Historical Use of Medical Devices in the Home

The most common types of medical devices, found in nearly every home, are used for delivering medications or first aid. Common medication administration equipment includes dosing cups for measuring medications in liquid form, such as cough medicine, and splitting devices for reducing the size and dosage of pills. First aid equipment includes thermometers (including oral, rectal, in-ear, and forehead), bandages, ace bandages, heating pads, and snakebite kits. Other types of medical devices commonly used in the home are assistive technologies and durable medical equipment. Assistive technologies are most often either mobility aids (e.g., wheelchairs, walkers, canes, crutches) or sensory aids (e.g., glasses, hearing aids). Other common assistive technologies are prosthetic devices (e.g., artificial arms or legs) or orthotic devices (e.g., leg braces, shoe inserts). Durable medical equipment includes environmental devices, such as specialized beds, person-lifting and transferring equipment, and toileting aids.

Recently some medical devices have been produced as consumer products that enable people to manage their own health care more conveniently and independently (and inexpensively). For example, a wide variety of blood and urine testing kits are available that detect different chemicals and conditions (e.g., illegal drugs, cholesterol, pregnancy). Various types of monitors and meters are available to measure health status indicators, such as blood pressure or blood glucose levels (for people with diabetes). Newer consumer devices include ones that measure blood coagulation (prothrombin time and international normalized ratio, PT/INR) for people taking blood thinning medications, blood oxygen levels (pulse-oximeter), and sleep apnea.

Increasing Migration of Medical Devices into the Home

Climbing costs of health care services and hospital stays and shortages of health care facilities and of nurses and other skilled personnel have put pressure on the medical system to provide more care on an outpatient basis. Consequently, the range and complexity of medical devices being used outside formal health care institutions by diverse user populations are increasing. Even complex devices, such as ventilators, infusion pumps, and dialysis machines, are being used outside the hospital or clinic, often by lay users, even though many of those devices were not designed for and were not specifically labeled for this type of use. There are few regulations that limit the practice of using these devices in the home.

One of the problems associated with medical devices used in the home is that they often are not the same models as the ones used in formal health care settings. The devices may be older or of lower quality, and professionals who encounter the devices, either in the home or when patients bring them to the clinic or hospital, may not be familiar with them. Speaking on behalf of AdvaMed, Susan Morris, vice president for government affairs for Kinetic Concepts (a wound care technology firm), said, “One of the biggest concerns [of manufacturers] … is that legacy devices, old products that were used in the institution that may have been replaced by newer versions, are now migrating into the home because they’re available … but they aren’t products that we originally designed for use in the home” (Taft, 2007). Health care professionals sometimes send people home with medical devices, but consumers sometimes give the devices to other people or resell them, for example, through the Internet on Craigslist or eBay. Devices acquired in this manner are much less likely to be appropriate for the end-user, to be properly operated or maintained, or even to come with complete instructions.

Another challenge for medical device manufacturers is that the device user often is not the person who selected or purchased it. The device provider may be a health care professional, or it may be a distributor or supplier. In the latter cases, the device may not be the optimal choice for the end-users, and the users may not receive the education, training, or ongoing customer support they need. In turn, the device manufacturer may not understand its end-users well because it may not recognize these populations as users of its products, and its designers may never come into direct contact with them.

Users of Medical Devices in the Home

The Centers for Medicare & Medicaid Services reported that approximately 8.3 million Americans received Medicaid home care in 2004, which represents a dramatic increase over the 1.64 million who received services in 1995 (National Association for Home Care and Hospice, 2008) (see Figure 8-1). The growth trend is likely to continue.

FIGURE 8-1

Medicaid home care recipients, 1995-2004. SOURCE: Data from National Association for Home Care and Hospice (2008).

Users of medical devices in the home are a diverse population. Some users are professional caregivers, such as physicians, nurses, nurse practitioners, physical and occupational therapists, social workers, and home care aides. These professionals are typically associated with home care organizations (e.g., home health agencies, hospices, homemaker and home care aide agencies, staffing and private-duty agencies, companies specializing in medical equipment and supplies) or they may be from registries or operate as independent providers. Other device users are lay caregivers, usually family members or friends of the person receiving care. Some care recipients operate devices themselves (while providing self-care). Lay caregivers may be of any age and may have developmental or acquired disabilities, a temporary or intermittent condition, a chronic disease, or a terminal illness (see Chapters 6 and 7).

