Systems and methods for replacing signal artifacts in a glucose sensor data stream

• US 9,724,045 B1
• Filed: 04/06/2017
• Issued: 08/08/2017
• Est. Priority Date: 08/22/2003
• Status: Expired due to Term

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Goode, Jr., Paul V., Brauker, James H., Kamath, Apurv U., Thrower, James Patrick, Carr-Brendel, Victoria
• Primary Examiner(s): JANG, CHRISTIAN YONGKYUN
• Application Number:
  US15/481,347
• Publication Number:
  US 20170209101A1
• Time in Patent Office: 124 Days
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/0271 Thermal or temperature sensors
• CPC Class Codes: A61B 2562/08 Sensors provided with means for identification, e.g. barcodes or memory chips
• CPC Class Codes: A61B 5/0004 characterised by the type of physiological signal transmitted
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence
• CPC Class Codes: A61B 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors
• 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: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61B 5/7475 User input or interface means, e.g. keyboard, pointing device, joystick

Abstract

Systems and methods for minimizing or eliminating transient non-glucose related signal noise due to non-glucose rate limiting phenomenon such as ischemia, pH changes, temperatures changes, and the like. The system monitors a data stream from a glucose sensor and detects signal artifacts that have higher amplitude than electronic or diffusion-related system noise. The system replaces some or the entire data stream continually or intermittently including signal estimation methods that particularly address transient signal artifacts. The system is also capable of detecting the severity of the signal artifacts and selectively applying one or more signal estimation algorithm factors responsive to the severity of the signal artifacts, which includes selectively applying distinct sets of parameters to a signal estimation algorithm or selectively applying distinct signal estimation algorithms.

Claims

1. A glucose sensor system that detects a signal artifact that can result in an erroneous glucose concentration measurement and responds to the detected signal artifact differently depending on a corresponding evaluated level of severity, the system comprising:

an electrochemical glucose sensor comprising a plurality of electrodes and an enzyme-containing membrane, wherein the enzyme-containing membrane is positioned to provide a medium for a conductive pathway between electrodes of the plurality of electrodes when a voltage is present across the electrodes while the electrochemical glucose sensor is in contact with a biological sample; and

sensor electronics comprising a processor for executing a computer program code stored in a memory to cause the sensor electronics to;

apply a voltage across the electrodes of the electrochemical glucose sensor,

measure a signal response of the electrochemical glucose sensor responsive to the applied voltage, the measured signal response having a signal content associated with a local environment at the electrodes, wherein the local environment contributes to a signal artifact in a glucose signal generated by the electrochemical glucose sensor,

evaluate a level of severity of the signal artifact based at least in part on the signal content of the measured signal response, and

dynamically adjust the sensor electronics based on the level of severity evaluated to generate;

(i) a first glucose value for display based on an output from the electrochemical glucose sensor when the signal artifact is evaluated having a first level of severity, and

(ii) a second glucose value, different from the first glucose value, for display based on the output from the electrochemical glucose sensor when the signal artifact is evaluated having a second level of severity different from the first level of severity, wherein the second glucose value accounts for the signal artifact affecting glucose measurement.

2. The system of claim 1, wherein the biological sample is blood.

3. The system of claim 1, wherein measuring the signal response comprises measuring a current output of the electrochemical glucose sensor.

4. The system of claim 1, wherein measuring the signal response comprises measuring a voltage output of the electrochemical glucose sensor.

5. The system of claim 1, wherein the measured signal response is a voltage response of the electrochemical glucose sensor.

6. The system of claim 1, wherein evaluating the level of severity comprises comparing the signal content to one or more thresholds.

7. The system of claim 1, wherein the electrochemical glucose sensor is a continuous glucose sensor.

8. The system of claim 1, wherein the sensor electronics are configured to

not display a glucose value based on the output from the electrochemical glucose sensor when the signal artifact is evaluated having a third level of severity that is different from the first level of severity and the second level of severity.

