In a major advance in the development of an artificial pancreas, researchers have shown that an insulin pump can be programmed to temporarily shut off when blood glucose levels dip too low, successfully reducing the duration and incidence of nighttime hypoglycemia, according to study results published in the New England Journal of Medicine and presented concurrently at the American Diabetes Association's 73rd Scientific Sessions® this week.
The artificial pancreas system – which includes an insulin pump, software and sensors that track blood glucose levels on a continuous basis – reduced the incidence of nocturnal hypoglycemia events by 32 percent and the duration and severity of those incidents by 38 percent, by shutting off insulin delivery for two hours once glucose levels reached a predefined threshold value (usually 70 mg/dL) the study showed. The threshold suspend feature is part of the MiniMed 530 G system, made by Medtronic and is currently undergoing review by the U.S. Food and Drug Administration. This feature is available internationally in the MiniMed Veo System, where it is called Low Glucose Suspend.
Hypoglycemia is of great concern because it can lead to unconsciousness, seizures and even death. Overnight hypoglycemia is a concern for most patients and family members of those with type 1 diabetes. Overall, 247 patients with type 1 diabetes were randomized to the three month study; 121 patients in the sensor, pump and threshold suspend group, and 126 individuals in the sensor and pump group.
“Our work is the first large randomized controlled trial testing the threshold suspend feature. This technology promises to be valuable to patients today and is a key step in the development of a fully automated artificial pancreas for people with diabetes,” said Rich Bergenstal, MD, Executive Director of the International Diabetes Center at Park Nicollet in St. Louis Park, Minn., and a principal investigator in the Automation to Simulate Pancreatic Insulin Response (ASPIRE) In-home study.
"The next step is to continue to refine the shut off and restart of insulin to prevent hypoglycemia, then to program the pump to be able to safely add more insulin when the glucose is too high," Dr. Bergenstal said. "We will eventually modify the pump to be able to adjust the delivery of insulin and possibly other hormones to control glucose levels all day, including during meals and exercise, which is very hard to do today."
Using the insulin pump with the threshold suspend feature linked to a continuous glucose monitor, researchers were able to effectively reduce hypoglycemia overnight without any deterioration in A1C levels, minimizing potentially dangerous low blood glucose while maintaining good glucose control. "This gives a lot of credence to the whole notion of putting 'intelligence' in a pump," Dr. Bergenstal said.
Though the pump turns off automatically, it can be manually overridden if the person wakes up and wants to drink some juice to raise their blood glucose levels rather than waiting the two hours for levels to return to normal, Dr. Bergenstal said. If they do not wake up, insulin delivery automatically resumes after the two-hour period.