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AAMI HE75 2009 RA 2018

AAMI HE75 2009 RA 2018

$246.57

ANSI/AAMI HE75:2009/(R)2018 – Human factors engineering-Design of medical devices

Published By Publication Date Number of Pages
AAMI 2009 465
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This recommended practice covers general human factors engineering (HFE) principles, specific HFE principles geared towards certain user-interface attributes, and special applications of HFE (e.g., connectors, controls, visual displays, automation, software–user interfaces, hand tools, workstations, mobile medical devices, home health care devices).

PDF Catalog

PDF Pages PDF Title
2 Objectives and uses of AAMI standards and recommended practices
3 Title page
4 AAMI Recommended Practice
Copyright information
5 Contents
15 Glossary of equivalent standards
17 Committee representation
18 Acknowledgments
19 Foreword
21 Introduction
25 1 Scope
1.1 General
1.2 Inclusions
1.3 Exclusions
26 2 Normative references
27 3 Definitions and abbreviations
34 4 General principles
4.1 Introduction
4.2 Seek user input
4.2.1 Involve users early and often
4.2.2 Refine designs through usability testing
4.3 Establish design priorities
4.3.1 Keep it simple
35 4.3.2 Ensure safe use
4.3.3 Ensure essential communication
36 4.3.4 Anticipate device failures
4.3.5 Facilitate workflow
4.4 Accommodate user characteristics and capabilities
4.4.1 Do not expect users to become masters
37 4.4.2 Expect use errors
4.4.3 Accommodate diverse users
38 4.4.4 Maximize accessibility
4.4.5 Consider external factors that influence task performance
39 4.5 Accommodate users’ needs and preferences
4.5.1 Prioritize user input
4.5.2 Do not rely exclusively on “thought leaders”
4.5.3 Let users set the pace
4.6 Establish realistic expectations of users
4.6.1 Do not rely on training
40 4.6.2 Do not rely on instructions for use
4.6.3 Do not rely on warnings
4.6.4 Do not rely on users’ memory
4.6.5 Avoid information overload
4.6.6 Do not assign users tasks that are better suited to the device
41 4.7 Consider real-world demands
4.7.1 Consider the context of use
4.7.2 Consider worst-case scenarios
42 4.7.3 Make devices as rugged as necessary
4.7.4 Limit user workload
4.7.5 Consider the potential for device migration into other uses or use environments
43 4.8 Develop compatible designs
4.8.1 Accommodate mental models
4.8.2 Establish natural or conventional mappings
44 4.8.3 Follow industry conventions and consensus standards
4.9 Optimize user interactions to enhance safety and effectiveness
4.9.1 Make devices error-tolerant and fail in a safe manner
4.9.2 Avoid physical strain, repetitive motions, and cumulative traumas
4.9.3 Help users anticipate future events
4.9.4 Confirm important actions
45 4.9.5 Make critical controls robust and guard them
4.9.6 Clarify operational modes
4.9.7 Employ redundant coding
46 4.9.8 Design to prevent user confusion
4.9.9 Don’t neglect device appeal
4.10 Summary
47 4.11 References
49 5 Managing the risk of use error
5.1 Introduction
5.1.1 Overview
5.1.2 Use-related hazards vs. traditional device-failure hazards
50 5.1.3 Behavioral variability in human users
5.1.4 Definition of use error
5.2 Types of use errors
54 5.3 General considerations for managing use-related hazards
5.3.1 Use-error consequences in regulatory submissions
5.3.2 General considerations for managing risk
5.4 Methods of managing the risk of use errors
5.4.1 Overview
5.4.2 Risk, risk management, and use safety
55 5.4.3 Use-error risk management process
56 5.5 Definition of intended use, user, and the use environment
57 5.6 Identification of use-related hazards
5.6.1 Overview
5.6.2 Analysis of predecessor and similar devices
5.6.3 Analysis of device use tasks
58 5.6.4 Application of best practice for user-interface design
5.6.5 Consideration of user workload in device use
5.7 Estimation and prioritization of risk of use-related hazards
5.7.1 Overview
5.7.2 Failure mode effects analysis
59 5.7.3 Fault tree analysis
5.7.4 Usability testing
60 5.8 Implementation of risk controls
5.8.1 Overview
5.8.2 Most preferred use-related hazard mitigation strategies
5.8.2.1 Design modification
5.8.2.2 Safeguards
5.8.3 Less preferred use-related hazard mitigation strategies
5.8.3.1 Modification of intended use
5.8.3.2 Training
61 5.8.3.3 Warnings and labeling
5.9 Validation of safety of use (effectiveness of risk controls)
5.10 Decision on whether risks are acceptable
5.11 Determination of whether new risks were introduced
5.12 Documentation of the use-related risk management process
62 5.13 Monitoring, identification, and control of use-related issues post-marketing
5.14 Summary
5.15 References
64 6 Basic human skills and abilities
6.1 Introduction
6.2 Design guidelines
6.2.1 Overview
6.2.2 Vision
6.2.2.1 Major parameters of human vision
6.2.2.2 Visual threshold
6.2.2.3 Visual acuity
65 6.2.2.4 Focusing abilities
6.2.2.5 Visual angle
67 6.2.2.6 Visual perception
6.2.2.6.1 Limits to visual perception
6.2.2.6.2 Distance and perceived size
6.2.2.6.3 True object size
68 6.2.2.6.4 Object size and distance misperceptions
6.2.2.6.5 Minimum type size
70 6.2.2.6.6 Common visual illusions
6.2.2.6.7 Perception of motion
6.2.2.6.8 Flickering lights
6.2.2.6.9 Photosensitive epilepsy
6.2.2.6.10 Display flicker
71 6.2.2.7 Color vision
6.2.2.7.1 Overview
6.2.2.7.2 Color coding
72 6.2.2.7.3 Recommendations for printed colors
74 6.2.2.7.5 Recommendations for color combinations (legibility and visibility)
75 6.2.3 Audition and speech
6.2.3.1 Overview
6.2.3.2 Loudness measurements
76 6.2.3.3 Hearing thresholds
77 6.2.3.4 Effects of aging on hearing sensitivity
78 6.2.3.5 Speech
6.2.3.5.1 Speech recognition systems
6.2.3.5.2 Loudness levels of speech
6.2.3.5.3 Frequency characteristics of speech
6.2.4 Other sensory modalities
6.2.4.1 Overview
6.2.4.2 Skin (somesthetic) senses
80 6.2.4.3 Muscle sense
6.2.4.4 Sense of balance
6.2.4.5 Chemical senses
6.2.5 Human information processing
6.2.5.1 Overview
6.2.5.2 Stimulus discrimination
6.2.5.3 Attention
81 6.2.5.4 Vigilance (sustained attention)
6.2.5.5 Speed of information processing
