Introduction
This guidance is intended to promote the design and purchase of accessible medical products for people with disabilities, both as healthcare patients and providers. Overall, there are many ways to design products to be accessible, as reflected by the overall structure of this document.
It should be noted that Section 1: General Guidance overlaps some with Section 11: Accessibility Considerations of the Human Factors Engineering (HFE) Committee of the Association for the Advancement of Medical Instrumentation (AAMI), which is part of HE-75: Human Factors Design Guidelines for Medical Devices (which will become ANSI/AAMI HE-75 in 2008). This overlap exists because RERC-AMI staff representing Marquette University (Winters, Lemke) and Human Spectrum Design (Story) were the primary authors of the Accessibility Considerations section. A more extensive, refined version of the committee draft is provided here. Section 2: Specific Guidance is fully new material.
Background
Unlike for usability, accessibility has legal status in that access to certain types of products is viewed in many societies, including the United States (U.S.), as a human right, and as such there are often rules and regulations that relate to the accessibility of products or services. This social priority is embodied in civil rights legislation such as the Americans with Disabilities Act (ADA), which prohibits the discrimination against or segregation of people with disabilities in all public facilities, activities, programs, or services (ADA, 1990), including public hospitals and healthcare facilities. In the U.S., standards have avoided defining the term accessibility. Rather, U.S. federal regulations state that products are accessible if they meet specified guidelines that are maintained by the U.S. Access Board. Accessibility has been defined by ISO as the “usability of a product, service, environment or facility by people with the widest range of capabilities” (ISO 9241-171, 2003). Notice that this definition ties usability to accessibility. This ISO tie between the two is controversial and is one reason that U.S. voting representatives to ISO committees may not accept this definition of accessibility and often abstain for certain votes, as U.S. laws provide guidance that goes well beyond considerations typically considered to be within the realm of “usability.” Accessibility has also been defined as the “ability to access the intended use of a product or service for which there is a possibility of benefit” (Winters, 2006), which ties the human right of access to a benefit to the intended use of a product. In short, accessibility may be considered the “ability to access” an entity, whether that entity is a product, service or environment.
While the concepts of accessibility and usability are often synergistic, this is not always the case, as reflected in federal laws that allow a number of alternative approaches for meeting accessibility requirements. For instance, one acceptable strategy is for a product to support use of an individual’s assistive technology (e.g., screen reader); this is called indirect access. Awareness of such options can influence the design process. Accessibility solutions often tend to emphasize multi-modal interfaces, which can end up adding complexity to devices. Yet in general, good use of human factors principles can enhance device accessibility as well as obviously usability, as can good use of the Principles of Universal Design (or design for all or inclusive design) [CUD, 1997]. Often medical device designers can take advantage of relatively mature concepts and commercially-available methodologies developed for achieving accessible designs.
It is well documented that many persons with disabilities lack access to use of medical devices (Winters et al., 2006a). It is also a reality that many current users of medical devices have diverse abilities, and that design strategies that improve their ability to use a product can make the product safer. The size of this user population is also large. The U.S. Census (2000) found that 1 in 5 persons over the age of 5 in the U.S. has a disability, and this proportion is probably low because many older adults do not consider themselves to be “disabled,” just aging. Importantly, it is also likely that the proportion of users of certain medical devices (e.g., patients who use equipment in the home) who have disabilities is well above one-fifth of expected users. Some people are born with disabilities, and some acquire them through accident or illness; some disabilities are temporary and may be related to the reason for presenting at a medical facility. For example, many patients who use medical devices (e.g., crutches, hospital beds, dialysis machines) have temporary or progressive functional limitations. Over time, the intended users of many medical products are likely to include much higher proportions of individuals with disabilities. Some disabilities are situational and may be exacerbated by poorly designed medical equipment. For example, in dim lighting, everyone has a visual impairment, which can make labels difficult to see; in noisy situations, everyone has a hearing impairment, which can make alarms difficult to hear or distinguish; and when the hands are full or gloved and wet, everyone has a manual limitation, which can make disposable packaging difficult to open.
