DEVELOPMENT OF A MINIATURIZED GLUCOSE MONITORING-SYSTEM BY COMBINING A NEEDLE-TYPE GLUCOSE SENSOR WITH MICRODIALYSIS SAMPLING METHOD - LONG-TERM SUBCUTANEOUS TISSUE GLUCOSE MONITORING IN AMBULATORY DIABETIC-PATIENTS

OBJECTIVE - To develop a reliable and practical glucose monitoring sys tem by combining a needle-type glucose sensor with a microdialysis sam pling technique for long-term subcutaneous tissue glucose measurements . RESEARCH DESIGN AND METHODS - A microdialysis Cuprophan hollow-fiber probe (inner diameter, 0.20 mm; length, 15 mm) was perfused with isot onic saline solution (120 mu/h) and glucose concentrations in the dial ysate were measured by a needle-type glucose sensor extracorporeally. This system was tested both in vitro and in vivo. Subcutaneous tissue glucose concentrations were then monitored continuously in 5 healthy a nd 8 diabetic volunteers for 7 to 8 days. A hollow-fiber probe was ins erted into the abdominal subcutaneous tissue. RESULTS - This monitorin g system achieved excellent results in vitro. Subcutaneous tissue gluc ose concentrations were measured in a wide range from 1.7 to > 27.8 mM glucose, 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 the glucose level (means +/- SE). The overall correlation between subcutaneous tissue (Y) and blood (X) glucose concentration was Y = 1.08X +/- 0.19 (r = 0.99). The subcutaneous tissue glucose concentration could be monitored precisel y for 4 days without any in vivo calibrations and for 7 days by introd ucing in vivo calibrations. CONCLUSIONS - Glycemic excursions could be monitored precisely in the subcutaneous tissue by this microdialysis sampling method with a needle-type glucose sensor in ambulatory diabet ic patients.