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A H Clemens

Publications and source records attributed to A H Clemens.

12 recordsLinked to original sources
PubMed1979

Feedback control dynamics for glucose controlled insulin infusion system.

Miles Laboratories has developed a Glucose Controlled Insulin Infusion System (GCIIS) designated by the Trademark (BIOSTATOR) as a tool to investigate the physiologic control parameters of carbohydrate metabolism and regulatory deficiencies in diabetes. It consists, in principle, of a rapid on-line glucose analyzer, a computer/controller for the calculation and control of insulin or dextrose infusion, and a multichannel infusion system. A silent printer records, on a minute-by-minute basis, the glucose value measured, the insulin and/or dextrose infusion rates, and the cumulative total of the insulin infused. The on-line glucose analyzer employs an electrochemical sensor with immobilized glucose oxidase and measures the hydrogen peroxide produced. Its linearity extends beyond 700 mg/dl glucose; it permits a rapid two-point calibration of the sensor and the overall calibration of the on-line analyzer without disconnecting the catheter from the patient. The system's response time, including blood sample transport from the patient, is less than 90 seconds with a blood loss of approximately 50 ml per 24 h. The insulin and dextrose infusions are governed by control algorithms; various mathematical models have been developed and employed toward improved feedback control dynamics. The rapid glucose analyzer eliminates the need for the calculation of a "predicted" glucose value and permits, instead, the use of a derivative function for dynamic control. A multichannel infusion system combines the principles of a peristaltic pump with the advantages of a precision pump performance and individual computer control for each of the pump channels.

Blood Glucose↗
PubMed1979

Evaluation of the BIOSTATOR systems glucose analyzer.

The BIOSTATOR Systems have an on-line glucose analyzer for use with whole blood. This analyzer utilizes a novel enzyme (glucose oxidase) membrane configuration and an electrochemical cell to measure the H2O2 generated. The analyzer response is fast, accurate, precise, stable, and linearly related to the blood glucose concentration over the full range of clinical interest. Extensive correlation studies have been completed to show the agreement between this analyzer and the U.S. Food and Drug Administration's recommended hexokinase-glucose-6-phosphate dehydrogenase procedure. In addition, studies on potentially interfering substance and the differences in whole blood and plasma glucose levels have been completed.

Autoanalysis↗
PubMed1979

Dynamic study of the blood viscosity of insulin-dependent diabetics by means of an artificial pancreas.

The blood viscosity of 15 insulin-dependent, poorly controlled, diabetic subjects was determined by using a microviscosimeter at low shear rates, with cylindrical cuvettes of the Couette type. It was found that the blood viscosity of these diabetics was more elevated than that of control patients (p less than 0.001). In ten diabetics, the return to a strict metabolic control over a period of more than 24 h by means of an artificial pancreas resulted in a significant systematic lowering of blood viscosity. These results suggest that the metabolic control of diabetes influences blood viscosity, and they underline the importance of an artificial pancreas for the dynamic study of the factors affecting blood viscosity during the course of diabetes.

Adolescent↗
PubMed1979

Control algorithms for artificial beta cell.

The evolution of control algorithms for closed-loop regulation of blood glucose levels is described. Because of the rapid response time of the BIOSTATOR Glucose Analyzer, a derivative algorithm can be applied to replace the previous generation of "predictor" algorithms for the calculation of dynamic insulin infusion rates.

Artificial Organs↗
PubMed1978

Development and evaluation of a glucose analyzer for a glucose controlled insulin infusion system ((Biostator).

The Glucose-Controlled Insulin Infusion System (Biostator) is a modular, computerized, feedback control system for dynamic control of blood glucose concentrations in diabetics. This on-line glucose analyzer for use with whole blood utilizes a novel enzyme (glucose oxidase)-membrane configuration and an electrochemical cell to measure the H202 generated. The analyzer exhibits both short- and long-range stability, and instrument response and analyte concentration are linearly related over the full range of clinical interest. The response is fast, accurate, and precise, and permits determination of blood glucose within 2 min from the moment the blood leaves the patient. Correlation studies were completed to show the agreement between the Biostator Glucose Analyzer and the FDA's recommended hexokinase/glucose-6-phosphate dehydrogenase procedure on whole blood (e.g., average per cent recovered for 11 concentrations between 250 and 900 mg/liter was: hexokinase, 95.6%, Biostator Analyzer, 95.9%; bias and SDd, respectively, at low, normal, and high glucose values were: 12 and 41 mg/liter at the 500 mg/liter level; 4 and 52 mg/liter at the 1000 mg/liter level, and 4 and 128 mg/liter at the 4000 mg/liter level). No appreciable interference is observed with above-normal concentrations of bilirubin, uric acid, creatinine, sodium salicylate, or dextran. Platelet adhesion, which tends to decrease the useful life of the membrane, has been significantly decreased.

Autoanalysis↗
PubMed1976

Attempts at perfect normalization of glucose tolerance test of severe diabetics by artificial beta cell.

The artificial beta cell is a Glucose Controlled Insulin (and dextrose) Infusion System (GCIIS) for maintaining normoglycemia in diabetic conditions and other disturbances of metabolism. The insulin and dextrose infusion rates are calculated by a microcomputer according to the static glucose concentration (proportional control) and to its rate of change (dynamic control). The algorithms controlling the computer can be adapted to the subjects' requirements. It has already been shown, that the artificial beta cell is able to maintain blood sugar values in diabetics within physiological ranges during the course of the day. In our present study we examined the response of the artificial beta cell using a 100 gm oral glucose load in severe diabetics. The first type of control algorithms applied effected a rather small initial insulin infusion following OGTT in 8 juvenile diabetics connected with the artificial beta cell. The glucose responses thus obtained were similar to latent diabetes. In contrast, when the computer was controlled by the second type of algorithms with a more responsive dynamic control and a consequently higher initial insulin infusion, in one diabetic OGTT was fully normalized, whereas an improvement was achieved in another diabetic patient. Furthermore it was shown that control algorithms must be varied individually, depending on residual beta cell function and glucose regulatory mechanisms.

Blood Glucose↗