Glucose Monitoring in Individuals With Diabetes Using a Long-Term Implanted Sensor/Telemetry System and Model

Objective: The use of a fully implanted firstgeneration prototype sensor/telemetry system is described for long-term monitoring of subcutaneous tissue glucose in a small cohort of people with diabetes. Methods: Sensors are based on a membrane containing immobilized glucose oxidase and catalase coupled to oxygen electrodes and a telemetry system, integrated as an implant. The devices remained implanted for up to 180 days, with signals transmitted every 2 min to external receivers. Results: The data include signal recordings from glucose clamps and spontaneous glucose excursions, matched, respectively, to reference blood glucose and finger-stick values. The sensor signals indicate dynamic tissue glucose, for which there is no independent standard, and a model describing the relationship between blood glucose and the signal is, therefore, included. The values of all model parameters have been estimated, including the permeability of adjacent tissues to glucose, and equated to conventionalmass transfer parameters. As a group, the sensor calibration varied randomly at an average rate of -2.6%/week. Statistical correlation indicated strong association between the sensor signals and reference glucose values. Conclusion: Continuous long-term glucose monitoring in individuals with diabetes is feasible with this system. Significance: All therapies for diabetes are based on glucose control, and therefore, require glucose monitoring. This fully implanted long-term sensor/telemetry system may facilitate a new era of management of the disease.