6.2.5.5.1 Overview
6.2.5.5.2 Reaction time
82 6.2.5.5.3 Speed vs. accuracy
6.2.6 Human memory
6.2.6.1 Three types of memory
6.2.6.2 Working (short-term) memory
83 6.2.6.3 Long-term memory
6.2.6.4 Estimation and decision-making abilities
85 6.2.7 Human response capabilities
6.2.7.1 Overview
6.2.7.2 Speed of movement
6.2.7.3 Principles of motion economy
87 6.2.8 Human vs. machine capabilities
88 6.3 References
91 7 Anthropometry and biomechanics
7.1 Introduction
7.2 General considerations
92 7.3 Anthropometric design guidance
7.3.1 Overview
7.3.2 Anthropometric data
93 7.3.3 One-dimensional measurements
7.3.3.1 General data
97 7.3.3.2 Specific user populations
7.3.3.3 Source database
7.3.3.3.1 Choice of database
7.3.3.3.2 Hand data
99 7.3.3.3.3 Foot data
101 7.3.3.4 Date for children
102 7.3.3.5 Additional data sources
7.3.4 Mobility and functional measurements
7.3.4.1 Three-dimensional data
7.3.4.2 Flexibility and mobility
7.3.4.3 Range of motion
105 7.3.4.4 Functional work
107 7.3.4.5 Visual work
7.3.5 Strength
7.3.5.1 Factors affecting strength
108 7.3.5.2 Strength and gender differences
7.3.5.3 Strength of the upper extremity
110 7.3.5.4 Strength of the fingers and hands
7.3.5.5 Strength of the feet
113 7.3.5.6 Special considerations
7.3.5.6.1 Disabilities
7.3.5.6.2 Designing for population extremes
114 7.3.5.6.3 Designing for the average user
7.3.5.6.4 Designing for adjustability
115 7.3.6 Derivation of missing data
116 7.4 Biomechanical design guidance
7.4.1 Overview
7.4.2 Critical design considerations
7.4.2.1 Body posture
7.4.2.2 Endurance
117 7.4.2.3 Repetitive motions
7.4.2.4 Methods and tools to quantitatively analyze biomechanics
7.4.2.4.1 Overview
118 7.4.2.4.2 Expert observation and video
7.4.2.4.3 Motion analysis
7.4.2.4.4 Electromyography
7.4.2.4.5 Measurement of joint angles and acceleration during movement
7.4.3 Special considerations
7.4.4 Design guidelines for tasks involving lifting
7.4.4.1 Injury risks
7.4.4.2 NIOSH revised lifting equation
119 7.4.4.3 ACGIH lifting threshold limit values
120 7.4.4.4 Industrial lumbar motion monitor risk assessment system
121 7.4.4.5 Psychophysical limits
7.4.4.6 Design guidelines for tasks involving use of the upper extremity
7.4.4.6.1 Injury risks
7.4.4.6.2 Strain Index
122 7.4.4.6.3 Rapid Upper Limb Assessment
7.4.4.6.4 Three-Dimensional Static Strength Prediction Program
7.5 References
125 8 Environmental considerations
8.1 Introduction
8.2 General considerations
126 8.3 Design guidelines
8.3.1 Interruptions and distractions
8.3.2 Acoustic noise
8.3.2.1 Overview
127 8.3.2.2 Medical equipment as a source of noise in health care environments
8.3.2.3 Medical equipment as a source of noise in home environments
8.3.2.4 Limits for exposure to acoustic noise
8.3.2.4.1 Overview
8.3.2.4.2 Acoustic noise exposure limits related to safety
128 8.3.2.4.3 Acoustic noise limits for auditory communication
129 8.3.3 Lighting
8.3.3.1 Overview
8.3.3.2 Ambient illumination
8.3.3.3 Device displays and lighting conditions
130 8.3.4 Temperature and humidity
8.3.4.1 Overview
8.3.4.2 Surface temperature
131 8.3.4.3 Humidity
8.3.5 Vibration
132 8.3.6 Slipperiness and friction
8.3.7 Atmospheric pressure
8.3.8 Ease of maintenance
8.3.8.1 Overview
8.3.8.2 Cleaning and sterilization
8.3.8.3 Component replacement and testing
8.3.8.4 Component protection
133 8.3.8.5 Battery-operated devices
8.3.9 Storage
8.3.10 Mounting of devices
8.3.11 Radiant energy
8.3.12 Emergency environment
134 8.3.13 Home environment
8.4 References
136 9 Usability testing
9.1 Introduction
9.2 General considerations
137 9.3 Design guidelines
9.3.1 Types of usability tests
9.3.1.1 Formative usability testing
9.3.1.2 Summative usability testing
9.3.2 Principles of good usability test design
138 9.3.3 Overview of usability test design
141 9.3.4 Content of the usability test plan
9.3.4.1 Introduction
9.3.4.2 Purpose
9.3.4.3 Setting
143 9.3.4.4 Participants
9.3.4.5 Prototypes and simulations
144 9.3.4.6 Methodology or test protocol
145 9.3.4.7 Tasks
9.3.4.7.1 Introduction
9.3.4.7.2 Task selection process
9.3.4.7.3 Task selection criteria
146 9.3.4.7.4 Order of task presentation
9.3.4.7.5 Examples of task scenarios
147 9.3.4.8 Usability objectives
9.3.4.8.1 Purpose of usability objectives
9.3.4.8.2 Specification of usability objectives
9.3.4.8.3 Examples of usability objectives
148 9.3.4.9 Data collection
9.3.4.10 Data analysis
9.3.4.11 Reporting
149 9.3.5 Logistics
9.3.5.1 Testing locations
9.3.5.2 Number of participants
9.3.5.3 Recruiting activities
150 9.3.5.4 Size of the testing staff
9.3.5.5 Duration of test sessions
9.3.5.6 Video recording
9.3.5.7 Note-takers
151 9.3.5.8 Language translators
9.3.5.9 Data-logging software
9.3.5.10 Screen capture
9.3.5.11 Eye-scan capture
152 9.3.6 Protocol-related activities
9.3.6.1 Introduction
9.3.6.2 Participant orientation
9.3.6.3 Consent forms
153 9.3.6.4 Nondisclosure
9.3.6.5 Pre-test questionnaire
9.3.6.7 Type of training
9.3.6.8 Directed tasks
9.3.6.8.1 “Think aloud” protocol
154 9.3.6.8.2 Interaction of co-discovery teams
9.3.6.8.3 Self-exploration
9.3.6.9 Interviews
9.3.6.10 Post-test questionnaires
9.3.6.11 Debriefing of test participants
9.3.6.12 Data
9.3.6.13 Debriefing of the testing team
156 9.3.6.14 Sources of test bias
9.3.6.15 Common testing mistakes
9.3.7 Supplemental usability evaluation methods
9.3.7.1 Introduction
9.3.7.2 Cognitive walk-throughs
157 9.3.7.3 Expert reviews
9.3.7.4 Heuristic reviews
9.4 References
159 10 Signs, symbols, and markings
10.1 Introduction
10.2 General considerations
160 10.3 Design guidelines
10.3.1 Overview
10.3.2 Labels for equipment identification
10.3.3 Descriptions of equipment functions
10.3.4 Hazard labels
161 10.3.5 Electrical receptacle and connector labels
10.3.6 Fuse and circuit-breaker labels
163 10.3.7 Labels on controls, keyboards, and keypads
10.3.8 Positioning and mounting of labels
10.3.9 Label orientation
10.3.10 Indications of functional relationships
164 10.3.11 Permanence and durability of labels
10.4 Specific design guidance
10.4.1 Consistency
10.4.2 Label content
165 10.4.3 Use of symbols
166 10.4.4 Legibility
10.4.4.1 Importance of legibility
