This past June 2011 marked the release of a new guidance document from the FDA titled Applying Human Factors and Usability Engineering to Optimize Medical Device Design. It is the first new guidance on human factors from the Agency in more than 10 years and it marks a significant evolution in the Agency’s thinking about the role of human factors in improving medical device safety. Like its earlier counterpart , the guidance focuses on how human factors methods can be used to identify and mitigate use-related hazards. But the new guidance is much more prescriptive and raises the bar for device manufacturers. It includes new requirements for human factors validation testing. These requirements apply not just to “traditional” device manufacturers, but to companies producing “combination products” as well – drug products delivered using specialized syringes, injectors, and inhalers.
What is Human Factors Anyway?
Human factors is a marriage of psychology and engineering. It is the application of our knowledge of human capabilities, limitations, and predispositions to the design of work, workspaces, and technology. Of course, technology includes medical devices.
Poorly designed devices put patients and device operators at risk. Problems arise when there is a mismatch between how a device should be used and the physical, perceptual, or cognitive abilities of the person using it. For example, the thumbwheel on a glucose monitor may be too difficult for a diabetic with neuropathy to operate, information on a patient monitor may be too small for a nurse to read accurately from across the patient’s bed, or the sequence of steps to set the dose and prime an injector may be too lengthy for an elderly patient to remember. Environmental factors such as lighting, noise, and vibration can create use-related risks as well. Imagine setting up and adjusting a heart monitor in a speeding ambulance. And situational factors such as lack of sleep or the competing demands of a busy ER can make operating an already complex and non-intuitive device more difficult.
Use-related hazards arise when design problems trigger use errors that pose risks to patients or device operators. The good news is that human factors engineering can play a valuable role in identifying, evaluating, and addressing use-related hazards during device design. A thorough human factors analysis considers all aspects of the user, intended use, the use environment, and the device user interface:
- User Considerations include who will use a device (a physician, nurse, patient, non-medical care giver): their physical strength, dexterity, and stamina; their attitudes, and emotional states; and what training they will receive and their knowledge of related devices.
- Intended Use includes what the device will be used for (e.g. self-administration of a medication), or the work the device is designed to support (e.g., monitoring a patient’s oxygen saturation level).
- Use environments may be hospital ICUs, labs, physician offices, emergency transport vehicles, patient homes, and public spaces; the environment may be crowded or cluttered, dark or well lit, quiet or noisy; environments may include other equipment or require the user to engage in other activities while operating a device.
- The Device User Interface includes not only switches, dials, touch screens, icons, menus, indicator lights and alarms, but operating instructions, labeling, packaging, and training materials as well.
Well-designed devices accommodate user and environmental factors. Their user interface is consistent with a user’s abilities and operate in ways that are aligned with a user’s experience and expectations. They facilitate correct actions and prevent or discourage use errors that pose risks to patients or users. Human factors engineering provides the knowledge and methodology to reliably create well-designed, user- and patient-friendly devices.
The New Guidance: Applying Human Factors to Optimize Medical Device Design
The new guidance provides an excellent introduction to human factors and its application to medical device design. It is a well-written Human Factors 101. Like its predecessor guidance released in 2000, it describes how human factors methods can be applied during device design to effectively manage use-related risks. But the new guidance also introduces new requirements for Human Factors Validation Testing and outlines how human factors activities should be summarized and reported.
Human Factors Validation Testing
In principle, device manufacturers will need to conduct human factors validation testing for their device if their risk analysis has found a moderate to high risk of use error or the FDA feels testing is warranted to justify its concerns about human factors issues. In practice, the FDA is requesting human factors validation tests in support of submissions for a broad range of devices. This includes combination products utilizing drug delivery systems such as an injector or inhaler. Human factors validation studies have become part of the review for approval of many New Drug Applications (NDAs). These reviews are facilitated by the Office of Combination Products working in conjunction with the Human Factors Team within the Center for Devices and Radiological Health (CDRH) and the Center for Drug Evaluation and Research (CDER).
