Hybrid Closed-Loop System Favorable for Type 1 Diabetes


Closed-loop systems help diabetes patients achieve blood glucose control, according to a presentation at the American Diabetes Association’s 77th Scientific Sessions.

Continuous glucose monitoring (CGM) devices provide real-time data about blood glucose levels and even provide alerts when levels become too high or too low, while insulin pumps administer the treatment throughout the day.

Recently, technology has combined CGM and insulin pumps to created closed-loop systems. These systems allow patients to receive insulin throughout the day from insulin pumps based on glucose measurements from the CGM system.

Researchers presented data from 2 studies about closed-loop systems and their impact on hypoglycemia at the American Diabetes Association’s 77th Scientific Sessions.

In the first study, the investigators explored the safety and feasibility of a hybrid closed-loop system in children with type 1 diabetes aged 6 to 12 years.

Children with type 1 diabetes have increased sensitivity to insulin compared with adolescents and adults. This population is also more at risk of severe hypoglycemia overnight, according to the session.

In the study, the researchers combined an Omnipod patch pump, Dexcom, G4 CGM sensor with Bluetooth built into the receiver, and a predictive control algorithm. While the closed-loop system continuously adjusts insulin delivery, patients are required to enter carbohydrates eaten during meal time to determine the proper dose, according to the session.

Included in the study were 12 patients with type 1 diabetes who underwent 36 hours of closed-loop assessment with meals and limited physical activity.

The investigators reported that 69.2% of glucose values were between 70- mg/dl to 180-mg/dl and overnight, 82% of glucose values hit that range.

“Hybrid closed-loop systems do a great job improving glucose control overnight, significantly lowering the risk of hypoglycemia, thus allowing patients and their families to get a good night’s sleep,” said chief investigator Bruce A. Buckingham, MD. “These systems also assist patients during the day in decreasing the magnitude of both high- and low-glucose fluctuations. And, many patients prefer wearing an ‘untethered’ patch pump, which provides more flexibility to enjoy physical activities without worrying about infusion set detachments, and a hybrid system provides some additional protection to prevent low blood glucose levels, resulting in improved quality of life for children with diabetes.”

However, the investigators concluded that additional, longer-term outpatient studies are needed to determine how the systems work in the real world.

In the second study, the investigators explored a closed-loop system that can detect exercise to prevent hypoglycemia.

For patients with type 1, controlling blood glucose levels during exercise can be challenging. While aerobic exercise has been known to benefit cardiovascular health, it can result in a significant drop in blood glucose levels.

Single-and dual-hormone closed-loop systems automate the dosing of insulin or insulin plus glucagon in patients with type 1 diabetes. Automated delivery of the drugs during exercise can result in better control of blood glucose by reducing insulin and increasing glucagon, according to the session.

The investigators aimed to determine whether this type of closed loop system was able to control blood glucose levels during exercise.

Included in the study were 20 patients with type 1 diabetes who used heart rate and accelerometer sensors that automatically detect aerobic exercise and deliver the proper dose of insulin or insulin plus glucagon.

The patients tested various systems, including: a single-hormone closed-loop system; a dual-hormone closed-loop system; a predictive, low-glucose suspend system that shuts off insulin if glucose is predicted to go too low; and the patient’s current standard of care, according to the session.

Patients underwent 4 different 4-day outpatient visits, exercised for 45 minutes at 60% VO2max on day 1 and day 1, and completed 1 or more in-home exercise sessions to determine time in the hypoglycemia range. Patients also entered estimated carbohydrate intake to deliver a proper pre-meal dose of insulin, and blood glucose levels were measured 4 times per day.

The investigators discovered that automated dosing of glucagon plus insulin during and after exercise dropped hypoglycemia from 6.3% to 3% compared with insulin monotherapy. The dual-hormone closed-loop system was found to be more effective compared with predictive low-glucose suspend dosing and current care approaches.

“Our findings show that fully automated insulin and glucagon delivery, combined with wearable physical activity sensors that detect exercise, effectively controlled glucose levels, reduced exercise-induced hypoglycemia and can safely be used in a home environment,” said investigator Peter G. Jacobs, PhD. “These results suggest that a dual-hormone closed-loop system with automated detection of aerobic exercise can be used as a tool to adjust dosing of insulin and glucagon during and after exercise.”

These findings suggest that the dual-hormone closed-loop system should be used for patients with type 1 diabetes who are at risk of exercise-induced hypoglycemia.

“We plan to explore migrating our system from a smart-phone platform to a smart watch, where exercise can be more easily detected,” Dr Jacobs concluded. “These exercise-enabled automated dosing systems may soon be able to help people with type 1 diabetes exercise safely without fear of hypoglycemia.”

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