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Open-source coding allows patients to build their own closed-loop systems


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5 minutes

Natalie J. Bellini, APRN, FNP-BC, BC-ADM, ADCES
Natalie J. Bellini, MSN, FNP-BC

Dissatisfied with the pace of innovation for automated insulin delivery (AID) systems, some people living with diabetes have taken matters into their own hands. Adopting the social media hashtag #WeAreNotWaiting, these patients and their families have rallied behind the development of open-source (OS) systems for diabetes management.

As a result, there are now thousands of people across the globe “looping”—using do-it-yourself (DIY) closed-loop AID, said Natalie J. Bellini, MSN, FNP-BC, Endocrine Nurse Practitioner, R&B Medical Group, one of four speakers during the Scientific Sessions symposium Who Should Loop? Pro/Cons, which was originally presented Sunday, June 27. The recorded session can be viewed by registered meeting attendees at through September 29, 2021. If you haven’t registered for the Virtual 81st Scientific Sessions, register today to access all of the valuable meeting content.

Bellini gave an overview of how a person could build their own OS-AID app using instructions available through To get started, the patient needs an insulin pump, continuous glucose monitor (CGM), a translator between the pump and CGM, a controller like a smartphone or a smartwatch, batteries for the equipment, the appropriate programming, and acknowledgment that a DIY system is considered experimental, she said.

“These systems are available to the public to build the code, but they are not FDA (U.S. Food and Drug Administration) approved,” noted Bellini, adding that there are several other tools used for diabetes management that also lack FDA approval for this purpose. Off-label use of glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter 2 inhibitors are two examples.

Dana Lewis, BA
Dana Lewis, BA

Providers do not build OS-AID systems, the patients must do it themselves, Bellini explained.

“In our practice, what we do is we have the patient set it up and start it themselves. But we do have a duty to provide ongoing health care and support,” she said.

Dana Lewis, BA, said that anyone who wants to loop can. A looping pioneer, Lewis is a founder of the Open Source Artificial Pancreas System (OpenAPS) and was among the first people to build an OS-AID system for personal use. That was more than six years ago, before closed-loop systems were available commercially. Since then, she has conducted research on OS-AID and written books on the subject for adults and children.

Replicating the function of the pancreas is not an easy task, Lewis explained. It requires a significant amount of math to dose and adjust insulin delivery multiple times a day.

“That is why this idea of automated insulin delivery, or closed looping, is so helpful,” she said. “Because instead of the human brain having to do all of this math, you could have a computer look at the CGM data, look at the insulin pump data, think through the insulin activity curves that it’s been programmed with, make a decision, and do it over and over again as often as every five minutes when it gets a new datapoint from the CGM.”

Anna Norton, MS
Anna Norton, MS

The information required to build an OS-AID system is freely available to everyone, including commercial interests, Lewis noted. The OpenAPS Data Commons is a retrospective, anonymized data set with input from more than 100 patients using OS-AID that is available for researchers.

“I’m hoping we will see more of these commercial entities learning from the open-source community and the features designed in these systems, and adding them into the commercial technologies to make them more widely available for people,” Lewis said. “That would be a win-win all around for people with diabetes, clinicians, and these companies.”

Anna Norton, MS, who has type 1 diabetes, shared her firsthand experiences with looping. Within four months of switching to a self-built OS-AID system, Norton experienced a drop in A1C from 7.5 to 6.6.

“I did not do anything different in my diabetes management as far as pumping or activity or diet or anything like that,” she said. “I just entered the data into the loop app as I normally would the pump.”

More than two and a half years later, Norton continues to loop and her A1C is 6.1. Her daily time-in-range has increased to 75% to 95%. It was previously 60% to 65% with conventional pumping.

David M. Maahs, MD, PhD
David M. Maahs, MD, PhD

“It has been very beneficial to my work life, my personal life, my sleep schedule, and just my overall psychosocial well-being and the way that I think about diabetes,” she said. “I’m spending so much less time thinking about staying in range because the loop is really helping me to continue to stay in range—still with input from me, but the algorithm is really helping to bring those highs down and to minimize those lows.”

David M. Maahs, MD, PhD, Professor and Chief of Pediatric Endocrinology, Stanford University, discussed provider concerns, patient autonomy, and the future of DIY looping.

“Health care providers want their patients engaged in their care, and I think the OS-AID certainly is that. I think it’s important to remember that advances in medicine require constant learning, especially with diabetes,” he said.

Beyond the real-world data demonstrating the safety of OS-AID systems and their ability to increase patient time-in-range and decrease episodes of hyperglycemia and hypoglycemia, the open-source coding expands the accessibility of closed-loop technology to a wider population, Dr. Maahs said. But there is no clear-cut answer to potential provider liability for patients using OS-AID, he noted.

“There’s variation in different countries on possible legal implications,” Dr. Maahs said. “There’s potential legal implications of supporting someone who chooses to use an unregulated OS-AID system. However, there’s also the importance of maintaining professional guidance and the other extreme of potential negligence.”

One drawback of OS-AID systems is that no commercial technical support exists, he said, but there is extensive support among the looping community.

“Patients have chosen to say ‘We are not waiting’ because we felt like we couldn’t afford to wait,” Lewis said. “And we still don’t feel like we can afford to wait because diabetes is risky every day and this technology absolutely helps us.”



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