) Model 1

(b) Model 2

Figure 19. Finite element models of tabs. MPa 4.6 3.7 2.8 1.8 0.9 0.0

(a) Model 1

(b) Model 2

Figure 20. Deformation and contact normal stress distribution of finger model.

Maximum value of contact normal stress of finger Contact areas of finger Maximum value of equivalent strain of finger

1.4 1.3 Ratio

1.2 1.1 1.0 0.9 1

2

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Tab Model No.

Figure 21. Comparison of two tab models.

4. INTEGRATION WITH STRUCTURAL OPTIMIZATION TECHNOLOGY As an example of integration of structural optimization into the ergonomics, a design example of the bottle for hot vending is illustrated [Han et al., 2006]. In winter, beverages are expected being offered hot. However, when aluminum bottles are warmed up to about 60°C in vending machines, some consumers feel it is too hot to hold them by hand due to the high thermal conductivity of aluminum. Therefore, in developing the aluminum beverage bottles

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for hot vending, it is also necessary to take the tactile sensation of heat into consideration. To make aluminum bottles adaptable to hot vending market, two ways are developed. As shown in Fig. 22, one way is to wrap bottle bodies with a plastic label to reduce the thermal conductivity, and the other one is to add ribs to the bottle wall by an embossing process. The ribs can reduce the amount of heat transmitted to the finger, and the air gap between the embossed body and the plastic label can weaken further the heat transfer.

Figure 22. Bottles with ribs and wrapped with PET label.

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Regarding embossing process, there are two methods to produce the rib-shape embossed bottles. The first method, rotary embossing method, is to emboss the bottle body by rotating a pair of convex and concave dies against each other with the bottle body being located over the concave die. This embossing method can provide better quality, however, cost more because an extra embossing machine is required. The second method, axial embossing method, is to emboss the bottle by axially imposing a cylindrical tube die with the rib-shaped inner surface on the outer surface of the bottles. This method cost less because the necking, screw forming, and embossing processes can be finished by only one horizontal-axis rotary machine; however, the quality is dependent on the shape of ribs and the forming condition. To develop the bottle for hot vending, the multi-objective optimization has been performed based on the numerical simulations of the tactile sensation of heat and embossing process.

4.1 Numerical Analysis of Tactile Sensation of Heat To evaluate numerically the touch feeling of the finger when holding the hot beverage bottle, the FEA of the tactile sensation of heat are performed. Numerical analyses of the tactile sensation of heat include contact deformation analyses and heat transfer analyses between the finger and rib-shape embossed bottle body, as shown in Fig. 23. In the contact analyses, the fingertip is contacted with the mountain of the rib, and a distributed load p toward the bottle is applied to the upper surface of the finger model. The deformed configuration of the finger obtained in the contact analysis is then used in the heat transfer analyses. Fig. 24 shows the cross-sections of the fingertip and rib-shape embossed bottle

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body. The complex structure of the inside of the finger is neglected, and the cross-section of the finger model is simplified by taking 25 mm from the fingertip and 8 mm from the contact point. The embossed body of 16 ribs is considered here, i.e., A1=22.5 o. The values of radii used for the analysis of the tactile sensation of heat are Ra=32 mm, Rb=33.15 mm. The material constants of the finger are assumed as follows: Young’s modulus E=100 MPa, Poisson’s ratio ν = 0.45, specific heat c = 3400 J/(kg K), thermal conductivity λ = 0.5 W/(m K). The finger model is discretized into four-node quadrilateral elements, and the embossed bottle is assumed as a rigid body of 60°C. The initial temperature of the finger is set at 35°C, and the temperature of the nodes on the upper surface of the finger model is fixed at 37°C. The MSC.MARC has been used to simulate the configuration change of the finger and to calculate the amount of heat transmitted from the hot bottle to the flesh of the finger when grasping the bottle body. To identify the contact heat transfer coefficient between the finger and the bottle body, the temperature change in fingertip when grasping the hot bottle has been calculated using several different values of the contact heat transfer coefficient to fit the experimental measurements of time and temperature. The contact heat transfer coefficient between the finger and the bottle body has been finally identified as 46 W/(m2 K). To gain a deeper understanding of the influence of rib dimensions A2, A3, and A4 to the tactile sensation of heat, Model M0 with no embossing process and nine embossed body models listed in Table 1 have been analyzed. It is clear that with the angle A2 or A3 increasing, A4 increases and the slope of the mountain and valley of the rib becomes steeper.

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(a) Model

p

Fixed temp. 37o C o

Initial temp. 35 C Finger

Finger Bottle body

(b) Contact analysis model

Bottle bo dy

60o C

(c) Heat transfer analysis model

Figure 23. Analysis model of tactile sensation of heat from bottle body.

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(a) Finger model (unit: mm).

137

(b) Rib-shape embossed bottle body.

Figure 24. Cross-sections of fingertip and embossed bottle body.

Table 1. Bottle models Model

A 2 (o)

A 3 (o)

A4 (o)

M0

--

--

--

M1

1.5

1.5

17.89

M2

1.5

3.5

20.35

M3

1.5

5.5

25.26

M4

3.5

1.5

19.92

M5

3.5

3.5

23.36

M6

3.5

5.5

30.57

M7

5.5

1.5

22.35

M8

5.5

3.5

27.26

M9

5.5

5.5

38.23

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The amount of heat transmitted from the bottle in a unit time is calculated using n

Q = c ⋅ ∑ S i ⋅ (Ti − Ti 0 ) , i =1

(1)

where, n is the number of elements, Si is the area of the element i, Ti 0 and Ti are the initial mean temperature and the mean temperature at a unit time of element i, respectively. The ratio of the amount of heat transmitted from the hot bottle is calculated as δ = Q / Q0 , where Q0 is the amount of heat transmitted from the bottle model M7 when p = 2.5 MPa is applied

to the finger model. The heat transfer analysis results at 0.03 s are compared in Fig. 25 for all models. It is obvious that all embossed bottle body models transfer less heat to the finger than the unembossed cylindrical body Model M0 does when the same load p is applied to the finger. Figure 26 shows the temperature distribution of the finger model at 0.03 s when

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grasping hot bottle models. It is found that the temperature of the finger grasping embossed bottle body is lower than that of unembossed bottle body. From the comparison of the amount of heat transmitted from the hot bottle body, it is clear that the sharper the mountain of the rib is, the smaller the contact area becomes and then the less the heat is transmitted. It is concluded that the rib shape of the embossed bottle of relatively small value of A2 as well as large value of A4 has better touch feeling. 1.2

δ

1.1

1.0

0.9 M0 M1 M2 M3 M4 M5 M6 M7 M8 M9

Model No. Figure 25. Heat transfer analysis results of bottle body.

(a) Model M0

(b) Model M6

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Figure 26. Temperature distribution of the finger while grasping hot bottle.

4.2 Simulations of Rib-Shape Embossing Process Fig. 27(a) shows the analysis model of the axial embossing process. The MSC.MARC has been used to simulate the cylindrical tube die with rib-shaped inner surface imposing axially on the outer surface of the bottle body. The dimensions of the bottle body and die are illustrated in Figs. 27(b) and (c), respectively. The length of the die model is 35 mm. Since the bottle body is axisymmetric, a 1/4 model is discretized into four-node quadrilateral shell elements. The sidewall thickness of the bottle body is 0.13 mm. The material model used is an elastoplastic von Mises material with isotropic hardening. The die is treated as a rigid body, and Rc = 32 mm, Rd = 33.15 mm. The number of ribs is specified as 16, i.e., A1 = 22.5 o. The embossing process simulations are performed using two kinds of die models, Model N1 (A2 = 1.5 o, A3 = 5.5 o), N2 (A2 = 5.5 o, A3 = 1.5 o). Figure 28 shows the radial positions of

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nodes at a section with an original axial distance l1 = 20.5mm from the shoulder side of the embossed bottle model. It is observed that the embossed bottle body dented much when using dies like Models N1 with a relatively large value of A3. Also, the smaller the value of A2 is, the more the embossed body dented and the worse the embossing formability becomes. The mean radii of the mountain and valley of the rib shape embossed bottle body, R1 and R2, are used to evaluate the axial embossing formability. The larger the radius difference ΔR = R1 − R2 is, the higher the rib is and the better the embossing property is evaluated. Moreover, R1 and R2 are not expected to be too small.

Bottle body

Die (a) Axial embossing model

l1

(b) Bottle body model (unit: mm)

(c) Cross section of die

Figure 27. Simulation model of embossing process.

Radial Position (mm)

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33.5

Model N1

Model N2

33.0 32.5 32.0 31.5 31.0 30.5 0

23

45

68

90

Theta ( Degree) Figure 28. Simulation results of the embossing process.

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4.3 Multi-Objective Optimization of Rib Shape On the bases of the numerical analyses of the tactile sensation of heat and the axial embossing process simulations, the hot touch feeling and embossing formability of the bottle with ribs can be evaluated numerically. Since the dimensions of ribs influence the touch feeling as well as the embossing formability, it is necessary to perform a multi-objective optimization subject to the rib dimension constraints. The problem is then posed as: Find design variables: X = {x i },

i = 1,..., n

(2)

(n : the number of design variables)

Q( X ) , Q0

(3)

ΔR0 , R1 ( X ) − R2 ( X )

(4)

minimize:

f2 =

f1 =

subject to: g 1 = 1 − R1 ( X ) / R1 min ≤ 0 ,

(5)

g 2 = 1 − R2 ( X ) / R2 min ≤ 0 ,

(6)

xi L ≤ xi ≤ xiU , i = 1,..., n

(7)

where f1 is for evaluating the hot touch feeling and f2 is for evaluating the embossing formability. R1min, R2min are the allowable minimum values of the mean radii (R1, R2) of the mountain and valley of the rib-shape embossed bottle body; Q0 and ΔR0 are scalars; xi

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L

U

and xi are the upper and lower bounds on design variable i, respectively. Fig. 29 shows the flowchart of the multi-objective optimization of a beverage bottle, considering tactile sensation of heat and embossing formability. The Response Surface Approximation method [Myeres & Montgomery, 1995] is applied to approximate response surfaces, and an appropriate approach is selected to solve the multi-objective optimization problem. At first, design variables and levels are defined, and design points are assigned by an orthogonal array in the design-of-experiment technique. The numerical analyses of the tactile sensation of heat and embossing process simulations are then carried out for all design points. On the basis of the numerical results, approximate functions of the amount of heat (Q), the mean radii (R1 and R2) of mountains and valleys of the embossed bottle are constructed by orthogonal polynomials in terms of design variables. According to the property of objective function space, an appropriate approach of the multi-objective optimization is then selected to minimize the objective function subjected to the constraints. This optimization process is repeated until the given convergence condition is satisfied.

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Start

Select design variables X and define design space

Arrange analysis points by the Design-of-experiment technique

Perform analyses of tactile sensation of heart

Perform embossing simulations

Approximate functions R 1(X) and R 2(X)

Approximate function Q (X)

Scale objective function 1: f1 = Q(X)/ Q 0

Scale objective function 2: f 2 =

ΔR0 R1 ( X ) − R2 ( X )

Improve Design space Calculate Pareto front and do optimization

No Judge convergence condition Yes End

Figure 29. Flowchart of the multi-objective optimization of a beverage bottle considering tactile sensation of heat and embossing formability.

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As a numerical example, dimensions A2 and A3 of the rib are selected as design variables with three levels of the same interval. The orthogonal array L9 is used to assign the design points. The lower bounds are 1.5o for two design variables, and the upper bounds are 5.5o, 3.5o, respectively. On the basis of numerical analysis results of the tactile sensation of heat and the axial embossing process, the response surfaces are approximated as shown in Fig. 30. The amount of heat Q transmitted from Model M7 is adopted as Q0, and the radius difference ΔR of the bottle embossed by using Model N2 is adopted as ΔR0 . If the constraints are given as R1min = 33.05 mm, R2min = 31.91 mm, the objective function space can be calculated by gradually changing the value of design variables in equal intervals ( ΔA2 = ΔA3 = 0.1° ) within the design space, as illustrated in Fig. 31. It is obvious that the Pareto front is a convex curve. Therefore, the weighted sum approach of the multi-objective optimization techniques is applied to optimize the embossed bottle considering both of the touch feeling and the embossing formability. The multi-objective optimization problem of the bottle is then formulated as: Minimize: f = w1 ⋅ f1 + w2 ⋅ f 2 ,

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(8)

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subject to the constraints. The weight coefficients w1 and w2 are defined as w1 + w 2 = 1 ,

0 ≤ w1 , w2 ≤ 1 . The series of Pareto front obtained with the weight increment

Δw1 = Δw2 = 0.2 are identified towards the lower left corner of Fig. 31 and are listed in Table 2. According to the embossing method employed as well as the use of the beverage bottles, designers may decide the weight coefficients, w1 and w2. For example, if the bottle is for hot vending, the touch feeling is then important, give w1 a larger value. While, if it is necessary to take the embossing formability into account more, give w2 a larger value. The optimum for w1 = 1 is upper left point F, while the optimum for w1 = 0 is lower right point A in the graph. Embossing simulation results of Pareto point A (w1 = 0, w2 = 1), point C (w1 = 0.4, w2 = 0.6), and point F (w1 = 1, w2 = 0) are compared in Fig. 32. The amount of heat transmitted from the optimized bottle model decreased about 30 to 35% as compared with that of the regular bottle. Therefore, it can be concluded that the optimum model has better touch feeling and better embossing formability.

ΔR (mm)

Q/Q0 1.00

1.20

0.96

1.16

0.92

1.12

A3 (o )

o

A3 ( )

o

A2 ( )

A 2 (o)

(a)

(b)

R2 (mm)

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R 1(mm) 33.13

31.96

33.07

31.92

33.01

31.88

A3 ( o) A2 (o )

A3 ( o ) A 2 (o)

(c)

(d)

Figure 30. Approximate response surfaces of bottle body.

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Integration of Ergonomic Design with Finite Element Analysis … 1.04

Feasible solutions Optimal solutions from Weightd Sum Approach

1.02 Embossing formability ( f2)

143

F E

1.00

0.98 Pareto front D 0.96 C B 0.94 0.90

0.92

0.94

A 0.96

0.98

1.00

Tactile sensation of heat ( f1) Figure 31. Objective space of bottle body design.

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Table 2. Optimal solutions from weighted sum approach Pareto Point A

0.0

B

A2 (o)

A 3 (o)

f1

f2

f

1.0

3.51

1.74

0.970

0.952

0.952

0.2

0.8

3.43

2.25

0.955

0.954

0.954

C

0.4

0.6

3.22

2.52

0.946

0.957

0.953

D

0.6

0.4

2.59

2.78

0.934

0.970

0.948

E

0.8

0.2

1.73

0.916

1.010

0.935

F

1.0

0.0

1.50

0.916

1.020

0.916

w1

w2

3.29 3.23

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(a) Pareto Point A (A2 = 3.51 o, A3 = 1.74o)

(b) Pareto Point C (A2 = 3.22 o, A3 = 2.52o)

(c) Pareto Point F (A2 = 1.50 o, A3 = 3.23o)

Figure 32. Embossing simulation results of Pareto Points A, C, F.

