Medical devices entering the market today have many barriers to overcome before being put into use, and for a good reason. The FDA and other governing bodies, as well as the guidance they set forth, exist to ensure that these devices are not only useful in administering treatment but safe for all users to operate. Suppose the common mistake is misinterpreting human factors and usability as the simple practice of instilling a device with greater comfort. In that case, it may be challenging to understand what interest these organizations might take in ensuring that they are adequately attended to in the development process. Yet, these principles go far beyond the barrier of convenience. Indeed, their influence over the general performance of a device has made them the subject of numerous regulatory documents and stringent guidance standards.
Clearly Defined Terms
It is first essential to note the terms ' accepted definitions in discussing human factors, usability, and corresponding regulatory guidance.
The American National Standards Institute and the Association for Advancement of Medical Instrumentation define human factors in the HE75 document as "the application of knowledge about human capabilities (covering physical, sensory, emotional, intellectual) and limitations to the design and development of tools, devices, systems, environments, and organizations." Human factors engineering is an applied science taking knowledge gathered in user and usability research and their related environment, limitations, behaviors, perceptions, processes, and leverages.
Usability, meanwhile, is considered "the extent to which a user can use a medical device to achieve specific goals," as defined by ISO/IEC 62366. The document goes on to state, "The characteristic outputs of usability must establish effectiveness, efficiency, ease of user learning, and user satisfaction in a specific context." Related to this is user experience, which is users' perceptions and responses that result from their experience of using a medical device.
While usability research and human factors are separately defined terms, they are hardly isolated concepts; each is intrinsically tied to and supports the other. Both are tools for analyzing and understanding users, their characteristics and environments, in the interest of identifying potential risks and devising methods of mitigating them. Using them in conjunction allows designers to construct user interfaces and experiences centered around correct and error-free usage without endangering users' potential.
The Origin of FDA Concerns
With strict regulations and guidelines in place surrounding human factors and usability, the FDA and other related parties take great interest in ensuring that the user, their safety, features, and challenges, are kept at the forefront of any medical device design. And, when considering current research, it is easy to see why. According to studies conducted by the FDA, CDC, and various medical institutions, hospital errors are the third leading cause of death in the United States, following only heart disease and cancer. Medical devices are no small contributor to this trend, and it is this fact that highlights the importance of human factors and usability in the design process. An estimated 50% of device failures are linked to design flaws resulting in user error. This relationship is further reflected in medical product recalls; FDA research shows that 36% of these recalls are initiated in response to device design issues.
To prevent avoidable tragedies, the FDA has a clearly defined minimum for human factors activities performed during a medical device's conception. Namely, it is required that usability research and human factors evaluation be implemented throughout design and development, with developer teams working under a robust, adequately guided design control process. Supporting this process must be thorough planning, documentation, and evidence of the HFE method defined and established and its correlating results. Another essential requirement is human factors documentation, which should be entered and maintained throughout design and development compliance with FDA standards. Further, all evaluations and research must be integrated into the overall risk management process to ensure a safe and effective medical device.
Performing to FDA Standards
While all these regulations and definitions may seem intimidating, the process of acting upon human factors and usability considerations may be simplified into three primary stages. The first of these is identifying hazard examples, which outline particular device failures during use. The second involves determining the exact risks to health that correspond to these hazard examples. The third stage, then, is pinpointing the use-related errors that may cause these device failures.
Illustrating this process is a next-generation wearable infusion pump. This device delivers controlled doses of liquid injections to the user, commonly used in cases such as diabetes and chemotherapy. A product of a collaborative effort between MIDI and the client, the device was developed utilizing the AGILE development process part of the DevelopmentDNA™ approach using the included design control methods. Employing usability research and human factors engineering, the acting project team defined and documented each stage.
One thread of examples begins with a hazard example: the infusion being stopped prematurely. This example's corresponding risks to health were then identified as an insufficient dose of medication and a delay of treatment. Finally, the use-related errors with the potential to influence the hazard example were found to be (1) the user forgetting to resume the pump after suspending it or (2) the user being unaware of the device's battery capacity.
Another hazard example encountered in the wearable infusion pump design was the user failing to detect or understand the device's notifications. In this case, corresponding risks to health were one or more of four possibilities:
- An overdose of medication
- An underdose
- A delay in therapy
- An incorrect application of the therapy
Use-related causes ultimately determined to be linked to this failure were background noise or nuisance alarms, causing the user to fail to notice or ignore the device notification and the user either intentionally or unintentionally muffling the pump's speaker system.
One final instance of the human factors engineering process in motion was identifying incorrect dosage or medication as a hazard example. Its corresponding health risks were a delay of therapy and inaccurate therapy. The use-related errors seen as potential causes of this hazard were then determined to be the user setting up the pump with the incorrect medication or the user selecting the wrong concentration or delivery rate.
These examples should clarify that designing around usability and human factors research goes far beyond merely making a device more comfortable or convenient for use; it may be the difference between sufficient and insufficient treatment, even life or death. Having a carefully outlined process for performing usability research and human factors engineering, such as that performed under MIDI's DevelopmentDNA™ approach, is not only a matter of FDA approval, but an essential part of creating a device that is safe and optimally effective for users, whether they be patients, doctors, or otherwise.
In the next part of this series, we will dive deep into the specifics of standards and regulations, regulatory bodies and their governance areas, and those requirements that target particular medical devices. Stay tuned to learn more.