Nonclinical Environments for Medical Devices

Medical devices are used in nonclinical environments that include homes, workplaces (which may or may not be in office buildings), schools, hotels, stores, places of worship, entertainment venues, and transportation systems (cars, buses, trains, airplanes, ships, etc.). Depending on the device and the procedure, people may use medical devices in a private space, such as a bedroom, office, or restroom, or in a public space, such as an airplane, theater, or park. The variety of use environments presents significant challenges for device and user safety.

User Issues

The characteristics of individuals who use medical devices in the home are not well known by many medical device designers. Indeed, some designers do not understand well even the needs of “average” users, and home device users often have capabilities that are far different from average. Particularly due to the conditions that require them to need home health care, individuals receiving care at home may have reduced physical strength or stamina (e.g., fatigue associated with chronic pain), diminished visual or hearing abilities, impaired cognitive abilities (including confusion caused by the effects of medication), or combinations of these conditions. Illness, medications, and stress can intensify the severity of any preexisting limitations in the user’s physical, perceptual, and cognitive functions.

People’s ability to operate a medical device depends on their personal characteristics, including the following:

• physical size, strength, and stamina;
• physical dexterity, flexibility, and coordination;
• sensory capabilities (i.e., vision, hearing, tactile sensitivity);
• cognitive abilities, including memory;
• comorbidities (i.e., multiple conditions or diseases);
• literacy and language skills;
• general health;
• mental and emotional state;
• level of education and training relative to the medical condition involved;
• general knowledge of similar types of devices;
• knowledge of and experience with the particular device;
• ability to learn and adapt to a new device; and
• willingness and motivation to use a new device.

It is important to recognize that lay users may also be affected by their own emotional states, which may be caused or aggravated by the news that they or their loved ones are seriously ill. They may be overwhelmed by new terminology and the critical responsibilities associated with home care, including awareness of the potential for harm—to the equipment, to their loved ones, or to themselves—if they make an error. Instructions may be confusing, and users may have little preparation and insufficient personal or institutional support for the tasks they must perform.

Regardless of their capabilities, individuals using medical devices in the home should be able to use the devices safely and effectively and without unintentionally making errors that could compromise the health of the person receiving care (Kaye and Crowley, 2000). This requirement has implications for medical device design, user training programs, and ongoing support. If the human factors demands of the medical device exceed the capabilities of the user, the equipment burden may be too great to manage, and the person receiving home health care may be forced to move to a long-term care facility or a nursing home.

In 2005, Hancock, Pepe, and Murphy proposed a “hierarchy of ergonomics and hedonomic needs” (see Figure 8-2). The purpose of the article was to suggest that once people’s needs for safety and functionality were fulfilled, designers should address the need for pleasure.

FIGURE 8-2

Hierarchy of ergonomic needs. SOURCE: Adapted from Hancock, Pepe, and Murphy (2005).

This hierarchical structure could also represent the relationships among safety, accessibility, and usability. For individuals with any sort of physical, sensory, cognitive, or emotional disability, accessibility equates to functionality. The primary imperative is that home-use medical devices be safe; the secondary imperative is that they be functional (accessible) for the people who need to use them. Ideally, devices would satisfy all levels of the pyramid: they would be safe and functional, but also usable and pleasurable, and even offer customization to individual users’ needs and preferences. There is no reason why medical devices, especially those intended for personal use, cannot be satisfying to use and aesthetically pleasing, and possibly even enable users to achieve their own health and life goals.

