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Design Defined: How Root Cause Probing Improves Medical Device Design

(This post is based on the video, “Root Cause Probing” in the Design Defined: Design Principles Explained series.)

It’s no secret that the number of medical devices on the market is increasing drastically. In 2020, the global medical device market was valued at $456.9 billion, and by 2023, it is expected to exceed $600 billion.

As product designers, we have a responsibility to make sure the medical devices coming to market are safe. That means predicting misuse and trying to proactively prevent it.

While product designers always want to mitigate misuse, the stakes are higher for medical devices. For these products, a use error can have serious safety consequences for the user or patient. User errors can also lead to product recalls, damaging profits and brand trust.

In order to prevent misuse, it is important to understand what errors might occur and why. To do this, we use Simulated Use Studies and Root Cause Probing. We’ll explain both below.

Simulated Use Studies to Identify Misuse

To determine what errors might occur, researchers use Simulated Use Studies. These studies allow researchers to observe how representative users interact with a product in a situation that is as realistic as possible.

For instance, if a product will be used in a hospital setting, researchers should watch representative users interacting with the product in a mock hospital room. Or, if the medical device is intended for home use, researchers might observe users testing a prototype in their homes.

As we’ve written previously, testing a product in the environment where it will be used improves the quality of data researchers can glean. Simulated Use Studies yield more authentic results than testing products in, for instance, a conference room, in part because researchers can observe external factors that might come into play.

Root Cause Probing to Understand Misuse

During Simulated Use Studies, researchers are watching for use errors and trying to understand why they occurred, or what the root cause of the error is. This is called Root Cause Probing.

Often, users don’t know why they made a mistake, so the art of Root Cause Probing is digging deeper to uncover what went wrong. To do this, human factors researchers have some tried-and-true methods.

At Bresslergroup, we often use the five methods detailed below.

1. Focus on the user interface, not on blaming the user.

An unintentional medical device error is never the user’s fault. The medical device manufacturer must accept fault, so rather than blame the user, it’s important to focus on how the user interface may have contributed to the error.

For instance, if someone can’t read the label on a device, it’s not because they can’t read. It could be because the font is too small.

2. Use light language that doesn’t sound accusatory.

When asking questions, it’s important to set a tone of open acceptance and understanding. Researchers can do this by using light language. Don’t label actions as good or bad, right or wrong.

Instead of saying “Why did you press the wrong button?,” the researcher might say, “I noticed you pressed this other button, why do you think that may have happened?”

3. Don’t interrupt someone’s workflow.

If you have a question about something a user did, make a mental or written note, but don’t interrupt the user. You want to see their behaviors and choices through the full workflow. If you stop a user to ask a question, you might end up missing another error.

In order to be a silent observer, save your questions until the end.

4. Don’t ask leading questions.

To elicit honest answers, you’ll want to ask open-ended questions.

For instance, don’t say, “Did you select that button because it was green?” Instead, ask “Why did you select that button?”

5. Ask “why” five times.

Each time you ask why, consider if you can follow up with another why question. Each iteration of “why” is intended to get deeper and deeper. Remember, you’re digging for the root cause.

(Invented by Sakichi Toyoda, the ‘Five Whys’ technique was first used at the Toyota Motor Corporation to drill down to the root cause of manufacturing problems.)

Turning “Why” Into Root Cause Analysis

After you’ve completed Root Cause Probing, you can use the data collected for Root Cause Analysis. This analysis considers subjective feedback from the user, along with other factors, to better understand root cause.

The resulting insights can then be used to develop a corrective course of action to take with the product’s design. By removing the root cause of user errors during the design phase, product developers can avoid misuse altogether–preventing recalls, avoiding patient harm, and potentially saving lives.

How Can You Incorporate Root Cause Probing?

This might sound like a lot to remember, but with Root Cause Probing, practice makes perfect. Eventually it will start to come naturally.

Can you incorporate Simulated Use Studies and Root Cause Probing into your design process? Or are you using these strategies already? If so, how have they helped you improve your products?

If you’re looking to learn more, we recommend Medical Device Use Error: Root Cause Analysis. Written in 2016, it’s one of the definitive texts on the subject. And of course, don’t hesitate to reach out to Bresslergroup, if you’d like to learn more.

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