Studies on the clinical importance of the constants used in the algorithm of an artificial B-cell (Biostator)

The clinical importance of different constants used in the algorithm of a glucose-controlled insulin infusion system (Biostator) with respect to insulin requirement was studied in 9 insulin-dependent juvenile-onset type diabetics. After normalizing the fasting blood glucose level (around 4.5 mmol/l), 3 consecutive glucose infusions (12 mg . kg-1 . min-1) followed by a 1 h post-infusion period were carried out in all individuals. The blood glucose was controlled by the Biostator using three sets of constants: A (KR = 160, KF = 50, QI = 30, RI = 12), B (KR = 70, KF = 50, QI = 40, RI = 12) and C (KR = 20, KF = 50, QI = 50, RI = 20). The algorithm constants were changed in an arbitrary order before the start of each glucose infusion in the same patient. Mean blood glucose profiles were comparable whereas the mean total insulin dose infused by the Biostator amounted to 13 +/- 1.3 U/h, 7.8 +/- 1.2 U/h and 7.0 +/- 1.0 U/h when sets A, B and C were applied (A versus B and C p less than 0.01). The higher insulin amount during control of set A was mainly due to a high insulin infusion during the first 20 min. In summary, the results emphasize the clinical importance of appropriate algorithm constants of a glucose-controlled insulin infusion system for evaluation of the insulin requirement in insulin-dependent diabetics.