By Sean Hägen | Late Founder
Human factors engineering (HFE) must be considered by every medical device manufacturer at some phase of the design and development journey to ensure the end product can not only gain FDA approval but also meet the needs of the users and patients. The regulatory risk classification, level of potential harm associated with the use of the device, and product complexity are general determinants for the scope of HFE involvement.
While some companies may view HFE activities as a final required check-off in the overall design and development process, human factors processes are a critical component that should be considered throughout the development continuum. If HFE is left to fill in regulatory mandates during the last steps in the design cycle, final validation results can lead to the emergence of unrecognized usability and safety issues that can require expensive redesigns and costly schedule delays in bringing the device to market. Of course, this impacts the bottom line as well as delaying product launch, giving the competition a significant advantage.
So, the question is, at what point in the design/development cycle does the company engage the HFE process? This article will review HFE practices and discuss how, if initiated early on, they can be a significant driver in identifying key product safety issues and usability challenges and how they impact efficiencies in development time and successful regulatory compliance.
So Just What Is A Comprehensive HFE Process?
HFE is sometimes considered just a focus on regulatory approval but, in fact, it’s a fundamental process that should be integral throughout the entire product development cycle and thus should be a partnership with project management and system engineering from the onset of the project.
To quote the FDA, HFE is “Understanding how people interact with technology and studying how user interface design affects the interactions people have with technology is the focus of how human factors engineering (HFE) and usability engineering (UE).” The definition attempts to cover all factors involved in the design and usage of a medical device, whether it will be managed by a trained medical practitioner or by a patient in an in-home setting.
Generally, in the medical device development context, HFE determines exactly how a user interacts with the device or system, including performing a task analysis, then characterizing those interactions in such a way that usability challenges are identified and subsequent use-related risks are codified. Ultimately, the results of the HFE process generate design inputs that drive user interface design features, which are intended to prohibit the use errors that have been identified as critical to safe and efficacious operation.
When Should HFE Practices Become Involved In The Design Process?
The short answer is “as early as possible.” If HFE is involved early, there are methodologies like contextual inquiry and comparative studies where the development team can watch and participate in the generation of relevant design inputs at the systems engineering level. During earlier development phases like feasibility, cross-functional teams should develop and tailor a usability engineering plan for the project in order to enable this process.
There should be a portion of the Design History file, called the Usability Engineering (UE) file (per IEC 62366-1), where a rigorous HFE process documents usability engineering activities and design inputs, such as inputs into system-level requirements. The product development team should be oriented in the process that developed the UE file as well as the insights within.
An example that supports early integration of HFE is the opportunity for usability specialists to conduct rigorous studies directly in the context of use, including observations of typical behavior of both clinicians and patients, a function not typically undertaken by development engineers. In this approach, if the device has a user interface that the patient directly interacts with, patients will be recruited for usability studies. These studies are undertaken in a controlled lab or simulated environment. Design development teams can then often observe these studies in real time and contribute questions.
Companies that do not bring the HFE team into the process early on and simply take the device to an HFE validation test vastly increase the chances of discovering use-related errors after the design has been frozen, and making design changes is significantly more expensive and impactful on commercialization schedules.
Product teams that proactively evaluate HFE early in the product development cycle can greatly increase their confidence in the performance of the product during final testing.
What Will The FDA Look For In Compliance?
The FDA is tasked with determining that medical devices are safe to use and effective. This requires that all elements, from users, use scenarios, and use environments, have been examined and incorporated into a plan for conducting rigorous HFE analysis and usability testing with the intended uses and users. This process should include a summary of use-related risks; a common tool for this is a use failure mode and effects analysis (UFMEA), which provides the FDA with critical information regarding use error.
There are discussions within the HFE community that question whether UFMEA and/or a use-related risk analysis (URRA) should be differentiated. Conversations are addressing the development of a standardized, comprehensive use-related risk assessment tool that either complements an existing UFMEA or supplants it. Keep in mind that the tool that was adapted from an FMEA (UFMEA) was developed for characterizing reliability in a system or part (objective), not usability (subjective).
A URRA may share elements with a UFMEA but rarely has the same metrics for tracking the process of design controls that mitigate risks and the subsequent residual risks, to not duplicate traceability information in two different documents. The URRA also does not include frequency of occurrence since it is not a determinant for assessing the criticality of a task. A URRA may also have more detail regarding use scenarios, tasks, user types, and characterization of user errors in order to inform design mitigations.
A URRA should at least address the following parameters:
- Use Task Description
- Possible Use Error
- Description of Potential Clinical Harm
- Severity of Harm
- Critical Task? Yes/No
- Risk Control Measure(s)
- Validation Methods
The landscape of healthcare scenarios, device technologies, integrated medication and delivery systems, and software with AI applications within which clinicians and patients interact is constantly changing. The FDA is sensitive to these new developments, which means its processes, methodologies, and policies will continue to evolve. However, the industry is an important part of this evolution. By providing inputs to the FDA’s processes and technologies and engaging the agency early on, before submissions, medical device developers can gain alignment on a human factors engineering approach before the device is submitted for validation.
In summary, engaging an HFE approach in medical device design early in the development phases, like during feasibility assessment, allows cross-functional teams to develop and tailor a usability engineering plan for the project. Recognizing human factors engineers as partners in the overall product development process greatly reduces both use-related risk and commercial risk. This approach will enhance the chance for a successful product launch and help to eliminate the emergence of last-minute risk factors that require costly redesigns and that may impact successful FDA validation required for product launch.