10.4.4.2 Contrast
10.4.4.3 Lettering
10.4.4.4 Character height
167 10.4.4.5 Legibility test criteria
10.4.5 Coding
10.4.5.1 Purpose of coding
10.4.5.2 Coding by size and shape
10.4.5.3 Coding by location
10.4.5.4 Coding by color
168 10.4.6 Application of color to mimics and flow lines
10.4.7 Flow lines
10.4.8 Language
10.4.9 Package labels
10.4.10 Hierarchical schemes
169 10.5 References
171 11 User documentation
11.1 Introduction
11.2 General considerations
11.2.1 Overview
172 11.2.2 Overall process for user documentation development
11.2.2.1 Design process consistency
11.2.2.2 Concept development
11.2.2.3 Design input
11.2.2.3.1 Overview
11.2.2.3.2 User profiles
11.2.2.3.3 Task analyses
173 11.2.2.3.4 Scenarios of use
11.2.2.3.5 Use environment
11.2.2.4 Design output and review
11.2.2.5 Verification and validation
174 11.2.2.6 Post-market surveillance
11.2.3 Basic design principles for layout, comprehension, and organization
11.2.3.1 Overview
11.2.3.2 Provide device background information
11.2.3.3 Provide task-oriented instructions
11.2.3.4 Organize instructions in a step-by-step format
175 11.2.3.5 Facilitate translating the instruction into action
11.2.3.6 Clarify alternative courses of action
11.2.3.7 Allow for efficient information retrieval
176 11.2.3.8 Simplify language for ease of understanding
11.2.3.9 Minimize the time required to read, understand, and perform an individual step
177 11.2.3.10 Use white space and lines to separate steps
11.2.3.11 Use visuals and graphics to facilitate performance
178 11.2.3.12 Use color in illustrations appropriately
11.2.3.13 Match warnings or cautions to the relevant step
179 11.2.4 Control of user risks
11.2.4.1 Overview
11.2.4.2 Describe the required user preparations before use
11.2.4.3 Identify actions that could affect accuracy or damage the device
11.2.4.4 Identify risks associated with user disabilities
180 11.2.5 Documentation design for diverse environments
11.2.5.1 Overview
11.2.5.2 Design to accommodate the constraints of the user’s physical workspace
11.2.5.3 Design to accomodate the user’s protective attire
11.2.5.4 Design for storage, handling, and transport
11.3 Specific design guidelines for various types of user documentation
11.3.1 Overview
11.3.2 User guides, operator manuals, and owner’s manuals
11.3.2.1 Description
181 11.3.2.2 Purpose
11.3.2.3 When to use paper-based manuals
11.3.2.4 Special design considerations
11.3.3 Quick-reference guides
11.3.3.1 Description
11.3.3.2 Purpose
11.3.3.3 When to use quick-reference guides
11.3.3.4 Special design considerations
182 11.3.4 Electronic documentation
11.3.4.1 Description
11.3.4.2 Purpose
11.3.4.3 When to use electronic documentation
11.3.4.4 Special design considerations
184 11.4 References
186 12 Packaging design
12.1 Introduction
12.2 General considerations
12.2.1 Overview
12.2.2 The user
187 12.2.3 The use environment
188 12.3 Principles of good medical device packaging design
12.3.1 Overview
12.3.2 Opening packages
190 12.3.3 Assembling or sequentially using components
191 12.3.4 Labeling packages
192 12.3.5 Identifying devices
12.3.6 Indicating sterilization status
193 12.3.7 Storing packaged devices
194 12.3.8 Handling packaged devices
12.3.9 Disposing of packaging
a) Packaging should list appropriate disposal methods (e.g., biohazard disposal, non-biohazard disposal, returnable to manufacturer, recyclable) and should provide users with salient and clear disposal information.
b) Packaging that can be used as a disposal container for a medical device should be easily recognizable by the user.
c) Packaging for devices intended to be used only once and then disposed of should clearly indicate the single-use status of the device.
d) Inappropriate means of disposal should be clearly identified as such.
e) Device packaging may include the means of disposal (e.g., a sharps container).
12.4 References
196 13 Design for post-market issues
13.1 Introduction
198 13.2 General considerations
13.2.1 Type of user: health care professional or home-use consumer
13.2.2 Type of use environment: health care facility or home
13.2.3 Device longevity
199 13.3 Design guidelines
13.3.1 Overview
13.3.2 Disposables
13.3.2.1 Definition of disposables
13.3.2.2 Identity of disposables
13.3.2.3 Access to disposables
13.3.2.4 Tools
13.3.2.5 Improper installation of disposables
13.3.2.6 Automatic “safe” mode
13.3.2.7 Proper disposal method and protection from hazards
13.3.3 Single-use devices
13.3.3.1 Definition of single-use devices
200 13.3.3.2 Obvious device type
13.3.3.3 Disposal
13.3.3.4 Current status and post-usage condition
13.3.4 Labeling
13.3.4.1 Storage requirements
13.3.4.2 Expiration date
13.3.5 Setup and installation
13.3.5.1 Overview
13.3.5.2 Simplicity of setup
13.3.5.3 Setup tasks
13.3.5.4 User abilities
201 13.3.5.5 “Ready for use” indication
13.3.5.6 Setup and installation documentation and training
13.3.6 Routine maintenance
13.3.6.1 Overview
13.3.6.2 Lay users and non-professional maintenance personnel
13.3.6.3 Periodic maintenance activities
13.3.6.4 Cleaning
13.3.7 Repair
13.3.7.1 Overview
202 13.3.7.2 Lay users
13.3.7.3 Need for repair
13.3.7.4 Self-monitoring
13.3.7.5 Protection from damage
13.3.7.6 Accessibility
13.3.7.7 Modularity
13.3.7.8 Field-repairable vs. non-field-repairable
13.3.7.9 Tools
13.3.7.10 Design for maintenance
13.3.7.11 Hazardous conditions
13.3.7.12 Minimizing out-of-service time
13.3.7.13 Maintenance records
203 13.3.8 Upgrades
13.3.8.1 Overview
13.3.8.2 Usability and risk analyses
13.3.8.3 Skills for upgrade tasks
13.3.8.4 Clear information about upgrade status
13.3.8.5 Information about effects on safety and efficacy
13.3.8.6 Information about user interaction changes
13.3.8.7 Documentation upgrades
13.3.9 Obsolescence
13.3.10 Disposal
13.3.10.1 Overview
204 13.3.10.2 Hazardous components
Any toxic or otherwise hazardous components should be clearly and unambiguously identified. Explicit instructions on the proper management and disposal of hazardous components should be provided. The designer should objectively demonstrate that the labeling and instructions are reliably understandable by the intended user.