Device Issues

Some medical devices may not be safe for all users or use environments, but medical device manufacturers have a responsibility to recognize and mitigate hazards to the greatest extent possible. In the FDA guidance document, Medical Device Use-Safety: Incorporating Human Factors Engineering into Risk Management, Kaye and Crowley (2000, p. 7) explain that use-related hazards occur for one or more of the following reasons:

• Devices are used in ways that were not anticipated.
• Devices are used in ways that were anticipated, but inadequately controlled for.
• Device use requires physical, perceptual, or cognitive abilities that exceed those of the user.
• Device use is inconsistent with user’s expectations or intuition about device operation.
• The use environment … [affects] device operation and this effect is not understood by the user.
• The user’s physical, perceptual, or cognitive capacities are exceeded when using the device in a particular environment.

The FDA’s Center for Devices and Radiological Health collects data on adverse event incidents associated with medical devices. One of the FDA databases is the Medical Product Safety Network (MedSun), in which more than 350 health care facilities (primarily hospitals) currently participate and submit reports through the Internet. The database has several subnetworks that focus on specific clinical areas, including HomeNet, which focuses on medical devices used in the home environment (U.S. Food and Drug Administration, 2009b).

Another FDA database collects reports from manufacturers and health care professionals in the Manufacturer and User Facility Device Experience (MAUDE) database. The data include all voluntary adverse event reports since June 1993, user facility reports since 1991, distributor reports since 1993, and manufacturer reports since August 1996. (User facilities are defined as hospitals, nursing homes, long-term care facilities, and ambulatory and outpatient treatment facilities, including home care and hospice care.)

In evaluating reports of adverse device events in the MAUDE database between June 2008 and August 2009, the FDA found 1,059 events for which the location of the event was reported as “home.” The devices involved in the greatest number of events were

• insulin infusion pump,
• implantable cardioverter defibrillator,
• automatic implantable cardioverter defibrillator with cardiac resynchronization,
• ventricular (assist) bypass device,
• mechanical walker,
• implantable pacemaker pulse generator,
• piston syringe,
• intravascular administration set, and
• continuous ventilator (facility use) (U.S. Food and Drug Administration, 2009d).

Note that this list identifies the types of devices with which professionals have had greatest difficulty in the home; lay users do not have access to these reporting systems, nor do they have any good mechanism for providing this type of feedback to the FDA.

Infusion pumps, the most frequently reported device on this list, are notoriously complicated to operate and put a particularly high cognitive burden on the user. This is especially problematic because the person receiving infusion tends to be sicker than the typical home health care recipient and the medications are more critical; consequently, the margin for error is small.

Three of the most common use errors when administering intravenous medications via a pump are (1) dosage miscalculation, (2) transcription data entry error, and (3) titration of the wrong medication. For home use, the first two errors (both of which result in wrong dosage) are less likely if a professional sets up the pump when it first enters the home. The third error (wrong medication) is more likely, especially if the person receiving care uses more than one type of medication. In any use scenario, the pump operator may accidently and erroneously change the rate of drug delivery. All of these types of errors can be life-threatening.

The MAUDE database contains a report of a dosing incident involving an individual who had been using an insulin pump for about 4 years. He had been using his previous pump for 2 years but had purchased a new one 3-4 months before the incident. A few hours after he arrived home one evening, he was found unconscious in his bedroom and could not be revived by paramedics. His cause of death was determined to be a severe hypoglycemic insulin reaction. The report said, “User reported having difficulties with pump outputs. No similar pump issues with older style pump” (U.S. Food and Drug Administration, 2009c). This suggests possible usability problems with the new pump.

To minimize the possibility of pump use errors, it is important that the pump clearly display the type of drug and infusion dose rate. If the pump has built-in intelligence and self-checks (e.g., bar code recognition, reference drug libraries, dosing limits, and best-practice guidelines), or transmits data to a remote health care facility, the chance of error is reduced (B. Braun Medical, Inc., 2000; Beattie, 2005; DiConsiglio, 2005).

Another example of home device user difficulty involved a home ventilator. A family member went into the patient’s room one night and discovered that the patient had died and his ventilator was not functioning. The family member reported that no alarm had sounded and there was a problem with the ventilator’s power cord. The police officer who arrived at the house manipulated the power cord’s plug at the wall outlet, and the ventilator powered up again (Weick-Brady and Lazerow, 2006, p. 203).