Some healthcare professionals could be considered to have disabilities or activity limitations (although many deny it or at least would not use those labels). Some individuals enter the profession with disabilities, and others acquire them along the way. Of particular importance are those individuals who develop disabilities through repetitive stress injuries or traumatic incidents on the job, such as back injuries from patient handling and carpal tunnel syndrome from extended computer use. In addition, all professionals age and as they do, most will experience functional decrements including decreased near vision and some amount of hearing loss; arthritis is also common. An important fact is that overall the healthcare workforce is getting older; for instance, the median age of the user population for operating room nurses is roughly 50. Increasing the employment of people with disabilities in the healthcare professions is a federally mandated goal, and this has special significance for certain professions such as nursing, in which there are both an aging workforce and a shortage of new workers entering the field. Every healthcare profession requires specific skill sets and ability profiles, so not everyone is a potential user of all equipment and many types of medical equipment do not need to be accessible to or usable by people with all disabilities. But in general, accessible medical device designs can help enable aging and injured providers to continue practicing medicine.
It is important to recognize that anyone could be a medical patient, and that many patients seeking healthcare have either permanent or temporary functional limitations. Regardless of disability, all patients need to be able to use medical devices easily, safely, and effectively, but many people with disabilities and older adults receive inadequate healthcare services because of factors such as inaccessible medical equipment, even though these populations are more vulnerable to some health problems (Grabois & Young, 2001; Gibson et al., 2003). More accessible medical devices can enable patients with disabilities to obtain the healthcare they need.
Accessibility is also a civil rights issue that has legal status. U.S. legislation that applies to medical device design includes the Americans with Disabilities Act ( ADA, 1990), Section 255 of the Telecommunications Act of 1996 (Section 255), and Section 508 of the Rehabilitation Act of 1973 as amended in 1998 (Section 508). The ADA prohibits discrimination against or segregation of people with disabilities in all public facilities, activities, programs, or services, including public hospitals and healthcare facilities. While the ADA ensures that accessibility is considered for architectural access to healthcare facilities, it is also important to maximize accessibility of the medical devices that are intended for use within those facilities or other potential use environments, such as the home. Approaches for usability testing are available that systematically address accessibility by embedding universal design concepts into protocols, identifying access barriers and use error events for users with diverse abilities, and integrating post-activity questionnaires into the process (Winters et al., 2006b). Section 255 requires that telecommunications products and services be accessible to and usable by people with disabilities, if readily achievable; and where it is not, devices and services must be compatible with peripheral devices and specialized customer premises equipment commonly used by people with disabilities. Section 508 requires Federal agencies to make their electronic and information technology (E&IT) accessible to people with disabilities; this law applies to all Federal agencies when they develop, procure, maintain, or use electronic and information technology. The US Access Board (http://www.access-board.gov) implements the regulations associated with these laws, and a design is considered accessible if it meets specific regulations.
While some industries depend on “separate but equal” alternative designs to achieve accessibility (e.g., separate, accessible toilet stalls in public restrooms to comply with the ADA), this approach is generally not economically viable in healthcare when serving diverse user populations. To cite an extreme example, no facility is going to have a special, accessible MRI machine that is used only for patients who use wheelchairs. The most logical and cost-effective solution is to have equipment that can serve the needs of the most diverse possible group of patients in a single unit that may have optional components or modes of use.
This approach of designing for people with all kinds of disabilities and everyone else at the same time has several names, such as universal design, inclusive design, design for all, or transgenerational design. Regardless of the name it is given, the goal is the same. In healthcare, the goal is to optimize medical device usability for as large and diverse a potential user population – whether lay or professional users – as is technologically practicable (readily achievable) and financially feasible.
It is not possible to design medical devices to suit absolutely every individual in every potential situation, but designers can usually get closer to this ideal than is true for many current equipment designs, and small design changes can make big differences in usability. When direct access is impossible, medical equipment needs to offer indirect access by being compatible with auxiliary “assistive” equipment that is either available to all (such as a magnifying device) or supplied by the individual user (such as reading glasses or a screen reader). Awareness of such options can influence the design process. Accessibility solutions often rely on multi-modal interfaces, which can end up adding complexity to devices; but in general, good use of human factors principles can enhance device accessibility as well as usability.
The guidance that follows is intended to provide information that directly relates to designing for users with a diversity of abilities. For most medical devices, the effective application of human factors practices will be synergistic with enhancing accessibility as long as designers recognize and include individuals with disabilities as potential device users in all stages of the usability evaluation process. Approaches are available for usability testing that systematically address accessibility by embedding inclusive design concepts into protocols, identifying access barriers and use error events for users with diverse abilities, and integrating post-activity questionnaires into the process (Winters et al., 2007).
Design Considerations
What are the most important general aspects of designing medical devices to be accessible for people with disabilities? In practice, this requires that devices accommodate the widest possible diversity and range of human abilities. This section presents a summary of various strategies for providing accommodation, including direct access through universal design, multimodal interfaces and alternative formats, and indirect access through commonly used assistive technologies (e.g., text-to-speech screen reader, pointing device, and wheelchair) and the interface requirements associated with use of such technologies in conjunction with medical devices.
