A dynamic app to practice capillary refill tests

When you were a kid, you may have tried the following experiment on yourself. You pressed on your finger as hard as you could it until it turned white. You then watched the blood quickly flow back into your nailbed after you released the pressure.

You didn’t know it at the time, but you were actually using a common practice among clinicians to check an individual’s capillary refill time. This simple test measures how long it takes for a patient’s finger, toe or ankle to regain its color. Anything longer than three seconds could be an early indicator of a variety of health issues, such as dehydration, hypothermia and even sepsis.


While it’s not a definitive way to diagnose any of these illness, it can help providers make informed decisions on how to proceed with care. About four years ago, Jump Simulation Medical Visualization received a grant to develop an app that could help clinicians practice this skill and support curriculum around sepsis.

The team recently revamped the app to react to learner performance.

Capillary refill trainer

The newest version of the Capillary Refill app opens with a tutorial that teaches users how to play the game by requiring them to engage with the experience. As this takes place, learners will see tips, timers and other information to guide the training. The idea is to help learners retain the knowledge they are gaining and get a sense for how the training will proceed.

As users get into the real game and conduct a simulated capillary refill test on a randomly selected finger, toe or ankle, they will no longer see the guides that were included in the tutorial. Participants have to choose whether a test is normal, abnormal or borderline.

Behind the scenes, the app uses a dynamic difficulty adjustments system to keep track of a user’s actions and gently guides them if they appear to be struggling. For example, let’s say someone incorrectly selected that a capillary refill time was normal. The app would respond by displaying a timing circle to help them count the seconds. If they get it wrong again, the app will present the time ranges that correspond with a normal, abnormal or borderline case.

Likewise, as users choose the correct answers, those helpful indicators will disappear. The app also responds if a learner fails to find the proper location on the finger, toe or ankle for evaluation, and it senses when a user is taking too much time to choose an answer.

The Capillary Refill app is available for Apple iOS and Android devices. Efforts are underway to make internal instructors aware of its availability for our own clinicians.

Why enhance the app?


We saw the refresh of this app as an opportunity to test a dynamic difficulty adjustments system within one of our learning platforms. What we learned is that the implementation itself is relatively simple. The difficult part is thinking through the user experience and determining what we want to track and to what end.

As clinicians come to us with ideas for educational apps, we see a future in designing dynamic difficulty adjustment systems. We believe this could potentially enrich pre-existing and future Jump Med Vis projects to improve the user experience.

Categories: Education, Education, Innovation, Medical Students, Medical Visualization, OSF Innovation, Simulation