Abstract
We have developed a miniaturized extracorporeal glucose monitoring system which combines a needle-type glucose sensor and a microdialysis hollow-fiber probe. This paper dealt with the in vitro and in vivo characteristics of this glucose monitoring system. 1) In in vitro experiments, by recording rapid changes of the glucose concentrations by switching the medium from 100 to 200 mg/100ml glucose and vise versa, the times to reach 90% of the maximum and minimum values were 5.6±0.4 min and 7.4±0.5 min, respectively (mean±SEM). 2) In in vivo experiments, subcutaneous tissue glucose concentrations were measured with a time delay of 6.9±1.2 min associated with a rise in glucose and 8.8±1.6 min with a fall in glucose level. During continuous tissue glucose monitoring, a highly significant correlation between subcutaneous tissue glucose concentrations (Y) and blood glucose concentration (X) was observed (Y=1.08X+3.42, r=0.99). Regression lines obtained during 5 to 7 days monitoring were significantly different from those obtained during I to 4 days monitoring, However, by introducing the in vivo calibration technique every morning afler 4 days continuous monitoring, subcutaneous tissue glucose concentrations measured by this system correlated again with the glycemic excursions for 7 days. By exchanging the probes every 5th day, this system can be used for continuous glucose monitoring and for glyceric control with the wearable artificial endocrine pancreas in diabetic patients for longer periods.
