The Role of UX/UI in Medical Device Safety and Adoption

This article was written by Sean Corona, Human Factors Consultant at ClariMed.

When a nurse reaches for an infusion pump at 3 AM during a critical care situation, there's no time to decipher confusing interfaces or ambiguous controls. Lives depend on medical devices being immediately intuitive and unmistakably clear in their operation.

In our previous article, we explored how design consistency and positive transfer can dramatically improve device usability by leveraging users' existing mental models. We showed how familiar patterns and consistent interfaces reduce cognitive load and minimize errors. But understanding mental models goes deeper than just consistency—it requires us to examine the fundamental ways people interact with and interpret device interfaces.

In this article, I expand on how people utilize mental models during device interaction, and outline critical considerations when researching and designing user interfaces that bridge the gap between human intention and device response.

What is a User Interface (UI)?

UIs are often thought of as displays, which present information and ideally guide our attention to the most relevant parts of the display. For example, a patient monitoring system includes a screen that visualizes patient vitals. Or, an infusion pump would have a screen that shows the dosage of a drug.

While displays and UIs both present information, UIs go a step further. The distinct difference is that UIs allow for an input, a choice, and control the system’s behavior.

In medical devices, UI elements include touchscreens, buttons, and dials. For example, when an audible alarm on a ventilator sounds, a user can press a button to silence the alarm.

How to design safe and adoptable UI?

Figure 1. Don Norman's Gulf of Execution and Evaluation [1]

To design safe and adaptable UI, you must understand what influences a person’s decision-making process. People start with a goal and interpret a physical system (e.g., medical device) to perform an intended action. Don Norman describes two gaps that often lead to a use error: the gulf of execution and the gulf of evaluation [2].

The gulf of execution is the gap between a person’s intended action and their ability to carry out the action using the system. When designing UI with the gulf of execution in mind, we might ask ourselves the following:

• Is a button easy to identify?

• Does the icon communicate the right information?

• Would someone know how to operate the control?

Once a person has performed an action on the system, they will interpret the system’s response to their action. When designing UI with the gulf of evaluation in mind, we might ask the following questions:

• Is there an indication that an action was successfully received?

• Can someone clearly understand the result of their action?

• Does the result match the person’s expectation?

The aim is to close the gap between the gulf of execution and evaluation as much as possible.

Closing these gaps creates an intuitive process where users can confidently and accurately take an action that fulfills their desired goal.

Closing the Gap with Good UX/UI Design

People utilize their existing mental models to make sense of the devices they interact with. Therefore, it is advised that products and services are appropriately conceptualized to allow a person to establish a connection with their existing model.

Consider a scenario where a patient has to record their blood pressure using an at-home blood pressure monitor. The blood pressure monitor has a screen with two buttons. One button is labeled “Start/Stop” for initiating or terminating their test. The other button is labeled as “Save” for storing the results of the test on the blood pressure monitor’s internal memory.

The device seems fairly intuitive, but what if the buttons were labeled using icons? The “Start/Stop” button is now just an image of a triangle and square, and the “Save” button is now an image of a floppy disc. While some people may know what a floppy disc is and what it means, others ─ specifically younger people ─ may not know what a floppy disc is.

Now imagine they chose to select the floppy disc button, but the display offered no message or tone to confirm that the blood pressure was recorded. That person may press the button again or navigate to another part of the UI.

An unclear icon or lack of feedback prevents someone from utilizing their mental model, and increases cognitive effort and uncertainty.

This scenario highlights both gulfs:

• the gulf of execution widens if a user is not sure which button to press to save their blood pressure result.

• the gulf of evaluation widens if the user is not sure if the blood pressure result successfully saved.

By designing UIs that reduce ambiguity and support a person’s expectations, we make devices easier to adopt and safer to use.

Here are a few ways you can close the gap in your design [3]:

• Utilize metaphors. Design UI elements to look and act like a real-world element a person is familiar with (remember the floppy disc example?).

• Keep people in the loop. Let users know what is happening after they performed an action. This can be done through the use of loading screens or audible tones.

• Be consistent. Ensure typical patterns are included in the design such as the use of color and grouping of information.

Want to learn more about designing UI in medical devices?

Our human factors experts can help you implement these principles to create intuitive, efficient, and error-resistant interfaces that leverage your users' existing mental models. Whether you are developing a new medical device or improving an existing one, we can guide you through the process of designing user-centered interfaces to enhance safety and adoptability.

Contact us today to discuss how we can help optimize your medical device UI design and ensure regulatory compliance.

References

[1] Roy, K. (2022). Feedback Cycle and the Gulfs of Execution and Evaluation. Medium. https://medium.com/design-bootcamp/feedback-cycle-and-the-gulfs-of-execution-and-evaluation-84647b8028fe

[2] Whitenton, K. (2018). The Two UX Gulfs: Evaluation and Execution. Nielson Norman Group. https://www.nngroup.com/articles/two-ux-gulfs-evaluation-execution/

[3] Lee, J. D., Wickens, C. D., Liu, Y., & Boyle, L. N. (2017). Designing for People: An Introduction to Human Factors Engineering (3rd ed, Revision 1). CreateSpace.