9. The system of claim 1, wherein applying the voltage comprises switching a voltage applied to the electrodes.

10. The system of claim 1, wherein applying the voltage comprises cycling a voltage applied to the electrodes.

11. The system of claim 1, wherein applying the voltage comprises pulsing a voltage applied to the electrodes.

12. The system of claim 1, wherein the signal artifact is associated with a pH.

13. The system of claim 1, wherein the signal artifact is associated with a temperature.

14. The system of claim 1, wherein the signal artifact is associated with an available electrode surface area.

15. The system of claim 1, wherein the signal artifact is associated with a biochemical species.

16. A glucose sensor system, the system comprising:

an electrochemical glucose sensor configured to be in contact with a biological sample for measuring a glucose concentration, wherein the electrochemical glucose sensor comprises a first electrode, a second electrode, and an enzyme-containing film;

sensor electronics comprising a processor for executing a computer program code stored in a memory to cause the sensor electronics to;

apply a voltage to the electrochemical glucose sensor at a first setting,

switch the voltage applied to the electrochemical sensor to a different setting,

measure a signal response of the electrochemical glucose sensor responsive to the switching,

evaluate a severity associated with a signal artifact based on the measured signal response of the electrochemical glucose sensor to the switching, wherein the signal artifact is associated with a non-glucose rate limiting phenomenon, and

generate an estimated glucose concentration value when the severity associated with the signal artifact is evaluated to be under a predetermined threshold, wherein the estimated glucose concentration value accounts for the severity associated with the signal artifact; and

a user interface configured to display the estimated glucose concentration value.

17. The system of claim 16, wherein the biological sample is blood.

18. The system of claim 16, wherein measuring the signal response comprises measuring a current output of the electrochemical glucose sensor.

19. The system of claim 16, wherein measuring the signal response comprises measuring a voltage output of the electrochemical glucose sensor.

20. The system of claim 16, wherein the measured signal response is a voltage response of the electrochemical glucose sensor.

21. The system of claim 16, wherein the electrochemical glucose sensor is a continuous glucose sensor.

22. The system of claim 16, wherein the non-glucose rate limiting phenomenon is associated with a pH.

23. The system of claim 16, wherein the non-glucose rate limiting phenomenon is associated with a temperature.

24. The system of claim 16, wherein the non-glucose rate limiting phenomenon is associated with an available electrode surface area.

25. The system of claim 16, wherein the non-glucose rate limiting phenomenon is associated with a biochemical species.

26. A glucose sensor system, the system comprising:

an electrochemical glucose sensor configured to be in contact with a biological sample for measuring a glucose concentration, wherein the electrochemical glucose sensor comprises a first electrode, a second electrode, and an enzyme-containing film;

sensor electronics comprising a processor for executing a computer program code stored in a memory to cause the sensor electronics to;

apply a voltage to the electrochemical glucose sensor at a first setting,

switch the voltage applied to the electrochemical sensor to a different setting,

measure a signal response of the electrochemical glucose sensor responsive to the switching,

evaluate a severity associated with a signal artifact based on the measured signal response of the electrochemical glucose sensor to the switching, wherein the signal artifact is associated with a non-glucose rate limiting phenomenon, and

generate;

(i) a first glucose value for display based on an output from the electrochemical glucose sensor when the signal artifact is evaluated having a first severity level, and

(ii) a second glucose value different from the first glucose value for display based on the output from the electrochemical glucose sensor when the signal artifact is evaluated having a second severity level different from the first severity level, wherein the second glucose value accounts for the signal artifact affecting the glucose concentration measurement; and

a user interface configured to display;

(i) the first glucose value when the signal artifact is evaluated having the first severity level; and

(ii) the second glucose value when the signal artifact is evaluated having the second severity level.

27. The system of claim 26, wherein the biological sample is blood.

28. The system of claim 26, wherein measuring the signal response comprises measuring a current output of the electrochemical glucose sensor.

29. The system of claim 26, wherein measuring the signal response comprises measuring a voltage output of the electrochemical glucose sensor.

30. The system of claim 26, wherein the measured signal response is a voltage response of the electrochemical glucose sensor.

31. The system of claim 26, wherein the electrochemical glucose sensor is a continuous glucose sensor.

32. The system of claim 26, wherein the sensor electronics are configured to:

(iii) not display a glucose value based on the output from the electrochemical glucose sensor when the signal artifact is evaluated having a third severity level that is different from the first severity level and the second severity level.

