CONTINUOUS AMPEROMETRIC MONITORING OF GLUCOSE IN A BRITTLE DIABETIC CHIMPANZEE WITH A MINIATURE SUBCUTANEOUS ELECTRODE

The performance of an amperometric biosensor, consisting of a subcutan eously implanted miniature (0.29 mm diameter, 5 x 10(-4) cm(2) mass tr ansporting area), 90 s 10-90% rise/decay time glucose electrode, and a n on-the-skin electrocardiogram Ag/AgCl electrode was tested in an unc onstrained, naturally diabetic, brittle, type I, insulin-dependent chi mpanzee. The chimpanzee was trained to wear on her wrist a small elect ronic package and to present her heel for capillary blood samples, In five sets of measurements, averaging 5 h each, 82 capillary blood samp les were assayed, their concentrations ranging from 35 to 400 mg/dl. T he current readings were translated to blood glucose concentration by assaying, at t = 1 h, one blood sample for each implanted sensor, The rms error in the correlation between the sensor-measured glucose conce ntration and that in capillary blood was 17.2%, 4.9% above the intrins ic 12.3% rms error of the Accu-Chek II reference, through which the il lness of the chimpanzee was routinely managed. Linear regression analy sis of the data points taken at t>1 h yielded the relationship (Accu-C hek) = 0.98 x (implanted sensor) + 4.2 mg/dl, P = 0.94. The capillary blood and the subcutaneous glucose concentrations were statistically i ndistinguishable when the rate of change was less than 1 mg/(dl.min). However, when the rate of decline exceeded 1.8 mg/(dl.min) after insul in injection, the subcutaneous glucose concentration was transiently h igher.