Medical devices used in the home should be easy for lay users to operate and have minimal requirements for calibration and maintenance. While hospitals have departments dedicated to performing these tasks, lay users should not be expected to have this level of interaction with equipment. Devices should be self-calibrating whenever possible. Maintenance should generally be limited to only the most basic, routine functions, such as simple cleaning and battery replacement. Depending on the device involved, however, some home care providers will need to sterilize components or dispose of used supplies, and the device system should be designed so that these tasks are easy to perform.

Human Factors Standards and Guidance

U.S. and international standards provide guidance to industry on the importance of and methods for applying human factors to medical device design. Standards offer companies models for including various processes in corporate operating procedures and allow them to utilize bodies of knowledge about best design practices without having to conduct their own research. Following standards enables companies to demonstrate to the FDA (and other regulatory bodies) that they have applied best practices.

One of the key U.S. standards is referred to as ANSI/AAMI HE74:2001, Human Factors Design Process for Medical Devices. The document describes “a recommended human factors engineering process for use in fulfilling user interface design requirements in the development of medical devices and systems, including hardware, software, and documentation.” The standard includes an overview and a discussion of the benefits of human factors engineering, a review of the human factors engineering process and its analysis and design techniques, and a discussion of implementation issues.

One of the most important international standards is ISO/IEC 62366:2007, Medical Devices—Application of Usability Engineering to Medical Devices, which refers to and builds on HE74. Its abstract says that the document:

Specifies a process for a manufacturer to analyze, specify, design, verify and validate usability, as it relates to safety of a medical device. This usability engineering process assesses and mitigates risks caused by usability problems associated with correct use and use errors, i.e., normal use. It can be used to identify but does not assess or mitigate risks associated with abnormal use. If the usability engineering process detailed in this International Standard has been complied with and the acceptance criteria documented in the usability validation plan have been met, then the residual risks, as defined in ISO 14971, associated with usability of a medical device are presumed to be acceptable, unless there is objective evidence to the contrary.

ISO/IEC 62366 incorporates HE74 as an informative appendix (with the exception of a description of the relationship between HE74 and the FDA Quality Systems Regulation). These two documents describe human factors methods that may be applied to assess device safety and performance.

A new standard, ANSI/AAMI HE75:2009, Human Factors Engineering—Design of Medical Devices, supplements these process documents with design guidelines. The recommended practice is approximately 500 pages long and is organized into 25 sections, including one explicitly on home health care. In an interview in August 2008, shortly before his retirement as the FDA’s human factors team leader, Peter Carstensen praised the document but cautioned against applying its contents without judgment (Swain, 2008, p. 52):

HE75 is a very comprehensive handbook describing almost everything a designer needs to know. It’s a one-stop shopping text with most all the information a designer would need to design a good user interface and validate it. But it still requires intelligent interpretation. It’s like someone could write a detailed text on how to perform brain surgery, but careful study and practice will be needed to pull it off. HE75 is a very good start but it’s not a substitute for expertise in the field.

HE75 is massive and may be difficult to apply for engineers and designers who are unfamiliar with human factors and do not know how to prioritize the recommendations for a particular device or how to choose among the inevitable trade-offs that must be made when guidelines conflict. Human factors engineering is an art as well as a science and must be practiced differently for every application.

To complement national and international standards, guidance associated with the concept of universal design provides useful information related to the needs of lay users. Universal design considers the needs of the broad spectrum of potential design users, which is relevant when designing medical devices (Story, 2007), especially for home use.

In 1995 a group of architects, product designers, engineers, and envi ronmental design researchers convened to articulate the fundamental concepts that underlie universal design. The purpose of the resulting document, called The Principles of Universal Design (see Table 8-2), was to support evaluation of existing designs, inform development of new designs, and educate both designers and consumers about the characteristics of more usable products and environments (Connell et al., 1997; Story, Mueller, and Mace, 1998). Implicitly, their purpose was to integrate accessibility into as much of the built environment as possible in order to make it more usable by people of all ages and abilities or disabilities.

TABLE 8-2

The Principles of Universal Design.