When appropriate, manufacturers should provide packaging mechanisms (e.g., a needle guard or a labeled, sealable biohazard bag) for protection of users from and disposal of the hazardous components.
For devices or components that would be toxic or dangerous if disposed of in a specific manner (e.g., mercury- containing devices or potentially explosive devices), it should be clearly and unambiguously indicated that they should not be placed in refuse destined for such disposal.
13.3.10.3 Recycling
13.3.10.4 Ruggedness of labels
13.4 References
205 14 Cross-cultural/cross-national design
14.1 Introduction
206 14.2 General considerations
14.2.1 Differences among nations and cultures
207 14.2.2 National issues
14.2.2.1 Languages
14.2.2.2 Regulatory issues
14.2.2.3 National units and formats
209 14.2.3 Cultural issues
14.2.3.1 Technical environment
14.2.3.2 Use environment
14.2.3.3 Social context
210 14.2.3.4 Professional traditions and work organization
14.2.4 Culture-specific or nation-specific user profiles
14.2.4.1 Demographics
14.2.4.2 Anthropometric characteristics
14.2.4.3 System of values
14.2.4.4 Preferences and expectations
211 14.2.4.5 Attention
14.2.4.6 Knowledge, experience, and educational background
14.2.4.7 Interpretation of colors and symbols
214 14.2.4.8 Learning style
14.3 Guidelines for cross-cultural/cross-national design
14.3.1 Overview
215 14.3.2 Direct issues associated with the user–device interface
14.3.2.1 Hardware
14.3.2.2 Interface structure
14.3.2.3 Sequence of operations
14.3.2.4 Information presentation
14.3.2.4.1 Language issues
216 14.3.2.4.2 User–device interface orientation
14.3.2.4.3 Format issues
14.3.2.4.4 Symbols
217 14.3.2.4.5 Color coding
218 14.3.3 Indirect issues associated with the user–device interface
14.3.3.1 Functionality
14.3.3.2 Technical features
219 14.3.3.3 User support
14.3.3.4 Technical documentation
220 14.3.4 Cross-cultural/cross-national design process
14.3.4.1 Overview
14.3.4.2 Analysis phase
14.3.4.3 Design phase
221 14.3.4.4 Evaluation phase
14.4 Summary
222 14.5 References
225 15 Alarm design
15.1 Introduction
15.2 General considerations
15.2.1 Overview
226 15.2.2 Goals
15.2.3 Verifying that the alarm system works
227 15.2.4 Initializing alarm monitoring
15.2.5 Avoiding false alarms
15.3 Considerations regarding specific requirements from IEC 60601-1-8
15.3.1 Attended-use model
229 15.3.2 Distributed alarm systems
230 15.3.3 Alarm priority, urgency of response, and allowable latency
231 15.3.4 Distributed-alarm-system requirements of IEC 60601-1-8
232 15.3.5 “Latching” alarm signals
15.3.6 Initiation and termination of alarm conditions
15.3.6.1 Annunciation of alarm signals
15.3.6.2 Initiation of alarm conditions
233 15.3.6.3 Termination of alarm conditions
15.3.7 Default alarm limits and alarm-limit adjustment
234 15.3.8 Alarm-signal inactivation states
15.3.8.1 Definition of alarm-signal inactivation states
15.3.8.2 Disabling of alarm signals or portions of alarm systems
235 15.3.9 Simultaneous monitoring of multiple physiological states
236 15.4 Step-by-step guidelines for developing an alarm system
15.4.1 Developing an alarm system early
15.4.2 Gathering information
15.4.3 Generating a list of alarm conditions that require alarm signals
15.4.4 Creating signal-processing algorithms
237 15.4.5 Identifying the information to communicate about alarm conditions
15.4.6 Allocating signaling modalities to alarm conditions
239 15.4.7 Creating alarm signals for each signaling modality: visual alarm signals
15.4.7.1 Applications of visual alarm signals
15.4.7.2 Attention-getting visual alarm signals
15.4.7.3 Information-providing visual-alarm signals (information displays)
240 15.4.7.4 Other considerations regarding visual alarm signals
15.4.8 Creating alarm signals for each signaling modality: auditory alarm signals
15.4.8.1 Inherently meaningful vs. abstract auditory alarm signals
15.4.8.2 Construction of abstract auditory alarm signals
15.4.8.3 Design of alarm-signal pulses
15.4.8.3.1 Overview
241 15.4.8.3.2 Frequency
242 15.4.8.3.3 Timing
15.4.8.3.4 Loudness
15.4.8.4 Design of bursts
15.4.8.5 Urgency
243 15.4.8.6 Speech-based (or verbal) auditory alarm signals
15.4.9 Creating alarm signals for each signaling modality: other alarm signals
15.4.10 Creating a simulated use environment
15.4.10.1 Overview
15.4.10.2 Visual environment
244 15.4.10.3 Auditory environment
245 15.4.11 Testing prototype alarm systems with potential users
246 15.4.12 Refining alarm systems on the basis of testing results
15.5 References
249 16 Accessibility considerations
16.1 Introduction
16.2 General considerations
16.2.1 User considerations
250 16.2.2 Design considerations
252 16.3 Design guidelines based on legislative guidance documents
16.3.1 Overview
16.3.2 Users with lower-extremity disabilities
16.3.2.1 Body posture
16.3.2.2 Reach
253 16.3.2.3 Sight lines
16.3.2.4 Neutral body positions
16.3.2.5 Access space
254 16.3.3 Users with upper-extremity disabilities
16.3.4 Users who are deaf or hard of hearing
255 16.3.5 Users who are blind or have visual impairments
16.3.5.1 Nonvisual modes
256 16.3.5.2 Text descriptions and electronic navigation
16.3.5.3 Visual acuity
16.3.5.4 Color deficiencies
16.3.5.5 Tactile features
16.3.5.6 Vibration
16.3.5.7 Accidental activation
257 16.3.6 Users with limited tactile sensitivity
16.3.7 Users with cognitive or memory impairments
16.3.8 Users who could benefit from having more time for device operation
16.3.9 Users with speech impairments
16.4 Research-based design guidelines for patient-support surfaces
16.4.1 Overview
16.4.2 Width of device base
258 16.4.3 Clearance for lift equipment
16.4.4 Adjustability of surface height
16.4.5 Transfer path
16.4.6 Hand-holds
259 16.4.7 Contact surfaces
260 16.4.8 Controls for support surfaces
16.5 Design guidelines for Web-based, mobile, and home-use health care products based on industry guidance documents
