An Artificial Endocrine Pancreas

Abstract

In order to regulate the blood sugar in the intact depancreatized dog as precisely as that accomplished by its normal pancreas, specific equipment has been devised to deliver insulin or glucose continuously and establish normoglycemia both in the fasting and glucose-loaded states. A minicomputer was programmed to respond to the constantly monitored whole blood glucose by injecting appropriate insulin or glucose intravenously to maintain or restore the normal blood sugar. Standardized glucose challenges consisting of uniform infusions of 10 mg. glucose per kg. min. for sixty minutes were applied to assess the performance of the artificial pancreas. Direct control which relates insulin dosage to the level of the circulating blood sugar results in a response to the challenge resembling mild maturity-onset diabetes both in the abnormally high blood sugar response to glucose loading and in the large amount of insulin required to effect a return to normoglycemia. In contrast, control based on projected (predicted) values of blood sugar not only prevents the abnormal rise but consumes in some cases only 10 per cent of the insulin used for the same glucose load. The performance of the system parallels that of the normal pancreas and lends support to the hypothesis that biphasic insulin responses to glucose challenges are essential for the economy of insulin and the precision of regulation seen in healthy subjects.