Medical Device UX Design: Human Factors, Usability & Safety

A common question for medical device innovators is: how important is human factors engineering?

The answer is: more important than most realise, and the gap between knowing that and acting on it is where recalls are born. Human factors engineering is the discipline that sits at the heart of medical device UX design - the structured, evidence-based process of ensuring devices can be used safely and effectively by real people in real environments, without error.

Where consumer UX is concerned with satisfaction and engagement, medical device UX design is a risk management discipline, shaped entirely by human factors principles.

Medical device recalls reached a four-year high in 2024 (1,059 events recorded) with device failure emerging as the leading cause for the first time in over five years. That is not bad luck - it’s the predictable consequence of underestimating how people interact with devices under real-world conditions.

Human factors capabilities are central to how we develop safe, effective products across our medical device portfolio, from injection pens to surgical equipment. The companies treating human factors as a submission formality are, with increasing frequency, the ones issuing those recalls.

Why Medical Device UX Design Is Different to Other UX Disciplines

In consumer UX, a poor design causes a frustrated user. In medical device UX, it causes an adverse event.

The implications are clear - think a nurse who misreads a drug concentration display, a patient who cannot distinguish between two similar controls on a self-injection device or a caregiver who silences the wrong alarm. These are documented, recurring failure patterns that drive recalls, serious injury reports, and preventable deaths.

Human factors engineering (HFE) and usability engineering (UE) are broadly synonymous: the application of knowledge about human behaviour, abilities, limitations, and characteristics to the design of devices people must operate safely.

The FDA, MHRA, and global regulators require manufacturers to demonstrate that devices can be used safely by intended users in anticipated use environments. This is the mechanism by which regulators hold manufacturers directly accountable for the real-world consequences of their design decisions. It is not paperwork. It is accountability.

The Three Pillars of Medical Device UX Design

Device Users

Who will actually use this device?

Not who you assume will, but who will encounter it in the real world? Users may be highly trained clinicians or patients with no medical background. They may be elderly, anxious, cognitively impaired, or administering treatment to a child in a crisis.

A device optimised for one population can be actively dangerous for another. Age, dexterity, visual acuity, cognitive load, stress, and training retention all shape interface requirements in ways that cannot be inferred from engineering expertise.

Use Environments

In reality, devices don’t have the luxury of controlled conditions. They are used in noisy emergency departments, poorly lit bedrooms, moving ambulances, and cluttered operating theatres.

An alarm calibrated for a quiet clinic is functionally useless in an ICU. A touchscreen designed for bare hands fails when wearing surgical gloves. The use of environment analysis is a primary design constraint.

User Interfaces

Every touchpoint between user and device, controls, displays, software interactions, feedback, labelling, and documentation, constitutes the interface. Increasingly these are software-driven, with touchscreens, voice control, and adaptive displays bringing flexibility and new failure modes in equal measure.

The interface is where human factors engineering becomes tangible, and where its absence becomes a liability.

Human Factors Engineering Is a Regulatory Requirement. Treating It as a Best Practice Is a Mistake

The FDA's 2016 guidance "Applying Human Factors and Usability Engineering to Medical Devices" sets clear market access expectations. ANSI/AAMI HE75:2025 provides over 500 pages of current principles and design guidance. IEC 62366-1:2015 defines the international usability engineering process. Regulatory submissions must demonstrate that devices have been tested with representative users performing critical tasks under realistic conditions - not just described or modelled, but truly tested.

With Class I recalls at a 15-year high in 2024, regulatory tolerance for inadequate human factors evidence is contracting. The FDA's 2022 draft guidance introduced a risk-based approach scaling documentation requirements to the severity of potential use-related hazards. Organisations that have treated HFE as a late-stage documentation exercise are discovering that this is no longer viable.

Critical Tasks, Risk Analysis, and Validation

The central question of medical device UX design is deceptively simple: what happens if a user gets this wrong?

Critical tasks are interactions where an error could cause serious harm. Identifying them requires use-related risk analysis, typically through Failure Mode and Effects Analysis (FMEA), where teams evaluate each interface element, map credible use errors, and assess clinical consequences.

This reliably surfaces failure modes that experienced engineers did not anticipate, because engineers are not representative users.

Validation testing (summative usability testing) is where intent becomes evidence. Participants must work independently under realistic conditions: relevant lighting, noise, time pressure, and competing cognitive demands. An appropriate gap between training and testing is required to simulate training decay. A device that only performs safely when instructions are fresh is not a safe device. Sample sizes typically range from 15 to 25 participants per user group, with results demonstrating that critical tasks are completed without harmful error.

Formative Evaluation: The Work That Makes Validation Succeed

Validation confirms whether a final design is safe - formative evaluation throughout development is what ensures it is.

Cognitive walkthroughs reveal confusion points before hardware exists. Heuristic evaluations surface interface violations systematically. Iterative prototyping cycles answer specific usability questions progressively rather than accumulating uncertainty until validation.

Every formative cycle is an opportunity to catch a problem for a fraction of what it would cost at validation, and a small fraction of what it would cost post-market. Teams that compress formative evaluation in the name of speed characteristically spend more time and money in total, not less.

How IDC Integrates Human Factors Throughout Development

The most expensive place to find a human factors problem is post-market - the second is validation. Our approach is structured to find problems in formative evaluation, where they are cheap, fast, and recoverable.

We begin with user research that goes beyond identifying user groups to understanding how they actually behave, what they systematically misunderstand, and which environments will create the most challenging conditions for safe use. Formative evaluation runs iteratively through development, supported by our in-house prototyping capabilities which enable rapid physical iteration without external timelines. Use-related risk analysis runs in parallel, keeping design decisions grounded in clinical consequence throughout.

Validation testing occurs when the design has genuinely stabilised, providing the FDA, MDR, and NMPA submission evidence that reflects actual device performance. ISO 13485 certification at both our UK and China facilities ensures the entire process is auditable, consistent, and built to withstand regulatory scrutiny.

Human Factors Engineering: Build It In or Pay the Price

When teams treat human factors engineering as a phase (a documentation exercise before submission) it’s more likely to fail. Consistently and expensively.

When it is embedded throughout development, products are safer, submissions are stronger, and commercial outcomes are better.

That is why rigorous human factors engineering, and the medical device UX design it defines, is how we do product development, not a supplementary service alongside it.

Explore our medical device design services further, or get in touch to discuss how we can bring your next product to life with the usability and safety it demands.