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5. CONCLUSIONS This chapter introduced the integration of ergonomics with metal decorating techniques, FEA and structural optimization technology. Several ergonomic design examples of aluminum beverage cans and bottles have been illustrated. In developing innovative containers to make consumers feel refreshed, specific metal printing and sheet embossing techniques have been used to change appearance in different temperature environments, surface conditions and shape of containers. In developing the can end to improve finger accessibility of the tab, FEA has been successfully applied to simulate the action of the finger pulling up the tab and to numerically evaluate discomfort in the fingertip. In developing the bottle to ensure that consumers do not feel discomfort when grasping a too-hot or too-cold bottle, structural optimization technology based on FEA has been applied to optimize the ribshape embossed bottle body. Similar estimations also can be given; for example, containers featuring embossing or debossing can keep containers warmer or cooler in the hand for a longer period of time compared with regular containers.

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With the improvement of existing technology and development of new technology, better ergonomic designs can be expected in the near future.

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REFERENCES Brennum, J., Kjeldsen, M., Jensen, K., Staehelin, J.T., 1989. Measurements of human pressure-pain threshold on fingers and toes, Pain, 38, pp.211–217. Fransson-Hall, C., Kilbom, A., 1993. Sensitivity of the hand to surface pressure, Appl. Ergon., 24, pp.181–189. Fung, Y.C., 1981. Biomechanics: Mechanical Properties of Living Tissues, Springer. Goodwin, A.W., Wheat, H.E., 1992. Magnitude estimation of contact force when objects with different shapes are applied passively to the fingerpad, Somatosens. Motor Res., 9–4, pp.339–344. Gorsuch, R. L., 1983. Factor Analysis, 2nd Ed., Lawrence Erlbaum. Han, J., Itoh, R., Nishiyama, S., Yamazaki, K., 2005. Application of structure optimization technique to aluminum beverage bottle design, Struct. Multidisciplinary Optim., 29–4, pp.304–311. Han, J., Nishiyama, S., Yamazaki, K, Itoh, R., 2008. Ergonomic design of beverage can lift tabs based on numerical evaluations of fingertip discomfort, Applied Ergonomics, 39-2, pp.150-157. Han, J., Yamazaki, K., Itoh, R., Nishiyama, S., 2006. Multi-objective optimization of a twopiece aluminum beverage bottle considering tactile sensation of heat and embossing formability, Struct. Multidisciplinary Optim., 32–2, pp.141–151. Han, J., Yamazaki, K., Nishiyama, S., 2004. Optimization of the crushing characteristics of triangulated aluminum beverage cans, Struct. Multidisciplinary Optim., 28–1, pp.47–54. Iwashita T., 1983. Measurement of image by SD method, Kawashima Publishing (in Japanese) Johansson, L., Kjellberg, A., Kilbom, A., Hagg, G., 1999. Perception of surface pressure applied to the hand, Ergonomics, 42–10, pp.1274–1282. Myeres, R.H. & Montgomery, D.C, 1995. Response surface methodology-process and product optimization using designed experiments, John Wiley & Sons, New York. Nagamachi, M., 1995. Kansei Engineering: A new ergonomic consumer-oriented technology for product development, International Journal of Industrial Ergonomics, 15, pp.3-11. Nagamachi, M., 2000. Kansei Engineering, Perspectives of Kansei Engineering, Technical Report of IEICE. OME, 100-252, pp. 167-173. Nagamachi, M. et al., 1974. A study of emotion-technology, The Japanese Journal of Ergonomics, 10-4, pp. 121-130. Netter, H.F., 2004. Atlas of Human Anatomy, third ed. Nankodo Co., Ltd. Japanese version, pp. 454. Nishiyama, S., 2001. Development and future subjects of aluminum beverage cans, Packpia, 2, pp.10-15. (In Japanese) Nishiyama, S., 2002. Aluminum can recycling in a synthesized closedloop, Corros. Eng., 51, pp.381–394. Reynolds Metals Company, Aluminum Can Division, 1984. Stay-on-Tab pamphlet.

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Serina, E., Mockensturm, E., Mote Jr., D., Rempel, D., 1998. A structural model of the forced compression of the fingertip pulp, J. Biomech., 31, pp.639–646. Serina, E., Mote Jr., D., Rempel, D., 1997. Force response of the fingertip pulp to repeated compression—effects of loading rate, loading angle and anthropometry, J. Biomech., 30– 10, pp.1035–1040. Shiba, S., 1979. Factor Analysis, University of Tokyo Press (in Japanese) Srinivasan, M., Dandekar, K., 1996. An investigation of the mechanics of tactile sense using two-dimensional models of the primate fingertip. Trans. ASME J. Biomech. Eng., 118, pp.48–55. Srinivasan, M., Gulati, J., Dandekar, K., 1992. In vivo compressibility of the human fingertip, Trans. ASME Adv. Biomech. Eng., 22, pp.573–576. Suzuki, K, Nishihara, T., 2004. The design of surface shape of resin considering tactile sensation, Proc. 3rd China–Japan–Korea Joint Symposium on Optimization of Structural and Mechanical Systems, Kanazawa, Japan, pp.329–334. Ueno, H., 2003. Drinks cans with customer convenience. In: Proceedings of the Canmaker Summit, Singapore, in CD-ROM. Wu, J.Z., Dong, R.G., Rakheja, S., Schopper, A.W., 2002. Simulation of mechanical responses of fingertip to dynamic loading, Med. Eng. Phys., 24, pp.253–264. Yamazaki, K., Itoh, R., Watanabe, M., Han, J., Nishiyama, S., 2007a. Applications of structural optimization techniques in light weighting of aluminum beverage can ends, J. Food Eng., 81, pp.341–346. Yamazaki, K. Chihara, T., Itoh, R., Han J., Nishiyama, S., 2007b. Evaluation method of drinking ease for aluminum beverage bottles, Proceedings of ASME 2007 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC/CIE 2007), Paper No. DETC2007-35637, Las Vegas, USA. Yoshida, M., Yoshizawa, T., 1996. Japan Utility Model No. 2508637.

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Chapter 5

ERGONOMICS IN THE OPERATING ROOM: DESIGN FRAMEWORK A. Albayrak∗, L. S. G. L. Wauben and R. H. M. Goossens Delft University of Technology, Faculty of Industrial Design Engineering Landbergstraat 15, 2628 CE Delft, the Netherlands

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ABSTRACT Healthcare is one of the most dynamic and expanding areas in the world. This introduces a multi-disciplinary approach to deal with, on one side the technology-driven trends and on the other side the social-economic consequences on the healthcare system. Regardless of the field of application, in healthcare the human plays a central role. Healthcare is practiced by humans to cure, care and prevent other humans from illness. Beside healthcare, there is another field in which humans also plays a central role, namely ergonomics. ‘Ergonomics (or human factors) is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance’. Because care, cure and prevention are human-centered, ergonomics plays an important role in healthcare. On this perspective, it is not surprising that knowledge in the field of ergonomics has significant contributions to the improvement of the healthcare sector. Application of ergonomics in healthcare is not only based on a fundamental and theoretical framework of ergonomics as a science, but also other aspects such as legislations, methodology and communication define the precondition of the design space. As a result, highly skilled engineers in this field are needed who are capable of translating practical needs of the healthcare sector into products specially designed for low-tech as well as high-tech medical applications. First, the engineer and the medical specialist have to speak the same language. This can be improved by using the ‘Participatory Design’ as a methodology during the design process. Participatory Design actively involves the user into the design process, leading to a designed product that meets the user’s specific needs. The design process is based on ‘trial-and-error’ whereby the emphasis is on doing feasibility studies with a prototype in practice. The feedback ∗

Telephone: +31(0) 152781932; Fax: +31(0) 152787179; E: [email protected]

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A. Albayrak, L. S. G. L. Wauben and R. H. M. Goossens from the user is then used to improve the product. In the faculty Industrial Design Engineering at Delft University of Technology this approach is integrated and applied in education and design projects. This chapter discusses three cases of the application of this method regarding three domains of ergonomics. In the first case the emphasize lies on the sensorial domain; the design of an abdominal wall tension measurement device. The second case shows how the ergonomics of minimally invasive surgery can be improved by means of an integrated surgical suite, within the cognitive domain. Finally, within the physical domain the design of a curved instrument for minimally invasive surgery to improve the surgeon’s body postures will be illustrated.

INTRODUCTION History of Industrial Design The faculty of Industrial Design Engineering (IDE) at Delft University of Technology is since 1969 an independent faculty and since her foundation more than 3200 Industrial Design Engineers graduated. IDE was the first university design program in the Netherlands and nowadays the largest in her kind in the world. Industrial design as a field originates from the industrial revolution in the 19th century. With the arrival of the mass production the way of manufacturing, trade and distribution changed dramatically from handcraft product design into industrial design. Due to these developments, the design of a new product has become a more comprehensive process called ‘product development’. Product development demands a multidisciplinary approach and therefore an industrial design engineer who possesses the scientific and professional knowledge. Which disciplines have to contribute largely depends on the characteristics of the product to be developed, but engineering design, industrial design, ergonomics, marketing and innovation management are nearly always involved.

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Medisign Healthcare is one of the most dynamic and expanding areas in the world. This introduces a multi-disciplinary approach to deal with, on one side the technology-driven trends and on the other side the social-economic consequences on healthcare system. Regardless of the field of application, in healthcare the human plays a central role. Healthcare is practiced by humans to cure, care and prevent other humans from illness. Beside healthcare, there is another field in which humans also plays a central role, namely ergonomics. ‘Ergonomics (or human factors) is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance’ [16]. Because care, cure and prevention are human-centered, ergonomics plays an important role in healthcare.

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At IDE, designers are educated to design ‘products people love to use’ and therefore ergonomics play a central role in both education and research programs. A program that especially focuses on these human factors of medical specialists is Medisign Delft. Medisign Delft is an educational and research program on Master- and PhD-level that focuses on the research and product development in healthcare, especially on medical products of the future. This includes designs aimed at satisfying human needs and extending possibilities for as well the medical staff, like nurses and medical specialists, as for patients and their family. It involves not only problems in human-product interaction, but also increases the opportunities offered by improved conditions of life and by the development of new technologies. What this means for IDE is that it will have to provide designers capable of translating the practical needs of the healthcare sector into products specially designed for medical applications in low-tech as well as high-tech applications. In this way, they can contribute to the diagnosis, treatment and prevention of disease and disorders. The Medisign track trains dedicated and skilled designers in human anatomy, physiology, medical technology, healthcare systems and some basic surgical techniques.

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Design Framework According to Roozenburg and Eekels product development is a goal-directed thinking process in which problems are analyzed, objectives are defined and adjusted, proposals for solutions are developed and the quality of those solutions is assessed [10]. This thinking process and the procedures that industrial designers follow can be structured by ‘design methodology’. Design methodology provides designers with knowledge on the design process and also provides a body of methods and rules to be used in designing. Nearly all rules and methods for designing are heuristics; these help in finding a solution for some problems, but do not guarantee that a solution will always be found. Before discussing the structure of a design process the term ‘design’ has to be defined. The focus is on designing material products and therefore ‘design’ is defined as ‘to conceive the idea for some artifact or system and/or to express the idea in an embodiable form’ [10]. Roozenburg and Eekels describe designing as a special form of problem solving and reasoning which takes place from goal (the function) to means (the design) [10]. As in problem-solving in general, in designing many means can realize the goal and it is initially uncertain what means is (the most) effective. It therefore needs no further explanation that design is in essence a trial-and-error process that consists of a sequence of empirical cycles, in which the knowledge of the problem as well as the solution increases spirally. The basic design cycle is illustrated in Figure 1. As illustrated in Figure 1 the design cycle consist of different stages. The stages in the gray boxes have a divergent character, which means that the designer should look very broadly to the content. Conversely, the white boxes have a convergent character and define the focus of the content for the next step. The design process is iterative and it comprises a sequence of reductive steps and deductive step [10]. The designer compares the so far attained results and the desired results between these two steps. The different stages will be discussed briefly.

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Figure 1. Basic design cycle according to Roozenburg and Eekels [10].

Analysis Phase Generally, an assignment or a direction for a new product idea is provided whereby also the target group is defined. In the analysis phase the designer starts to explore the problems around the new product idea, do research on the target group and try to get insight in their ‘world’. This explorative research will result in a problem statement. The problem statement should reflect on, who have the problem, what is the problem and what causes this problem. Within this problem statement the designer and his/her team has to define their goals clearly to be able to assess later whether the design proposal is indeed a solution of the defined problem. A list of requirements is mostly drawn up. This is a tool to define the goal more clearly and represents the design specifications, which define the design space for the next step.

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Synthesis Phase In this phase a provisional design proposal is generated. It is a crucial phase since the creativity of the design team plays an important role. In this phase the designer makes a ‘synthesis’ of the separate ideas, solutions and present information to make an integral solution. The design proposal generated in this phase is a possibility to solve the problem of which the value will be assessed in the later phases of the design cycle.

Simulation Phase According to Roozenburg and Eekels simulating is forming an image of the behavior and properties of the designed product [10]. In product development often the term ‘prototype’ is used which represents the properties of the new product idea as closely as possible. These properties are related to technical functioning, ergonomics, and the semantic and aesthetic values of the product idea. Simulation of the product gives the design team an impression of the expected functioning in a certain context. This can be done in many different ways but user research gives the design team a well-considered feedback about the expectations of the user of the product, the actually usage, the interaction, anthropometrics and technical functioning.

Evaluation Phase In this phase the value of the provisional design proposal is assessed by testing, which means the expected properties are compared with the desired properties as formulated in the design specifications.

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Decision The expected and desired properties will always differ from each other but it is important to decide if those differences are acceptable or have to be redefined. Since the design cycle is iterative the design team can return to the synthesis phase, for example to generate a better design proposal or to define different design specifications which fit better or formulate recommendations to approve the design proposal. The basic design cycle as illustrated in Figure 1 is the most fundamental model of designing and it can be perfectly used with different kind of methodologies.

METHODOLOGY The medical specialists are professional users with their specific needs, work conditions, language, culture and work environment. When designing products for professional users their involvement in the design process is crucial since designers can use their input to

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improve the design proposal. A methodology, which can be used from this perspective, is ‘Participatory Design’ which actively involves the user into the design process, leading to the designed product that meets the user’s specific needs. Participatory Design (PD) is an approach that is ‘characterized by concern with a more humane, creative, and effective relationship between those involved in technology’s design and its use’ [8]. PD is started in Norway in the late 60s and early 70s with the development of the first object-oriented programming language. Since its inception more and more product designers are using this approach during their product development. PD assumes that: ƒ ƒ

ƒ

ƒ

ƒ

Users are experts; PD acknowledges the importance of using the expertise of users and treating them as equal partners on a design team. Tools should be designed for the context in which they will be used; PD realizes that an important step to designing new tools is to know where these will be used and in what context. This makes it difficult to design a tool away from the environment in which it will be used. There should be methods for observing or interviewing end-users; to gain an understanding of the environment in which the product will be placed and used, there are several techniques used to watch, observe and interview users in their workplace. Recreating or play-acting a work situation will facilitate the design phase; it mediates the expectations of the users by not providing a nonfunctional prototype at the very beginning of the design phase. Iterative development is essential; the ideal PD project has several iterations of a design-feedback loop, where the designers ask the user for their opinion.

Hereafter three cases will be discussed regarding the phases of the design cycle. In all of the cases PD was applied as a methodology. These three cases are selected regarding the three domains of ergonomics, which were discussed in the chapter ‘Ergonomics in the operating room: An Overview’.

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CASE I: SENSORIAL ERGONOMICS – ABDOMINAL WALL TENSION MEASUREMENT DEVICE Text and drawings are derived from the master thesis of N.A. Alvarez. Graduation project Delft University of Technology, Faculty of Industrial Design Engineering. June 2006 [1].

