Original Article Evaluation of the Effect of Gain on the Meal Response of an Automated Closed-Loop Insulin Delivery System

A continuous closed-loop insulin delivery system using subcutaneous insulin delivery was evaluated in eight dia-betic canines. Continuous glucose profiles were obtained by extrapolation of blood glucose measurements. Insulin delivery rate was calculated, using a model of -cell insulin secretion, and delivered with a Medtronic MiniMed subcu-taneous infusion pump. The model acts like a classic pro-portional-integral-derivative controller, delivering insulin in proportion to glucose above target, history of past glucose values, and glucose rate of change. For each dog, a proportional gain was set relative to the open-loop total daily dose (TDD) of insulin. Additional gains based on 0.5 TDD and 1.5 TDD were also evaluated (gain dose response). Control was initiated 4 h before the meal with a target of 6.7 mmol/l. At the time of the meal, glucose was similar for all three gains (6.0 0.3, 5.2 0.3, and 4.9 0.5 mmol/l for 0.5 TDD, TDD, and 1.5 TDD, respectively; P> 0.05) with near-target values restored at the end o