Glycaemic control in pancreatectomized dogs with a wearable artificial endocrine pancreas

Abstract

A needle-type glucose sensor has been developed using a platinum electrode covered with immobilized glucose oxidase. Experiments with albumin-saline solution in vitro showed that at 5.5 mmol/l glucose concentration the output current generated was 1.2 +/- 0.4 nA (mean +/- SD). The current increased as a linear function of glucose concentration over the range (0-27.7 mmol/l). The response time to reach 90% of the final plateau value was 16.2 +/- 6.2s. The signal-to-noise ratio of the sensor was 15.8 +/- 2.6 decibels. The temperature coefficient in output was 2.3 +/- 1.0%/degrees C. The current output was not affected significantly by changes in oxygen tension of the solution in the range 25-150 mmHg. In vivo, the output current of sensors inserted into the subcutaneous tissues of dogs was directly related to blood glucose concentrations after oral glucose or meals. Daily checking of the sensors maintained in subcutaneous tissues in five dogs showed that the sensitivity decreased gradually to 87.2 +/- 7.6% at 72 h, and dropped significantly to 57.4 +/- 7.0% of the initial output by 96 h. A wearable artificial endocrine pancreas (18.0 x 17.7 x 7.9 cm, 700 g) was developed, consisting of a needle-type glucose sensor, a microcomputer system and a pump driving mechanism. Three pancreatectomized dogs were fitted with the system by inserting the sensor into subcutaneous tissue. By renewing the sensor every fourth day, the device could maintain the daily glucose variations in diabetic dogs within the range 5-9.5 mmol/l for 7 days.

Subcutaneous implantation of a ferrocene-mediated glucose sensor in pigs

“…We chose the pig as the experimental model since it is one of the few species which possesses subcutaneous tissue similar to that of man. Several previous studies of subcutaneously implanted glucose sensors have employed dogs [6,7,10,11], in which the responses may not easily be extrapolated to the human situation, We also, in this study, showed that a surface electrocardiogram electrode functions well as a reference; results, indeed, were not different from experiments in which an implanted silver/silver chloride wire was used as the reference electrode (unpublished observations).…”

Functional and morphological evolution of remnant pancreas after resection for pancreatic adenocarcinoma

“…However, it has been reported that exogenous insulin supplementation and oral hypoglycemic medications affect serum glucose usually a 1-sided manner and would not significantly alter DSG were it not for counter regulatory hormones. [24] Of note, a lowering of GTI does not necessarily mean that blood glucose has decreased. Rather, it should be interpreted as an indicator of improved glucose control, and although DM may develop or worsen postoperatively, GTI reduction indicates the condition is easier to control, presumably through the preserved glucagon function.…”

Management of diabetes using adaptive control

“…More advanced algorithms were developed by Salzieder, Fisher and colleagues using proportional-derivative control [76] or pole-placement technique [16]. Shichiri's group [77,78] used a similar approach. Although not obvious, the clinical application of these algorithms requires re-assessment of controller/model parameters.…”

“…References [77,78,86], most approaches did not get beyond the theoretical stage. Furthermore, the theoretical development and testing of these controllers often employed the minimal model of glucose kinetics [92] to represent the glucoregulatory system.…”