Tia Geri is the shortest player on her club soccer team. But that doesn’t stop her teammates from looking up to her. Geri, who turned 17 last month, has been playing with the same group of girls for almost as long as she’s been living with type 1 diabetes. And while she’s not the only one on the team with the disease, she is the only one with an artificial pancreas---a computer system that can control her insulin levels without her telling it to. A sensor on her abdomen monitors the glucose in her blood, and a pump adds the insulin her body needs to turn that sugar into energy.
Geri is one of the first people in the country to get the MiniMed 670G, the first bionic pancreas to be approved by the US Food and Drug Administration. She's been wearing hers since the fall of 2015, when she enrolled in the clinical trial that would eventually win the partially autonomous device regulatory approval. During a recent Monday night practice in Palo Alto, California, a teammate named Caroline watched Geri chase a soccer ball around a game of keep-away, while checking her own glucose meter and sipping a Capri Sun from the sidelines. “Tia’s so lucky,” she said. “I can’t wait until I get mine.”
Caroline and the rest of America's type 1 diabetics don’t have much longer to wait. Medtronic, the Minneapolis-based company that makes the device, is currently taking pre-orders it will ship to patients starting this June. And while the MiniMed 670G is not a technological cure for diabetes---patients still have to program in their meals, adjust their blood sugar targets when they want to exercise, and change out the sensor every week---it's a milestone for machine-mediated disease management. Five years ago it wasn’t obvious the feds would ever be comfortable letting a computer control a drug delivery system that could kill you if something went wrong. In the interim, DIY communities stepped in to solve the problem of automation themselves. And today, as a result of aggressive patient lobbying, the FDA's risk/benefit analysis has shifted.
Of the 1.2 million people in the US living with type 1 diabetes, most wear a sensor that continuously monitors the glucose in their systems, and a pump to deliver insulin when they need it. But with these types of systems, the patient has to manually tell the pump what to do---a never-ending carbohydrate calculus. Removing that burden is the goal of scientists developing so-called closed loop systems, where a computer does 100 percent of the work. The MiniMed 670G gets most of the way there, thanks to sophisticated algorithms and a reworked sensor with more surface area for increased glucose sensitivity.
Those personalized algorithms (which get to know the patient's insulin processing patterns over the first few days of using it) keep the pump much busier than traditional systems. If you compare their base-level activity side-by-side, a manual pump looks like the topography of a very flat bike ride---a step up here, a step down there, but mostly a consistent level of insulin. The hybrid closed-loop system, on the other hand, looks like riding the entire Pacific Crest Trail in an afternoon. It’s basically microdosing insulin in response to constant, precise glucose measurements.
For patients, the glucose highs aren’t as high and the lows not as low. Which means fewer swings between feeling tired or nauseous and shaky, hungry, and headache-y. “It really decreases the variability patients see in their glucose values,” says Bruce Buckingham, a pediatric endocrinologist at Lucile Packard Children’s Hospital Stanford who helped run Medtronic’s pivotal clinical trial for the MiniMed 670G. He says the system makes a big difference at night, when 75 percent of diabetic seizures occur. “If you or your child has ever had a severe low overnight, it’s something you don’t ever forget,” he says. “This lets parents and kids actually get a good night’s sleep.”
But closing the loop all the way means accounting for all 24 hours in a day, including the waking and eating ones. And no number of deeply-learned algorithms or super-sensitive sensors will solve that. Insulin, which acts like a key to let glucose into your cells for energy production, takes between 60 and 90 minutes to really get going. But it only takes 15 minutes for your body to convert food in your stomach to glucose in your blood stream. Which is why diabetics have to tell their pumps ahead of time how many carbs they’re going to be eating.
No sensor can intuit that you’re thinking about eating a sandwich an hour from now. So the solution doesn’t lie in smarter computers---it lies in chemistry. Faster-acting insulin is the last step to a fully autonomous system. And that is still years away from being market-ready.
Which is why members of the DIY artificial pancreas community aren’t hopping on the MiniMed 670G train just yet. Dana Lewis, who built an open-source hybrid loop system using Raspberry Pi, her smartphone, and some spare electronics, has since shared her code with hundreds of people around the world. She says the Medtronic device is a good step forward, but that its cost---a few thousand dollars---and the fact that it’s not approved for kids under 14 has many people still concerned about access to the technology. “With the commercial systems, you’re being told to just trust this black box,” Lewis says. “I think there are benefits to the DIY approach in the long-run; I can make changes very quickly, add new features, code them, and test them all in the same day.”
For Tia Geri and her family, trusting the black box isn’t figurative, it’s literal. And it’s the chief perk of the hybrid loop system. That little hip-clipped, beeper-sized system makes Geri’s mom feel comfortable letting her drive to classes at a nearby community college. It’s the reason she didn’t have to bring along an adult chaperone on a school trip to Yosemite last year. And it’s why her parents aren’t freaking out (too badly) that she wants to go to college all the way on the east coast. “It does all the work that we used to do together,” Geri says. “It’s given me my freedom.”
