Abstract
An artificial endocrine pancreas has been developed by combining a glucose infusion system with the artificial beta cell system. In this system, glucose was infused on the basis of the proportional and derivative actions to blood glucose concentration with a time delay constant. The glucose infusion algorithm so prepared was as follows:
G.I.R. (t) =Cp·BGp-BG (t-τ) +Cd·-ΔBG (t-τ)
where G. I. R. (mg/kg·min) represents the glucose infusion rate, BGp the projected value of the blood glucose concentration, ΔBG the rate of change in blood glucose concentration, Cp and Cd are coefficients for the proportional and derivative actions, and τ(min) is the time delay constant between blood withdrawal and the initiation of glucose infusion. Cp is calculated from the equation: Cp=GS/100·T, where GS is the glucose space per body weight (g/kg) and T is the time to be set for supply of the glucose deficient amount. In the present series of experiments, T was selected as either 10 or 4.
1) When glucose was infused on the basis of the proportional action with a 20-min time delay, the insulin-induced hypoglycemia in depancreatized dogs could be restored to normoglycemia in the same manner as seen in normal dogs.
2) A speedier and less fluctuating restoration to normoglycemia could be obtained when the glucose was infused on the basis of the proportional plus derivative action with a 4-min time delay.
These results indicate that the artificial endocrine pancreas so developed constitutes not only a useful device, for the safety control of blood glucose, but also an elegant research tool for analyzing the blood glucose regulatory mechanism.
