2016 年 5 巻 p. 124-131
An increasing number of closed-loop blood glucose (BG) control algorithms have been developed in recent years with the ‘artificial pancreas’ as the ultimate goal, although tight postprandial BG control remains an elusive goal. In this report, the authors propose a novel semi closed-loop BG control algorithm with meal announcement, which involves computation of the optimal continuous subcutaneous insulin infusion for a specific meal 60 min prior to mealtime. It utilizes a mathematical model of glucose-insulin metabolism to predict the impact of carbohydrates on postprandial BG levels based on carbohydrate intake and glycemic index (GI) value. The optimal pre-meal insulin is infused until mealtime, after which the control algorithm switches to model predictive control (MPC) to stabilize postprandial glycemia at the target value of 100 mg/dL (5.55 mmol/L). In silico results for four representative foods with GI values spanning a wide range show that in the case of exact patient-model match with precise information of carbohydrate composition and mealtime, postprandial BG levels can be maintained between 86–134 mg/dL (4.78–7.44 mmol/L) and 86–152 mg/dL (4.78–8.44 mmol/L) for 50 g and 100 g of carbohydrates, respectively. With consideration of intra-patient variability and meal-related uncertainties regarding the estimated carbohydrate amount and start of meal consumption, the BG control range is 75–159 mg/dL (4.17–8.83 mmol/L) with no critical hypoglycemic episodes.