Table 1 provides some self-reported disability incidences (for male and female U.S. populations) and some examples of functional limitations that may affect the design of medical devices. Table 2 summarizes information on the functions and types of interfaces needed for some commonly used assistive technologies. Table 3 provides a useful classification scheme for delineating between types of sensorimotor, interface, and device modes. Note that there are three primary sensory modes, each of which represents varying degrees of ability. For example, a reasonable accommodation for an individual who is blind may be different than for a person with a specific type of partial visual limitation. Such degrees of ability are also true for motor abilities such as manual control and speech production. Also note that many interface modes are inherently multimodal; for instance, a “control” device such as a keyboard has a tactile component (e.g., excursion and stiffness of keys), plus a visual component (labeling and motion of keys), and an audio component (sound associated with key depression or retraction).
Table 1: Incidence of self-reported causes of disability among 41.2 million adults (age 18 and older) in the United States in 1999 and some possible functional limitations associated with each disability |
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Cause of Disability |
Total (%) |
Men (%) |
Women (%) |
Possible Functional Limitations |
Arthritis or Rheumatism |
17.5 |
11 |
22.4 |
Joint stiffness, joint contracture/deformity, joint pain, muscle weakness, joint weakness/instability (Arthritis Foundation) |
Back or Spine Problem |
16.5 |
16.3 |
16.6 |
Back stiffness, pain, limited side/forward reaching/bending |
Deafness or Hearing Problem |
4.4 |
6.7 |
2.6 |
Loss of ability to hear specific tones, inability to perceive sounds |
Limb/extremity stiffness |
4.2 |
4.7 |
3.9 |
Loss of fine and/or gross motor control, limited joint range of motion |
Mental/emotional problem |
3.7 |
4.1 |
3.5 |
Difficulty concentrating, indecisiveness, slowed or fuzzy thinking |
Diabetes |
3.4 |
3.4 |
3.4 |
Decreased tactile sensation, vision loss, hearing loss, limb loss, decreased mobility |
Blindness/vision problems |
3.3 |
3.5 |
3.1 |
Blurred vision, cloudy vision, double vision, difficulty with color discrimination, loss of central vision |
Stroke |
2.8 |
3.3 |
2.4 |
Dysphasia, loss of sensation, visual deficits, joint contractures, spasticity, muscle weakness or atrophy, changes in muscle strength, tone and response, loss fine and/or gross motor control, upper extremity flexion synergy patterns (Thorn et al., 2006; Shumway-Cook and Wollacott, 2000) |
Broken bone/fracture |
2.1 |
2.1 |
2.2 |
Limited strength, limited mobility, reaching difficulty |
Mental retardation |
2 |
2.9 |
1.4 |
Limited memory, |
Cancer |
1.9 |
1.7 |
2.1 |
Fatigue |
Head/spinal cord injury |
1.1 |
1.6 |
0.7 |
Limited memory, paralysis, spasticity, limited mobility |
Learning disability |
1 |
1.4 |
0.6 |
Reading difficulties, limited memory |
Alzheimer/senility/dementia |
0.9 |
0.6 |
1 |
Short term memory loss, speech impairment |
Paralysis |
0.8 |
1.0 |
0.6 |
Limited mobility, reaching difficulty, skin pressure sensitivity |
Missing limbs |
0.7 |
1.2 |
-- |
Balance, dexterity |
Epilepsy |
0.5 |
0.7 |
-- |
Seizures |
From CDC, 2001, Prevalence of Disabilities and Associated Health Conditions Among Adults-United States, 1999. MMWR 2001: 50(7): 120-125. |
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Providing compatibility with existing assistive technologies often is the easiest approach for making devices more accessible to people with disabilities. Table 2 provides summary information on a small sample of some commonly used assistive technologies and their functions, as well as brief descriptions of device interface characteristics that may be needed to work effectively with each assistive technology. Some of the assistive technologies included in the table are devices that are owned by individuals for their personal use: some of them are portable and people take them along when they leave home, for example wheelchairs, hearing aids, and mouth sticks; others tend to remain in the home or workplace, for example text telephones, speech recognition software, and a stepping stool. It is important to recognize that most of these technologies are also useful in medical facilities, particularly those types that are not portable.
