SYSTEMS AND METHODS FOR PROCESSING ANALYTE SENSOR DATA

• US 20130245401A1
• Filed: 03/12/2013
• Published: 09/19/2013
• Est. Priority Date: 03/16/2012
• Status: Active Grant

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Estes, Michael J., Kamath, Apurv Ullas, Peyser, Thomas A., Mahalingam, Aarthi, Simpson, Peter C., Vanslyke, Stephen J., Bohnett, Lucas, Garcia, Arturo, Rack-Gomer, Anna Leigh, Bohm, Sebastian Sebastian
• Granted Patent: US 9,433,376 B2
• Time in Patent Office: Days
• US Class Current: 600/309
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2562/02 Details of sensors specially adapted for in-vivo measurements
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/14503 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors A61B5/1459, A61B5/1464, A61B5/1473, A61B5/1482, A61B5/14865 take precedence
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: G01D 3/022 having an ideal characteristic, map or correction data stored in a digital memory
• CPC Class Codes: G16H 20/17 delivered via infusion or injection
• CPC Class Codes: G16H 40/67 for remote operation

Abstract

Systems and methods for applying time-dependent algorithmic compensation functions to data output from a continuous analyte sensor. Some embodiments determine a time since sensor implantation and/or whether a newly initialized sensor has been used previously.

Claims

1. A method of processing sensor data output by a continuous analyte sensor implanted within a body, comprising:

measuring a change in sensitivity or baseline of the sensor over a time interval;

determining a drift compensation function to be applied to a plurality of time-spaced data points output by the sensor; and

applying the drift compensation function continuously to the data points.

2. The method of claim 1, wherein measuring the change in sensitivity or baseline of the sensor comprises comparing a measured sensitivity or baseline of the sensor to a predetermined sensitivity or baseline of the sensor.

3. The method of claim 2, wherein determining a drift compensation function to be applied is based, at least in part, on the predetermined sensitivity or baseline.

4. The method of claim 2, wherein a value of the predetermined sensitivity or baseline is encoded on sensor electronics.

5. The method of claim 1, further comprising comparing the measured change in sensitivity or baseline of the sensor to a priori knowledge regarding the change in sensitivity or baseline of the sensor over the time interval.

6. The method of claim 1, further comprising, based on the measured change in sensitivity or baseline of the sensor, determining whether the sensor has been previously used.

7. The method of claim 1, wherein measuring the change in sensitivity or baseline of the sensor occurs only after the sensor has been implanted within the body for at least a minimum duration.

8. The method of claim 1, further comprising prompting a user for a reference analyte value when the measured change in sensitivity or baseline of the sensor exceeds a criterion.

9. The method of claim 1, further comprising applying boundaries to the drift compensation function.

10. The method of claim 7, wherein the boundaries are based on a priori knowledge.

11. The method of claim 1, further comprising measuring an absolute sensitivity or baseline of the sensor at a time t, and wherein determining the drift compensation function to be applied to the plurality of time-spaced data points output by the sensor is based on the measured absolute sensitivity or baseline.

12. The method of claim 1, further comprising ceasing applying the drift compensation function continuously to the data points when the measured change in sensitivity or baseline of the sensor is below a threshold value.

13. The method of claim 1, further comprising ceasing applying the drift compensation function continuously to the data points after a predetermined amount of time has elapsed.

14. The method of claim 1, wherein the step of measuring a change in sensitivity or baseline of the sensor occurs over a first time interval, the step of determining a drift compensation function is based on the measured change in sensitivity or baseline of the sensor over the first time interval, and the step of applying the drift compensation function is to continuously adjust the sensor data output to compensate for changes in sensitivity or baseline of the sensor over a second time interval.

15. The method of claim 1, wherein measuring the change in sensitivity or baseline of the sensor comprises comparing a first measured sensitivity or baseline of the sensor to a second measured sensitivity or baseline of the sensor, wherein the first and second measured sensitivities or baselines of the sensor are taken at a beginning and an end, respectively, of the time interval.

16. The method of claim 15, wherein a value of the predetermined sensitivity or baseline of the sensor is assigned according to known characteristics of the body in which the sensor is implanted.

17. The method of claim 16, wherein the characteristics include at least one of age, body type, gender, diabetes type, diabetes duration, concomitant diseases and/or sensor location.

