Adaptive tuning of basal and bolus insulin to reduce postprandial hypoglycemia in a hybrid artificial pancreas

• Published in: Journal of process control 2019-08, Vol.80, p.247-254
• Main Authors: Resalat, Navid, El Youssef, Joseph, Reddy, Ravi, Castle, Jessica, Jacobs, Peter G.
• Format: Article
• Language: English
• Subjects: Adaptive control; Hybrid artificial pancreas; Type 1 diabetes
• ISSN: 0959-1524; 1873-2771
• DOI: 10.1016/j.jprocont.2019.05.018

•Adaptive basal insulin dosing after meals can help reduce postprandial hypoglycemia within a hybrid artificial pancreas.•Adapting postprandial insulin is better than adapting pre-meal insulin boluses for preventing hypoglycaemia.•The ALPHA algorithm can be used to tune postprandial dosing to help people with type 1 diabetes avoid hypoglycaemia. We introduce an adaptive learning algorithm to better adjust postprandial basal and pre-meal bolus insulin for reducing postprandial hypoglycemia in a hybrid artificial pancreas (AP). An AP uses a control algorithm and sensed glucose to automate the delivery of insulin to people with type 1 diabetes (T1D). A hybrid AP requires the person to dose insulin in advance of a meal. Insulin sensitivity is dynamic in people with T1D, making it challenging for an AP to maintain euglycemia. Adaptive approaches to meal dosing can help prevent postprandial hypoglycemia. An adaptive learning postprandial hypoglycemia-prevention algorithm (ALPHA) is introduced. One implementation of ALPHA adjusts the rate of postprandial insulin (ALPHA-BR) proportionally in response to prior postprandial episodes. This is achieved by an adaptive aggressiveness factor applied to postprandial basal insulin. The second implementation adaptively updates the pre-meal bolus insulin by changing the insulin-to-carbohydrate ratio (ALPHA-ICR), also proportionally in response to prior postprandial hypoglycemia. Both implementations were evaluated within an AP on an in-silico T1D virtual population of 99 subjects with circadian insulin sensitivity variations and 30% errors on meal estimations. Twenty real-world 4-day meal scenarios were given and glycemic outcomes were compared with an AP with no adaptation. Out of the 99 in-silico subjects, 23 of them experienced postprandial hypoglycemia leading to greater than 1% overall time in hypoglycemia. Of these 23 subjects, we evaluated the benefit of using ALPHA-BR and ALPHA-ICR to prevent postprandial hypoglycemia. ALPHA-BR yielded substantially fewer percent time in hypoglycemia compared to AP (0.54% vs 1.92%, p