16.5.1 Overview
16.5.2 Existing guidelines and standards
261 16.5.3 Built-in multimodal capabilities
16.5.4 Devices that use home-based technologies
16.5.5 Existing laws related to use of hearing aids with telecommunication products
16.5.6 Training and informational materials
16.6 References
264 17 Connectors and connections
17.1 Introduction
17.2 General considerations
17.2.1 Overview
265 17.2.2 Critical design considerations
17.2.3 Key design criteria issues
17.2.4 Types of connection failures
17.2.4.1 Categories of connection problems
17.2.4.2 Misconnections
266 17.2.4.3 Failed connections
17.2.4.4 Disconnections
17.3 Prioritizing types of connections
17.3.1 Overview
268 17.3.2 Direct patient connections for therapeutic purposes
17.3.3 Direct patient connections for diagnostic purposes
269 17.3.4 Connections between patient and device
17.3.5 Routinely connected non-patient connections
270 17.3.6 Permanent exterior device connections
17.3.7 Permanent connections inside devices
17.4 Differentiating connectors
17.4.1 Overview
17.4.2 Active differentiators
17.4.2.1 Definition
17.4.2.2 Unique color coding
271 17.4.2.3 Unique labels
17.4.2.4 Unique geometry
17.4.2.5 Unique alignment marks
272 17.4.2.6 Unique connector barrel key configuration
17.4.3 Passive differentiators
17.4.3.1 Definition
17.4.3.2 Unique pin configuration
273 17.4.3.3 Unique key and shoulder configurations
17.4.3.4 Built-in chips or other electronic identification
17.5 Preventing disconnections
17.5.1 Overview
17.5.2 Rotating locking rings
274 17.5.3 Push–pull locking devices
17.5.4 Locking levers
17.5.5 Screw-captive devices
17.5.6 Capture clips
17.5.7 Friction fit
275 17.5.8 Positive feedback
17.5.9 Engagement of the locking mechanism
17.5.10 Engagement indicators
17.6 Facilitating connections
17.6.1 Connector design (shape, fit, feature)
276 17.6.2 Receptacle design
277 17.6.3 Connector use and testing and user training
17.7 Preventing misconnections
17.8 Protecting connectors
278 17.9 User documentation
17.10 References
279 18 Controls
18.1 Introduction
18.2 General considerations
18.2.1 General considerations
18.2.1.1 Functions to be controlled
280 18.2.1.2 Users and the use environment
18.2.1.3 Control characteristics and labeling
18.2.2 Advantages and disadvantages of various types of controls
18.2.3 Control selection
282 18.2.4 Human factors principles that apply to all controls
18.2.4.1 Control force
18.2.4.2 Control feedback
18.2.4.3 Control layout
18.2.4.3 Control layout
283 18.2.4.4 Control labeling
18.2.4.4 Control labeling
18.2.5 Design considerations for medical device controls vs. controls for consumer products
284 18.3 Design guidelines
18.3.1 Control-panel controls
18.3.1.1 Overview
18.3.1.2 Pushbuttons
18.3.1.2.1 Applications
18.3.1.2.2 Geometry and layout
285 18.3.1.2.3 Force and feedback
286 18.3.1.3 Thumbwheels
18.3.1.3.1 Applications
18.3.1.3.2 Geometry and layout
18.3.1.3.3 Force and feedback
18.3.1.4 Rotary knobs
18.3.1.4.1 Applications
287 18.3.1.4.2 Geometry and layout
18.3.1.4.3 Force and feedback
288 18.3.1.5 Toggle switches
18.3.1.5.1 Applications
18.3.1.5.2 Geometry and layout
18.3.1.5.3 Force and feedback
289 18.3.1.6 Small levers
18.3.1.6.1 Applications
18.3.1.6.2 Geometry and layout
18.3.1.6.3 Force
18.3.1.7 Rocker switches
18.3.1.7.1 Applications
290 18.3.1.7.2 Geometry and layout
18.3.1.7.3 Force and feedback
18.3.1.8 Sliders
18.3.1.8.1 Applications
18.3.1.8.2 Geometry and layout
291 18.3.1.8.3 Force and feedback
18.3.1.9 Key-operated controls
18.3.1.9.1 Applications
292 18.3.1.9.2 Geometry and layout
18.3.1.9.3 Force and feedback
18.3.1.10 Membrane controls and keypads
18.3.1.10.1 Applications
18.3.1.10.2 Geometry and layout
293 18.3.1.10.3 Force and feedback
18.3.2 Input devices
18.3.2.1 Overview
18.3.2.2 Touchscreens
18.3.2.2.1 Applications
295 18.3.2.2.2 Geometry and layout
a) Size and configuration: Design guidance regarding button sizes and separation is similar to that for membrane controls when fingers are used to select objects on the screen (see 18.3.2.5 for guidance on selection devices with smaller selection surfaces, such as styli and light pens). The height and width of the actuation areas for objects on the screen should be at least 13 mm (0.5 inches). Spacing between adjacent areas should be at least 6 mm (0.25 inches) (Figure 18.13). Errors increase as controls get smaller than approximately 23 mm (0.9 inches), but providing “dead space” between keys helps prevent errors. Error-prevention software (e.g., temporary disabling of adjacent objects when a given object is selected) can allow the use of less space between keys. Touch areas larger than 30.5 mm x 30.5 mm (1.2 x 1.2 inches) are associated with more accuracy and fewer entry errors. The active area can be larger than the visible target provided on the screen. Regardless of key geometry, center-to-center key spacing should not be less than 20 mm (0.8 inches).
b) Shape: Visually “concave” and “convex” shapes should be used to indicate button status.
c) Labeling: Placing labels in the center of touchable areas improves usability because users are drawn to and tend to touch them. Labels next to touchable areas often cause confusion and frustration, leading to use errors.
d) Parallax: A common problem with touchscreens is parallax, which is the misalignment between an object’s perceived position on a screen and the position of the object’s associated touch area (Figure 18.14). It is important to consider the mounting of the device relative to the user’s line of sight. Parallax causes users to miss the intended target or select an unintended one. To avoid or minimize the effects of parallax, the distance between the touch surface and the screen surface should be minimized (or made coincident). When parallax is unavoidable, the size or distance between selectable screen objects should be increased to compensate.
