Medical Device Development Insights: Human Factors and Usability Engineering in Medical Device Design

This article is part of ATL’s Medical Device Development Insights series, which explores the engineering processes used to bring safe, effective medical devices from concept to market.

Overview

In our previous articles, we explored how Design Thinking helps teams identify user needs and define the right problems early in the development process.

Once those needs are understood, Human Factors and Usability Engineering (HFUE) ensures that solutions can be used safely and effectively in real-world conditions.

To innovate in the medical device arena can mean creating something entirely new or improving something that already exists. Many devices on the market today are trusted, widely used, and perform their intended function well.

But what happens when you ask the end user for their perspective?

In some cases, feedback may seem unrealistic or difficult to implement. In others, it may highlight challenges that users have simply adapted to over time. Occasionally, it reveals issues that have gone unaddressed entirely.

By involving users early in the design process, teams can better understand what would make their work easier, safer, and more effective. This input plays a critical role in shaping devices that perform well not just technically, but in practice.

The Role of Usability in Medical Device Development

Medical devices are often used in complex, unpredictable environments.

Users may be working in low visibility conditions, handling multiple tasks at once, or operating under time pressure. In these situations, even small usability issues can have a meaningful impact.

A device may function exactly as intended from an engineering perspective, but still present challenges in use.

Human Factors and Usability Engineering addresses this by focusing on how users actually interact with devices. Rather than relying on assumed workflows, it brings real user behavior into the design process, helping teams make more informed decisions throughout development.

Formative Studies: Informing Design Decisions

Most of the critical usability decisions in a project are made long before validation.

Formative studies are where those decisions begin to take shape.

They are used to gather feedback early and throughout development, allowing teams to understand how users interact with concepts before designs are finalized.

This is where assumptions about user interaction are first tested in practice.

Figure 1. Early-stage prototype evaluation during a formative usability study allows teams to explore user interaction before designs are finalized.

These studies can vary significantly depending on the stage of the project.

At one end, they may involve small groups reviewing early concepts using sketches or written descriptions. At the other end, they may involve multidisciplinary teams interacting with high-fidelity prototypes in realistic environments.

At each stage, the goal is different.

Early in development, teams may be trying to understand:

• What problems users are actually experiencing
• Whether a concept aligns with real workflows

Later in development, the focus shifts to:

• Whether a feature can be used correctly
• Whether interactions are intuitive and efficient

A well-structured formative study can provide valuable input into the design—but only if the team understands what information is needed before the study begins.

Who to Include in Usability Studies

Who you include in a usability study directly impacts the quality of the insights you get.

Different users interact with devices in different ways. If key groups are missing, the design may reflect only part of the real-world use case.

These differences often only become visible when multiple user groups are observed directly.

Figure 1. Early-stage prototype evaluation during a formative usability study allows teams to explore user interaction before designs are finalized.

In one project, despite multiple formative studies, feedback from female surgeons had not been included. With the device intended for a broad market, this meant a significant portion of users had not been considered.

Fortunately, there was still time to address this—but it highlights how easily gaps can appear if participant selection is not carefully planned.

Guidance such as ANSI/AAMI HE75 helps define participant numbers. While human behavior is not exact, research shows that:

• With a 25% probability of detecting a usability issue
• 5–8 participants can identify approximately 75–90% of issues

However, this applies per user group.

Different user profiles should be treated separately, as their interactions, environments, and expectations may vary significantly.

A comprehensive study may include:

• surgeons
• nurses
• biomedical engineers
• cleaning and sterilization staff

Each group brings a different perspective, and those differences directly influence how a device should be designed.

A diverse set of users provides more complete insight—and ultimately leads to more robust design decisions.

The Cost of Usability

The cost of usability is often questioned. The cost of getting it wrong is rarely discussed.

Usability studies require time and resources, but their value depends on when and how they are used.

A study should be conducted when it is needed to inform decisions, such as:

1. Early in development, when user needs are not fully understood
2. When evaluating specific features or interactions
3. During final validation

When usability is not properly addressed, the impact can be significant.

Missed use scenarios or incomplete understanding of user interaction can lead to:

• redesign
• delays in development
• lost revenue

In one case, a laparoscopic device was evaluated in a simulated environment before release. The study was well structured, and users completed the intended tasks successfully.

However, a specific use scenario was not identified until after the product had been released.

The issue was not with the engineering—it was with the assumptions made about how the device would be used.

The result was a redesign and a six-month delay in sales.

Even with the best intentions, gaps can remain if the right users, scenarios, or questions are not included early enough.

Summative Studies: Validating the Design

By the time a project reaches summative testing, the goal should no longer be discovery—it should be confirmation.

Summative studies are the final stage of usability evaluation, where the focus shifts from learning to validating.

At this point, teams are not looking for new insights or unexpected feedback. Instead, they are confirming that:

• Defined requirements have been met
• Use-related risks have been mitigated
• The device can be used safely and effectively in its intended environment

If formative work has been done correctly, a summative study should feel controlled and efficient.

In practice, this often means:

• Observing users completing tasks with minimal intervention
• Asking fewer, more targeted questions
• Focusing on whether expected behaviors are achieved

A well-executed summative study can feel uneventful—but that is usually a positive outcome.

It reflects that:

• Key usability issues were identified earlier
• User interactions are predictable
• The design aligns with real-world use

In some cases, summative studies can also be combined with other validation activities, improving efficiency without compromising rigor.

Where Human Factors and Usability Engineering Fits

Human Factors and Usability Engineering is not a single phase or activity.

It is applied throughout the entire development lifecycle, influencing decisions at each stage.

Concept Phase: Understanding user needs and identifying potential use-related risks

Design & Development Phase: Refining interactions through formative studies and iterative feedback

Verification & Validation Phase: Confirming usability through summative testing

By integrating HFUE throughout development, usability becomes an input into design decisions—not just a final check.

Conclusion: Designing for Real-World Use

A device can meet every requirement on paper and still fail in practice.

That gap often results from how a device is used, not from how it was designed to function.

Human Factors and Usability Engineering addresses this by bringing real user interaction into the development process—early, often, and with intent.

By integrating usability throughout development, teams can:

• reduce risk
• avoid costly redesigns
• create devices that align with real-world workflows

When combined with Design Thinking, HFUE ensures that devices are not only well-conceived, but also effective in use.

Next in the Series

In the next article in the Medical Device Development Insights series, we explore how user needs are translated into engineering requirements—and why defining inputs correctly is critical to successful development.