Analysis Phase The abdominal wall is an important structure serving many different functions [5]. The two major functions are movements of the trunk and regulation of intra abdominal pressure. Moreover, it supports respiration and plays a role in stabilization of the spine. All these functions are facilitated by the coordinated and task specific activation pattern of the abdominal muscles. Due to its vital related functions, the abdominal wall is impossible to keep motionless even for a short period [7].

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Intra Abdominal Pressure (IAP) Intra Abdominal Pressure (IAP) is the internal force that counteracts with the abdominal wall tension. As defined by the World Society of the Abdominal Compartment Syndrome IAP is ‘the pressure concealed within the abdominal cavity’ (Figure 2) [17]. As mentioned before, muscles and IAP are directly related to each other (changes in posture and actions that involve abdominal muscles’ activation have an effect on the IAP). When IAP is measured in healthy non-obese adults during 13 different actions, the highest IAP was generated while coughing and jumping. It was also found that IAP correlated with the Body Mass Index (BMI) [3].

Figure 2. Intra Abdominal Pressure (IAP).

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Palpation There are different methods of physical examination of the abdomen: observation (inspection), percussion, auscultation (listening to the internal sounds of the body) and palpation. During superficial palpation the specialist assesses the abdominal area by evaluating with his/her hand the tension (tonus), tenderness and soreness of the abdominal wall as well as the presence of superficially localized resistances. The quality of the examination depends on specialist’s experience and the cooperation of the patient during this examination (Figure 3).

Figure 3. Palpation of the abdomen.

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Problem Statement From literature it can be concluded that the abdominal wall tension is related with the IAP, which can influence the wound healing process. Therefore, abdominal wall tension is probably associated with development of incisional hernias [3; 9; 13]. IAP is currently measured by means of the bladder pressure, performed invasively with a urinary catheter and is considered an important element to be controlled after abdominal surgeries. IAP is an active measure influenced by many different elements such as the organs’ location and the abdominal wall’s muscular behavior. For research purposes the abdominal wall tension can be calculated through mathematical models. In practice it is estimated qualitatively by means of palpation but there are no quantitative measurements done in patients yet. If the abdominal wall tension could be measured by means of a non-invasive device, research could be done to evaluate its relation in the development of abdominal conditions such as incisional hernia. Although many research would be necessary to find if there is a relation between the abdominal wall tension and the development of incisional hernias (or any other abdominal condition), the design of a device to measure such tension could be an initial step in that direction. The aim of this project was to design a device that measures the abdominal wall tension non-invasively. User Research: Observational Research To gain insight into the palpation process and to identify possible common procedural elements in the patient-specialist interaction, two different specialist were observed; an obstetrician and a gastroenterologist. Although the objectives of the examination and the patient’s abdominal wall’s muscular behavior are different by these specialists, they both use their hands to evaluate the condition of the abdominal area, and they both first asses the tension and general situation of the abdominal wall. The observations focused on: ƒ ƒ

Actions of the specialist during palpation. Other factors that could have an influence on the outcome of the examination, e.g. environment, kind of patient, etc.

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In addition, both specialists were interviewed before and after the examination. The results of the observations and interviews showed: ƒ ƒ ƒ ƒ

ƒ

During the examination of the abdominal wall different kinds of feedback are used for prognoses; Hardness of the abdomen is relatively evaluated with the reaction of the patient. General geometry of the abdomen, and expected situation of the structures underneath the ‘irregularities’. For assessment of the abdominal wall’s tension, both specialists pressed with a line of fingers (one or two hands indistinctively) and evaluate the amount of force needed to indent the fingers. Concerning the interaction, the patient had to be kept as relaxed as possible to perform the examination.

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Technical Research The technical research aimed to answer the questions related to the measurements: how to measure? and where to measure? Force measurement tests were done on different points on the abdominal wall with an existing force measurement device. These points on the abdominal wall reacted differently on the force measurement. List of Requirements The requirements, expressed in terms of needs and desires, were divided in ‘Technical' and ‘Use’ because these were the two main concern areas for the design of the device. Technical requirements were derived from the technical research and were complemented with those necessary to enable the usage of the tool in a clinical research setting. Grouped in ‘Input’, ‘Data processing’ and ‘Output’, these requirements were addressed mainly to software qualities, although the inclusion of the position measurement involved usage qualities with impact either on the hardware and/or the software. The applied requirements (grouped in ‘specialist’ and ‘patient’) included those elements that would have an indirect impact, through the actions or reactions of the users during the measurements. From this set those requirements related to the patient where directed to the tool’s aspect and interface that should point to keep the patient ’relaxed’. Summarizing, the concept development should focus on a design for a device to measure the abdominal wall tension by means of force and distance. To facilitate research purposes, the possibility to record elements correlated with the basic measurements, as well as the option to measure and tracks one to seven different points on the abdomen should be included. Such device should be possible to be used in a clinical setting (e.g. intensive care unit, examination room), considering the patient’s reaction on the measurements.

Synthesis Phase

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Based on the list of requirements four concepts were developed. The main intention was to explore and define the interaction between the specialist, the device, and the patient. The main aim was to consider different possible ways in which the measurements could be performed in a fast and efficient way while the patient was relaxed. These concepts were evaluated afterwards concerning their feasibility to be made into prototypes in a short time.

Concept Evaluation For the evaluation of the four concepts a selection of the list of requirements was made. The concepts were evaluated regarding: cost, availability of components, amount of parts, easiness of use and technical complexity. The fourth concept was chosen, as it contained the fewer components, which were commercially available (except from the positioning grid). Another important feature of the chosen concept was its possibility to be modified, as the hand tool could be updated without necessarily affecting the software.

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Simulation Phase The chosen concept was re-evaluated and the functions were divided into hardware and the software, looking for flexibility, efficiency and possible cost reduction. One of the main changes made during detailing was the elimination of the silicone-positioning surface. Its functions were reassigned. Regarding the internal detailing, once the sensors were defined and their dimensions known, sketches were done to define the structure. Table 1. Concepts Concepts Concept 1

Concept 2

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Concept 3

Mean features ƒ Soft, warm and semi transparent material containing an array of coupled force and distance sensors. ƒ One side ended in the microprocessor, which included input (touch screen or buttons) and output (screen, USB port to download information, etc.) and on the opposite side a counter weight fixed the belt. ƒ As the different sensors were fixed on the belt, which at the same time was centre with the middle line and the navel, there was no need to leave marks on the patient or on the device to recognize the points measured the previous time. ƒ A pair of ‘glove like’ devices with the sensors in the core and an external replaceable latex protection, which can be used in a similar way as current palpation procedure. ƒ On the navel a kind of Global Positioning System (GPS) tracked the position of the measurements every time the hand sensors were activated, sending the sensors’ information along with the relative coordinates. ƒ All the components were linked to a microprocessor to control the sensors and store the obtained data. ƒ A soft blanket of an elastic material, located over the patient’s abdomen to keep the abdomen warm, intended to enable the specialist to measure on the entire surface as it tracked the point where the pressure was applied. ƒ The hand held device measured distance and the blanket measured force and position. ƒ Information from the hand device was transmitted wireless to the microprocessor. ƒ The big surface area covered sufficiently both thin and big abdomens.

Concept 4 ƒ One hand tool with one pair of force and distance sensors held by the specialist over the patient’s abdomen. ƒ For tracking the points, a grid of silicone with wholes that recorded the position of the measurement. ƒ Also connected to a microprocessor.

A prototype of the design proposal was built to evaluate the dimensions, construction and function of the internal structure (Figure 4). The final shell was made by means of rapid

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prototyping for user research. Figure 4 presents the prototype and Figure 5 a rendering of the final design.

Figure 4. Prototype.

Figure 5. Rendering of the final design.

Evaluation Phase

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The prototype was evaluated in an experimental setting (Figure 6). Eight different points were measured regarding the exerted force and the distance. The prototype was connected to a PC for data recording.

Figure 6. User research.

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The prototype could transport the recorded values of force and distance correctly to the PC. The prototype was used without any problems.

Decision Phase During this phase several recommendation were made: ƒ

ƒ ƒ

The force sensor used in the user research should be replaced with a calibrated one and the software should be detailed to subtract the resistance of the spring in the measurements. The interface has to be transferred from a desktop version to the pocket PC version. This interface is necessary if the test is going to be done in the clinical setting. In a clinical setting the prototype should be evaluated to assess how patient characteristics like BMI, age, gender, etc influence the measurements. This test could be used to estimate the possibilities and limitations of the tool.

CASE II: COGNITIVE ERGONOMICS - IMPROVING ERGONOMICS OF MINIMALLY INVASIVE SURGERY - GETTING THE MOST OUT OF AN INTEGRATED SUITE Text and drawings are derived from the master thesis of G. Scheepens, graduation project Delft University of Technology, Faculty of Industrial Design Engineering. October 2007 [12].

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Analysis Phase Short Introduction into Minimally Invasive Surgery During the mid to late 1980’s minimally invasive surgery (MIS) emerged and proved to be a surgical revolution [4]. The most widespread performed MIS procedure is the laparoscopic cholecystectomy (LC, gallbladder removal) and other common procedures are hernia repair and obesity procedures (like the gastric band). MIS thanks its popularity to the fact that patients experience less trauma and recover more quickly than after open procedures. This is a major benefit and makes the longer operating time and more complex procedure worthwhile. Problem Statement The Karl Storz OR1 integrated suite is implemented in one of the ORs of a teaching hospital. This integrated suite is capable of providing an ergonomically sound working environment, but now it is not used to its full potential. An explorative observational study showed that indeed the positioning of supporting equipment is a major source of physical inconvenience for the surgical team. Therefore this project focused on the positioning of surgical monitors.

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During the developments of the concepts two surgical procedures were kept in mind, LC and gastric bypass. These procedures were chosen because the LC takes only 45 minutes and is performed mostly by novice surgeons while the gastric bypass takes up several hours and is performed by an expert surgeon. During these procedures the designed product needs to ensure an ergonomically sound surgical monitor placement. The aim of this project was to improve patient safety by enhancing the working environment of the surgeon, creating an ergonomically sound workspace for the surgical team, focusing on the positioning of surgical monitors, where correct positioning is defined as compliance with the ergonomic guidelines. Many other factors influence the working environment, ranging from the design of instrument handles to the illumination of the operating room. The problem to solve within this project reads as follows: Design of a product that supports users in placing monitors in an ergonomically optimal position. It should work with or be an add-on to the Karl Storz OR1 integrated suite. A connection needs to be made between the ergonomic possibilities the integrated suite offers and OR staff who actually uses these possibilities.

The main problems identified were: Awareness: Observance of ergonomic guidelines during surgery needs to be enforced and encouraged. This includes communicating that there is a possibility to adjust the settings and why it is important to do so. Interaction: Optimal configuration of the equipment needs to be apparent during its positioning. This includes feedback about what the correct settings are, what these are for and how these can be adjusted. Continuity: For every MIS procedure correct positioning is needed and therefore must invoke its use every time a procedure is prepared.

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To solve the problem, its sub-problems have been divided over the seven characteristics of good interaction design to provide focus points during the synthesis [11]. The characteristics are of equal importance. 1) Trustworthy ƒ

ƒ ƒ

The product should prove that it is capable of helping the circulating nurse the monitors, it will be likely that there will be surgeons that demand a different setting than the optimal. Availability of the product is essential, it should always work and be present and not be especially be switched on or fetched from afar. To get the surgical team to trust the product, results are essential, on short term in the form of feeling of working in an environment adapted to them and in long term as decrease of physical complaints.

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The product should fit with the OR environment and work within its boundaries. Its communication should be innovative, inviting and effective, it should not take away attention from more important informational devices. The boundaries of OR1 should also be respected (not hinder other functionalities of OR1). Although the product should somewhat force its use on the users, it should allow its users to have the freedom to do what they like. The desire to use the product should be directed at the surgical team and the circulating nurse, while the ‘how’ of the use should be directed towards the circulating nurse. The product should be self-explanatory.

3) Smart ƒ

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The product should support its users in doing that what can be difficult in the demanding OR environment, remembering to position monitors, guidance in where monitors should be placed and propagate the need for positioning the monitors. The positions for the monitors are not absolute and need to be adjusted to the surgeon, specific procedures and to other equipment. Not always is the most ideal position the most optimal position. It is up to the product to direct towards preferred positions and prevent incorrect positioning. There are many skills that are better developed in humans than in machines and the products’ responsibilities should not try to replace those skills.

4) Responsive ƒ

The product should communicate incorrect positions as well as correct positions, without annoying users by creating saturated feedback in which important changes are difficult to detect.

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5) Clever ƒ

Using the product should ease workload, by taking away confusion and disagreement about what the correct positions of the equipment are. Taking away confusion about how settings relate to the human body and who has set specific preferences and what these are as well.

6) Lucid (playfulness) ƒ

Making errors in positioning monitors should be made difficult instead of displaying warnings. The opportunity to undo and redo actions is also important, so the users cannot get the feeling that pressing a button can get them trapped in a part of the system they do not need to visit. Confirming key actions comforts the users and reassures them that accidentally pressing a wrong button cannot lead to serious

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consequences. This last option gives them the opportunity to use and learn the system by browsing around, without it having serious consequences. 7) Pleasurable ƒ

ƒ

There are two sides to pleasure in using products: aesthetic and functional. People are more easily content with the performance of a beautiful product, products that look good are more pleasurable in use and will be used more and better [14]. Not neglecting this quality needs to be combined with the product functioning properly, obviously improper functionality leads to frustration and irritation in product use. The product does not need to fit the visual aesthetics of OR1’s software since these are about to change drastically in the near future.

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List of Requirements This list of requirements is based on the problem definition and design vision and Bitterman’s specific conditions and restrictions typical for the OR [2]. 1. The product will need to be used by inexperienced and experienced users, since in some hospitals the employee directory can change rapidly. 2. During some procedures two people view one monitor. 3. The maximum time during which the product can be used is three minutes. 4. There is no time for users to learn how to use the product. 5. Before the first trocar is inserted the preparation of the procedure needs to be complete, this includes equipment positioning which should not hinder other parts of the preparation. 6. During the procedure the system should not hinder any activities and should comply in case of unforeseen events (e.g. converting a MIS procedure to an open procedure). 7. Therefore the product should… a. …be silent. b. …not take up much space. c. …not cause electromagnetic disturbances. d. …not interfere with sterility during the procedure. e. …not affect the OR temperature. f. …not interfere with the illumination of the procedure (cast shadows, etc.). g. …not be visually distracting. 8. The product’s performance should not be affected by the characteristics of the OR environment. The product should be able to withstand… a. …the vapors caused by surgery. b. …moisture deposits on it. c. …thorough cleaning activities 9. The product should always be directly available, charged and switched on when OR1 is in use. 10. The product should posses a possibility to have its standard settings changed and have personalized settings created. 11. The life span of the product should be longer than at least ten years.

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Synthesis Phase

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Idea evaluation Eight ideas for equipment positioning were generated and evaluated along the design vision based on the factors awareness, feedback, continuity and viability (Figure 7). Other factors contributing to the evaluation are the positives and difficulties of every idea.

Figure 7. First-phase ideas: Eight ideas meeting the requirements and evaluated (rating in stars) on four aspects: Awareness, Feedback, Continuity and Viability. The italics lines capture the reasons for the particular ratings in a single line.

