Originally Published MDDI January 2003

HUMAN FACTORS

For the agency, human factors is more than a buzzword. Manufacturers lacking a comprehensive approach to user-centered design are likely to find this out firsthand.

Michael E. Wiklund

Manufacturers planning to bring a medical device to the U.S. market should ask themselves the following questions: "Are we ready for FDA to inspect our human factors program? Will our user-interface designs and related test data easily navigate the premarket review process?" How a company answers these queries will reveal a great deal about its likely success in dealing with FDA and appealing to the marketplace.

If the answers are an honest yes, this is probably a company that has made a deliberate and thoughtful investment in a human factors program. It is likely to encounter few problems with FDA, at least with respect to human factors design, and can expect to enjoy a competitive advantage in the marketplace.

If the answers are no, or even maybe, the company may be in for trouble. This may be a company that has paid too little attention to the regulation requiring companies to utilize a systematic design process in the course of product development. As a result, it may have left itself open both to trouble with FDA and to liability claims related to use error.

Background

Since June 1997, the FDA quality system regulation's design controls section has required manufacturers of Class II and Class III medical devices (along with certain Class I devices) to demonstrate adherence to good design practices. According to FDA human factors scientists Pete Carstensen and Dick Sawyer, the critical language with respect to human factors is including the needs of the user and patient. FDA's objective is to improve the quality of user-interface design in order to reasonably minimize the incidence of use errors that could cause patient injury or death. Examples of common use errors include placing a device on the wrong setting, misprogramming its automated behavior, or improperly connecting its components.

In the ensuing five years, many manufacturers have responded positively to the requirement by establishing robust human factors programs. Others have been less responsive. Their hesitance may be due to a lack of technical understanding or to a lack of commitment—whether philosophical, financial, or both—to setting up an effective human factors program. Some companies seem to be taking a wait-and-see approach, unsure how serious FDA is about enforcing its human factors mandate.

Along with the Association for the Advancement of Medical Instrumentation (AAMI), FDA has taken steps to address these barriers, through education, standards development, and enforcement measures. In 2001, AAMI sought to improve the level of understanding of the new regulations among manufacturers by publishing a new national standard entitled AAMI HE74:2001 Human Factors Engineering of Medical Devices. This new standard replaces in part AAMI HE48: 1993 Human Factors Engineering Guidelines and Preferred Practices for the Design of Medical Devices.

Endorsed by FDA, the standard delineates the appropriate steps toward producing a user-friendly and error-resistant design. It acknowledges that human factors research, design, modeling, and testing activities should be scaled to match the complexity of the device and its manner of use. As such, a hemodialysis machine would probably warrant a more substantial investment than a pulse oximeter, due to the extent of user interactions and the opportunity for detrimental use errors.

FDA is increasingly holding manufacturers accountable to its human factors expectations through field inspections, product reviews, and postmarket surveillance. The agency's human factors specialists speak passionately and often about protecting the public against products with human factors shortcomings. At industry conferences and sponsored workshops, they cite numerous examples of patient injury and death attributable to user-interface design flaws. The agency points to the design processes described in AAMI HE74:2001 as an important part of the solution. They also rattle the saber a bit, noting that FDA now has the regulatory responsibility to take action in cases of bad user-interface design.

Field Inspections

Every facility inspection by FDA brings with it a chance that field investigators will ask to see evidence of the company's human factors program. Depending on the situation, field investigators may ask to review examples of human factors analyses and tests associated with products already on the market or currently under development. In such cases, manufacturers should be prepared to open up their design history files, which might include the following items:

• Human factors program plan.
• User research reports and videotapes.
• Task analysis report.
• User requirements specification.
• Conceptual, preliminary, and final design drawings and descriptions.
• Computer-based prototype software files.
• Usability test reports and videotapes.
• User-interface style guide.

Field investigators may also ask to meet the company's human factors specialists, who may be formally trained staff, professionals in related disciplines who learned human factors on the job, or consultants.

Notably, few if any of FDA's field staff have hands-on experience or degrees in human factors or even related disciplines, such as psychology or industrial design. To some extent, this limits their ability to identify subtle issues related to the design process and user-interface design. However, the agency provides its field staff with basic human factors training and background materials to distinguish a good human factors program from a bad one, assuming one exists at all. If an investigator finds cause for concern, he or she may investigate the matter more deeply, drawing support from the agency's experts as needed. Thus, field inspectors will at least catch gross human factors deficiencies.

If a company is unable to demonstrate proper attention to human factors, FDA is empowered to issue a warning letter, a uniformly dreaded outcome among medical device developers. Warning letters give manufacturers a deadline to correct documented problems before the agency imposes a severe penalty.

Carstensen spearheads the agency's human factors efforts. He says that a company can be written up for not having the necessary design controls in place, even if the device appears to have a good user interface. The company must have a design control process in place—one that includes the required human factors steps, he says. Sawyer points out that device developers must verify the match between design inputs (users' needs identified through research) and design outputs (specific user-interface design characteristics).

