Strong implementation of human factors principals, processes, tools, and techniques by designers and management alike is a pathway to successful medical device development [1]. Due to the FDA’s increased emphasis on the application of human factors as a risk management activity—focusing on foreseeable misuse and how that interaction affects the inherent risk of using a device—we have witnessed a substantial increase in the number of organizations looking to include human factors (a.k.a. ergonomics) as a critical activity in their design and development process. Yet, it’s worth noting that not all definitions or implementations of human factors are created equal. With the increase in organizations embracing human factors comes substantial variability in both the companies claiming expertise in human factors and processes being used.

The impending release of ANSI/AAMI HE75:2009 Human Factors Engineering -- Design of Medical Devices will be a step towards universal understanding and application of human factors principals. However, there continues to be an increase in the misuse of human factors engineering (HFE), especially by those who use it as a new marketing avenue, or who generalize its application by combining it in their “design research” activities. On the surface this might seem like a trivial notion, but misuse of HFE can wreak havoc on the development timeframe, launch date, allocated resources and most critically, the safety and efficacy of the device. Since misuse often stems from lack of understanding, defining human factors is as important as it is challenging. There are many variations of definitions for the terms human factors and HFE. A study conducted two decades ago in response to a request by the Human Factors Committee of the National Research Council revealed approximately 90 unique definitions [2]. For our purposes, however, we are concerned with the fact that the FDA defines human factors as “the study of how people use technology. It involves the interaction of human abilities, expectations, and limitations, with work environments and system design.” The FDA goes on to define HFE as “the science and the methods used to make devices easier and safer to use. When applied to medical devices, HFE helps improve human performance and reduce the risks associated with use.”

What HFE is not

The FDA does not dictate how to implement human factors into the development process; it is interested only in whether a company can provide documented evidence of human factors science and methods being applied to address user error and safety considerations. That said, let’s take a look at what human factors is not, and why basing a human factors program on these definitions will prove inadequate in addressing the FDA requirements for documented, quantitative evidence of consideration for safe human use.

• Human factors is not clinical or counseling psychology wherein the researcher is primarily interested in “analyzing people” and investigating their mental, emotional, and behavioral responses to a task, environment or relationship. Clinical and counseling psychologists perform valuable research; however, this line of research is well outside the realm of FDA consideration for the design of safe and effective medical devices. This is not viewed as the preferred and primary human factors approach to medical device design.

• Human factors is not “just common sense.”

Beyond the Department of Defense, the adoption of human factors principals has been slow and less than fully embraced. This has been traditionally attributed to the lack of emphasis on human factors within university engineering programs, with the notable exception of industrial engineering [3]. It is further a function of the lack of data generated by human factors professionals to document and demonstrate the impact of human factors considerations on product costs and business profits.

Much work still needs to be done in educating engineers and designers, both experienced and newcomers. Many human factors practitioners have encountered the refrain of “human factors is just common sense engineering, right?” from their potential clients or, even worse, from their own design, engineering, and management coworkers. This attitude must be addressed early and often with clients and coworkers alike; and it may best be done through the development of a shared philosophy model, which promotes human factors awareness, concepts, and approaches through a variety of related design, engineering, and management disciplines. Establishing this philosophy and organizational culture, however, is a long process and will not help those currently battling this attitude.
In the short-term, one might counter with, “If it’s just common sense, why are human factors principals so easily violated and why do error-prone and hazardous designs continue to appear in the marketplace?” We believe it’s because many of these “common sense” revelations come to light in hindsight to an accident or incident in which human error has been identified as the culprit, and not through the deliberate and rigorous application of human factors design principals and test activities. Incident and accident databases and reports are valuable tools for reference; however, once your product shows up in these databases and reports, it is too late for “20/20 hindsight design” on a product that has caused irreparable harm or death to its user; not to mention the potentially disastrous exposure to litigation and the payment of a large sum of money for personal injury or death.

• Human factors is not industrial design.