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Figure 7 provides a quick assessment of all the ideas’ pros and cons, but some influence the choice for a particular idea more than others. Awareness, feedback and continuity are equally important, but a high score on viability is essential for the successful implementation of an idea on short term. A low-tech solution has the most potential at the moment. The firstphase ideas (Figure 7) are technically quite complex and will be difficult to prototype and are more future solutions. Of the first-phase ideas, ideas 5 and 8 seem to be the most promising (Figure 8).

Figure 8. Second-phase ideas: Evaluation on eight aspects of two promising design directions.

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Idea 7 does not comply with the need to be an add-on for the integrated suite and ‘advice’ is a relatively expensive solution (viability problems). Finally, the visual feedback solution was chosen to elaborate.

Simulation Phase

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The most viable concept was the visual feedback solution in which a Light Emitting Diode (LCD) screen on the monitor’s back gives feedback on the ergonomics of the monitor position. A user research was designed mainly to test the usability of the product. Though initially planned, approximate positioning could not be tested. The product was validated with a simulated prototype in the hospital. The set-up consisted of a cart that was used for MIS before the integrated suite became available, with a boom-arm attached monitor (Figure 9). At the back of the monitor a small video display was attached that displayed the image from a camera mounted on top of the monitor. A laptop was used to project an image overlay on the video.

Figure 9. Set up user research.

There are several points of attention that emerged from the user research. Most importantly, distance assessment needs to be improved. The reaction of the surgical team towards the product (or at least towards someone looking into this matter) is favorable. This can also be concluded from the fact that 21 subjects participated in just a few hours and the fact that in the afternoon people started to come in after hearing about the user research from colleagues.

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Evaluation Phase The results of the user research are used to improve the design proposal (Figure 10). The essential element of the final product is the LCD that communicates ergonomic positioning of all team members to the circulating nurse. They are the people that have the most direct need for feedback about equipment positioning and are most likely to welcome it. This feedback on the LCD is available during the entire procedure; the LCD’s are mounted to the monitors’ backs and their illumination is therefore directed away from the surgical team.

Decision Phase

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The final design proposal should be evaluated with the users. Regarding the results of this user research the final design proposal should be improved for production.

Figure 10. Final design.

Future versions need to be integrated and joint ventures need to be considered, to be able to provide a complete solution.

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CASE III: PHYSICAL ERGONOMICS - DESIGN OF A HANDLE FOR CURVED INSTRUMENTS Text and drawings are derived from the master thesis of F. Hoolhorst, graduation project Delft University of Technology, Faculty of Industrial Design Engineering. May 2005 [6].

Analysis Phase Minimally invasive surgery (MIS) is a universally adopted way of surgery next to the conventional open procedures. The patient benefits from MIS. However, the disadvantage for the surgeon and his team are bad ergonomics, longer operation times, higher budget for OR equipment, less freedom of movement and the need of extra training. Therefore new methods and products to improve MIS are regularly introduced.

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Problem Statement At this moment most of the instruments that are used during MIS are straight and long instruments. It is believed that curved instruments might offer a solution to some ergonomic problems of the surgeon (Figure 11). Especially when used in solo-surgery, i.e. a form of surgery in which the numbers of team members is minimized. The current curved instruments still introduce many problems in the field of physical and cognitive ergonomics. Van Veelen states that problems in this field may lead to higher muscle-activity of the surgeon, resulting in fatigue and discomfort for the surgeon, excessive pressure on sensitive areas of the hand and fingers causing nerve injuries [15]. The aim of this project was to improve the handle of a curved instrument, paying extra attention to ergonomic problems of the current handles.

Figure 11. A curved and straight instrument.

List of Requirements Literature was reviewed on curved instruments, handles for MIS instruments, anatomy of the shoulder, elbow, wrist and hand and body posture. In addition, a practical study to evaluate the use of current curved instruments in the OR was performed A set of requirements for the new handle was formulated. The most important requirements are described below.

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Functional requirements ƒ ƒ ƒ ƒ ƒ ƒ

The handle allows one-handed use. The handle can be used with an existing shaft. The handle allows force grip and precision grip. The handle incorporates opening and closing of the tip. The handle allows for fixation of the tip. The relation between force exercised on the handle for opening a closing of the tip and the force on the tip is between 1:5 and 1:7.

Ergonomic body posture and instruments comfort ƒ ƒ ƒ ƒ ƒ

The handle can be held comfortably for different rotations within certain limits. The handle should be operated by the sensitive area of the hand. Functional elements like buttons should be easy accessible. The shaft of the instrument has to be in-line with rotation of the forearm. Low muscle activity is necessary to manipulate the functional elements.

Synthesis Phase

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Based on these requirements different ideas were generated. Several product ideas were based on a bar shaped grip (Figure 12). Other ideas were based on pistol handles (Figure 13) and finally mouse handles were sketched (Figure 14). Based on these ideas two concepts for a new handle were introduced. The handles’ shape was based on different clay models and technical principles for opening, closing and fixation of the instruments were made (Figures 15 and 16).

Figure 12. Product ideas for a bar shape grid.

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Figure 13. Product ideas for a pistol handle.

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Figure 14. Product ideas for a mouse grip.

Figure 15. Concept 1.

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Figure 16. Concept 2.

Idea Evaluation The concept choice is based on the evaluation of the idea regarding the general guidelines and requirements that were defined earlier in this project. The requirements were of equal importance. The concept meeting the most requirements was chosen for further development. Some of the requirements could not be used during this phase. Concept 1, based on the mouse grip, met 12 of the important requirements, against Concept 2 that met only 10. Therefore Concept 1 was chosen to be materialized.

Simulation Phase

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The final design was based on the grip of a ball of Ø50 mm. This ball shape has two asymmetric surfaces, which provide the surgeon a more stable grip. Also by doing so, the grip provides the surgeon feedback on the orientation of the tip. The shape of the buttons has been optimized in order to improve the control. Figure 17 shows the final product design.

Figure 17. Final product design.

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Evaluation Phase The prototype was evaluated in a simulated environment in the OR (Figures 18 and 19). The tasks of the subjects were to cut out a circle (diameter 40 mm), which was drawn on a piece of paper. For executing this task, in the left hand the curved instrument was held. Each subject had to perform the test twice, namely with a straight instrument and with a curved instrument with the new handle. During execution of the user research, the body posture was recorded with two cameras. After the user research, the posture was visually inspected every ten seconds during the task and the following joint angles were measured: ƒ ƒ ƒ ƒ

Angle of the elbow. Flexion and extension of the wrist. Horizontal flexion of the shoulder. Pronation and supination of the forearm.

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Figure 18. User research in a simulated OR environment.

Figure 19. User research during cleaning and sterilization.

The results of the user research are shown in Figure 20. The results are based on a comparison, which was made with an existing straight instrument. The circle diagrams give insight into the subjects’ body posture during the user research. These show how long a certain posture was adopted. The green parts show how long a body posture was adopted

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regarding the ergonomics guidelines. Practically, no differences could be found in the elbow’s posture. For both instruments the angle between the upper arm and forearm was almost constantly held in the green zone. It seems that instruments handles do not only influence the posture of the elbow. Elbow posture is mainly influenced by the height and the angle of the instrument’s tip. The main difference in body posture could be found in the flexion and extension of the wrist. With the prototype, the wrist was adopted in an ergonomic posture for 85% of the time. The horizontal flexion of the shoulder was always within the ergonomic zones. There was a slightly difference in the pronation and suppination of the forearm. The posture using the prototype was 20% of the time not in the ergonomic zone and for the curved instrument this was 26%.

Figure 20. Results of the user research.

Decision Phase At the end of the project it was concluded that the new handle design has many advantages with respect to the already existing MIS handles.

General Design The new handle provides an integral design solution. The ball shape allows hiding controls that can disturb the surgeon during his activity.

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Ergonomic Comfort The user research results indicated that many ergonomic advantages are expected for the handle. The handle also allows the surgeon to assume a more ergonomic posture. Indications from the User Research Remarks of the test subjects during the research indicated that the new handle did not cause pressure points on the hand during use. Furthermore subjects experienced the prototype as comfortable. Another advantage is that both hands can use the handle.

CONCLUSION The chapter ‘Ergonomics in the Operating Room – an Overview’ showed the several disciplines of ergonomics and its related problems. At the faculty of Industrial Design Engineering (IDE) of the Delft University of Technology (DUT) products relating to these domains are developed and researched by means of the basic design cycle of Roozenburg and Eekels as a design framework. Within each design cycle all domains of ergonomics are included. However, the focus is different. In addition, the problem statement and the amount of available information in analysis phase influences the outcome of other phases. For example, in case of product redesign information on working principles, material, production and usage are already available. These can be used as valuable input for the synthesis phase. In case of a new innovative product no information is available. This has to be researched in the analysis phase, reducing the amount of time to be spent in other phases such as evaluation by means of user research. This shift of focus is reflected in the three described cases. The differences are discussed briefly.

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Case I: Sensorial Ergonomics – Abdominal Wall Tension Measurement Device The starting point of this case was rather hypothetical. The assumption was that the abdominal wall tension was probably associated with development of incisional hernia. There was no quantitative method available to measure the abdominal wall tension directly on patients’ abdomen which means that questions as: What to measure? How to measure? and Where to measure? arises. The hypothesis that abnormalities in the abdominal wall tension were associated with development of incisional hernia was an answer to the question ‘What to measure?’. By measuring the abdominal wall tension an indication of a potential development of incisional hernia was obtained. The next question was ‘How to measure?’. The performed observational research and interviews with the specialists gained insight into which factors are relevant to formulate a prognosis. From this research it has concluded that the level of force exerted needed to indent the fingers was a valuable feedback for the specialist. An existing force measurement device was used to evaluate this principle.

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Figure 21. Adjusted design cycle Case I.

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Since the abdominal wall has different structures it was important to assess which points will provide reliable data. As should be clear the design team had a lack of knowledge and therefore from a very early phase in the design process input from research and feedback from the user was needed. The adjusted design cycle for this case is illustrated in figure 21. The outcome of this project was a working prototype. With this working prototype user research was performed to evaluate the design proposal. Because of the extensive analysis phase, which was time-consuming, the user research was only superficial. However, the design proved to be a good starting point for further product development.

Case II: Cognitive Ergonomics – Improving Ergonomics of Minimally Invasive Surgery- Getting the Most Out of an Integrated Suite The starting point of this case was very different than the previous case. There was already an integrated suite available and this suite was capable of providing an ergonomically sound working environment. Therefore, define the pre-conditions of the design proposal. However, the ergonomic possibilities were not used to its full potential. Design team’s approach was: first assess why the surgical team was not using the already existing functionality and second how to convince them to use the functionalities. After an observational study it became clear that the positioning of supporting equipment was a major

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source of physical inconvenience for the surgical team. The focus was on positioning the surgical monitors. Anticipating on future developments, OR aesthetics and usage, the design had to be an interface. Therefore, approach from the interaction design was chosen as a starting point. Seven characteristics of a good interaction design, which were already evaluated by other experts, were used during synthesis phase to convince the surgical team about its benefits. As should be clear the design team already knew in an early phase of the design process what to design and therefore the project focused on how to design. The adjusted design cycle for this case is illustrated in figure 22.

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Figure 22. Adjusted design cycle Case II.

The outcome of this project was a detailed simulation. The performed user research with this simulation was in-depth resulting in an improvement of the design proposal.

Case III: Physical Ergonomics – Design of a Handle for Curved Instruments The starting point of this case was as Case I rather hypothetical. The assumption was that curved instruments might offer a solution to some ergonomic problems experienced by the surgeon. Although, this case had a hypothetical starting point there were differences with Case I. In this case there was an existing curved instrument, which had limitations that had to be improved. This well-defined and focused starting point of the process increases the level of elaboration in the next phase of the design cycle. In the synthesis phase next to the drawings,

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early models (i.e. clay models) were used to evaluate the shape and some technical principles. This gives the design team the advantage of anticipating on the future use of the product. With the knowledge gathered from the first user research the quality of the final design proposal was improved. The adjusted design cycle for this case is shown in figure 23.

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Figure 23. Adjusted design cycle Case III.

The outcome of this project was a detailed prototype. With this prototype a user research was performed whereby the existing straight instrument was compared with the prototype of the design proposal. The results of this user research were sufficient to evaluate the design proposal objectively. The basic design cycle is a robust design framework that can be used during product development with different insights. At the same time it gives the design team the flexibility to do user research in each phase depending on the kind of proposal. The iterative character of the design cycle makes this possible. Since the basic design cycle contains a few decision moments between the phases, actively involvement of the user is essential. Each decision made in a phase forms a starting point for the next phase. The ‘Participatory Design’ methodology requires that end-users have to involved and actively participate during the process. This way of involvement provides the knowledge from the professions to the design team. When designing for the OR, this means involving all the members of the surgical team. However, the design team consists of more people of different

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disciplines. Some of them are involved continuously, others intermittent. Involving additional expert creates a better understanding of problems and possible solutions can be implemented and tested in an earlier stage. However, the design team should not consist of too many people, as this could slow down the process of decision-making. The products designed at IDE include user research in different phases of the design cycle, in which the intended end-users are actively involved. However, this research sometimes has to be conducted in an experimental setting. Especially when designing products for the OR, it is difficult to test these in the sterile field. However, with the increased awareness of the importance of the environment, and therefore the environmental ergonomics, testing in a ‘real’ environment is important, because sudden events during procedures cannot be simulated. Many of the products developed at IDE are innovative. The number of patents and national and international prizes prove this. In addition, more products are being actually produced by industry. This can be improved by involving the industry and companies during the design process, which in addition also leads to more realistic prototypes. In the end, smart products and processes for the OR are designed which specialist love to use, in order to fulfill the patients’ needs.

REFERENCES [1] [2] [3]

[4]

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[5]

[6] [7]

[8]

[9]

Alvarez, N. A. (2006). Master thesis: Abdominal wall tension measurement device: Delft University of Technology, Faculty of Industrial Design Engineering. Bitterman, N. (2006). Technologies and solutions for data display in the operating room. J. Clin. Monit. Comput., 20(3), 165-173. Cobb, W., Burns, J., Kercher, K., Matthews, B., Norton, H. J., and Heniford, B. T. (2005). Normal Intraabdominal Pressure in Healthy Adults. Journal of Surgical Research, 129(2), 231-234. Gallagher, A. G., and Smith, C. D. (2003). Human-Factors Lessons Learned from the Minimally Invasive Surgery Revolution. Seminars in Laparoscopic Surgery, 10(3), 127-139. Grässel, D., Prescher, A., Fitzek, S., Keyserlingk, D. G., and Axer, H. (2005). Anisotropy of human linea alba: a biomechanical study. Journal of Surgical Research, 124(1), 118-125. Hoolhorst, F. (2005). Master thesis: Design of a handle for curved instruments: Delft University of Technology, Faculty of Industrial Design Engineering. Junge, K., Klinge, U., Prescher, A., Giboni, P., Niewiera, M., and Schumpelick, V. (2001). Elasticity of the anterior abdominal wall and impact for reparation of incisional hernias using mesh implants. Hernia, 5(3), 113-118. Namioka, A. H., and Rao, C. (1996). Introduction to participatory design. In Field methods casebook for software design (pp. 283 - 299 ). New York: John Wiley and Sons, Inc. park, A. E., Roth, J. S., and Kavic, S. M. (2006). Abdominal wall hernia. Current problems in surgery, 43(5), 326-332.

