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

• US 20070032706A1
• Filed: 08/02/2006
• Published: 02/08/2007
• Est. Priority Date: 08/22/2003
• Status: Active Grant

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Brauker, James, Li, Ying, Kamath, Apurv, Mahalingam, Aarthi
• Granted Patent: US 9,247,901 B2
• Time in Patent Office: Days
• US Class Current: 600/300
• CPC Class Codes: A61B 2560/0252 using ambient temperature
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/145 Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissuemeasuring of blood pressure or blood flow A61B5/02; non-radiation detecting or locating of foreign bodies in blood A61B5/06
• 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 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors
• CPC Class Codes: A61B 5/6848 Needles
• 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 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: A61B 5/742 using visual displays A61B5/339 takes precedence
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

Systems and methods for minimizing or eliminating transient non-glucose related signal noise due to non-glucose rate limiting phenomenon such as interfering species, ischemia, pH changes, temperatures changes, known or unknown sources of mechanical, electrical and/or biochemical noise, 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 processes some or the entire data stream continually or intermittently based at least in part on whether the signal artifact event has occurred.

Claims

1. A method of analyzing data from an analyte sensor, the method comprising:

receiving data from the analyte sensor, the data comprising at least one sensor data point;

determining whether a signal artifact event has occurred; and

processing the received data, wherein the processing is based at least in part upon whether the signal artifact event has occurred.

2. The method of claim 1, further comprising filtering the received data to generate filtered data.

3. The method of claim 2, wherein determining whether a signal artifact has occurred comprises comparing the received data with the filtered data to obtain at least one residual.

4. The method of claim 3, wherein a signal artifact event is determined to have occurred if the residual is exceeds a threshold value.

5. The method of claim 4, further comprising determining whether another signal artifact event has occurred, wherein another signal artifact event has occurred if the residual exceeds a second threshold value.

6. The method of claim 3, wherein a signal artifact event is determined to have occurred if the residual is exceeds a threshold value for a predetermined period of time or for a predetermined amount of data.

7. The method of claim 6, wherein determining whether a signal artifact has occurred further comprises determining whether a predetermined number of residuals exceeds a threshold over a predetermined period of time, or whether a predetermined amount of data exceeds a threshold.

8. The method of claim 3, wherein determining whether a signal artifact event has occurred further comprises determining a differential between a first residual at a first time point and a second residual at a second time point.

9. The method of claim 8, wherein determining whether a signal artifact event has occurred further comprises determining whether a predetermined number of differentials exceeds a threshold over a predetermined period of time, or whether an amount of data exceeds a threshold.

10. The method of claim 1, further comprising receiving reference data from a reference analyte monitor, the reference data including at least one reference data point.

11. The method of claim 10, wherein processing the received data further comprises determining a reliability of the received data, wherein processing is conducted if the signal artifact event is determined to have not occurred.

12. The method of claim 10, further comprising matching the reference data to substantially time corresponding received data to form a matching data pair, wherein the reference data is matched if the signal artifact event is determined to have not occurred.

13. The method of claim 10, further comprising including the reference data in a calibration factor for use in calibrating the glucose sensor, wherein the reference data is included if the signal artifact event is determined to have not occurred.

14. The method of claim 1, further comprising prompting a user for a reference glucose value, wherein prompting is conducted if the signal artifact event is determined to have not occurred.

15. The method of claim 1, wherein processing the received data comprises displaying a graphical representation of the received data.

16. The method of claim 1, wherein processing the received data comprises filtering the received data, wherein filtering is conducted if the signal artifact event is determined to have occurred.

17. The method of claim 1, further comprising filtering the received data, wherein processing the received data comprises displaying a graphical representation of the filtered data, wherein processing is conducted if the signal artifact event is determined to have occurred.

18. The method of claim 1, further comprising filtering the received data to generate filtered data, wherein determining whether a signal artifact event has occurred further comprises comparing the received data with the filtered data to obtain a residual, and wherein processing the received data comprises utilizing the residual to modify the filtered data.

19. The method of claim 1, further comprising filtering the received data to generate filtered data, wherein determining whether a signal artifact event has occurred further comprises comparing the received data with the filtered data to obtain a residual and deriving a differential of the residual by calculating a first derivative of the residual, and wherein processing the received data comprises utilizing the differential to modify the filtered data.

20. The method of claim 1, wherein processing the received data comprises compensating for a time lag.

21. The method of claim 1, wherein processing the received data comprises displaying a graphical representation of the received data.

22. The method of claim 21, wherein the received data is an unfiltered digital signal.

23. The method of claim 1, wherein processing the received data comprises disabling display of a graphical representation of the received data, wherein processing is conducted if the signal artifact event is determined to have occurred.

24. The method of claim 1, wherein processing the received data comprises displaying a range of glucose values, wherein processing is conducted if the signal artifact event is determined to have occurred.

25. The method of claim 1, wherein processing the received data comprises displaying a graphical indication of glucose trend, wherein processing is conducted if the signal artifact event is determined to have occurred.

26. The method of claim 1, wherein processing the received data comprises generating at least one estimated glucose value and displaying a graphical representation of the estimated glucose value, wherein processing is conducted if the signal artifact event is determined to have occurred.

27. The method of claim 26, wherein processing the received data comprises generating a confidence interval for at least one estimated glucose value and displaying a graphical representation of the confidence interval, wherein processing is conducted if the signal artifact event is determined to have occurred.

