San Diego, CA—An initial evaluation of a fully automated artificial pancreas demonstrated that the system can safely regulate glycemia in patients with type 1 diabetes, even after a meal challenge without previous meal information, said Howard Zisser, MD, Director of Clinical Research and Technology, Sansum Diabetes Research Institute, and Adjunct Professor, Department of Chemical Engineering, University of California, Santa Barbara, during the 2011 Scientific Sessions of the American Diabetes Association.
Short of a physiologic cure, the best hope for the management of type 1 diabetes may lie in continuous glucose sensing and automated insulin delivery to simulate the glucose control loop that is automatically regulated in persons without diabetes. The fully automated closed-loop system that Dr Zisser tested combines 2 continuous subcutaneous glucose monitors and 3 continuous subcutaneous insulin infusion pumps with a sophisticated control algorithm. All the insulin calculations and delivery are done automatically.
First, Dr Zisser and colleagues at Sansum generated a personalized model and insulin-on-board control algorithm from 3 days of data, including meal information, from patients with outpatient insulin pumps and sensors. The model predicted the effect of past control moves on future outputs. “It computes the optimal control moves, implements the first move, and repeats the procedure,” he explained.
During the evaluation of the system, 10 patients who had type 1 diabetes for more than 20 years were studied with the artificial pancreas for 8 to 10 hours each, during which time they consumed 1 or 2 meals consisting of 35 g of carbohydrates. The closed loop was initiated at the glucose concentration at the time the patients came in for the study. The aim was to determine if the system could maintain euglycemia, defined as a target glucose level of 110 mg/dL (±30 mg/dL), and then overcome the meal.
“What we wanted to do with this project was to run a fully automated pancreas where we brought the patient in, flipped the switch, and stood back and didn’t do anything else but observe from a safety standpoint,” he said. “We used small meals…just to prove the concept.”
The controller successfully brought patients back to the euglycemic range, he said. The system recognized all the unannounced meals and gave appropriate meal boluses of insulin. The average percent time in the target glucose range (80-180 mg/dL) was 77%, with 1 episode of mild hypoglycemia.
“We met our goals and did not have to interrupt delivery or intervene in any of these patients,” Dr Zisser noted.