Below are examples of how the principles can be applied to medical devices for home health care.

• Principle 1. Equitable Use—i.e., design for all. Optimizing universal accessibility can increase the number of people for whom a medical device, such as a dialysis machine, is appropriate and therefore extend the option of home health care to more people.
• Principle 2. Flexibility in Use—i.e., design for each. A bed control can accommodate users’ personal characteristics, abilities, and preferences if it can be operated with a variety of switches that can be activated with a variety of body parts (e.g., hand, foot, cheek).
• Principle 3. Simple and Intuitive Use—i.e., design for the mind. User interfaces for pumps (e.g., infusion, insulin, enteral) should be easy to understand and intuitive and logical to use.
• Principle 4. Perceptible Information—i.e., design for the senses. A blood coagulation (PT/INR) meter should transmit information in multiple sensory modes in order to maximize communication. It could allow users to enlarge the size of the information on the display (for people with vision impairments) and offer voice output (for people who are blind or who understand auditory information better than visual). The voice output should have a volume control (for people with different hearing abilities) that can be turned off (for people who cannot or do not want to hear it).
• Principle 5. Tolerance for Error—i.e., design for error. Having the device’s user interface request confirmation of irreversible or potentially critical operations can reduce the chance of inadvertent actions. Having devices that revert to benign settings when the operator takes no action for a period of time, or that automatically shut off in case of a power surge (such as by using a ground-fault interrupter), can reduce the level of hazard.
• Principle 6. Low Physical Effort—i.e., design for limited strength and stamina. Buttons that activate in response to body heat require no force (however, they are unusable for people with limb pros theses or cold hands). Some devices may be controlled with voice commands.
• Principle 7. Size and Space for Approach and Use—i.e., design for body sizes and postures. A medical device should provide clearance for people who use it. The diameter of a cylindrical handhold can be tapered to allow users to place their hands along whichever section best suits the size of their hands as well as their needs and preferences for the specific task.

These universal design principles can help improve accessibility and usability (and safety) for laypeople who operate medical devices in the home.

Device Labeling and User Training Issues

Device labeling, instructions, and training can all affect the occurrence of use errors. Use errors may be categorized as either active or latent. Active errors have immediate and potentially serious consequences, such as from an incorrect medication dose or an injection in an incorrect site. Latent errors occur on an ongoing basis and can be much more difficult to identify, such as failure to replace the code key on a blood glucose meter or placing old test strips into a vial of new strips that have a different code (Patricia Patterson, Agilis Consulting Group, personal communication, 2004).

Instructions and labeling that accompany medical devices used in the home must also be designed for lay users. Too often, medical device documentation and labeling are written not for novice users but for health care professionals—that is, to the education and knowledge levels of people who know about medical technology in general and the subject device in particular. Poor labeling increases the likelihood that users will need to call either the doctor’s office or the device manufacturer’s customer service line, which is expensive and may not answer all the user’s questions. User confusion can lead to use errors or product abandonment, either of which compromises quality of care.

All home caregivers, whether professional or lay, must be adequately trained to use and maintain the medical devices that they will use in the home. All household residents who are capable should learn how to interact with the medical equipment. Some residents should be taught about the limits of their involvement, such as children who may be taught to get help if an alarm sounds.

Home users may have multiple problems with training. As described by Fisk and colleagues (2004, p. 131):

The training may be provided under the stressful and emotional context of being newly diagnosed with an illness. Training provided by a health care professional may be presented too quickly, using jargon, with little practice by the patient, and without adequate explanation of the difficulties that may arise if the steps are not followed properly. When users are at home attempting to use a system, they may forget the details of the steps, have no idea about what to do if the system does not operate as expected, and have no immediate access to help.

Lack of ongoing training and support is a particular challenge when device users are faced with purchasing a device when the reimbursement period ends. When a device, such as oxygen therapy equipment, is used under reimbursement, the distributor or supplier usually sets it up, services and maintains it, and delivers any necessary supplies. However, at the end of the reimbursement period, patients must purchase the device if they want to continue using it, but if they do, they lose the supports that the distributor or supplier used to provide. The home user typically has not been trained to service or maintain the device and may not know what supplies they will need or where to procure them, which can lead to serious problems.

