Research: Practical Use of Closed-Loop Insulin Pumps


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Closed-loop insulin pump technology has been a true game-changer for people with type 1 and type 2 diabetes. Today, there are manufacturer-designed looping systems and “do it yourself” systems fueled by the patient community. 

How these automated insulin delivery systems (AIDs) perform in real life demonstrates their potential to lighten the hour-by-hour burden of insulin management on those living with diabetes.

While closed-loop systems are primarily used in type 1 diabetes, people with type 2 diabetes taking multiple daily injections are also eligible for this technology. The following research pertains specifically to those with type 1 diabetes but could be largely applied to both types.

Presentation: Clinical Pearls in the Practical Use of Automated Insulin Delivery Systems

Speakers at this ADA Scientific Sessions presentation included: Laurel Messer, Ph.D., RN, CDCES (Barbara Davis Center for Diabetes), Boris Kovatchev, Ph.D. (University of Virginia) Stuart Weinzimer, MD (Yale University), and David Maahs (Stanford University).

The benefits of closed-loop insulin pump systems

All youth and adults taking insulin for diabetes interested in closed-loop technology should be offered it.

Today, there are over 400 proposed closed-loop algorithms, but only five have been FDA-approved and implemented by manufacturers. Experts cautioned against comparing data from one system to another due to the many different characteristics of each system and variances in continuous glucose monitor (CGM) results.

A variety of studies have pinpointed the following benefits of using a closed-loop system:

  • Overall time-in-range improvement by an average of 10 percent.
  • Dramatic improvement in time-in-range overnight.
  • Increased percentage of children with A1c levels below 7%.
  • Increased percentage of children with A1c levels below 9%.
  • Significantly reduced frequency of diabetic ketoacidosis (DKA) hospitalizations.
  • 11 percent increase in time-in-range (equates to 2.6 hours per day). 
  • Significant decrease in hypoglycemia and time-below-range

“The effect of closed-loop is evident almost immediately after system initiation,” explained Stuart Weinzimer, MD. “But appears to be stable thereafter, without further gradual improvement. Why? Physiology? Behaviors?”

In other words, patients using a closed-loop system see an immediate improvement in time-in-range and A1c levels, but those measurements don’t seem to improve further over time.

The increased safety and protection from hypoglycemia during sleep and physical activity have reduced the worry and emotional burdens on the entire family. 

Stuart added that the benefits of closed-loop systems apply to all genders and ages, and people with type 1 or type 2 diabetes.

Important Education Tips for Patients While Looping

Closed-loop systems should be available to anyone of any age with type 1 or type 2 diabetes who is interested. Experts emphasized the importance of proper education and support for those patients.

  • Hypoglycemia events may need fewer carbohydrates compared to open-loop pumping.
  • Teach patients how to respond to CGM arrows, trends, and insulin on board with a closed-loop pump compared to open-loop pumping.
  • Help patients make alarms actionable to prevent alarm fatigue.
    • Minimize alarms to only those that require immediate attention.
    • Encourage treating hypoglycemia with fewer grams of carbohydrates to prevent rebound highs.
    • Consider starting with only alerts for hypoglycemia.
    • Add hyperglycemia alerts at higher levels (250 mg/dL) if a patient can tolerate it.
  • Teach patients the risks of trying “trick the system”.
    • “Tricks” include entering fictitious carbohydrates, overriding bolus calculators, taking extra insulin outside of the system.
    • Trying to “trick” the system increases blood sugar fluctuations and decreases the system’s ability to perform properly.
  • Teach patients how to handle specific variables (sick days, exercise, pregnancy, etc.) while looping.
    • Patients may need to switch to manual pumping during sick days, ketosis, athletic competitions, intense exercise, throughout pregnancy, etc..
    • If a closed-loop system is disconnected for more than 15 to 30 minutes, you should suspend insulin delivery so the system does not automate insulin while disconnected.
    • Exercising with a closed-loop pump still requires significant intervention from the patient to reduce insulin rates and prevent hypoglycemia.
    • Exercising with a closed-loop pump is still a trial-and-error process individualized for each patient.
    • Read: Using a Closed-Loop Pump During Exercise & Exercise with Diabetes.
  • Teach patients about sick-day management while looping.
    • Patients might be better off switching to an open-loop manual mode when sick.
    • Patients should still monitor ketones and potentially increase open-loop insulin if ketones are present, even with in-range blood glucose levels.
    • Before medical procedures, closed-loop systems can be used with an adjusted glucose target or “hypoglycemia protect” mode.
  • Teach patients how to handle meals that are high in both carbs and/or fat and protein which digest more slowly.
    • Dosing too much insulin too soon for high-fat or high-protein meals with carbs increases the risk of hypoglycemia as the meal digests slowly.
    • Using a dual-wave “extended” bolus when eating high-fat meals by getting less insulin up front and more insulin during the four to five hours after eating.

What would further improve closed-loop technology?

While closed-loop systems are a huge step forward in diabetes management, they aren’t perfect. Some potential future innovation that would improve their functioning includes:

  • Better interoperability between different pumps and CGMs
  • Insulin that acts faster and clears the system faster
  • Implantable CGM technology
  • Easier general usability and simplifying the overall work of using a closed-loop system
  • Making closed-loop systems affordable and accessible to everyone who is interested

Closed-loop technology is a tremendous step forward in helping people with diabetes taking insulin improve their overall time-in-range and lessen hour-by-hour blood sugar fluctuations. The future of this technology can only hope to get better.

WRITTEN BY Ginger Vieira, POSTED 06/04/22, UPDATED 12/16/22

Ginger Vieira is the senior content manager at Beyond Type 1. She is also an author and writer living with type 1 diabetes, celiac disease, fibromyalgia and hypothyroidism. She’s authored a variety of books, including “When I Go Low” (for kids), “Pregnancy with Type 1 Diabetes,” and “Dealing with Diabetes Burnout.” Before joining Beyond Type 1, Ginger spent the last 15 years writing for Diabetes Mine, Healthline, T1D Exchange, Diabetes Strong and more! In her free time, she is jumping rope, scootering with her daughters, or walking with her handsome fella and their dog.