While industrial design and human factors share a common desire to create solutions users prefer, this is where the comparisons should stop. According to the Industrial Designer Society of America (IDSA)(, Dulles, VA, the definition of Industrial Design is “the professional service of creating and developing concepts and specifications that optimize the function, value, and appearance of products and systems for the mutual benefit of both user and manufacturer” [4]. The inherent problem with this definition, and ultimately the industrial design profession, is the assumption that designers should be responsible for the creation of optimized systems. One would argue that the true value industrial designers bring to medical device development is not “out of the box” creative thinking, but more the unique ability to take multiple inputs from stakeholders (HFE, marketing, R&D, manufacturing, etc.) and synthesize into solutions that highlight the benefits of the system to each stakeholder.

An unfortunate trend we are seeing in the development community is HFE being misused in the upfront “design research” activities. We would agree that human factors representation in the early stages of a project is extremely valuable. However, if you don’t fully understand the downstream impact of these upstream insights and fail to implement these lessons appropriately, you are leaving out a critical risk management step. One common example of this misuse of HFE is the ubiquitous “user testing” activity. Distributing models and prototypes to elicit feedback can be useful during early concept generation as it assures the development is free from biases and leverages the experience of others. However, this should never be considered or marketed as a human factors activity unless the population is representative of the intended users, conducted in the actual context of use and designed to document a performance outcome as part of the risk management activity. Anything else should effectively be considered market research.

• Human factors is not the investigation of user preferences. In fact, the word “preference” appears only once in the 90 definitions found in the 1989 document cited earlier. And in this case it was not used to mean a subjective preference for one element of design over another.

The FDA has clearly stated the following regarding application of user preference in medical device design for use safety [5]:

A focus solely on user preference in the development of a design does not assure that safety and effectiveness have been adequately considered. Users generally prefer devices that are easy and satisfying to use and are aesthetically pleasing. Too often, device manufacturers and users emphasize these device characteristics at the expense of safety and effectiveness.

Although design features that assure safety and effectiveness could decrease user preference in some instances, they are necessary nevertheless. For instance, safety-related user interface design features such as shields over critical controls, mechanical or software-based interlocks, or verification requirements could slow down the use of a device or affect its aesthetics.

A focus on user preference as the primary human factors approach and qualitative metric is too often advertised as appropriate to meet the FDA’s needs; it is clearly not. Safety and effectiveness are paramount considerations when applying human factors design principles. Further, the qualitative nature of preference data does not generally lend itself to rigorous analysis or defensible results with respect to risk-management activities.

What human factors is

Human factors is a data-based, rigorous discipline that seeks to quantify human performance capabilities and limitations and apply that to the design of products and systems to meet requirements for safe and effective use.

Human factors professionals have studied the fundamentals of sensation, perception, information processing, decision making, learning, biomechanics, anthropometry, human error and reliability, as they pertain to systems and product design. In addition, they are well-versed in the various methods of analysis, knowledge elicitation, and experimental design. When such research is well documented and repeatable, and the results achieved are rigorously examined, these data-driven, defensible activities satisfy the core of FDA’s expectation for proper use of HFE.

To illustrate the increased rigor that must be applied to medical device design, refer to the March 2010 article by Philip Hodgson summarizing the international standard, ISO/IEC 62366: Medical Devices – Application of Usability Engineering to Medical Devices[6]. According to the standard, the minimum documentation that must accompany a declaration of conformance includes:

• Documentation of the Usability Engineering Process in a Usability Engineering File.
• Identification of the most important characteristics relating to the use of the device (such as intended medical indication, patient population, intended user profile, conditions of use, the device’s operating principle, etc.)
• Identification of the device’s frequently used functions.
• Identification of hazards and hazardous situations related to usability.
• Identification of the device’s primary operating functions.
• Development of the usability specification.
• Preparation of the usability validation plan.
• Design and implementation of the user interface.
• Verification of the user-interface design.
• Validation of the device’s usability.

What’s next?

With the increased focus on HFE in medical device development, there has been an alarming increase in the number of design and development firms inaccurately marketing their competence in this area. To prevent choosing the wrong partner, cross functional teams representing marketing, R&D, and regulatory must be involved in the review process, as outputs of the new HFE activity will impact all of these disciplines.
Experienced partners should be able to easily articulate how they effectively capture the voice of the customer, derive appropriate requirements and execute studies that satisfy the FDA’s expectations. Anything less leads to misuse of human factors.