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[10] Roozenburg, N. F. M., and Eekels, J. (1995). Product Design: Fundamentals and Methods. Chichester: John Wiley and Sons Ltd. [11] Saffer, D. (2007). Designing for Interaction: Creating Smart Applications and Clever Devices. Berkeley. [12] Scheepens, G. (2007). Master thesis: Improving ergonomics of minimally invasive surgery - getting the most out of an integrated suite: Delft University of Technology, Faculty of Industrial Design Engineering. [13] Song, C., Alijani, A., Frank, T., Hanna, G., and Cuschieri, A. (2006). Elasticity of the living abdominal wall in laparoscopic surgery. Journal of Biomechanics, 39(3), 587591. [14] Tractinsky, N., Katz, A. S., and Ikar, D. (2000). What is beautiful is usable. Interacting with Computers, 13(2), 127-145. [15] Van Veelen, M. A. (2003). Human-Product Interaction in Minimally Invasive Surgery: A Design Vision for Innovative Products. Delft University of Technology, Delft. [16] www.iea.cc. The International Ergonomics Association. Retrieved 27 May 2008, 2008. [17] www.wsacs.org. Concensus definitions and recommendations. Retrieved March 15, 2006.

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In: Ergonomics: Design, Integration and Implementation ISBN 978-1-60692-327-6 Editor: Bram N. Brinkerhoff © 2009 Nova Science Publishers, Inc.

Chapter 6

ERGONOMIC CONSIDERATIONS FOR THE RADIOLOGICAL WORKSPACE P. M. A. van Ooijen1,∗ and A. W. G. van Ooijen2 1

University Medical Center Groningen, University of Groningen, Groningen, The Netherlands 2 Van Ooijen Design, Zwijndrecht, The Netherlands

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ABSTRACT With the digitalisation of the radiology department, the workspace of the radiologist moved from the dark room with walls covered with lightboxes to an office workplace equipped with a multi-monitor workstation. Besides the basic workstation required for examining the images, many peripherals are added to this workspace for interaction and digital dictation. A default workspace can be equipped with a keyboard, mouse, foot controls and digital speech microphone. However, other peripherals such as dedicated keyboards (e.g. for mammography) or a special mouse can be added. All these changes that were introduced with the transition from lightbox to workstation greatly changed the way a radiologist works. Therefore, the ergonomics of the radiological workspace has gained interest in recent years and studies have been performed to evaluate and enhance the ergonomic conditions of this workspace. Furthermore, different input devices are studied and tested within the radiological workspace many of which originate from either graphical design or the gaming applications.

1. GENERAL INTRODUCTION Radiology has shown a shift to (fully) digital operation in the past decades with an increasing number of radiology departments starting to adapt to a digital, soft-copy, ∗

Corresponding Author: P.M.A. van Ooijen, MSc, PhD. University Medical Center Groningen, University of Groningen. Department of Radiology, Hanzeplein 1, 9713 GZ Groningen. The Netherlands. Phone: +31503612286. Email: [email protected]

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workflow. Although this shift in some cases resulted in a little increase of the interest in ergonomics, the traditional lack of space in hospitals and the habit of having dark rooms for image viewing hampers the implementation of decent ergonomic workspaces. To support the transition to a digital radiology workspace, many papers have been written on the introduction of Picture Archiving and Communication Systems (PACS) within radiology departments and the deployment of workstations for patient evaluation [Steckel94] [Shimamoto94] [Carrino98] [Bick99] [Foord99] [Strickland01] [Hayt01] [Hirschorn02] [Sacco02]. Some of these publications demonstrate that the introduction of workstations instead of film alternators in the radiology department has put high requirements on these workstations [Arenson03] [Harisinghani04]. Other articles describe the use of multi-monitor systems and discuss the optimal number of monitors to use for a PACS workstation [Bennett02] and some years ago also whether LCD displays could replace the generally accepted and installed CRT displays [Reiner97]. However, although it is the main interest of the radiologist, only recently articles have been published that evaluated the design and implementation of the actual PACS workstation itself and its environment [Arenson03] [Nagy03] [Harisinghani04] [Siddiqui06]. Earlier articles were published evaluating user satisfaction with commercially available workstations [Foord99] [Honea98] [Bazak00] [Pollack00] showing that satisfaction with these workstations varies widely and is not optimal. However, they only evaluated the workstation viewing software and not the full range of software tools in combination with the whole workstation environment. The PACS workstation is the replacement of the lightbox of the radiologist. This workstation has to provide him with the same functionality as his lightbox and more. Therefore, PACS workstations should meet certain requirements and should be capable of certain tasks and, additionally, careful attention has to be paid to the full workstation environment in all its aspects. Commonly named requirements of the radiological workstation are: fast and easy availability of all current and historical image data, fast and easy availability of additional resources (e.g. lab reports, old radiology reports, ECGs, etc.), availability of easy to use three-dimensional (3D) visualization capabilities on the desktop, digital speech recording and recognition with high level of speech recognition close to 100%, one single workstation with multiple displays and as little log-in procedures as possible (single sign-on principle), avoid typing information and manual tasks by integrating separate software modules, easy use with integrated software, and a flexible workspace (every radiologist should be able to use every workstation). However, most of these requirements only focus on the workstation hard- and software, and not on the complete environment. The first papers on the negative effects of radiologists working at workstations for multiple hours per day have already been published showing complaints of eyestrain, neck pain, shoulder pain and cubital tunnel syndrome that are most likely related to workstation tasks [Nagy03] [Ruess03] [Kumar04] [Pradhu05] [Siddiqui06]. Therefore, the careful evaluation of the radiological workspace incorporating important ergonomic considerations is very critical for the next few years. In this chapter we will cover the whole range of ergonomic considerations that could influence the way the radiological workspace environment is designed and implemented. Different aspects of implementation are covered ranging from the software to the peripherals and environmental aspects. Furthermore, a perspective into the future of the rapidly evolving digital radiological workspace is presented.

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2. ISSUES TO BE COVERED IN RADIOLOGICAL WORKPLACE DESIGN When designing the digital radiology workplace, different considerations have to be made about hardware configuration, software configuration and integration, environment (lighting, climate control), general workplace properties, and peripherals. An overview of all these different topics will be presented in this chapter.

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2.1. Number and Configuration of Displays One issue discussed in literature which is a very important factor for ergonomics of the radiological workplace is the number and configuration of the displays used on a PACS workstation [Bennett02] [Nagy03] [Siddiqui06]. In the early days of PACS and soft copy reading, the tendency was to configure a PACS workstation similar to a conventional lightbox environment to provide a similar working environment to the radiologist. This meant that workstations were equipped with four or even more diagnostic displays. However, other concepts also arose where it was advocated to use fewer displays. However, there is a trade off between too few and too many displays. Too few displays will lead to the inability to effectively place and use all different applications needed and a lack of space when viewing multiple series with many images at the same time. Too many displays will introduce the fact that the mouse cursor tends to get lost and has to travel a long way across multiple displays to reach the target area and the need for large head and eye movements required to observe all data. An additional problem with multiple displays used for reading images is the large bezel in between adjacent images on different displays. It was shown by Bennett et al. [Bennett02] that the number of displays required by a radiologist decreases with increasing experience with softcopy reading. A main reason for this decrease was the ability to interact with CT and MR datasets in a stack using a mouse to scroll through the images. Siddiqui et al. [Siddiqui06] declare that going from a one display workstation to a two display solution increases productivity (a 21% increase in radiologist reading speed when reading chest X-rays) and accuracy. Furthermore, they state that no additional advantage was found when expanding the workstation from two to four diagnostic displays. A similar result was published by Nagy et al. [Nagy03]. They stated that interpretation times are similar for workstation setups with 2 or 4 diagnostic displays. The selection and amount of the software tools to be used on a PACS workstation not only influences the number of monitors to use because they need to support efficient handling of the different windows, but also their setup as either landscape, portrait, or mixed. The trend towards a setup with as few displays as possible has positively effected the penetration of PACS workstations in most hospitals, since the cost per workstation decreased considerably with fewer displays but it also changed the ergonomic issues concerned with multi display workstations. In summary, when using multiple displays the ergonomic considerations are:

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Portrait, landscape or mixed

Technically, using only one direction will provide easier travel with the mouse than using a mixed setup. Required desk space is also an issue since the footprint of two landscape monitors is much larger than that of two portrait monitors. Modality type viewed on the displays also influences the choice. Since standard, conventional, X-rays are rectangular and are taken mostly in portrait mode, a portrait display can present this type of image more efficiently than a landscape display. However, CT and MR are mostly square images, so display orientation is not really an issue. Other modalities, such as e.g. Ultrasound, are acquired in landscape mode and could be viewed more efficiently on a landscape display.

•

Display resolutions

Mixed use of different display resolutions can be inconvenient because of the mouse jumps and the difference in mouse speed which will hamper the eye-to-hand coordination when moving from one display to the other. Besides these more technical issues, again the type of image displayed plays an important role. Typical CT examinations have a resolution of 512x512 pixels, so a 1 on 1 presentation of these images is possible on a low resolution display. However, a typical digital mammogram will be acquired with over five mega-pixels, thus requiring a very high resolution display. The increased integration of text-based applications, such as speech recognition, requires the use of lower resolution displays since font size tends to get too small on the five mega-pixel displays. This is why in many cases, mixed display setups are realized with high resolution, medical grade, displays for the images and lower resolution displays for additional information sources.

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•

Number of Displays

The more displays, the easier it is to get lost and the more movement of eyes and head is required during reporting. Fewer displays decrease these issues, but may hamper the correct positioning of all required images and tools on the screen and thus lead to a large amount of application switching. Besides this, as already explained above, the requirements of different types of information to be presented on the workstation might require the use of multiple displays of mixed type (for example: high-resolution, grey scale, portrait displays for X-rays combined on the same workstation with lower-resolution, color displays for speech recording software and display of medical records).

2.2. Multi-Vendor Functionality Integration Diversity in functionality is required on the radiological workstation to guide and support the process of reporting which involves searching and displaying the right image data,

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examining this data together with additional clinical information of the patient, formulating and dictating a report and finally transcribing the report and storing it into the radiological information system (RIS). Although some investigators decided to build their own PACS workstation from scratch by designing their own software [Tahoyori02] or even hardware [Kim03], a more common decision is to configure a workstation by combining and integrating multiple components from different vendors to handle different portions of the process. So, in most cases, a best of breed approach is taken because no vendor has it all. This approach requires advanced and extensive integration between the different software components to obtain a workable and an ergonomic solution. As an example, the typical radiology workstation contains software packages for radiological information system (RIS) access, basic radiology viewing, advanced 3D rendering and image processing, speech recording and recognition, electronic patient record (EPR), and possibly also software for maintaining teaching files. Besides these dedicated applications, general software tools such as webbrowsers, e-mail software, and word processors are also common. Although some vendors are using Linux based workstations, most provide software tools running under a version of Microsoft WindowsTM on a, more or less, standard high-end personal computer. The RIS provides the radiologist with a personalized worklist and with information about studies waiting to be reported or to be signed off. Furthermore, after selection of the study to report, access to additional information of that particular patient such as the previous studies performed by the radiology department in this patient including their reports has to be provided. In a teaching hospital, a radiologist would typically also get information in the worklist screen about the temporary reports of the residents under his or her supervision. The standard radiology viewer provides fast access to the complete patient image history. After displaying the desired images the user has access to basic viewing capabilities such as, for example, window/level, cine loop, and measurements. Personalized settings about default on-screen buttons and other preferences should be connected to the user and not the machine. An ergonomic feature included in many standard radiology viewers is the hanging protocols feature. Hanging protocols provide default display configurations specific to the image data loaded at that moment. A key issue with these hanging protocols is that they should be easily configurable by the user since the setup of the screen is not standardized but really more a matter of taste and habit. The 3D visualization software provides 3D viewing. Depending on the setup this functionality can either be integrated into the standard PACS viewer or available as a separate module form a dedicated company. Increasingly, 3D visualization software is available as some kind of client server setup in which all rendering is performed on a central server allowing fast and easy access to advanced visualization capabilities. The local machine only runs a small client application that displays the results calculated by the central server. Speech recording and recognition software can also be server based. This means that both the speech profile and the dictation voice files are stored on the central server, providing maximum flexibility to the user. For example, a user can stop dictation of a report, save his partially completed report on the server, and commence dictation later on using the same logon on a completely different workstation. The electronic patient record (EPR) discloses patient information from various resources throughout the hospital through one single web interface. This includes textual information

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such as lab and surgery reports, but also information like electrocardiograms (ECG) or even visible light images from digital cameras. From this EPR, selected radiological images (both source and reconstructed images) are also available to other physicians outside radiology. When all separate components have been selected in a best of breed process, the question is how to integrate the different components and how they should be integrated (level of integration, which component will be leading, etc.) to obtain an environment that is both user friendly and ergonomic. The requirement is to integrate the separate components into one integrated workspace. To achieve this goal different connections between the separate software modules have to be defined and implemented based on the workflow of a radiologist. The general workflow that can be defined for the work of a radiologist [Horii99] contains the gathering of general information (patient history, clinical data, etc.), the rapid review of the image set (studies, series, images) to detect possible pathological candidates and the careful exploration of the possible pathological candidates to exclude significant and relevant findings that form the basis of the final report. Since all of the components described above are equally crucial during this workflow, their optimal integration is a major issue. This means that all software packages should be capable of sharing patient information and ideally will keep all other components informed about their status in order to make sure that information about the same patient is displayed in all software tools and therefore avoid mistakes. However, a good integration of the software tools does not only have the clinical reason of avoiding mistakes, but it also has an ergonomic reason. In a well integrated system, the mouse movement and interaction of the user with the system is minimized without compromising the quality of the work. A first step would be the synchronisation of the patient loaded; this can be achieved two different ways. The first possibility is by automatically updating a patient in all applications when a patient switch is made in one of them. A second solution could be to define one application as the leader and having all other applications follow this leader including closing down when the patient is closed in the leading application. Furthermore, the same level of integration should be achieved on the level of the studies and series of a patient. For example, a 3D application should, upon request of the radiologist, load in the series of the patient that the radiologist is reviewing at that moment, not a random selection from the series within the current study. A proper integration will not only lead to a reduction in keyboard use, but also to a decrease in mouse interaction since the correct data is readily available in all applications. In summary, the integration of different resources into one single PACS workstation is obligatory for fast reporting by the radiologist in a digital radiology department. This integration is only possible by careful selection of commercially available soft- and hardware and by requiring a predefined level of integration as part of the acceptance test of a new functionality.

2.3. Workspace Table/Chair Configuration The importance of the general ergonomics of the workspace was extensively covered by Harisinghani et al [Harisinghani04]. They stated that considering general ergonomic issues when designing a radiological workspace can reduce fatigue and increase productivity.

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General ergonomics include the position of, for example, the monitor(s), input devices, desk and chair. Properly positioning your equipment, desk and chair is a fairly easy way to increase ergonomic efficiency, but often forgotten [Buurman01] [Boston01].

2.3.1. Setting Your Chair and Desk Height The forearm should be in a straight line with the hand, so the wrist bends as little as possible. The thighs should be parallel with the floor and the back has to be straight with the curved lumbar portion of the back of the chair to fit the bottom of the rib case. This can be achieved by adjusting the chair and if possible the height of the desk. When the desk height is not or not sufficiently adjustable, a possible solution could be to introduce an adjustable foot rest (figure 1).

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Figure 1.Position of user behind the desk.