296 18.3.2.2.3 Force, activation, and feedback
a) Force: Some touchscreens do not require direct touch and, therefore, require no force to activate. Activation resistances for direct-touch implementations should be in the range of 0.25 N to 1.5 N (0.9 to 5.3 ounces-feet) and the resistance should be adjusted as needed to minimize inadvertent activation.
b) Activation:
 “Up-triggers” (activation upon release) are generally preferable to “down-triggers” (activation upon initial touch) because activation upon release of the finger decreases errors. A good approach is to highlight an item when it is touched and then execute the choice when the finger is removed.
297  Making the entire area of a button touchable facilitates use and reduces confusion. Buttons with touchable areas at least the size of the button (rather than some part of the button) produce less user confusion about the location of a valid touch.
 Displaying crosshairs can be helpful when accurate target selection is needed.
 Highlighting the currently selected area compensates for the lack of tactile feedback by clearly identifying the selected area, decreasing use-error rates.
 Coding by shape or color permits differentiation of active areas from text and background graphics.
c) Feedback: Touchscreens should generally provide auditory feedback to indicate activation or selection input. Auditory feedback, including speech, is helpful for users with vision impairments or those who are distracted. Touchscreens intended for regular use should provide users with the option of muting auditory feedback to prevent sound distraction or redundancy. As with membrane controls, buttons on touchscreens should provide immediate feedback with a press-and-hold repeat time (with continuous pressing) of 0.09 seconds. “Touch mice” are cursors (indicated by crosshairs or arrows) that are controlled by the finger. They decrease mistakes in finger placement and provide clear feedback for positioning. They are typically used with up-triggers, so that users can clearly see the to-be-controlled function and “where they are” before lifting their finger to activate a choice.
18.3.2.2.4 Text displayed on touchscreens
Testing should verify that cleaning (and the possible use of excessive cleaning solutions) does not harm the touch surface or the touchscreen electronics. A temporary “lockout” function should be provided to disable the touchscreen when the device is being cleaned, maintained, or moved.
Device designs incorporating touchscreens should be evaluated in near-actual use conditions if those devices will be used in a dirty environment. For example, significant surface contamination on an acoustic-wave touchscreen can interfere with touch detection until the screen is cleaned.
18.3.2.2.5 User and use environment considerations
18.3.2.3 Keyboards
18.3.2.3.1 Applications
298 18.3.2.3.2 Geometry and layout
18.3.2.3.3 Force, activation, and feedback
18.3.2.4 Mice
18.3.2.4.1 Applications
299 18.3.2.4.2 Geometry and layout
18.3.2.4.3 Force and feedback
300 18.3.2.4.4 Other requirements
18.3.2.5 Styli and light pens
18.3.2.5.1 Applications
18.3.2.5.2 Geometry and layout
301 18.3.2.5.3 Force and feedback
18.3.2.6 Trackballs
18.3.2.6.1 Applications
302 18.3.2.6.2 Geometry and layout
18.3.2.6.3 Force and feedback
18.3.2.7 Displacement joysticks
18.3.2.7.1 Applications
303 18.3.2.7.2 Geometry and layout
18.3.2.7.3 Force and feedback
18.3.2.8 Isometric joysticks
18.3.2.8.1 Applications
18.3.2.8.2 Geometry
18.3.2.8.3 Force and feedback
304 18.3.2.9 Other input devices
18.3.2.9.1 Pointer sticks
18.3.2.9.2 Touchpads
19.3.2.9.3 Body-mounted input devices
305 18.3.3 Large mechanical controls
18.3.3.1 Overview
18.3.3.2 Cranks
18.3.3.2.1 Applications
18.3.3.2.2 Geometry and layout
18.3.3.2.3 Force
18.3.3.3 Handwheels
18.3.3.3.1 Applications
18.3.3.3.2 Geometry and layout
18.3.3.3.3 Force
306 18.3.3.4 Large levers
18.3.3.4.1 Applications
18.3.3.4.2 Geometry and layout
18.3.3.4.3 Force and feedback
18.3.3.5 Whole-hand-operated pushbutton controls
18.3.3.5.1 Applications
18.3.3.5.2 Geometry
307 18.3.3.5.3 Force
18.3.3.6 Foot controls
18.3.3.6.1 Applications
18.3.3.6.2 Geometry and layout
18.3.3.6.3 Force and feedback
308 18.4 References
310 19 Visual displays
19.1 Introduction
19.2 General considerations
19.2.1 Overview
19.2.2 Understanding and accommodating user population characteristics
311 19.2.3 Accommodating the range of use postures
19.2.4 Determining typical mounting positions and variations in mounting positions
19.2.5 Examining the physical environmental conditions
19.2.6 Identifying the requirements for displayed information
19.2.6.1 User information requirements
19.2.6.2 Visual-display specifications
19.2.6.3 Criticality and frequency of use
19.2.6.4 Qualitative vs. quantitative visual-display information
312 19.2.6.5 Character, symbol, and pattern Information
19.2.7 Performing objective display measurements
313 19.2.8 Conducting usability tests
19.3 Guidelines for specifying visual-display performance
19.3.1 Overview
19.3.2 Visual-display viewing conditions
19.3.2.1 Applicability
19.3.2.2 Viewing distance
19.3.2.3 Range of viewing angles
314 19.3.2.4 Visual-display location and orientation
19.3.3 Spatial characteristics
19.3.3.1 Image quality
315 19.3.3.2 Pixel grid modulation
19.3.3.3 Fill factor
19.3.3.4 Geometric distortion
19.3.3.5 Moiré patterns
19.3.4 Temporal characteristics
19.3.4.1 Flicker
316 19.3.4.2 Jitter
317 19.3.4.3 Display response time
19.3.5 Luminance and color characteristics
19.3.5.1 Luminance
19.3.5.2 Luminance contrast
19.3.5.3 Contrast polarity
19.3.5.4 Luminance uniformity
318 19.3.5.5 Specular glare
19.3.5.6 Color uniformity
19.3.5.7 Color differences
319 19.3.5.8 Color usage
19.4 Guidelines for display formatting
19.4.1 Size and spacing of displayed characters or symbols
