The use of a fully implanted, first-generation prototype sensor/telemetry system is described for long-term monitoring of subcutaneous tissue glucose in a small cohort of people with diabetes.
Sensors are based on a membrane containing immobilized glucose oxidase and catalase coupled to electrochemical oxygen detection and telemetry systems, integrated as an implant. The devices remained implanted for up to 180 days, with signals transmitted every 2 minutes to external receivers.
The data include signal recordings from blood glucose clamps and spontaneous glucose excursions, matched to reference blood glucose 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 conventional mass transfer parameters. As a group, the sensor calibration varied randomly at an average rate of -2.6%/week. Statistical correlation indicated strong association between sensor signals and reference glucose values.
Continuous, long-term glucose monitoring in individuals with diabetes is feasible with this system.
All therapies for diabetes are based on glucose control and require glucose monitoring. This fully implanted, long-term sensor system may facilitate new approaches for improved management of the disease.