Evaluation of exogenous insulin homoeostasis by the artificial pancreas in insulin-dependent diabetes

Abstract

With the artificial pancreas used by the authors, insulin was delivered through a venous infusion and the rate of delivery was adjusted according to data provided by a continuous blood glucose monitor. After different trials we selected control algorithms integrating two parameters: instantaneous blood glucose concentration and increasing or decreasing patterns of blood glucose. A constant basal insulin infusion rate was added and improved the control of glycaemic excursions. Different parameters concerning exogenous insulin homoeostasis were determined. The delay to reach an insulin effect was 18+/-2 min and was shortened by a priming-dose at the beginning of the infusion. The insulin effect remained for 28+/-2 min after the infusion had been stopped, but differences were noted in the morning (21+/-2 min), in the afternoon (32+/-2 min) and during the night (25+/-3 min). Insulin needs were evaluated during meals. Related to the amount of carbohydrates, the doses fell from 0.53 units/hr/g of carbohydrate for breakfast to 0.15 for dinner. From these data, it appears that the efficiency of exogenous insulin exhibits a circadian rhythm.

Effects of somatostatin added to insulin in a glucose-controlled insulin infusion system

“…On day INS the reservoir of the artificial pancreas was filled with insulin (Actrapid), Novo) diluted in 0.154 mmol/1) saline to a final concentration of 3 U/ml. According to the algorithm used [8] the maximum infusion rate was 15 U/h. On day som insulin was replaced in the reservoir by cyclic somatostatin (Clin-Midy, France) diluted in 0.154 mmol/1 saline to a final concentration of 100 ~tg/h.…”

Intravenous insulin infusion system to determine insulin regimen in diabetics.

“…There have been no proper system to determine insulin regimen. Albisser et al (1974), Pfeiffer et al (1975), Clemens (1975), Mirouze et al (1977), and Kawamori et al (1978) reported that by using an artificial pancreas, blood glucose could be maintained within an almost physiological range in diabetics. However, these methods could not be applied upon the diabetics who need insulin treatment throughout their lives for a long time.…”

AP@home

“…1,2 This type of algorithm aims to address the challenging delays when insulin is infused subcutaneously and glucose changes are monitored in the subcutaneous tissue. 4,18 To evaluate the 2 different algorithm approaches available within the AP@ home consortium, a head-to-head study was performed comparing the MPC algorithm developed by 1 of the AP@ home consortium partners at the University of Cambridge (CAM) 5,6 and the algorithm developed by the partners at the Universities of Padua and Pavia (PAD; Italy) together with engineers in Virginia and Santa Barbara (USA). 7,8 The algorithms were implemented on different hardware platforms.…”

“…2 Already some decades ago attempts have been made in Europe to develop an AP system. 3,4 One of the major bottlenecks for a successful implementation of an AP system in daily practice is that the currently available algorithms relating the glucose information to insulin infusion rates have to handle widely different insulin requirements during the day: from the more stable situation during the night toward the challenging situation after a carbohydrate rich meal. In other situations a reduction in insulin supply is required, for example, after physical exercise.…”