Table 2: Examples of assistive technologies (AT) that a designer may need to interface with to provide indirect access to the device, or to accommodate for when providing direct access. |
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Assistive Technology |
Function |
Interface |
Text Telephone (TTY/TDD) |
Enables users who are deaf, hard of hearing, or have speech limitations to communicate via telephone by typing and reading messages instead of talking and listening (or sometimes with intermediary voice relay operator). Letters typed into the machine are turned into electrical signals that travel over regular telephone lines, and are converted back into letters that appear on a display screen and/or are printed on paper. |
May include phone jack, keyboard with 20 to 30 character keys, display screen, ring indicator (flashing light), telephone modem, printer |
American Sign Language (ASL) |
Enables users to communicate using signs made with the hands and other movements, including facial expressions and postures of the body. |
Requires clear line of sight; if remote, must include visual display, may include tactile display for individuals who are deaf-blind |
Braille |
Enables users who are blind (and deaf-blind) to read by touching with their fingers an array of raised dots that represent letters, numbers, and punctuation. |
Tactile labeling, consider user reach range to such labels |
Screen Reader |
Converts text into synthesized speech so users can listen and navigate through software content. The user can allow the screen reader to read everything from top to bottom, or one line at a time, or use the tab key to navigate from link to link, from one heading to the next, from one frame to the next, or by other methods. |
Requires software, audio display, text based content |
Magnification |
Enables displayed information, such as that on a computer screen, self-contained monitor or a control, to be readable by a person who has low vision. |
Consider approach space, clear line of sight, software or physical magnifier (may be carried by the user or embedded in the product) |
Voice recognition/activation software |
Enables use of voice commands as an input mode to devices. Two categories: systems with limited vocabulary that are intended for many users, and systems that use learning algorithms and involve training that are customized to a specific user. |
Requires user speech, microphone, software, compatible operating system; may involve a visual and/or audio display |
Cane, crutches, walker |
Facilitates user balance while standing or walking |
Consider approach space, reach space, one- or no-hand operation of controls, grab bar for balance aid and/or AT storage during medical device use |
Guide cane |
Enables users to detect their environment while moving through space; for example a person who is blind tapping for spatial orientation and object detection |
Consider approach space, shapes of devices near floor may be tapped |
Headstick, mouthstick, dowel |
Enables users to activate buttons and keys without use of fingers. Often held in the mouth or strapped to the forehead or hand splint. |
Buttons and keys should be flat or preferably, concave. |
Assistive listening system |
Used to transmit sound as directly as possible to a transducer in the ear of a user who is hard of hearing. |
Small personal amplifier, microphone, extension cord. |
Lift equipment |
Generally used to transfer an individual from one support surface, such as a wheelchair, onto another, such as an exam chair. Includes a controller and mechanical interface (with a surface that supports the individual in a sitting or lying position. |
May be portable, ceiling- or wall-mounted, etc., but in all cases the occupant, perhaps with aid, must be placed into the lift, the controls must be operated, and the occupant must safely exit the lift. |
Wheelchair, scooter |
Enables users with limited mobility to move through the environment without bearing weight on their legs. |
Consider clear path of travel, approach space, reach space |
A useful classification scheme is provided in Table 3 for delineating between different types of sensorimotor, interface, and device modes. Note that there are three primary sensory modes – vision, hearing, and touching/manual – each of which can have varying degrees of ability; for example from users who have full vision to users who are blind. This table helps point out that designs that are ideal for one population of users may be suboptimal for another population. Also, appropriate solutions within a disability category may not lie on a smooth continuum. For example, individuals who are blind often require fundamentally different approaches than do people with a specific type of partial visual limitation, such as needing audio displays versus larger font size and more color contrast. Such degrees of ability are also true for motor abilities such as manual control and speech production. Table 3 also implies that even though a sensory or motor mode is often the focus of a particular design specification, the desired solution often involves integration of both motor and sensory capabilities because of the two-way nature of interfaces. For instance, a control device such as a keyboard may improve usability for all and enable access for some by having a tactile component (e.g., excursion and stiffness of keys), plus a visual component (e.g., labeling and motion of keys), and an audio component (e.g., sound associated with key depression or retraction).
Table 3: Categories of sensory, interface and device “modes” |
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Sensorimotor Modes and Key Categories of Functional Limitations Associated with Each |
Interface Modes |
Device Modes |
Vision (Visuomotor) Blindness Partial sight Visuomotor limitation Colorvision limitation Hearing Deafness Hearing limitation Touching/Manual Loss of sensation, motor Partial sensation, motor Biomechanical loss or joint contracture Gross sensorimotor, reaching Fine sensorimotor, dexterity Speaking |
Input Control buttons, knobs Keyboard Mouse pointer (e.g., standard, roller-ball, touchpad, force-pointer) Touch screen Joystick Microphone/Speech recognition Head/mouth pointer Output Display/captions Dial, gauge Magnifier Audio/speakers Volume control Vibration |
Conceptual modes associated with device use, often associated with grouping of functions, that a user should be able to easily understand, and switch between, in the process of using the device.