2.3.2. Monitor and Keyboard Position The monitor should be right in front of you. If you have to use multiple monitors which is often the case with a PACS workstation, it is best to place the monitor which shows the most valuable information right in front of you, other monitors should be placed close to this monitor. Try to keep the angle that the head should make to view the second or third monitor 30 degrees or less. The distance between the eye and the monitor should be somewhere between 50cm and 70cm (figure 2). An easy reminder of the right distance of the monitor is to stretch the arm, the palm of your hand should just be able reach the top of the monitor, when you are in the upright sitting position [Boston01]. The most comfortable field of view for the eyes is 0-30 degrees vertical. It is best to tilt the monitor a little to make the distance from your eyes to the top of the screen the same as the distance from your eyes to the bottom of the screen, when your desk and chair are properly adjusted this should be about 15 degrees [Buurman 01], see figure 1. When you look straight forward you should look at the first line on your monitor [Boston01].

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Figure 2. Second monitor and optimal stretch of arm.

2.3.3. Position of Other Input Devices Also shown in figure 2 is the optimal and maximum stretch of the arms. Input devices should all be in the optimal reaching zone. If devices which are often used, like the mouse, are not in the optimal reaching zone it will be at the least uncomfortable. Devices which are not often used can be placed in the maximal reaching zone. If devices are out of the maximal reaching zone the user has to bend forward or move to get them.

2.4. Selection of Adequate Peripherals

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To work adequately with a modern radiological workstation, several peripherals are required. Besides the general ones that are available on any workstation (mouse and keyboard), additional peripherals are required for voice dictation (microphone, headset, speechmike, foot switches) (figure 3) and playback of recorded files (headset, speechmike, speakers, foot switches), and perhaps for scanning barcodes (speechmike, barcode reader). Choices for these different peripherals and the way they are used and provided is a main concern to obtain an ergonomic workstation.

Figure 3. Typical headset and speechmike that can be used for dictation. Note the added interaction keys on the speechmike for controlling the recording. With the headset the control of the recording has to be performed using a mouse or foot controls.

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A frequently heard ergonomic problem with the radiological workstation is the multitude of peripherals that have to be used consecutively. Constantly switching peripherals will probably reduce the risk of repetitive strain injury (RSI) but it will also slow down the work and thus possibly increase the time spent behind the workstation each day. For example, when using a speech mike and a mouse during dictation, the radiologist has to put down his speechmike in order to type something or to use control keys on the keyboard that have to be used together with the mouse (e.g. CTRL or Shift key) [Pradhu05]. Several solutions could be introduced with other peripherals. A first possibility would be to change to a headset with recording controls on foot switches by which the radiologist will have one free hand to operate the keyboard. Another solution could be to introduce foot switches for often-used key strokes such as the CRTL or Shift keys so the keyboard is not needed anymore to press those keys. Advanced mice with task keys in combination with a table microphone are a third possible solution. Current hardware suppliers also provide speechmikes with trackballs included (figure 3). The experience in our hospital is that most radiologists are not using this possibility since the thumb operated trackball is too difficult to use and too slow. This example shows that the choice of (a combination of) peripherals can largely influence the satisfaction of and the strain on the user. However, different combinations are specifically made for different ways of working. Therefore, the combination of peripherals and how to use them is very personal and can vary per radiologist. Careful considerations have to be made to select the most ergonomic, efficient and satisfactory solution for a particular situation and radiologist. Our advice is not to stay too focused on the default peripherals that are provided with the computer but to look at the workflow and computer experience of the individual radiologist in order to be able to replace or add those peripherals that could help to obtain a more efficient and ergonomic workflow.

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2.5. Environmental Issues Besides the Workstation and the workspace, the environment surrounding the radiological workplace also plays an important role [Harisinghani04]. Issues like temperature, ventilation, (ambient) sound and lighting also influence the productivity of the radiologists [Ratib00] [Abdullah01]. Ambient sound can be produced by many factors that can be both human and mechanical. Human ambient sound is likely to be caused by colleagues working at neighbouring workstations or having conversations in traffic areas. Mechanical noise can be caused by the workstation itself with different possible causes such as the ventilators and hard drives [Huang04] or also by other equipment in the reading room such as the air-conditioning [Nagy03]. Possible solutions can be found in placing sound barriers between different workspaces or in installing sound-masking devices. With sound-masking devices, a white noise similar to the noise produced by an air-conditioner is added to the room. By doing this, unwanted noise is covered-up and less annoying [Nagy03]. With lighting two different problems are defined: glare and ambient luminance. Glare concerns the sensation produced within the visual field by luminance that is sufficiently greater than the luminance to which the eyes are adapted. Glare can be caused by bright objects such as windows, bright lights and light objects (e.g. clothing) that reflect into

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the computer screen and can lead to annoyance, discomfort or loss in visual performance and visibility. In the hospital situation, particularly the white cloths typically worn by most physicians can cause glare. Glare can be either direct, e.g. light sources in the visual field behind the computer screen, or indirect, e.g. a reflection of a light-source on the computer screen. Figure 4 shows that placement of light behind the user can cause glare on the computer screen and light in front of the user can blind the user which also makes it difficult to view the screen. Ambient luminance concerns the global lighting of a room. Whereas high ambient lighting is favourable in general working situations, in the case of evaluation of radiological images, it can reduce the quality of the perceived image on the display. When the global lighting level (ambient luminance) is too high, this will degrade the ability to distinguish detail on the workstation. However, when it is too low, additional sources of information such as paper can not be read. The difficulty is to find the right balance to allow reading and not to degrade the workstation display quality. Nagy et al. [Nagy03] described their experience with decreasing accuracy of radiological interpretation with increasing levels of ambient lighting ranging from 85% accuracy with lights off to only 74% accuracy with overhead fluorescent lighting fully on. However the research of Brennan shows that the luminance of LCD monitors is far less than that of the lightboxes [Brennan01]. In his test 79 experienced radiologists had to examine 30 postanterior wrist images and had to decide whether there was a fracture or not. These images were being shown with five different ambient light levels: 480, 100, 40, 25 and 7 lux. The best results were with 40 and 25 lux, meaning lesser false positive and false negatives than with the other ambient lighting levels. Experience in musculoskeletal trauma appeared to compensate in part for inappropriate lighting levels.

Figure 4. Glare and blinding lights.

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3. CURRENT STATUS 3.1. Literature A lot of research has been done on workstation design and analysis of work patterns of radiologists [Bennett2002] [Boehm2004] [Moise2004] [Huang2004] [Moise2005a] [Moise2005b]. When considering the workstation itself, workflow is a returning theme. It is mentioned multiple times in literature that workflow should not be copied from hard-copy to soft-copy reading but that redesign of the workflow is required. With a good workstation design, the workflow of the radiologist can achieve over 40% of increased efficiency [Moise2004]. According to Moise et al. [Moise2004] the main focus should be put on the careful design of hanging protocols. The radiology working environment has also been the topic of multiple studies [Ratib2000] [Horii2003] [Harisinghani2004] [Siddiqui06]. Important considerations here are the use of the room, its size, the location and the environment supporting services (e.g. heating, ventilation, air conditioning, etc). Important to acknowledge is that different types of institutions (e.g. teaching hospital versus general hospital) can have completely different requirements when determining the working environment [Horii2003] [Ooijen2006]. Therefore, different approaches are taken to improve the design process of the radiological workplace. One example to structure the design process is the use of user-centred design (UCD). UCD aims to obtain the optimal solution in a 3-phase, iterative, process [Nagy03]. The three phases are: analysis, design, and evaluation. In the analysis phase an analysis is made about the experience of the users with their current product or design. This involves interviews and questionnaires as described in the next paragraph. The design phase involves the development of new design concepts that would help to overcome the problems stated in the first phase. In the evaluation phase a mock-up of the new design is implemented and users are asked to evaluate this mock-up (usability testing). The second and third steps are iteratively applied until an optimal setup is reached.

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3.2. User Questionnaire Examples of how to obtain information about the current situation and to get informed about possible ergonomic improvements based on user questionnaires was published earlier by several groups [Nagy03] [Rumreich03] [Ooijen2006]. Rumreich et al. [Rumreich03] showed that almost half of the respondents (46%) were dissatisfied or even very dissatisfied with their digital reading room environment. The main areas that caused the low rating were work environment ergonomics and room layout. In a study performed at the radiology department of the University Medical Center Groningen in the Netherlands [Ooijen2006], a structured questionnaire was presented to all 25 radiologists and radiology residents to evaluate the current system and to develop new improvements and designs. The questionnaire consisted of three different groups of questions in a score sheet (Workstation functionality, Reading room, and Comfort and ergonomics), supplemented with two multiple choice questions and two open questions to obtain general

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information. The score sheet questions were rated on a five-point scale with a score of 1 for very dissatisfied, 2 for dissatisfied, 3 for neutral, 4 for satisfied, and 5 for very satisfied. The results of the questionnaires were collected and evaluated by calculating the mean and standard deviation as well as the median score. Of the 25 questionnaires, twelve (48%) were completed and returned.

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3.2.1. Workstation Functionality Performance All workstation related parameters had a median score in the neutral range (3) or higher (3.5 and 4), no features were rated with dissatisfied, very dissatisfied, or very satisfied (figure 5). A neutral median score of 3 was obtained for 6 out of 13 parameters (46%). Of these 6 parameters, 4 had a mean score below 3 (Worklist Performance, Navigation/Patient and study search, Report generation, and Dictation system performance). These 4 would be the main focus for improvement. The remaining 7 parameters (54%) performed with a median score of 3.5 (Image annotation) or 4 (Overall performance, Speed, Image quality, User interface ease of use, Retrieval of past studies and Image viewing facilities).

Figure 5. Mean and median scores of different workstation related issues.

Ratings of satisfied or very satisfied were given by 50% or more of the respondents for Overall performance, Speed, Image Quality, User Interface ease of use, Retrieval of past studies, Image viewing facilities, and image annotation (figure 6). Highest number of satisfied to very satisfied responses were found for Image quality (92%) and Image viewing facilities (90%). However, although the questionnaire result indicates that the image viewing facilities are performing well, it also shows that the tools for image measurement and annotation are rated close to neutral, which could be a good direction for further optimization and improvement. When the percentage of respondents with ratings of satisfied or very satisfied drops below 50%, the percentages for the three categories tend to become close to each other (6).

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One obvious point of concern is the report generation and dictation system performance with 44% and 42% of the respondents with a rating of dissatisfied or even very dissatisfied. Stated problems with dictation and report generation mainly focus on ergonomic issues such as too many manual interactions for the dictation mechanism the need to hold the dictation microphone and non-optimal control during the dictation process. Another issue that rises is slow report turnaround time.

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Figure 6. Responses on different questions showing the percentage of users that were (very) dissatisfied, neutral, and (very) satisfied.

The reading room parameters show a remarkably low rating for all parameters (figure 7). The median scores of 3 out of 6 parameters (location, noise level and temperature) are rated as neutral or above, while the other three parameters (room space, layout and lighting) are rated below the neutral level with layout even scoring a median score of 1.5. This shows that careful attention should be given to the design of the working environment and room layout. The room layout and space should be arranged to give privacy for each workstation, yet provide room for traffic and small conferences and consultations. Reasons for the low scores can be found in the fact that most workstations were scattered around the department, just replacing all locations where a lightbox was already installed. The satisfaction with the setup in the central reading room was higher than with the isolated workstations located all over the department. For the same reasons, workplace-related parameters also show low median scores. Three out of four (75%) parameters are scoring below neutral both for the median and the mean score (figure 8). The only parameter with a score above neutral was the chair and table position and adjustability with a mean score of 3.5 and a median score of 4. The overall picture obtained from the survey shows that for all topics the percentage of responses of neutral and above ranges from 60% to 92% (Figure 6). In 7 out of 13 topics, 50% or more of the respondents are either satisfied or very satisfied.

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Figure 7. Mean and median scores for environmental issues.

Figure 8. Mean and median scores for workplace-related issues.

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The survey results show that the majority of the users are satisfied with the overall performance of the system. It has the fundamental functionalities and is running smoothly. The users have worked with this system for over a year, hence the familiarity with the system is high. The biggest dissatisfaction of the users are caused by the poor ergonomics of the environment and workspace. Based on the results of our questionnaire, improvements could be implemented. First, the computer screens in the central reading room are now mounted onto a ceiling-mounted arm. This frees up desk space and simplifies changing the orientation of the computer screens. Individual lighting was added to each workspace. To prevent constriction of the pupils the lights are of low brightness and can be dimmed and switched on and off independently at each workspace. The main reasons to keep these task lights are writing and reading of paper referral forms that are still used within our hospital, and reading paper reference books and other educational materials by residents. An additional wall was positioned between opposing workspaces to avoid glare and ambient light as well as ambient sound annoyance from nearby workspaces. The situation before and after the changes is shown in figure 9. Furthermore many of the workplaces previously scattered all around the department are now centralized in a new reading room. Again, much attention was given to the individual wishes of the users and fully adjustable tables were installed.

Figure 9. Setup before and after improvement. Before improvements monitors are placed on the height adjustable table. General lighting is in place, workstation is located below the table. No room to store papers is available. After improvements dimmable individual lights were added to each cubicle, monitors are suspended from the ceiling leaving more open desk space using a height adjustable arm. The combination of screens can be turned and tilted, but the angle between the two monitors is fixed. The workstation is on top of the ceiling and all cabling runs through the pole of the monitor arm leaving less clutter below the table (not possible to kick something loose anymore).

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Displays are mounted on flexible arms for optimal adjustments, task lights were added and enough workspace was created. Furthermore, soundproofing was added in between the workspaces. Changes related to the workstation were the replacement of the speech system and the PACS viewer. This allowed better adherence to the requirements of the users and provided a higher degree of integration between the different software packages. It also resulted in the elimination of some of the shortcomings found in the questionnaire.

4. CURRENT AND FUTURE DEVELOPMENTS 4.1. Development of New Peripherals

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In the gaming industry many peripherals are developed that allow the user to effectively interact with the more and more complex gaming environment that requires navigation in 3D space together with the gathering, selection and use of multiple items and the communication with fellow gamers. Examples of these are 3D gaming mice which might also be used effectively in radiology to interact with 3D visualizations. Additional buttons on the average gaming mouse can be used to control additional functions (figure 10). Furthermore, the development of other more ergonomic input devices besides the conventional mouse will continue in the years to come in which the average amount of hours spent behind a workstation each day will probably only increase [Krupinski06]. Since voice dictation and recognition is a crucial part of the radiology workflow, voice dictation systems will continue to improve and could also allow voice control using the same microphone [Krupinski06]. The first commercial implementations of voice control in combination with voice dictation in radiology are currently entering the market.

Figure 10. Example of a dedicated gaming mouse with advanced capabilities (Microsoft SideWinderTM Mouse, www.microsoft.com/hardware/gaming).

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Figure 11. (Courtesy Emotiv, www.emotiv.com).

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New developments in the area of control beyond voice control are also introduced. One of these developments is the recently introduced Emotiv EPOCTM neuro headset (http://emotiv.com) (Figure 11). This headset primarily developed for gaming, is based on electro encefalography (EEG) and allows the user to control the computer by using thoughts, feelings and expressions. The headset is communicating with the workstation using wireless technology and can last a full working day on one battery charge. Applications of these kinds of devices into radiology might be a future possibility.

Figure 12. The Optimus Maximus keyboard with programmable OLED displays in each key. The keys can be programmed to display any image.