19.4.1.1 Measurement of screen objects or character height
19.4.1.2 Optimal character height
19.4.1.3 Character width-to-height ratio
320 19.4.1.4 Character stroke width
19.4.2 Font style
321 19.4.3 Character, line, and word spacing
19.4.4 Size of color objects and alphanumeric strings
19.5 Guidelines for displaying data
19.5.1 Precision
19.5.2 Adequate signal duration
322 19.6 Guidelines for selecting electronic visual displays
19.6.1 Comparison of major types of visual displays
323 19.6.2 Liquid crystal displays
19.6.3 Active-matrix vs. passive-matrix displays
19.6.4 Large-screen displays
10.6.4.1 Applications
324 19.6.4.2 Control and content of displayed information
19.6.4.3 Viewing distance
19.6.5 Scale indicators
327 19.7 References
329 20 Use of automation
20.1 Introduction
20.2 General considerations
20.2.1 Types of automation systems and common issues
20.2.1.1 Categories of automation systems
330 20.2.1.2 Monitoring and alarm systems
20.2.1.3 Event-sequencing systems
20.2.1.4 Decision-support systems
20.2.1.5 Closed-loop physiological control systems
331 20.2.1.6 Hybrid or composite automation systems
20.2.2 Automation vs. human tradeoffs in medical systems
332 20.2.3 Automation status
20.2.4 User understanding of the automation
333 20.3 Design guidelines
20.3.1 Monitoring and alarm systems
20.3.2 Event-sequencing systems
20.3.3 Decision-support systems
20.3.4 Closed-loop physiological control systems
20.3.5 Hybrid or composite automation systems
334 20.4 References
335 21 Software–user interfaces
21.1 Introduction
21.1.1 Overview
21.1.2 Sample software–user interfaces
336 21.1.3 Factors influencing software–user interface design
337 21.2 General considerations
21.2.1 Overview
338 21.2.2 Make the software–user interface easy to use
21.2.3 Focus on user tasks
21.2.4 Provide user guidance
21.2.5 Safeguard against use error
339 21.2.6 Optimize interaction requirements
21.2.7 Improve software and hardware integration
340 21.2.8 Select the interaction style
21.2.9 Support product evolution
341 21.3 Special considerations
21.3.1 Overview
21.3.2 Screen size
21.3.3 Compatibility
21.3.4 Information priority
21.3.5 Information legibility
21.3.6 User population
342 21.3.7 Standardization
21.3.8 System integration
21.4 Design guidelines
21.4.1 Categories
343 21.4.2 Conceptual model
21.4.3 User-interface structure
344 21.4.4 Interaction style
345 21.4.5 Screen layout
346 21.4.6 Legibility
21.4.6.1 Importance of legibility
21.4.6.2 Text style
347 21.4.6.3 Text size
21.4.6.4 Figure-to-ground contrast
21.4.6.5 Text capitalization
21.4.6.6 Line spacing
348 21.4.6.7 Text justification
21.4.6.8 String Length
21.4.6.9 Touchscreens
21.4.6.10 Icons (symbols)
21.4.7 Aesthetics
349 21.4.8 Data entry
21.4.8.1 Completeness, accuracy, and efficiency
21.4.8.2 Data entry fields
21.4.8.3 Use of labels and units of measure
21.4.8.4 Label placement and appearance
21.4.8.5 Data justification
350 21.4.8.6 Data arrays
21.4.8.7 Automatic fill-in
21.4.8.8 Data validation and checking
351 21.4.9 Color
21.4.9.1 Functionality and aesthetics
21.4.9.2 Number of colors
21.4.9.3 Color conventions
352 21.4.9.4 Nonreliance on color
21.4.9.5 Color combinations
21.4.9.6 Color associations
21.4.9.7 Color customization
21.4.9.8 Using color to demarcate or indicate status
353 21.4.10 Dynamic displays
21.4.10.1 Trend displays
21.4.10.2 Waveform displays
355 21.4.10.3 Numeric values
21.4.11 Special interactive mechanisms
21.4.11.1 Soft-key user interfaces
356 21.4.11.2 Control-wheel user interfaces
358 21.4.11.3 Touchstone user interface
359 21.4.11.4 On-screen keyboards and keypads
360 21.4.11.5 Speech-emitting user interfaces
361 21.4.12 User support
363 21.4.13 Consistency
21.5 References
364 22 Hand tool design
22.1 Introduction
366 22.2 General considerations
22.2.1 Overview
22.2.2 Biomechanics
22.2.3 Hand grips and positions associated with tool use
367 22.2.4 Forces associated with the use of hand tools
368 22.2.5 Injuries and discomfort associated with tool use
369 22.2.6 Risk factors
370 22.2.7 Compensatory strategies and tradeoffs
371 22.3 Special considerations
22.3.1 Laparoscopic surgery
373 22.3.2 Catheter-based procedures
374 22.3.3 What to do if design data are not available
375 22.4 Design guidelines
22.4.1 Overview
22.4.2 Context of use
22.4.3 Location and environmental factors
377 22.4.4 The end-effector (tool interactions with anatomy)
22.4.4.1 General considerations
22.4.4.2 End-effector uses and functions
378 22.4.5 Characteristics of the tool
22.4.5.1 Considerations for the whole tool
22.4.5.2 Force output
22.4.5.3 Handle angulation
379 22.4.5.4 Handle shape
380 22.4.5.5 Handle length
22.4.5.6 Handle diameter (cross-sectional size)
381 22.4.5.7 Handle cross-sectional shape
382 22.4.5.8 Handle material
383 22.4.5.9 Handle surface and texture
22.4.5.10 Tool weight and center of gravity
384 22.4.6 Safety
22.4.7 User characteristics and related design considerations
22.4.7.1 Overview
385 22.4.7.2 Posture
22.4.7.3 Shoulder
386 22.4.7.4 Elbow
22.4.7.5 Wrist and hand
22.4.7.6 Grip
22.4.7.6.1 Overview
22.4.7.6.2 Gender
22.4.7.6.3 Wrist position
387 22.4.7.6.4 Grip span
388 22.4.7.6.5 Grip force
22.4.7.6.6 Number of fingers used
22.4.7.6.7 Handedness
22.4.7.6.8 Gloves and other PPE
389 22.4.7.7 Overall force requirements
22.4.7.8 Frequency (repetition) and duration of effort
390 22.4.8 Controls for hand tools
22.4.8.1 Control type and placement
22.4.8.2 Triggers
391 22.4.8.3 Slide controls
22.4.8.4 Pushbutton controls
392 22.4.8.5 Rotary controls
22.4.9 Sensory feedback
22.4.10 Guidelines specifically for laparoscopic instrument design
393 22.5 References
398 23 Workstations
23.1 Introduction
400 23.2 General considerations
23.2.1 Adaption of design to user needs
401 23.2.2 Safety
23.2.2.1 Protect users from hazards
23.2.2.2 Protect against use error
