William Hyman: Don’t Forget Secondary Human Factors Effects

Human factors generally focuses on the usability of a single medical device, addressing whether or not the device can be expected to be used safely and efficiently by real users in the real environment of use. The product features of concern often include knobs, buttons, interfaces, displays, alarms, visible and hidden information, instructions for use, and even assembly and durability.

Typically, as in the FDA’s human factors guidance, human factors considerations are treated as a one-way issue (i.e., how the environment affects the use of the device). However, the question should also be asked the other way around—how does the use of a device affect the overall environment?

Secondary human factors effects can arise because of several associated factors. One is that excessive time being spent on one device can detract from adequate attention to other devices and activities. This might be the result of conscious decisions about which devices require the greatest attention, with the consequence that other devices are actively or passively deemed to require less attention.

Excessive use challenges can also lead to general frustration and physical and mental fatigue which can also degrade user performance overall. On the other hand, an easy-to-use device can free-up time and mental energy to deal with more problematic devices.

Unfortunately, typical human factors and usability evaluation and testing conducted in isolation may not reveal these secondary effects. That is because the real issue may not be seen when users interact with an individual device outside of the actual care environment.

Instead, one would need to focus on how they interact with all of the devices within their domain while also dealing with non-device demands on their time and concentration. While human factors testing should be done with some level of realistic task simulation, this is not always the case.

There are at least four important opportunities to address human factors:

One, and potentially the most effective, is during design. This is the most effective because eliminating hazards is always the first choice in a hierarchy of safety measures. The need for human factors analysis is considered part of design controls and is addressed in the preamble to the Quality Systems Regulation, where it is stated that human factors must be applied “from the early stages of the design process until that point in development at which the interfaces with the medical professional and the patient are fixed.” A weakness of this admonition is that it does not preclude a weak design becoming fixed too soon.

The second opportunity for a human factors analysis is during pre-purchase device evaluation and selection, when hazards can be eliminated by not purchasing devices that have poor human factors design. During this phase, it is important to remember that devices may have multiple users, including clinicians, servicers, and patients.

The third opportunity is during deployment, training, and use of devices, which may still have identified human factors issues that have to be dealt with on a day-to-day basis.

Finally, human factors must be considered during incident analyses, after the fact. It is important to not be too quick to blame the user when examining these incidents.

William Hyman, ScD, is an adjunct professor of biomedical engineering at The Cooper Union and a consultant in New York. He is also a professor emeritus of biomedical engineering at Texas A&M University.

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