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Another example of innovation comes from the Art Lebedev studio and is called the Optimus Maximus Keyboard (http:/www.artlebedev.com). This keyboard is equipped with 113 small 48x48 pixel OLED displays instead of standard keys. This results in a very flexible programmable keyboard where not only the underlying functionality of the keys can be programmed, but also the appearance of the key itself so it matches the functionality (figure 12). A keyboard like this would allow the creation of a dedicated radiology keyboard where dedicated functionality is readily available to the user without having to memorize what key corresponds to what function. Furthermore, the flexibility of the keyboard allows the keys to adjust their displayed function to the software program that is currently active.

4.2. Replacement of Monitors In general, the transition from cathode ray tube (CRT) displays to flat panel Liquid Crystal Displays (LCD) is already made. However, currently a mix of greyscale and colour displays is still required since some applications, such as 3D visualization or colour Doppler ultrasound, require a colour display while the image quality of these colour displays is still not sufficient for greyscale X-ray image representation. The main reason for this is the lower luminance achieved by current colour displays when compared to greyscale. However, new generations of colour displays are being marketed now that will provide the luminance which allows adequate, diagnostic, viewing of conventional greyscale X-ray images on colour displays. Therefore, in the near future, diagnostic workstations will shift from a greyscale to a full colour setup [Siddiqui06] [Krupinski06]. This replacement will provide several, ergonomic, advantages. Examples are that less deskspace is required since the number of displays can decrease, and the workstation is easier to operate since the switch between the displays for colour and greyscale images is no longer required [Fratt07].

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4.3. Teleradiology and Its Ergonomic Risks Recently, teleradiology has emerged and radiologists are increasingly able to work from their homes. However, although an increasing effort is put into the improvement of the radiological workspace at the hospital, the home workspace is, in most cases, mainly left to the employee (radiologist). This leads to workspaces at home that are ergonomically far from optimal and could lead to earlier onset of repetitive strain injury (RSI) related complaints. When starting to work from home on a regular basis, one should take into account that the ergonomic soundness of that workspace at home is the responsibility of the employer and that there are multiple court decisions in which claims by employees are approved to back up this statement.

4.4. Future Hardware Developments Development in the field of displays will continue leading to large, possibly curved, colour displays that provide high resolutions in combination with high luminance. First

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developments are already presented, such as the 9 megapixel high luminance LCD colour display and the very promising technology of organic light-emitting diodes (OLEDs) that will certainly find its way into clinical applications in the near future [Krupinski06]. Another development which is now carefully marketed is the use of multi-touch computer displays (figure 13). These touch screens provides the user with a very high level of direct interaction with the data presented on the computer display without the intervention of peripherals such as a mouse or keyboard. Since in radiology one of the main tasks of the radiologists when using the workstations is image handling, the use of multi-touch displays could be a major advantage and greatly reduce strain to the radiologist. A technology nowadays still hampered by the fact that users have to wear dedicated goggles of some sort is stereoscopic viewing (figure 14). Preliminary studies using these solutions have shown improved performance when using stereoscopic images in medical applications [Krupinski06].

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Figure 13. Recently Microsoft launched a commercial application of multi-touch screens called Microsoft Surface. With Microsoft Surface, you can browse through pictures of your recent ski vacation by stretching, zooming and dragging the images with your fingers.

Figure 14. Example of a 3D setup using a half-reflecting mirror to provide two different images to the eyes based on polarization. Special polarized glasses are required to experience the 3D sensation.

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Nowadays, the first devices that allow stereoscopic viewing without the aid of goggles are entering the market. A main issue with these techniques still is the quality of the images and the fact that many people will get nauseous when looking at such screens. However, new technologies are being developed and the future might bring us high quality, high resolution and stable solutions for stereoscopic viewing based on holographic techniques.

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4.5. The Future Workspace In the same way as dedicated keyboards, we could also develop a dedicated workspace. When the user logs in to the system, the system will also set the desk and the chair to the user’s preference. These preferences can be programmed the first time a user uses the system. This is a system which is not known yet for workspaces, but is common in luxurious cars. When we think about what the future will bring for viewing workstations, we can use two kinds of approaches. The first is to look at what is currently being developed in other industries, like the gaming industry or in home entertainment, and how we could implement this in the viewing workstations. This is a good way to find short-term improvements. The other approach is to take a step back from current developments, think about the ideal viewing workstation and then look back and check if there are ways to realize this ideal system. Many questions can be asked when trying to imagine the ideal workstation. What would be the best way to view the data the MRI or CT acquires? Do you want to look at the data slice by slice, or would it be better to be able to have a three-dimensional image in front of you, which you can turn around, walk around, zoom in and out and maybe even touch. What would be the best interface? A normal keyboard, a dedicated keyboard, a speech driven interface? Or perhaps an interface based on direct interaction with the data by touch? Thinking about the ideal situation to view axial data such as from Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) one would probably want a 1:1 scaled hologram which you could walk around, rotate, zoom into or take slices from to investigate and store in the patient data file. Maybe we could even manipulate the hologram like lifting an arm to have a closer look. Communication with the computer should not require a mouse or keyboard, but should be done directly through speech and touch. Maybe a pen could be useful to pinpoint exact locations on the hologram. Unfortunately these kinds of three-dimensional techniques are not yet available. But from this idea we could try to derive a more realistic interface using today’s technology. For this set up, we have used three monitors: one for patient data, one for image data and one for email, typing letters and other tasks. There is a microphone to record speech, a dedicated joy-stick, a dedicated keyboard and a fingerprint scanner. First the user will log on to the system using only his fingerprint. The desk and chair will automatically set to his preference. Image data is, of course, shown on the main screen (figure 15). The screen shows the complete scan in 3D, a slice of the scan and a bar in which data can be stored (figure 16). Using the joy-stick the user can move through the scan. The more pressure the user applies the faster the computer will move through the scan.

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Figure 15. Desk setup.

Figure 16. Image data interface.

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Pushing the record button on the dedicated keyboard, the user can record speech which will be stored with the picture. Using the pen, the user can mark up comments or draw on the scan (figure 17).

Figure 17. Recording and comments can be stored for each slice

When the user moves on, the data is automatically stored in the patient data file (figure

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18).

Figure 18. Image data with voice recording and comments is stored.

This is only one example of a possible user interface and interaction setup, extensive research is required in a multi-disciplinary setting to develop ergonomic and effective workstation environments for future radiologists.

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CONCLUSION Ergonomic design is very important to ensure comfort, and therefore effectiveness and quality of work. The insufficient attention to ergonomic design factors can lead to complaints of fatigue, acceptance problems and decrease of overall effectiveness and probably even decrease of diagnostic accuracy. It is a very challenging job to provide an optimal working area for the radiologist, in a “filmless” radiology department, especially since the number of aspects to be taken into consideration is high and the workflow is completely different from a film-operated department. However, by continuous discussion with the radiologists, the areas for improvement have been mapped. The design and development of the environment, the software tools used, and the hardware have to be carefully directed and work environment components have to be carefully selected to achieve these improvements. Taking all aspects into consideration, an ergonomic working environment can be designed that is adapted to the personal preferences of the radiologist and allows him or her to work for long hours behind the workstation without it causing problems. Multi-disciplinary research including radiologists, computer scientists, (industrial) designers, and ergonomic specialists is required to constantly enhance the radiological working environment and to work on the radiological working environment of the future.

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REFERENCES Abdullah BJJ. In the eyes of the beholder: what we see is not what we get. The British Journal of Radiology 2001;74:675-676. Arenson RL, Chakraborty DP, Seshadri SB, Kundel HL. The Digital Imaging Workstation. Journal of Digital Imaging 2003;16(1):142-162. Bazak N, Stamm G, Caldarone F, Lotz J, Leppert A, Galanski M (2000) PACS workstations 2000: evaluation, usability and performance. In: Gell G, Holzinger A, Wiltgen M (eds) Proceedings of the 18th international EuroPACS conference, vol 144. Österreichische Computer Gesellschaft, Graz, pp 133–142. Bennett WF, Vaswani KK, Mendiola JA, Spigos DG. PACS Monitors: An Evolution of Radiologists’ Viewing Techniques. J. Digital Imaging 2002;15(suppl1):171-174. Bick U, Lenzen H. PACS: the silent revolution. Eur. Radiol. 1999;9:1152-1160. Boehm T, et.al. Evaluation of radiological workstations and web-browser-based image distribution clients for a PACS project in hands-on workshops. Eur. Radiol. 2004;14:908–914. Author unknown, Boston University Office of environmental health and safety – ergonomics self help guide, http://www.bu.edu/ehs/flash/ergonomics%20selfhelp%20guide.swf Brennan P.C., McEntee M, Evanoff M, Phillips P, O'Connor W.T., Manning D.J., Ambient Lighting: Effect of Illumination on Soft-Copy Viewing of Radiographs of the Wrist American Journal of roentgenology March 15, 2006. Prof.dr.ir Buurman R den, ide532 Beeldschermergonomie syllabus, march 1996. Carrino JA, Unkel PJ, Miller ID, Bowser CL, Freckleton MW, Johnson TG. Large-scale PACS implementation. J. Digit Imaging 1998 ;11(suppl 1) ;3-7.

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Foord KD. PACS workstation respecification: display, data flow, system integration, and environmental issues, derived from analysis of the Conquest Hospital pre-DICOM PACS experience. Eur. Radiol. 1999;9:1161-1169. Fratt L. Radiology turns color. HealthImaging.com September 1, 2007. Http://www/healthimaging.com, accessed April 7, 2008. Harisinghani MG, Blake MA, Saksena M, Hahn PF, Gervais D, Zalis M, da Silva Dias Fernandes L, Mueller PR. Importance and Effects of Altered Workspace Ergonomics in Modern Radiology Suites. Radiographics 2004;24:615-627. Hayt DB, Alexander S, Drakakis J, Berdebes N. Filmless in 60 Days: the impact of Picture Archiving and Communications Systems within a large urban hospital. J. Digit Imaging 2001;14(2):62-71. Hirschorn D, Eber C, Samuels P, Gujrathi S, Baker SR. Filmless in New Jersey: the New Jersey Medical School PACS project. J. Digit Imaging 2002;15(suppl 1):7-12. Honea R, McCluggage CW, Parker B, O’Neall D, Shook KA (1998) Evaluation of commercial PC-based DICOM image viewers. J. Dig. Imaging 11:151–155. Horii SC. Clinical Aspects of Workstation Design and Operation. Chapter 13, In: Filmless Radiology, Siegel EL and Kolodner RM editors. ISBN 0-387-95390-6. Springer Verlag, New York, 1999. Horii SC, Horii HN, Ki Mun S, Benson HR, Zeman RK. Evironmental Designs for Reading from Imaging Workstations: Ergonomic and Architectural Features. Journal of Digital Imaging 2003;16(1):124-131. Huang HK. Display Workstations, chapter 11, In: PACS and Imaging Informatics by H.K. Huang. ISBN 0-471-25123-2. John Wiley and Sons Inc, Hoboken, New Jersey, 2004. Kim Y, Fahy JB, DeSoto LA, Haynor DR, Loop JW. Development of a PC-based Radiological Imaging Workstation. Journal of Digital Imaging 2003;16(1):104-113. Krupinski EA. Technology and Perception in the 21st-Century Reading Room. J. Am. Coll Radiol. 2006;3:433-440. Kumar S, Moro L, Narayan Y. Perceived physical stress and musculoskeletal discomfort in xray technologists. Ergonomics 2004;47:189-201. Moise A, Atkins MS. Design requirements for Radiology Workstations. Journal of Digital Imaging 2004;17(2):92-99. Moise A, Atkins MS. Designing Better Radiology Workstations: Impact of Two User Interfaces on Interpretation Errors and User Satisfaction. Journal of Digital Imaging 2005;18(2):109-115. Moise A, Atkins MS, Rohling R. Evaluating Different Radiology Workstation Interaction Techniques with Radiologists and Laypersons. Journal of Digital Imaging 2005;18(2):116-130. Nagy P, Siegel E, Hanson T, Kreiner L, Johnson K, Reiner B. PACS Reading Room Design. Seminars in Roentgenology 2003;38(3):244-255. van Ooijen PMA, Koesoema AP, Oudkerk M. User Questionnaire to Evaluate the Radiological Workspace. Journal of Digital Imaging 2006;19(Suppl.1):52-59. Pollack T, Heuser H, Niederlag G, Brüggenwerth G, Kaulfuss K (2000) Evaluation of 7 PCbased diagnostic workstations. In: Gell G, Holzinger A, Wiltgen M (eds) Proceedings of the 18th international EuroPACS conference, vol 144. Österreichische Computer Gesellschaft, Graz, pp 114–125.

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Prabhu SP, Gandhi S, Goddard PR. Ergonomics of digital imaging. The British Journal of Radiology 2005;78:582-586. Ratib O, et.al. Computer-aided Design and Modelling of Workstations and Radiology Reading Rooms for the New Millennium. Radiographics 2000;20:1807-1816. Reiner B, Siegel E, Hooper F et al. (1997) Effect of screen monitor number on radiologist productivity in the interpretation of portable chest radiographs using a Picture Archiving and Communication System. J. Digit Imaging 10 (Suppl 1):175. Ruess L, O’Connor SC, Cho KH, Slaughter R, Husain FH, Hedge A. Carpal tunnel syndrome and cubital tunnel syndrome: musculoskeletal disorders in four symptomatic radiologists. Am. J. Radiol. 2003;181:37-42. Rumreich LL, Johnson AJ. From Traditional Reading Rooms to a Soft Copy Environment: Radiologist Satisfaction Survey. Journal of Digital Imaging 2003;16(3):262-269. Sacco P, Mazzie MA, Pozzebon E, Stefani P. PACS implementation in a University Hospital in Tuscany. J. Digit Imaging 2002 ;15(suppl 1) :250-251. Shimamoto K, Yamakawa K, Ishigaki T, Takahashi Y, Sugiyama N, Nishihara E. Clinical evaluation of newly developed PACS at Nagoya University Hospital. Radiology 1994;193:175. Siddiqui KM, Chia S, Knight N, Siegel EL. Design and Ergonomic Considerations for the Filmless Environment. Journal of the American College of Radiology 2006;3:456-467. Steckel RJ. Current applications of PACS to radiology practice. Radiology 1994;190:50A52A. Strickland NH. Hospital wide PACS: the Hammersmith solution. Current state of the art and future trends. In: Siegel EL, Kolodner RM, eds. Filmless Radiology. New York, NY: Springer-Verlag:2001;378-398. Tahayori B, Soltanian-Zadeh H, Zoroofi RAZ. A PC-based PACS display workstation with a language transparent interface. J. Digital Imaging 2002;15(suppl1):206-209.

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In: Ergonomics: Design, Integration and Implementation ISBN 978-1-60692-327-6 Editor: Bram N. Brinkerhoff © 2009 Nova Science Publishers, Inc.