33. The system of claim 26, wherein the non-glucose rate limiting phenomenon is associated with a pH.

34. The system of claim 26, wherein the non-glucose rate limiting phenomenon is associated with a temperature.

35. The system of claim 26, wherein the non-glucose rate limiting phenomenon is associated with an available electrode surface area.

36. The system of claim 26, wherein the non-glucose rate limiting phenomenon is associated with a biochemical species.

37. A glucose sensor system, the system comprising:

an electrochemical glucose sensor configured to be in contact with a biological sample for measuring a glucose concentration, wherein the electrochemical glucose sensor comprises a first electrode, a second electrode, and an enzyme-containing film;

sensor electronics comprising a processor for executing a computer program code stored in a memory to cause the sensor electronics to;

apply a voltage to the electrochemical glucose sensor at a first setting,

switch the voltage applied to the electrochemical sensor to a different setting,

measure a signal response of the electrochemical glucose sensor responsive to the switching, wherein the measured signal response is a time-varying voltage response of the electrochemical glucose sensor,

evaluate a severity associated with a signal artifact based on the measured signal response of the electrochemical glucose sensor to the switching, wherein the signal artifact is associated with a non-glucose rate limiting phenomenon, and

generate an estimated glucose concentration value when the severity associated with the signal artifact is evaluated to be under a predetermined threshold, wherein the estimated glucose concentration value accounts for the severity associated with the signal artifact; and

a user interface configured to;

display a first screen presenting generated glucose concentration data over a first time period,

display a second screen presenting generated glucose concentration data over a second time period, wherein the second time period is different in length from the first time period,

display a third screen presenting the estimated glucose concentration value,

allow a user to toggle between the first screen, the second screen, and the third screen, and

generate an alert responsive to detection of a hyperglycemic condition or a hypoglycemic condition.

38. The system of claim 37, wherein the biological sample is blood.

39. The system of claim 37, wherein the electrochemical glucose sensor is a continuous glucose sensor.

40. The system of claim 37, wherein the non-glucose rate limiting phenomenon is associated with a pH.

41. The system of claim 37, wherein the non-glucose rate limiting phenomenon is associated with a temperature.

42. The system of claim 37, wherein the non-glucose rate limiting phenomenon is associated with an available electrode surface area.

43. The system of claim 37, wherein the non-glucose rate limiting phenomenon is associated with a biochemical species.

44. A glucose sensor system, the system comprising:

an electrochemical glucose sensor configured to be in contact with a blood sample for measuring a glucose concentration, wherein the electrochemical glucose sensor comprises a first electrode, a second electrode, and an enzyme-containing film;

sensor electronics comprising a processor for executing a computer program code stored in a memory to cause the sensor electronics to;

apply a voltage to the electrochemical glucose sensor at a first setting,

switch the voltage applied to the electrochemical sensor to a different setting,

measure a signal response of the electrochemical glucose sensor responsive to the switching, wherein the measured signal response is a voltage response of the electrochemical glucose sensor,

evaluate a severity associated with a signal artifact based on the measured signal response of the electrochemical glucose sensor to the switching, wherein the signal artifact is associated with a condition selected from the group consisting of a pH, a temperature, a pressure, an available electrode surface area, and a biochemical species, and

generate;

(i) a first glucose value for display based on an output from the electrochemical glucose sensor when the signal artifact is evaluated having a first severity level, and

(ii) a second, different glucose value for display based on the output from the electrochemical glucose sensor when the signal artifact is evaluated having a second severity level different from the first severity level, wherein the second glucose value accounts for the signal artifact affecting glucose measurement; and

a user interface configured to;

display the first glucose value when the signal artifact is evaluated having the first severity level,

display the second glucose value when the signal artifact is evaluated having the second severity level,

display a first screen presenting generated glucose concentration data over a first time period,

display a second screen presenting generated glucose concentration data over a second time period, wherein the second time period is different in length from the first time period,

display a third screen presenting;

(i) the first glucose value when the signal artifact is evaluated having the first severity level, and

(ii) the second glucose value when the signal artifact is evaluated having the second severity level,

allow a user to toggle between the first screen, the second screen, and the third screen, and

generate an alert responsive to detection of a hyperglycemic condition or a hypoglycemic condition.