Transcutaneous analyte sensors and monitors, calibration thereof, and associated methods
Systems and methods are provided to calibrate an analyte concentration sensor within a biological system, generally using only a signal from the analyte concentration sensor. For example, at a steady state, the analyte concentration value within the biological system is known, and the same may provide a source for calibration. Similar techniques may be employed with slow-moving averages. Variations are disclosed.
1. A method of compensating for drift in an analyte concentration sensor within a biological system using only a signal from an analyte concentration sensor, comprising:
measuring analyte concentration values using an indwelling analyte concentration sensor to obtain an indwelling analyte concentration sensor reading;
determining a first slow-moving average of the measured analyte concentration values of the analyte over a first period of time, and basing a first apparent sensitivity of the indwelling analyte concentration sensor based at least in part on the first slow-moving average;
following the first determining, determining a second slow-moving average of the measured analyte concentration values of the analyte over a second period of time, and basing a second apparent sensitivity of the indwelling analyte concentration sensor based at least in part on the second slow moving average; and
adjusting an actual sensitivity of the indwelling analyte concentration sensor to an adjusted value based on a difference between the first apparent sensitivity and the second apparent sensitivity when the difference between the first apparent sensitivity and the second apparent sensitivity meets a predetermined criteria, wherein the predetermined criteria is based on a range of acceptable sensitivity changes with respect to time.
2. The method of claim 1 , further comprising prompting a user to enter data when the difference between the first apparent sensitivity and the second apparent sensitivity does not meet the predetermined criteria.
3. The method of claim 2 , wherein the prompting the user includes prompting the user to enter a calibration value, to generate a received calibration value, or prompting the user to enter meal or exercise information.
4. The method of claim 3 , wherein upon receiving the calibration value or the meal or exercise information from the user, the method further comprises determining if the change in apparent sensitivity is due to sensitivity drift or a change in the slow-moving average.
5. The method of claim 3 , further comprising adjusting the actual sensitivity of the sensor based on the received calibration value or meal or exercise information.
6. The method of claim 1 , wherein the range of acceptable sensitivity changes with respect to time is based on sensitivity drift.
7. The method of claim 1 , wherein the range of acceptable sensitivity changes with respect to time excludes changes in sensitivity based on the slow-moving average.
8. The method of claim 1 , wherein the range of acceptable sensitivity changes with respect to time comprise known behavior for sensitivity changes over time for a sensor.
9. The method of claim 8 , wherein the known behavior for sensitivity changes constitutes an envelope of acceptable sensitivity changes with respect to time.
10. The method of claim 1 , wherein the adjusted value is based at least in part on the second slow moving average.
11. The method of claim 1 , wherein the range of acceptable sensitivity changes with respect to time comprise known values for physiologically feasible analyte changes.
12. The method of claim 1 , wherein the adjusting the actual sensitivity of the sensor is configured to occur at a time when the indwelling analyte concentration sensor reading is substantially stable, or within a predetermined range of readings for a threshold period of time, whereby an occurrence of unexpected jumps in readings is reduced.
13. An analyte sensor system comprising:
an analyte concentration sensor;
a monitoring device, wherein the monitoring device is configured to detect when an analyte concentration value as measured by the analyte concentration sensor indwelling in a biological system; and
a processor, wherein the processor is a component of the monitoring device or of a device or a server operatively coupled to the monitoring device, wherein the processor is being programmed to perform operations comprising:
measuring analyte concentration values using an indwelling analyte concentration sensor to
obtain an indwelling analyte concentration sensor reading;
determining a first slow-moving average of the measured analyte concentration values of the analyte over a first period of time, and basing a first apparent sensitivity of the indwelling analyte concentration sensor based at least in part on the first slow-moving average;
following the first determining, determining a second slow-moving average of the measured analyte concentration values of the analyte over a second period of time, and basing a second apparent sensitivity of the indwelling analyte concentration sensor based at least in part on the second slow moving average; and
adjusting an actual sensitivity of the indwelling analyte concentration sensor to an adjusted value based on a difference between the first apparent sensitivity and the second apparent sensitivity when the difference between the first apparent sensitivity and the second apparent sensitivity meets a predetermined criteria, wherein the predetermined criteria is based on a range of acceptable sensitivity changes with respect to time.
14. The analyte sensor system of claim 13 , wherein the range of acceptable sensitivity changes with respect to time is based on sensitivity drift.
15. The analyte sensor system of claim 13 , wherein the adjusted value is based at least in part on the second slow moving average.
16. The analyte sensor system of claim 13 , wherein the adjusting the actual sensitivity of the sensor is configured to occur at a time when the indwelling analyte concentration sensor reading is substantially stable, or within a predetermined range of readings for a threshold period of time, whereby an occurrence of unexpected jumps in readings is reduced.
17. A processor for an analyte system, the processor being programmed to perform operations comprising:
measuring analyte concentration values from an indwelling analyte concentration sensor to obtain an indwelling analyte concentration sensor reading;
determining a first slow-moving average of the measured analyte concentration values of the analyte over a first period of time, and basing a first apparent sensitivity of the indwelling analyte concentration sensor based at least in part on the first slow-moving average;
following the first determining, determining a second slow-moving average of the measured analyte concentration values of the analyte over a second period of time, and basing a second apparent sensitivity of the indwelling analyte concentration sensor based at least in part on the second slow moving average; and
adjusting an actual sensitivity of the indwelling analyte concentration sensor to an adjusted value based on a difference between the first apparent sensitivity and the second apparent sensitivity when the difference between the first apparent sensitivity and the second apparent sensitivity meets a predetermined criteria, wherein the predetermined criteria is based on a range of acceptable sensitivity changes with respect to time.
18. The processor of claim 17 , wherein the range of acceptable sensitivity changes with respect to time is based on sensitivity drift.
19. The processor of claim 17 , wherein the adjusted value is based at least in part on the second slow moving average.
20. The processor of claim 17 , wherein the adjusting the actual sensitivity of the sensor is configured to occur at a time when the indwelling analyte concentration sensor reading is substantially stable, or within a predetermined range of readings for a threshold period of time, whereby an occurrence of unexpected jumps in readings is reduced.