Chapter 7

CURRENT ERGONOMIC ISSUES IN RADIOLOGY Xiao Hui Wang1, Walter F. Good1, Makoto Omodani2, J. Ken Leader1 and Bin Zheng1 1

Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA 2 Department of Optical and Imaging Science and Technology, Tokai University, Tokyo, Japan

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ABSTRACT Historically radiographic displays consisted of x-ray projections recorded on film and viewed by mounting the film on a lightbox. Once films were interpreted by a radiologist, they were manually filed in vast film libraries where they were maintained in anticipation of possibly being needed for comparison purposes at a later date. Other than adjusting acquisition parameters for optimal film exposure and controlling the brightness of the lightbox and the level of ambient lighting, radiologists had little control over the how images were viewed. Furthermore, because of the effort required to retrieve films from libraries, radiologists needed to wait on prior studies to be retrieved and often, previous films could not be provided in time to have an impact on the interpretation process. Over the past couple of decades radiology has moved toward digital acquisition, storage and display of image data, as well as a shift from the acquisition of 2-D projection images to the acquisition of large 3-D digital datasets, each of which can be equivalent to hundreds of individual images. Also, it has become customary to have a considerable amount of computer processing power between the acquisition process and the final display, and to provide radiologists with computerized control of the display. Thus, the opportunity for radiologists to interact with these processes, and the potential complexity of these interactions, have greatly increased. At the same time, because of the larger volume of image data when anatomical information is represented as a 3-D volume as opposed to a 2-D projection image, the workload on radiologists has increased dramatically. To take advantage of the opportunities provided by computerized methods, while increasing the efficiency of the overall practice of radiology, ergonomic considerations have become a topic of considerable interest to radiologists. This has included efforts to streamline user interface designs for radiographic workstations; to incorporate viewing

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Xiao Hui Wang, Walter F. Good, Makoto Omodani et al. methods such as stereographic display, that take advantage of innate human capabilities; and, to employ computerized methods such as computer aided diagnosis to assist with certain mundane tasks that are amenable to computerized analysis. The ultimate radiology workstation will likely be a system in which radiologists wear a head-mounted display and use their head motion to control roam and zoom within a 3-D image space, though there will be a long evolutionary process to get such a system adopted within radiology.

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INTRODUCTION The introduction of new technologies into the practice of radiology is causing a major shift in the operating paradigms of radiology departments, and along with this, a need to reconsider the relevant ergonomic issues. Historically, radiographic images were acquired by projecting x-rays through bodies to directly expose films. The films were then developed and hung on film alternators or on arrays of lightboxes for viewing. Once radiologists interpreted films, they filed reports by dictating into a recording system, after which the recordings were transcribed by a typist. Finally, the films were manually filed in vast film libraries where they were maintained in anticipation of possibly being needed for comparison purposes during subsequent exams. Overall, the logistics of these activities were relatively simple, but by today’s standards, this process was inefficient and often resulted in suboptimal performance. Other than adjusting acquisition parameters for film exposure and manipulating the brightness of lightboxes and the level of ambient lighting, radiologists had little control over how the images were viewed. Furthermore, because of the effort required to retrieve films from libraries, radiologists needed to wait on prior studies to be delivered and frequently, previous films could not be provided in time to have an impact on the interpretation process. Nevertheless, these traditional methods did exhibit a few ergonomic advantages. The simplicity of the process allowed radiologists to focus most of their effort on the interpretation of images rather than on the ancillary processes. Also, because there was usually only a single copy of a given film, and often it needed the attention of multiple individuals, it was common for radiologists to move between reading rooms or between lightboxes – reducing risks associated with sedentary activities. In any event, over many years of refinement, the various ergonomic issues were addressed adequately and overall, the process was considered to be nearly optimal given the state of technology at the time. As in many other fields, radiology has recently been impacted by the introduction of computerized systems as well as by other new technologies for handling image datasets. Specifically, radiology is rapidly transitioning toward a working environment in which all images are acquired, processed, and stored digitally and are interpreted on computer workstations. At the same time, radiology has been shifting from the acquisition of 2-D projection images to the acquisition of large 3-D digital datasets, by modalities such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). For example, CT use has increased from 9.2% in 1991-1992 to 15.3% in 2002-2003, while conventional radiography decreased from 70% to 57.1% over the same period [1].

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Because each of these 3-D datasets can be comprised of hundreds of individual 2-D images, and by tradition radiologists are required to view each individual image, the workload on radiologists has increased dramatically. For Medicare procedures, the average physician workload, as measured in RVUs per Medicare procedure, increased by 21.6% between 1992 and 2003 and this increase has been attributed to increased use of MRI and CT [1]. As part of this conversion to digital methodology, a considerable amount of computer processing power has been placed between radiologists and acquisition, storage and display devices. This is considered to be desirable for several reasons. Radiologists now have the opportunity to interact with the various processes and consequently have a greater variety of ways of optimizing the interpretation process, which should increase accuracy and efficiency [2]. By storing digital images in computer databases, the need to keep track of physical films is largely eliminated. When these databases are networked to multiple workstations, it is possible for the same image to be viewed concurrently at multiple locations. All data relevant to a particular case can be extracted from the various databases within a hospital (e.g., picture archiving and communication systems (PACS), radiology information systems (RIS) and hospital information systems (HIS)), and can be presented along with the images at any workstation. Additionally, other processing and display options, which depend upon the new computing power and generally do not have film analogues, have become routinely available. This includes such capabilities as the incorporation of 3-D viewing methods in which datasets are rendered in 3-D by computer algorithms; stereographic display methods that take advantage of innate human stereopsis capabilities, but require that stereographic views be generated by computers; and, employing computer aided diagnosis (CAD) to assist with certain tasks that are amenable to computerized analysis. Taken together, these factors should increase both efficiency and accuracy of radiologists. To take advantage of the new opportunities provided by computerized methods, while increasing performance, ergonomic considerations have again become a topic of considerable interest to radiologists. For the purpose of applying ergonomic considerations in this context, we adopt a broad definition of ergonomics, which covers both physical and mental stresses on radiologists, and how these stresses are related to both the physical environment and the mental tasks being performed. In some respects, radiology has many of the same ergonomic considerations as any task in which workers are required to sit at a computer workstation for long periods [3]. We will review these issues and then concentrate on those that are more specific to the practice of radiology.

AMBIENT READING ROOM CONDITIONS It is well known that the ambient conditions within a reading room are extremely important for maintaining the performance of radiologists. Unfortunately, in adopting new technology, most radiology departments do not have the opportunity to build new facilities, but must adapt existing reading rooms and this can severely constrain their ability to achieve an optimal ambiance. The main concerns with respect to ambient conditions relate to temperature, humidity, noise level, and lighting.

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As workstations replace lightboxes, the power load associated with computerized electronic equipment increases the heat load in reading rooms dramatically, and existing airconditioning equipment may be inadequate to maintain a reasonable temperature for a working environment. To avoid fatigue induced by higher room temperatures it is essential to provide increased air-conditioning capacity, where needed. It has been estimated that the temperature should be maintained between 68° and 75°F at a relative humidity of between 40% and 60% [4]. This temperature range is too wide for most individuals so it is also desirable to have individual temperature controls at each workstation. Ambient noise can cause distractions and prevent radiologists from concentrating on their particular tasks, and it can also interfere with the performance of automatic voice recognition software used in the report dictation process. A considerable amount of noise is generated in reading rooms by radiologists dictating reports and consulting, either in person or over the telephone. While this has historically been a problem, it has become more severe as hum generated by workstations, and possibly by the increased air-conditioning capacity, is added to the environment. Noise levels can be ameliorated with partitions between workstations and sound attenuation wall coverings, once the problem is identified. As discussed below, VDTs, whether based on CRT or LCD technology, have a much lower luminance than traditional lightboxes. To retain contrast on VDTs that is required for case interpretation, it is necessary that ambient lighting be reduced significantly. But at the same time, a sufficient level of ambient light must be maintained to permit radiologists to read hardcopy text documents that are associated with cases. Ambient lighting should also be relatively uniform within the visible work area to avoid unnecessary light adaptation of the eye.

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WORK AREA CONFIGURATION Individuals who customarily work at computer workstations for extended periods are at risk for a variety of injuries related to posture and to repetitive motions. Carter, et al., report that improperly arranged VDTs can cause eyestrain, backache, and neck and shoulder pain, but that these risks can be greatly reduced by carefully designing chairs and workstation layout [5]. Individuals who customarily work at computer workstations for 4 or more hours per day are considered to be at risk for cumulative trauma disorders [6]. Workers who use repetitive motions while maintaining a relative static posture for prolonged periods will likely eventually suffer injuries if the work environment has not been properly designed [7]. Monitor Distance – It is clear that there is insufficient understanding of the relationship between eyestrain and the position of VDTs to be able to justify monitor placement on purely theoretical grounds. Early recommendations were generally based on the resting point of accommodation (RPA) (i.e., the distance at which the eyes focus in the dark). The RPA is typically about 30 inches for young people and increases with age. The range over which RPA can vary for an individual decreases with age. The eyes also have a resting point of vergence (RPV) (i.e., the distance to the common point at which the axes of the eyes are aligned when in the dark), which averages typically 45 inches when looking straight ahead, and about 35 inches when looking downward at a 30° angle [8]. To complicate the issue somewhat, with prolonged viewing at a near distance, both RPA and RPV tend to decrease,

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though this may be one effect of eyestrain. The inward shift of RPA is also accompanied by a reduction in visual acuity [9]. Looking at an object causes stress based on differences between its distance and both RPA and RPV [10, 11], and by the rate at which its distance is changing while being viewed. It has been shown that RPV is more significant when looking at VDTs [9, 12]. One limitation in previous studies on the ergonomic effects of monitor placement is that there has not been a well-defined measure of eye fatigue. However, recent investigations in the context of electronic paper have demonstrated that near point distance (NPD) correlates strongly with subjective impressions of eye fatigue [13]. NPD is defined as the closest distance at which an individual can focus at a given time. This is age dependent, but for a given individual it tends to increase during prolonged reading tasks. It has also been shown to increase more rapidly when reading from lower quality displays [13]. Though more work is needed to fully understand the use of NPD as a metric for eye fatigue, this is a very promising concept for future research. .The study by Jaschinski-Kruza reported that regardless of a viewer’s RPA, they suffered less eyestrain at a viewing distance of 40 inches than at 20 inches [9]. More recent literature, directed specifically at radiology, recommends a viewing distance of at least 25 inches [4]. Harisinghani, et al. justify this with an argument based on RPV, but it may be the case that radiologists are using the shorter viewing distance to take advantage of the higher spatial resolution of their monitors. Many radiographic LCD displays have double the spatial resolution of commodity displays. This would suggest that as the resolution of monitors increases it is advisable to increase their physical size correspondingly so that a longer viewing distance can be maintained without loss of visual fidelity. The best recommendation at this time seems to be to allow sufficient space for monitors so that viewing distance can be adjusted from 25 to at least 40 inches based on a particular viewer’s experiences. Other ancillary devices that require regular viewing, such as holders for hardcopy documents should be placed at the same viewing distance in order to minimize unnecessary changes in viewing distance. There is also a suggestion that every 20 minutes a viewer should fixate on an object 20 feet away, for 20 seconds [4]. While there is no clear scientific basis for this, some claim it has passed the practical merit test. Monitor Height – Considerable work by the neck muscles is required to balance the head when it is in a non-neutral position. This should be the primary consideration in determining monitor height. If the monitor is too high, then it will be necessary for viewers to tilt their heads backward to view the screen. This can cause fatigue and pain in the neck muscles and in extreme cases, compress the neck vertebrae. Stress on the neck is exacerbated by viewers looking to the side to view ancillary documents or looking down to view a keyboard. Burgess-Limerick, et al., have shown that users alter both head orientation and gaze angle in response to changes in monitor height [8]. Head rotation is by a combination of cervical and atlanto-occipital flexion. Tension-like headaches are often associated with the Atlantooccipital joint. The Burgess-Limerick study reports that a “27 degrees change in monitor height was, on average, accommodated by 18 degrees of head inclination and a 9 degrees change in gaze angle relative to the head. The change in head inclination was achieved by a 6 degrees change in trunk inclination, a 4 degrees change in cervical flexion, and a 7 degrees change in atlanto-occipital flexion.” The same study found that when viewers were allowed to self-select a monitor height, they consistently selected heights that were lower than current

Ergonomics : Design, Integration and Implementation, edited by Bram N. Brinkerhoff, Nova Science Publishers, Incorporated, 2008. ProQuest Ebook Central,

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Xiao Hui Wang, Walter F. Good, Makoto Omodani et al.

'eye-level' recommendations. These kinds of considerations have lead to the recommendation that the top edge of the monitor should be between 15-50° below eye level. Chairs – Chairs are an important component for avoiding repetitive motion injuries and other muscle pains in a sedentary environment involving sustained use of VDTs. Nevertheless, radiologists often choose chairs as if they were interchangeable and seldom perform the adjustments that are required to avoid muscle problems. Chair height needs to be adjustable so that a reader’s body can be positioned correctly relative to the workstation surface [5]. The backrest of the chair must be adjusted to provide lumbar spine support so as to avoid excess pressure on the intervertebral disks. The height of the chair should be adjusted so that the wrists form the proper angle with the keyboard, with the elbows directly below the shoulders, and the forearms extended horizontally. The seat cushion should not interfere with the back of the knees. If the chair is correctly adjusted for the height of the keyboard and workstation table, and the feet do not reach the floor, then it will be important to provide a footstool. Chairs with the appropriate adjustments for VDT workers are readily available, but the adjustments must be made for each individual who sits in the chair for extended periods. Dictation and Automatic Voice Recognition – To reduce the time required to file diagnostic reports, radiology is shifting toward dictation systems that employ automatic voice recognition. But these systems are less robust than human stenographers and can incur high error rates in the presence of ambient noise. Once radiologists have dictated their reports, they must carefully edit the automatically transcribed versions – a process which takes longer than using human transcription. While this benefits patients and clinicians, it actually increases the workload on radiologists. To streamline reporting, either a hands free microphone should be used or the dictation microphone should be held in left hand so that the right hand can be used to manipulate controls on the workstation. The right elbow should be resting on the table directly under the shoulder, with the right forearm and hand extended horizontally (no angle formed at the wrist).

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DISPLAY CHARACTERISTICS Display Resolution – Historically, the spatial resolution of VDT was significantly less than that of film. In the early days of the adoption of PACS much research effort was directed at determining what resolution is required for radiologists to see features that are visible on film, given that the resolution of film is estimated to be about 10K pixels × 10K pixels. Many studies were performed, but the resolutions tested were generally lower than that available today. Nevertheless, results indicated that VDTs were competitive with film for most kinds of radiographic procedures. Recent LCD displays have a resolution of 10 mega pixels and certain acquisition systems are approaching that resolution. If images are acquired at a spatial resolution that is higher than that of the display, then it is possible for the viewer to magnify areas of interest on the display. There are potential problems with this. The process of magnifying and roaming an image is tedious and time consuming and is not likely to be used consistently unless a radiologist suspects an abnormality. But if an important indicator is not visible at the default magnification, then the

Ergonomics : Design, Integration and Implementation, edited by Bram N. Brinkerhoff, Nova Science Publishers, Incorporated, 2008. ProQuest Ebook Central,

Copyright © 2008. Nova Science Publishers, Incorporated. All rights reserved.

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radiologist may miss the area completely. For example, in mammography one indicator of a possible malignancy is the presence of microcalcification clusters which may not be visible at the normal magnification. Brightness – From the early applications of VDTs in radiology, concerns arose about the relative brightness between lightboxes and VDTs. Lightboxes achieve a luminance level of between 1700 and 3500 CD/m2 and are more than 10 times brighter than early VDTs. When early VDTs were used in the same ambient lighting conditions that were customary for lightboxes, there was a significant reduction in apparent image contrast. Efforts to increase the brightness of CRTs resulted in a deterioration of their spatial resolution. More modern VDTs can provide between 350 and 1400 CD/m2. One study that delineates the visual relationship between spatial resolution and brightness on posteroanterior chest radiographs, in a receiver operating characteristic (ROC) study has indicated that “the effect of image luminance was greater than that of resolution. The detection of pneumothorax, interstitial disease, and rib fracture showed statistically significant differences (P