Advances in sensing and signal processing are enabling new and innovative monitor designs that allow patients to check glucose readings continually with minimal intervention. By integrating improved materials, electronics and analyte sensing in a single product, implantable glucose monitors are creating new options for caregivers and their diabetes patients. The monitors contain a glucose sensor that can be implanted under the skin and relay values to a patient interface device.
The current generation of approved and late-stage development implantable glucose sensors utilizes enzymatic technology (glucose oxidase), in which a wire-like electrode covered or coated with a synthetic membrane senses the level of glucose in the interstitial fluid beneath the skin. The sensor relays measurement data via a wireless link to a receiver that stores readings and allows the user to view glucose values.
While the sensor technology in continuous glucose monitors is a major step forward for diabetes management, more work is needed to optimize the benefits of this technology for the diabetic patient. Warm-up time after sensor insertion for approved continuous monitors is now measured in hours, resulting in a “blind spot” for the diabetic patient. The lower glucose concentration in interstitial fluid (relative to blood) results in a lower level electrical signal from the sensing element, which needs to be amplified adequately for reliable detection. Amplification boosts not only the signal of interest but the background and circuit noise as well, requiring more advanced noise filtering approaches.
Sensor drift requires that the monitors be calibrated occasionally using whole blood from a finger prick. The current sensors also have a limited life that requires the sensor to be replaced every few days, which is accomplished by inserting the sensor under the skin using a disposable self-insertion device. Several companies are working on glucose sensor technology that will extend sensor life, with an informal industry target of six months to a year for the next generation continuous monitor.
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