抄録
The dynamic property of glucose-induced insulin secretion was simulated with the aid of control theory, and the relationship between the stepwise input of glucose concentration and the biphasic response of insulin as an output was expressed in the transfer function of proportional plus derivative action to glucose concentration.
By utilizing such a model, the following computer algorithm for the artificial beta cell was made-Rate of insulin infusion=KpBG+KdΔBG+Kc, where BG was the abbreviation for glucose concentration, ΔBG was the rate of change in BG, Kp, Kd were the coefficient for the proportional and derivative action, respectively, and Kc was the constant for basal insulin secretion.
Microcomputer, insulin infusion pump and digital printer were packed in a small case, which was connected with glucose analyzer.
Experiments were carried out in the depancreatized dogs to validate the insulin infusion program and the whole system. Against various kinds of glucose challenges, such as oral administration, iv impulsive or constant infusion, the blood glucose responses were controlled in physiological ranges when the derivative action was added to the proportional action properly in the insulin infusion regulatory system. The treatments of ketoacidosis were also performed and the results were satisfactory.
The characteristics of this system recognized in clinical applications to the diabetic patients were : 1) The rate of insulin infusion was small enough to keep the plasma concentration of insulin physiological, then insulin requirements were reduced to around a half of those given subcutaneously, 2) Glucose or glucagon infusion to restore hypoglycemia was not necessarily needed.
