People in the Know: What Is Looping?

Q: We keep hearing about looping, hybrid closed loop or closed loop systems for people with diabetes. How do these different systems work, and what are the options available for children with type 1?

A: This is a very exciting time in the field of type 1 diabetes, as many hybrid closed loop, automated insulin delivery systems are becoming available to people with diabetes, including children.

A closed loop system automatically adjusts insulin delivery from a user’s pump according to blood sugar readings from their CGM (continuous glucose monitor). Some call this system an “artificial pancreas” for this reason. The first closed loop system was actually a hybrid closed loop system that was approved by the FDA several years ago. They are similar to closed loop systems except they require input from the users when they eat a meal. The initial approval was for people with type 1 diabetes ages 14 years and older, then later it was also approved for children as young as age 7. This hybrid closed loop system typically requires two to four blood glucose calibrations (by taking a blood sugar check by finger stick) per day to remain in “auto-mode.” The system modulates (adjusts) basal rates to a glucose target of 120 mg/dL.

Recently, the FDA approved another hybrid closed loop system for patients ages 6 and up that does not require any blood sugar finger sticks for calibration. In addition to modulating basal rates, this is the first FDA-approved system that also gives automatic correction boluses. If blood sugar is projected to be above 180 mg/dL in the next 30 minutes, then the pump will give an automatic correction bolus to reach a target of 110 mg/dL.

Other hybrid closed loop systems now in trials include those using tubeless “patch pumps” as part of the automated insulin delivery system. The algorithm is built into the patch pump to communicate with CGM and enable basal rate adjustments to a customized target as low as 110 mg/dL or up to 160 mg/dL. Pivotal trials are underway, and FDA approval could eventually include children as young as 2 years old.

Significant progress is also being made on a “bi-hormonal” artificial pancreas system, which will include a dual-chambered device to deliver both insulin and low blood sugar medication. This system would be the first to include medication to help prevent hypoglycemia.

You may have also heard about “looping,” which refers to a do-it-yourself (DIY) automated insulin delivery system that was created as an open-source platform by people in the diabetes community. The “Loop” is not a commercially available device but an app template that users build on a smartphone. The app includes the crowd-sourced Loop algorithm for adjusting basal insulin based on glucose trends. The app connects a CGM and a compatible insulin pump via a communication device. The device is about the size of a small matchbox and must be carried by the user at all times. The user can bolus from the app by entering carbs and using emoji for food (fast, medium, and slow carbs).

[Disclaimer: The information below is not intended as medical advice. Safety of open source DIY devices has not been confirmed by the FDA as they are not FDA approved. Health care providers may not be familiar with these devices.]

Many people with diabetes including children and adults have described improved blood sugar control and ease of use with a DIY loop system. Some are concerned about safety since DIY loop systems are not FDA-approved. Development in this area is continuing, seeking FDA-approved versions of Loop, which, if approved, would be available as apps and work with commercially available insulin pumps and CGMs.

Automated insulin delivery systems can be helpful for kids with type 1 in both improving blood sugar control and reducing the burden of diabetes self-management. In studies with hybrid closed loop systems as well as rapidly growing real-world experience, the hybrid closed loop systems can help with improving time in range (the percentage of time with blood sugar between 70 and 180 mg/dL) to more than 70 percent, while also reducing hypoglycemia risk.

Are hybrid closed loop pumps or DIY looping right for your child? Potential downsides of these systems include having to wear both a pump and CGM, still having to remember to bolus before eating, and having to learn a new method for diabetes management.

Still, parents report that with hybrid closed loop systems, their children are able to think less about diabetes and focus more on school and having fun doing the activities they love. You can talk to your own diabetes care team about whether a hybrid closed loop system is a good fit for your child.

—Dan DeSalvo, M.D., is an assistant professor of pediatrics, diabetes, and endocrinology at Baylor College of Medicine/Texas Children’s Hospital, where he serves as type 1 diabetes clinic director and director of strategic collaboration.

How Other Parents Deal

“Our son has had diabetes since he was 4 years old. He is now 19 and has been using a hybrid closed loop system for just over a year. I think what he has come to understand is that ‘automatic’ does not equal ‘no attention required.’ He is still monitoring, still needs to respond to lows, and still needs to make good choices. But with that said, having a hybrid closed loop system has put T1D into a much smaller box in his life.”

—Kelly, California, mom of 19-year-old Liam

Disclaimer: The information in this article is not intended as medical advice. Families should check with their healthcare professionals regarding individual care.

Related topics:
People in the Know: Going Back to MDI
People in the Know: Transitioning to an Insulin Pump
What I Learned by Trying James’ CGM Device on Myself

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