18. The method of claim 1, wherein measuring the change in sensitivity of the sensor over the time interval comprises calculating a drift rate of the sensor over the time interval.

19. The method of claim 18, wherein calculating the drift rate of the sensor comprises comparing measured analyte values to substantially time-corresponding reference analyte values.

20. The method of claim 19, wherein an expected drift rate of the sensor is calculated based on a weighted average of a current calculated drift rate and at least one previously measured drift rate.

21. The method of claim 1, wherein measuring the change in sensitivity or baseline of the sensor occurs only after the sensor has been implanted within the body for at least a minimum duration.

22. A system for processing data, the system comprising:

a continuous analyte sensor configured to be implanted within a body; and

sensor electronics configured to receive and process sensor data output by the sensor, the sensor electronics including a processor configured to

measure a change in sensitivity or baseline of the sensor over an interval of time;

determine a drift compensation function to be applied to a plurality of time-spaced data points output by the sensor over a next interval of time; and

apply the drift compensation function continuously to the data points over the next interval of time.

23. The system of claim 22, wherein measuring the change in sensitivity or baseline of the sensor comprises comparing a first measured sensitivity or baseline of the sensor to a second measured sensitivity or baseline of the sensor, wherein the first and second measured sensitivities or baselines of the sensor are taken at a beginning and an end, respectively, of the time interval.

24. The system of claim 22, wherein the processor is further configured to compare a measured sensitivity or baseline of the sensor to a predetermined sensitivity or baseline of the sensor.

25. The system of claim 24, wherein determining a drift compensation function to be applied is based, at least in part, on the predetermined sensitivity or baseline.

26. The system of claim 24, wherein a value of the predetermined sensitivity or baseline is encoded on sensor electronics.

27. The system of claim 24, wherein a value of the predetermined sensitivity or baseline of the sensor is assigned according to known characteristics of the body in which the sensor is implanted.

28. The system of claim 27, wherein the characteristics include at least one of age, body type, gender, diabetes type, diabetes duration, concomitant diseases and/or sensor location.

29. The system of claim 22, wherein the processor is further configured to compare the measured change in sensitivity or baseline of the sensor to a priori knowledge regarding the change in sensitivity or baseline of the sensor over the time interval.

30. The system of claim 22, wherein measuring the change in sensitivity of the sensor over the time interval comprises calculating a drift rate of the sensor over the time interval.

31. The system of claim 30, wherein calculating the drift rate of the sensor comprises comparing measured analyte values to substantially time-corresponding reference analyte values.

32. The system of claim 30, wherein an expected drift rate of the sensor is calculated based on a weighted average of a current calculated drift rate and at least one previously measured drift rate.

33. The system of claim 22, wherein measuring the change in sensitivity or baseline of the sensor occurs only after the sensor has been implanted within the body for at least a minimum duration.

34. The system of claim 22, wherein the processor is further configured to prompt a user for a reference analyte value when the measured change in sensitivity or baseline of the sensor exceeds a criteria.

35. The system of claim 22, wherein the processor is further configured to store the change in sensitivity or baseline of the sensor for later use.

36. The system of claim 22, wherein the applied drift compensation function is a stepwise function.

37. The system of claim 22, wherein the applied drift compensation function functions to apply a mathematical inverse of a mathematical equation that describes the change in sensitivity or baseline of the sensor over the time interval.

38. The system of claim 22, wherein the processor is further configured to apply boundaries to the drift compensation function.

39. The system of claim 38, wherein the boundaries are based on a priori knowledge.

40. The system of claim 22, wherein the processor is further configured to measure an absolute sensitivity or baseline of the sensor at a time t, and wherein determining the drift compensation function to be applied to the plurality of time-spaced data points output by the sensor is based on the measured absolute sensitivity or baseline.

41. The system of claim 22, wherein the processor is further configured to cease applying the drift compensation function continuously to the data points when the measured change in sensitivity or baseline of the sensor is below a threshold value.

42. The system of claim 22, wherein the processor is further configured to cease applying the drift compensation function continuously to the data points after a predetermined amount of time has elapsed.

43. The system of claim 22, the processor configured to determine a drift compensation function based on the measured change in sensitivity or baseline of the sensor over the interval of time, and to apply the drift compensation function continuously to the data points over the next interval of time to continuously adjust the sensor data output to compensate for changes in sensitivity or baseline of the sensor over a second time interval.