Training should be provided in multiple formats, including visual and auditory information, because individuals have different capabilities, learning styles, and preferences. Some people understand information better when it is delivered in visual format, and others understand the spoken word better. Some device users have limited education or are illiterate. Some people do not understand English well or at all. Hands-on training is generally most effective.

Patricia A. Patterson, president of Agilis Consulting Group, is an expert in performance-based training and labeling systems for medical devices. She warns (Patterson, 2004, p. 145):

Getting information into people’s long-term memory so that they can recall it when needed—accurately and consistently—is like walking on thin ice: it’s risky, and when we’re talking medical, it’s dangerous. And it has less to do with the media (a.k.a. video) and more to do with the instructional design…. If the user needs information to perform a task—where is that information going to be stored: in their head (long-term memory) or someplace else? We try to opt for someplace else whenever appropriate for obvious reasons…. What labeling can do is to minimize the need for memory by making it accessible to the user when and where needed—like stuck to the device, in the [user interface] itself, etc.

In addition to clear device labeling and effective training, home caregivers need to have access to ongoing support, always by telephone but also through e-mail, on the Internet, or via telehealth connection. Ideally, some form of help should be available 24 hours a day, 365 days a year.

Environmental Issues

Residential environments vary considerably and can present a range of complexities for introduction of medical devices (see Chapter 10). Medical devices may be used under variable conditions involving such environmental attributes as space, lighting, noise levels, and activity:

• Rooms may be physically crowded or cluttered, making it difficult for the person providing or receiving care to maneuver in the space.
• Carpeting or stairs may hinder device portability or maneuverability.
• The lighting level may be low, making it hard to see device displays and controls.
• The noise levels may be high, making it difficult to hear device prompts and alarms.
• The temperature may be very high (e.g., in Florida) or very low (e.g., in Alaska), which can cause equipment to overheat or stall out.
• The humidity may be very high (e.g., in Louisiana), which can cause condensation, or very low (e.g., in Arizona), which can produce static electricity.
• The home may not be clean.
• The household may be busy with other residents and activities, providing distractions that may confuse people while they use medical devices.
• Children, unauthorized users, pets, or vermin in the home can cause damage to themselves (e.g., playing with syringes), cause damage to devices (e.g., chewing on tubing), or change device settings, which may not be noticed before the unit is used again.
• Electromagnetic interference from other equipment in the home (e.g., computer gear, such as Gameboys and Wii sets) can affect medical device functions.

These environmental influences can have a significant impact on how safe or risky a device is in the home. An example of electromagnetic interference in the home involved a motorized wheelchair. One day when the patient was at home in the wheelchair, it began spontaneously spinning around, out of control. The patient tipped backward in the chair and fell out, sustaining an injury. After the incident the patient reported that someone had been using a cell phone nearby, which may have contributed to the event (Weick-Brady and Lazerow, 2006, p. 203).

Not all medical devices stay at home. People who work may take their device along with them to the workplace. This situation has implications for device portability (size and weight) and appearance, particularly with regard to discretion. People may also take their device with them when they go out in their communities or when they travel away from home. In this case, battery life, durability, and ruggedness also matter.

A home dialysis patient who liked to travel offers an example of traveling with a significant medical device. After receiving dialysis in medical centers in 19 countries on 5 continents for 11 years, he began home dialysis and now takes a dialysis machine with him when he travels. He dialyzes himself five nights a week, unassisted, using a relatively compact, “portable” machine that weighs 99 pounds (Taylor, 2008).

The utilities available must be taken into consideration when selecting a medical device for nonclinical use. For example, for treatments that involve water (such as home dialysis), it will be important to have a clean and reliable source of tap water. For devices powered by electricity, the room will need a sufficient electrical supply (including outlets and circuit capacity). For foreign travel, this may require outlet or power adapters. The device or room will also need a source of backup power, such as a battery or generator, in case of power failure or other emergency (e.g., after a hurricane or earthquake). Some care recipients cannot survive long without the medical devices on which they depend.