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Finally, it is useful to introduce the concept of “roles” to help define the scope of intended users of medical devices, because as long as product designers clearly identify the roles of the individuals who are expected to use their products, additional considerations for accessibility may be unnecessary because certain roles may require certain abilities (e.g., vision and fine motor control for performing traditional surgery). Borrowing from terminology associated with the Health Level Seven (HL7) medical informatics standard (see http://www.hl7.org) that is used for both health information exchange and reimbursement, an “entity” in a “role” “participates” in an “act.” Thus, an “entity” only exists in the context of being associated with a “role,” and here “entities” include users and devices. Key “roles” for medical device users are practitioners and patients, which each have attributes within the HL7 system. Devices and individuals are only connected by virtue of their participation via “roles,” whereas the “role” of a medical device generally involves safe and effective use by a user (or users) “participating” in a specific “act,” and furthermore, perhaps within the context of a specific environment. It is the individual in a role who may have a disability, and once the roles for device use are defined then it should be recognized that it is likely that even those persons who are capable and trained to participate as users are likely to have a diversity of abilities (particularly as they age). This helps define the scope of intended users.
Guidance
There are many ways to design products to be accessible, and strategies that improve usability and sometimes accessibility are integrated throughout this guidance. The General Guidance document is based both on adapting aspects of existing guidelines to medical devices and on considerations of universal design principles. The Specific Guidance document provides guidance on accessible design approaches for specific types of medical equipment, some based on research (and often closely related to other sections of this standard) and some based on technical specifications developed for the implementation of federal legislation.
Key U.S. laws and their implementation by the U.S. Access Board include:
- Americans with Disabilities Act Accessibility Guidelines (ADAAG), which apply to employment (Title 1), government services and transportation (Title II), public accommodations and commercial facilities (Title III), and telecommunications (Title IV). Of special note is the provision of a “reasonable accommodation” for employment, which includes modification of a work environment that enables a qualified employee with a disability to perform essential functions of their job. Also relevant is that equipment, such as medical equipment, within facilities must meet Title III requirements (although no formal ADAAG rules for devices have yet been established), and that medical telecommunications devices must meet Title IV requirements (see http://www.access-board.gov/sec508/standards.htm).
- Telecommunications Act Accessibility Guidelines (TAAG) for accessibility, usability and comparability of telecommunications equipment covered by Section 255 of the Telecommunications Act of 1996. These guidelines are intended to assure that manufacturers of telecommunications equipment design and fabricate their equipment to be accessible to and usable by individuals with disabilities, if readily achievable. If not, it requires compatibility with existing peripheral devices (e.g., assistive devices) used by individuals with disabilities to achieve access, if readily achievable (see http://www.access-board.gov/telecomm/rule.htm).
- Electronic and Information Technology (E&IT) Accessibility Standards (Section 508 of Rehabilitation Act Amendments of 1998, with final rule established December 21, 2000). Section 508 requires that when Federal agencies develop, procure, maintain, or use electronic and information technology (E&IT) they provide equitable access for Federal employees with disabilities unless an undue burden would be imposed on the agency. It also requires that individuals with disabilities, who are members of the public seeking information or services from a Federal agency, have access to and use of information and data that is comparable to that provided to the public who are not individuals with disabilities, again if not an undue burden (see http://www.access-board.gov/adaag/html/adaag.htm)
Presently the Access Board chooses not to apply these rules to medical devices, but if this changes the field could be impacted greatly, given that federal procurement of some medical technologies is by far greater than that of any hospital chain (e.g., services for veterans). However, it is useful to provide the legal definition of electronic and information technology (E&IT), as defined by Section 508, which suggests that this could easily change if circumstances were different:
- “Electronic and information technology. Includes information technology and any equipment or interconnected system or subsystem of equipment that is used in the creation, conversion, or duplication of data or information. The term electronic and information technology includes, but is not limited to, telecommunications products (such as telephones), information kiosks and transaction machines, World Wide Web sites, multimedia, and office equipment such as copiers and fax machines. The term does not include any equipment that contains embedded information technology that is used as an integral part of the product, but the principal function of which is not the acquisition, storage, manipulation, management, movement, control, display, switching, interchange, transmission, or reception of data or information …” (Section 508 § 1194.4).