23.2.3 Usability
23.2.3.1 Avoid excess complexity
23.2.3.2 Allocate functions appropriately to the user versus the workstation
402 23.2.3.3 Arrange controls and displays to facilitate user tasks
23.2.3.4 Accommodate the users’ physical and functional characteristics
23.2.3.5 Provide affordances
23.2.3.6 Consider the intended use environment
403 23.2.4 User satisfaction
23.2.4.1 Choose an appropriate visual style
23.2.4.2 Refine touch points
23.3 Special considerations
23.3.1 Overview
23.3.2 Serve life-critical purposes
23.3.3 Accommodate evolving clinical practice
23.3.4 Accommodate a variety of user positions
404 23.3.5 Accommodate users with varying degrees of skill, training, and experience
23.3.6 Accommodate workstation use by individuals with disabilities
23.3.7 Accommodate patients who might be under stress
23.3.8 Accommodate caregivers who might be under stress
23.3.9 Anticipate potential migration from hospital to home use
23.3.10 Anticipate frequent or infrequent cleaning
405 23.3.11 Design for compactness
23.4 Design guidelines
23.4.1 Overview
23.4.2 Operational factors
23.4.2.1 Modes of operation
406 23.4.2.2 Prevention of use errors
407 23.4.2.3 Automatic versus manual control
23.4.2.4 Patient and user safety and security
408 23.4.3 Power supply
409 23.4.4 Readiness
23.4.5 Security
410 23.4.6 Privacy
23.4.7 Communication
23.4.7.1 Overview
23.4.7.2 Alarm signals
23.4.7.3 Warnings
411 23.4.7.4 Labeling
412 23.4.7.5 Instructions for use
23.4.8 Component configuration
23.4.8.1 Analysis of user requirements
414 23.4.8.2 Consistency
416 23.4.8.3 Display integration
417 23.4.8.4 Storage space
418 23.4.8.5 Features and customization
419 23.4.8.6 Cable (wire and tube) management
420 23.4.8.7 Housings
23.4.9 Physical interaction
23.4.9.1 Overview
23.4.9.2 Anthropometric characteristics
421 23.4.9.3 Physical accessibility
23.4.9.4 Clinician and patient position
422 23.4.9.5 Line of sight
23.4.9.6 Handedness
23.4.9.7 Repetitive motion and cumulative trauma
423 23.4.9.8 Compactness
23.4.9.9 Mobility
424 23.4.9.10 Stability
23.4.9.11 Adjustability
425 23.4.10 User accommodations
23.4.10.1 Overview
23.4.10.2 Seating
426 23.4.10.3 Hospital beds and examination tables
428 23.4.10.4 Work surfaces
23.4.10.5 Keyboards
429 23.4.10.6 Foot controls
430 23.4.10.7 Remote controls
23.4.10.8 Grips and handles
431 23.4.10.9 Supports and restraints
432 23.4.10.10 Surface characteristics
433 23.4.10.11 Material finish
23.4.10.12 Cleanliness
434 23.4.10.13 Maintenance
435 23.4.11 Environmental factors
23.4.11.1 Overview
23.4.11.2 Task lighting
23.4.11.3 Noise
23.4.11.4 Vibration
23.4.11.5 Venting
23.5 References
437 24 Design of mobile medical devices
24.1 Introduction
24.2 General considerations
24.2.1 Overview
24.2.2 User considerations
24.2.3 Use-environment considerations
438 24.3 Design guidelines
24.3.1 General design guidance
24.3.2 Mechanical design
24.3.2.1 Edges, corners, and pinch points
24.3.2.2 Weight considerations
439 24.3.2.3 Mobility mechanisms
24.3.2.4 Carrying handles and grips
24.3.2.4.1 Overview
24.3.2.4.2 Location
440 24.3.2.4.3 Form factor
24.3.2.4.4 Grasping points or grips
24.3.2.5 Attachment and mounting
24.3.2.6 Drop requirements
24.3.2.7 Ventilation
24.3.2.8 Location of displays
441 24.3.3 Electrical design
24.3.3.1 Power sources (line or battery)
24.3.3.1.1 AC mains
24.3.3.1.2 Batteries
24.3.3.2 Readiness for use
24.3.4 Display of information on computer-based medical devices
24.3.4.1 Selection of display type
24.3.4.2 Display size and visibility
24.3.4.3 Display colors
444 24.3.4.4 Display graphics and text
24.3.4.5 Display materials
24.3.4.6 Language of labeled or displayed text
24.3.4.7 Display layout and information
24.3.4.8 Lighted indicators
24.3.4.9 Auditory indicators
445 24.3.5 Controls and input devices
24.3.5.1 General guidelines
446 24.3.5.2 Keyboard
24.3.5.3 Auditory input devices
24.3.6 Connectors and cables
24.3.6.1 Overview
24.3.6.2 External connectors
24.3.6.3 Multiple connectors
24.3.6.4 Durability
24.3.6.5 Storage
447 24.3.7 Security
24.3.7.1 Theft of mobile devices
24.3.7.2 Tamper-proofing
24.3.8 Instruction manuals and other forms of device documentation
24.4 References
448 25 Home health care
25.1 Introduction
25.1.1 Trends in medical device use
25.1.2 The home user
25.1.3 The home environment
449 25.2 General considerations
25.2.1 Overview
25.2.2 Adjustability
25.2.3 Durability
25.2.4 Learnability and intuitiveness
25.2.5 Freedom from calibration, maintenance, and repair
25.2.6 Protection from unintended misuse and/or tampering
450 25.2.7 Portability and maneuverability
25.2.8 Power requirements
25.2.9 Aesthetics and unobtrusiveness
25.2.10 User guidance and training
25.3 Design guidelines
25.3.1 Overview
451 25.3.2 Design guidance related to sensory capabilities and limitations
25.3.2.1 Decline of sensory capabilities with age
25.3.2.2 Vision
452 25.3.2.3 Hearing
453 25.3.2.4 Kinesthetic and touch sensitivity
25.3.2.5 Sense of balance
454 25.3.3 Design guidance related to cognitive capabilities and limitations
25.3.3.1 Decline in cognitive abilities with age, medical conditions, and treatments
25.3.3.2 Attention
25.3.3.3 Information processing
455 25.3.3.4 Memory
456 25.3.4 Design guidance related to physical capabilities and limitations
457 25.3.5 Design guidance related to the use environment
25.3.5.1 Conditions and environment of use
25.3.5.2 Device maintenance
458 25.3.5.3 Security
25.3.5.4 Disposable device components
25.3.6 Medical device training materials and documentation for home users
459 25.4 References
461 Annex A Statistical justification for sample sizes in usability testing
A.1 Introducction
A.2 Sample size for formative usability testing
462 A.3 Sample size for summative usability testing
465 A.4 References
AAMI HE75 2009 RA 2018
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