Premarket Reviews

FDA has asked many companies that are seeking premarket clearance for their products to supplement their applications with additional proof that the device can be used safely by typical users working under the normal range of use conditions. Such proof often includes findings from evaluations of device operation conducted early in the design process using relevant use scenarios, effectively requiring usability tests of computer-simulated or working prototypes. And of course, discovering design deficiencies in a prototype will save the manufacturer the money and time that might be spent redesigning a production model.

The rigor of a human factors review is proportionate to the complexity of the device's user interface and the potential for deleterious use errors. According to Carstensen, reviewers may flag a particular product as having a relatively complicated user interface, perhaps because it has numerous controls or unusual interaction mechanisms. In such a case, the reviewer may contact CDRH's human factors group, and a staff member will be assigned to the review team. He or she will perform a more-intensive analysis that pays particular attention to submission materials related to hazards, use errors, design requirements, design features, and user instructions. In more-focused reviews, FDA staff seek answers to basic questions, such as the following:

• Does the device adhere to basic human factors design principles?
• Does the device preclude use errors that could lead to patient injury or death?
• Has the manufacturer tested the user interface with representative users to demonstrate its operability?

Review of a device's human factors aspects may raise concerns about specific features. For example, the reviewers may be concerned about the design of the imbedded alarm system or cable connections to peripheral devices. They may question whether users will be able to hear a high-pitched alarm tone, noting that older men suffer a predictable degradation in their ability to hear high-pitched sounds. Or they may be concerned about whether the device's cable connections provide sufficient tactile feedback to confirm that the connection is complete and secure.

Considerable attention is focused on usability test reports because many usability problems become evident only when representative users perform representative tasks. For example, the task of programming a single-channel infusion pump may seem logical according to a flow diagram. However, users may struggle to perform the task correctly, even after receiving training, due to the need to convert units of measure as part of a complicated dose calculation. This kind of problem could lead to an accidental patient overdose, but it is difficult to spot on a paper review. Therefore, FDA looks to manufacturers to conduct rigorous, dynamic usability tests to reveal such problems.

In fact, a glance at FDA's human factors guidance documents or the Web page www.fda.gov/cdrh/humfac reveals the agency's view that usability testing is the cornerstone of any human factors program. FDA's human factors team strongly encourages manufacturers to invest in a series of usability tests during the course of product development in order to make the product review process go more smoothly.

Postmarket Investigations

Occasionally, the agency's human factors staff may be called upon by the agency's Office of Surveillance and Biometrics to evaluate the human factors suitability of a device involved in an incident leading to a patient injury or death. In the past, they have scrutinized various catheters, glucose meters, infant apnea monitors, ventilators, infusion devices, and many other devices involved in multiple incidents.

According to Carstensen, these human factors reviews typically begin with an ad hoc meeting to discuss the given incident as well as concerns about the device's design. The discussion may escalate to include follow-up design analyses by FDA's human factors experts and a request for the manufacturer to conduct studies to address a specific concern. A particularly severe problem could trigger a device recall. However, according to Sawyer, "In the case of an obvious and serious user-interface deficiency, manufacturers often will be the first to recognize a problem and take necessary corrective and preventive actions on their own."

International Perspective

Recent changes to the good manufacturing practice regulations and AAMI HE74:2001 establish a clear mandate for U.S. medical device companies to focus on human factors. But many companies first introduce their products in Europe in order to accelerate market entry and build a base of clinical experience. What are the expectations abroad? Are the requirements significantly different?

In fact, the expectations are quite similar. For starters, the International Electrotechnical Commission is expected to incorporate an adapted version of AAMI HE74:2001 as a collateral standard to IEC 60601: IEC 60601-1-6, Edition 1, medical electrical equipmentPart 1-6: General requirements for safetyCollateral standard: Usability (currently under development, second draft circulated for comment in July 2002). Therefore, organizations such as TÜV, which evaluate medical devices against applicable standards, will also be seeking evidence of good human factors design.

Conclusion

Who should care about human factors? Certainly, any quality-conscious engineer or designer should. User interfaces are a particularly visible sign of design excellence and warrant close attention from the technical staff. Marketers should also be concerned. More than ever before, customers are able to distinguish good user interfaces from bad ones and choose to purchase devices with good ones.

But it is top management and the staff in a firm's regulatory affairs department that hold the final responsibility for demonstrating a good faith response to FDA's mandate. In the absence of such a response, not only is FDA regulatory action a real possibility, but marketing problems and liability concerns could arise as well. Michael E. Wiklund is vice president, human factors/usability engineering, at the American Institutes for Research. He is a frequent contributor to MD&DI.

The author will be responding to questions and comments about this article in MD&DI's Author Forums during the week beginning February 3, 2003. Visit www.devicelink.com/mddi and select the Author Forums link.

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