28. A method for processing data from a glucose sensor, the method comprising:

receiving data from the glucose sensor, the received data comprising at least one sensor data point;

displaying a graphical representation of the data corresponding to a time period; and

post-processing the displayed graphical representation of the data corresponding to the time period.

29. The method of claim 28, wherein post-processing is conducted periodically.

30. The method of claim 28, wherein post-processing is conducted substantially continuously.

31. The method of claim 28, further comprising determining whether a signal artifact event has occurred and processing the received data prior to the displaying step, wherein the processing is based at least in part upon whether the signal artifact event has occurred.

32. The method of claim 28, wherein post-processing comprises filtering the data to recalculate data corresponding to the time period and displaying a graphical representation of the recalculated data corresponding to the time period.

33. The method of claim 28, wherein the step of post-processing comprises:

recalculating data corresponding to the time period, wherein a time lag induced by real-time filtering is substantially removed from the data corresponding to the time period; and

displaying a graphical representation of the recalculated data corresponding to the time period.

34. The method of claim 33, wherein recalculating the data comprises algorithmically smoothing at least one sensor data point over a moving window, wherein the moving window comprises time points before and after the sensor data point is obtained.

35. The method of claim 28, further comprising displaying a current glucose value representative of the most recently obtained sensor data point.

36. A system configured to process data from an analyte sensor, the system comprising:

a data receiving module configured to receive sensor data from the analyte sensor, the data comprising at least one sensor data point;

a signal artifacts module configured to detect a signal artifact in the sensor data; and

a processor module configured to process the sensor data, wherein processing is dependent at least in part upon whether the signal artifact is detected.

37. The system of claim 36, wherein the signal artifacts module is configured to compare raw sensor data with filtered sensor data to determine a residual.

38. The system of claim 37, wherein the signal artifacts module is configured to detect a signal artifact if the residual exceeds a threshold value.

39. The system of claim 37, wherein the signal artifacts module is configured to detect a signal artifact if a predetermined number of residuals exceed a threshold value for a predetermined period of time or for a predetermined amount of data.

40. The system of claim 37, wherein the signal artifacts module is configured to compare a first residual with a second signal residual to determine a differential.

41. The system of claim 40, wherein the signal artifacts module is configured to detect a signal artifact if the differential exceeds a threshold value.

42. The system of claim 40, wherein the signal artifacts module is configured to detect a signal artifact if a predetermined number of differentials exceed a threshold value for a predetermined period of time or for a predetermined amount of data.

43. The system of claim 36, further comprising a reference data module configured to receive reference data from a reference glucose monitor, the reference data comprising at least one reference data point.

44. The system of claim 43, wherein the signal artifacts module is configured to determine a reliability of the sensor data if the signal artifact is detected.

45. The system of claim 43, wherein the processor module is configured to form at least one matched data pair by matching reference data to substantially time corresponding sensor data.

46. The system of claim 45, wherein the processor module is configured to form a matching data pair if a signal artifact is not detected.

47. The system of claim 43, wherein the processor module is configured to utilize the reference data for calibrating the glucose sensor if a signal artifact is not detected.

48. The system of claim 43, wherein the processor module is configured to prompt a user for a reference glucose value if a signal artifact is not detected.

49. The system of claim 36, wherein the data receiving module is configured to receive raw sensor data.

50. The system of claim 49, wherein the raw sensor data comprises integrated digital data.

51. The system of claim 49, wherein the processor module is configured to display a graphical representation of the raw sensor data if a signal artifact is not detected.

52. The system of claim 49, wherein the data receiving module is configured to receive filtered sensor data.

53. The system of claim 52, wherein the processor module is configured to display a graphical representation of the filtered sensor data if a signal artifact is detected.

54. The system of claim 36, wherein the processor module is configured to filter the sensor data.

55. The system of claim 54, wherein the processor module is configured to display a graphical representation of the filtered sensor data if a signal artifact is detected.

56. The system of claim 36, wherein the processor module is configured to not display the sensor data if a signal artifact is detected.

57. The system of claim 36, wherein the processor module is configured to display a range of glucose values if a signal artifact is detected.

58. The system of claim 36, wherein the processor module is configured to display a directional indicator of glucose trend if a signal artifact is detected.

59. The system of claim 36, wherein the processor module is configured to display at least one estimated glucose value if a signal artifact is detected.

60. The system of claim 36, wherein the processor module is configured to display a confidence interval for at least one estimated glucose value if a signal artifact is detected.

61. A system configured to process data from an analyte sensor, the system comprising:

a data receiving module configured to receive sensor data from the analyte sensor, the data comprising at least one sensor data point;

an output module configured to display a substantially real-time numerical value corresponding to a most recently received sensor data point and a graphical representation of sensor data corresponding to a time period; and

a processor module configured to post-process the graphical representation of the data corresponding to the time period, wherein the output module is configured to display the post-processed data.

62. The system of claim 61, wherein post-processing is conducted periodically.

63. The system of claim 61, wherein post-processing is conducted substantially continuously.

64. The system of claim 61, wherein the processor module is configured to automatically post-process the graphical representation of the data corresponding to the time period.

65. The system of claim 61, wherein the processor module is configured to post-process the graphical representation of the data corresponding to the time period responsive to a request.

66. The system of claim 61, wherein the output module is configured to automatically display the post-processed graphical representation of the data corresponding to the time period.

67. The system of claim 61, wherein the output module is configured to display the post-processed graphical representation of the data corresponding to the time period responsive to a request.