Blood glucose regulation using closed- and open-loop insulin delivery systems

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Abstract
Glucose was infused into anaesthetized dogs before and after pancreatectomy. In the diabetics blood glucose was regulated first by closed-loop and then by open-loop insulin delivery schemes. Insulin requirements for the latter were determined by resolving the former into a sequence of 3 different infusion rates: during the baseline and recovery periods, basal insulin was delivered at 0.37±0.02 mU/kg/min, while during the 60 min glucose infusion (10 mg/kg/min) there was an 8 min infusion at 4.96±0.37 mU/kg/min and a 52 min component at 1.85±0.08 mU/kg/min. With the open-loop method under these highly standardized conditions glycaemia was similar to normal controls but IRI levels were significantly higher, 13.5 vs 8.0 μU/ml (p<0.05) in the baseline and recovery periods and 74 vs 25 μU/ml (p<0.05) during the glucose infusion. It was concluded that: constant normogly-caemia can be maintained in the basal state by a constant rate of peripheral insulin delivery but at rates resulting in peripheral hyperinsulinaemia; the glycaemic response to glucose infusion can be normalized by a two component waveform of insulin delivery; and the closed-loop method can serve as a useful guide in determining insulin requirements.