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Bionic Pancreas User Interface (2/4) : Mental models and user research

July 16th, 2015

In order to wrap our head around how managing diabetes today with current insulin pumps will change with the bionic pancreas, we had to understand the experience. Our first question was Can we try it? An inherent challenge for good design of medical device: we can’t try it. Clinical trials have specific protocols, and we did not meet them. The closest we could get was to talk with people who had been in the trial. To begin, we did 5 interviews with people who had worn the current prototype of the bionic pancreas for one week.

Our questions going into the interviews…

  • How did it feel? How was your week?
  • What was it like to get started? Was there anything you wish you were told before using the system?
  • If you could talk to someone who was just starting, what would you tell them?
  • What was most exciting?
  • What was the biggest change?
  • What was useful in the device interface?
  • What did you get from looking at the main screen?
  • Did you feel safe?
  • Did you trust the system? What made you trust it? Did it ever do anything that you didn’t like?
  • How did you think about carbs at the end of the week? Did you still think in size or were the amounts relative to each other?
  • Did you worry about anything? What?

We put all the features we could think of on cards and asked our interviewees to sort them. This exercise helped us understand how people’s mental models were different with the BP than current pump therapy. We also brought paper prototypes of the interface to explore a specific interactions; disconnected CGM, Carb entry, and target adjustments).

A few things we learned…

1. The device learns, have patience. 

“I trusted it, after I learned it. I would say [to someone just starting] that every time you have a first, it’s not going to do well, but after that…[sigh of relief]”

2. Carb entry is about where in your day are you, not what time is it or what meal is it.


3. Need to know becomes nice to know. 

“Again, because it’s a machine, it’s doing all these things for you – you don’t have to know all of that stuff – it’s neat to see, but you don’t have to know that. It’s way cooler when you’re trying to explain to someone what’s going on. The interesting stuff becomes adjustments and actions… readings and other info become less interesting.”Screen Shot 2015-07-16 at 1.10.30 AM

We asked the people we talked to to organize the cards based on most important. Each person started with how it is now, and placed the data related cards in the most important group. When they thought about using the BP, the data cards moved over the not as important information. This understanding of need to know (with current therapy) → nice to know (with the BP) influenced how we designed the overall architecture which you will see the impact of in the following post.

Today, pre-BP, the main concern with diabetes is How am I doing? This question has three possible outcomes… 1. If BG is in range, do nothing 2. If BG is high, give insulin 3. If BG is low, eat sugar. It was really hard to embody, and still is foreign to me, that this question will stop being the primary one. What we heard, and what I came around to feeling is that with this device the main concern will lean more towards, How is the device doing? Does it have everything it needs? The majority of the time, if you are taking care of the device the answer to the “How am I doing?” question will be, You are good, the device is keeping or bringing your BG in range.

When you’re starting out, using physical prototypes and prompts is an incredibly rich way of understanding what you are designing. We also did usability testing at the end of the process when we had a working prototype of the full interface, this let us see if the text was big enough to read, if the wording made sense, what questions the interface prompted and basic stuff like ‘is this button big enough to touch and is it clear that it is being touched’. User research is all the rage these days because when you do it well, the feedback is invaluable. In the next post we will go into details about the decisions we made for the interface.

One Comment

  1. John Highet

    Can’t wait for these BPs to get released to the public. Thanks so much for sharing your part in it.

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