For most device manufacturers, human factors validation testing requires conducting a simulated use test, in which a minimum of 15 prospective users for each distinct user population are asked to operate the device in a meaningful way, in a realistic, but simulated environment. The test should be structured to mimic actual use, utilize a production version of the device, and be sufficiently sensitive to capture use-related problems, if they exist. This means test participants must be representative of actual users; the testing must be focused on the highest-priority tasks or use scenarios; and environmental and situational factors that can affect performance must be incorporated into the test environment (e.g., dim lighting, multiple alarms, distractions). The test should monitor participant performance for evidence of use errors and engage participants (after all test scenarios have been completed) in assessing any use issues that arose during testing.
Finally, test participants must be Americans . The FDA is responsible to US consumers. Rather than entertain arguments from foreign manufacturers about why Canadians or English-speaking Europeans are adequate surrogates, the Agency now requires that testing be done in the US.
The Human Factors Engineering Report
The new guidance also outlines how manufacturers should summarize and report on their human factors engineering activities. Table 1 outlines the FDA’s requirements for a Human Factors Engineering Report. The outline ensures that manufacturers discuss those topics of primary importance to human factors reviewers and follow a format that will facilitate the review process.
Manufacturers should draft the report as a defense lawyer might draft their closing statement in a legal case: first, review the facts of the case (the analysis you undertook to identify and address use-related hazards), then the evidence assembled (especially the results of your validation test), and finally, why the facts and evidence support the case (your definitive claim that the device can be used safely, and why any residual risks are acceptable without further efforts at mitigation).
|Analysis of Intended Users, Uses, Use Environments, and Training.
Describe your intended users, intended use, and context of use. Include a discussion of critical factors that influence user performance, including differences among distinct user groups, aspects of the use environment, or situational factors present in the context of use. Discuss whether device users will require training and how that training will be provided in practice.
|Device User Interface.
Provide a graphical depiction of your device user interface and a verbal description of device operation.
|Summary of Known Use Problems.
Summarize your analysis of known issues with predicate or related devices and what design modifications where introduced for your device to mitigate these issues.
|User Task Selection, Characterization, and Prioritization.
Summarize your risk analysis methods and the use-related hazards you identified. Relate these risk to user interactions to prioritize user tasks by their level of risk. Critical user tasks must be included in your validation testing protocol.
|Summary of Formative Evaluations.
Discuss formative usability testing conducted during your device’s design. Discuss key findings and design modifications introduced as a result, or insights that informed the design of your validation testing protocol.
Describe your methodology, including rationale for selection of test participants, approach to training, critical tasks and scenarios studied, technique for capturing unanticipated use errors, and definition of performance failures. Test results should review task failures and include an analysis that incorporates subjective assessments by participants about those failures.
Provide a statement that your device is safe and effective for intended users, uses, and use environments. Then discuss how the work you performed (described in the previous sections) supports this conclusion. Discuss any residual risk and provide a rationale for why further attempts at mitigation are not warranted.
Table 1. Outline for the Human Factors Engineering Report.
Canada, Europe and Beyond?
The new guidance is, of course, specific to the FDA and devices bound for the US market. What about Health Canada, Europe, or other jurisdictions? While Health Canada regulations do not deal specifically with human factors (a search of the Health Canada website for the term “human factors” turned up little in the way of guidance or requirements) Health Canada is following the FDA’s direction and has begun to ask device manufacturers to conduct human factors validation testing to support their submissions.
Manufacturers are already required to comply with ISO/EN 62366: Medical devices – Application of usability engineering to medical devices, in order to gain CE Marking for sale of their devices in the European Union. ISO/EN 62366 is similar in intent to the FDA’s new guidance document and includes a requirement for validation testing.
If your company is a medical device manufacturer or is planning a new drug application that includes a drug delivery device such as a syringe, injector, or inhaler, plan on conducting a human factors validation, in the United States, to support your regulatory submission. Don’t wait for a request from a reviewer. Manufacturers need to start human factors work early in their product’s design. Companies will not meet the FDA’s requirements for a well-designed human factors validation study if they have not conducted an analysis of device users, use environments, and situational factors that affect how well people can use the device; prioritized the risk of user interactions; and identified and taken steps to mitigate potential use-related hazards. The very good news is that doing this human factors work will ensure that your company develops a safer, more usable product.