Medical Device Usability: New Human Factors Standard HE-75

By Lynde Kintner

Ximedica recently hosted an event dedicated to the discussion of HE-75, the latest FDA human factors standard for the design of medical devices. It was co-sponsored by the IDSA Rhode Island and IDSA Medical Section. Led by Steve Wilcox, PhD, of Design Science, and Michael Wiklund of Wiklund Research and Design, both members of the committee that developed the standard and contributing authors to the HE-75 content, the review was well attended by a range of product development specialists.

The standard was developed by the Association for the Advancement of Medical Instrumentation (AAMI)Human Factors committee in cooperation with the FDA. The FDA is increasingly focused on increasing robust usability testing during device development and is placing an emphasis on human factors to increase a device’s ease-of use and to reduce use errors and associated adverse events. I learned a lot from the very knowledgeable speakers. For example, they explained the ideas and philosophies that help define human factors as a whole. One of the bedrocks of human factors is the idea that variability among humans has a large magnitude and successful designs should recognize this, and address the variability. The profession seeks to improve the quality of the relationship between people and the products that they use. As Wilcox put it, “the gold standard is when you can make the tool as invisible as possible and allow the user to focus on the task at hand rather than focusing on the tool”. That’s a great goal to focus on when trying to determine the optimal configuration for a device.

Ten years in the making, the standard is a guide offered to medical device developers – to be used as a resource when designing new products or redesigning older ones. While there are many sources available to developers today, this one has been created as a kind of comprehensive resource of the best known information on the range of ability and physical capacities of humans, as applied to device use. Although it carries a significant amount of ‘clout’ when utilization is cited to the FDA, the speakers made it clear that the guide is not a substitute for good professional judgment. Using good professional judgment is essential when developing both the device and the process through which you will test the device for usability.

The speakers mentioned that Ron Kaye, a human factors specialist within the FDA, has been specific in some instances by stating that the minimum number of subjects tested, per distinct user group, should be fifteen. Kaye has also noted that the development process should include enough formative studies (those that occur as the device is still under development) that by the time a final summative study (one conducted after the device design is finalized) is executed, there are no surprises.

For my work, I found it interesting to learn that current device developers are also instructed to ask users not just about use errors, but also ‘close calls’ or any event in which a subject nearly failed a task. This helps a study remain as comprehensive as possible, especially when test samples are relatively small. When it comes to a discussion of use errors, the FDA is seeking a “satisfactory explanation” which might include that the error was related to the fact that the device was being used in a testing situation or that the error could not be mitigated through device design. It was very interesting to learn that a satisfactory explanation does not include dismissing the use error as unlikely to occur, due to a statistically low occurrence rate.

Overall, it was a great opportunity to learn first-hand from developers who work directly with the FDA. It’s also great knowing that this information exists, and will surely result in many more better-designed devices that will ultimately improve patient safety and patient outcomes.