SYSTEMS AND METHODS FOR REPLACING SIGNAL ARTIFACTS IN A GLUCOSE SENSOR DATA STREAM

• US 20100036222A1
• Filed: 10/14/2009
• Published: 02/11/2010
• Est. Priority Date: 08/22/2003
• Status: Active Grant

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Brauker, James H., Carr-Brendel, Victoria, Thrower, James Patrick, Kamath, Apurv U., Goode, Paul V. JR.
• Granted Patent: US 7,998,071 B2
• Time in Patent Office: Days
• US Class Current: 600/365
• 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. In a glucose sensing system comprising a glucose sensor configured for producing an output representative of glucose concentration in a host and processing circuitry configured to process the output, a method for processing data from the output, the method comprising:

generating at least one data stream from the glucose sensor output;

detecting a signal artifact comprising transient non-glucose dependent signal loss in the at least one data stream based at least in part on data stream content; and

generating at least one estimated data stream or data stream portion to reduce or replace signal loss caused by the detected signal artifact.

2. The method of claim 1, wherein the data stream comprises a raw data stream.

3. The method of claim 1, wherein the data stream comprises a calibrated data stream of glucose concentration values.

4. The method of claim 1, wherein the signal loss has a higher amplitude than system noise.

5. The method of claim 1, wherein the detecting comprises analysis of a spectral content of the data stream.

6. The method of claim 1, wherein the detecting comprises a time series analysis.

7. The method of claim 6, wherein the time series analysis is based at least in part on a variance of the data stream over a window of data.

8. The method of claim 7, wherein the window of data comprises a time period selected from the group consisting of about 15 minutes, about 30 minutes, about 45 minutes, and about 60 minutes.

9. The method of claim 1, wherein the detecting comprises a frequency content analysis.

10. The method of claim 9, comprising monitoring the data stream for high frequency content.

11. The method of claim 1, comprising filtering the data stream.

12. The method of claim 11, comprising filtering the data stream with a recursive filter.

13. The method of claim 11, comprising filtering the data stream with a high pass filter.

14. The method of claim 1, wherein generating the estimated data stream or dta stream portion is initiated in response to detection of the signal artifact.

15. The method of claim 1, wherein generating the estimated signal is terminated in response to a drop in a severity of the signal artifact to a level below a predetermined threshold.

16. The method of claim 1, wherein the detecting comprises detecting an acceleration of glucose concentration higher than a threshold.

17. The method of claim 1, wherein the detecting comprises detecting a rate of change of glucose concentration higher than a threshold.

18. A glucose sensor system for monitoring a glucose concentration in a host, the system comprising:

a continuous glucose sensor configured to produce a data stream;

a signal artifact detection module configured to detect a signal artifact caused by transient non-glucose dependent signal loss in the data stream based at least in part on data stream content; and

a signal estimation module configured to generate an estimated data stream or data stream portion to reduce or replace the signal artifact.

19. The system of claim 18, wherein the signal artifact detection module is configured to perform an analysis of a spectral content of the data stream.

20. The system of claim 18, wherein the signal artifact detection module is configured to perform a time series analysis.

21. The system of claim 20, wherein the time series analysis is based on a variance of the data stream over a window of data.

22. The system of claim 21, wherein the window of data comprises a time period selected from the group consisting of about 15 minutes, about 30 minutes, about 45 minutes, and about 60 minutes.

23. The system of claim 18, wherein the signal artifact detection module is configured to perform a frequency content analysis.

24. The system of claim 23, wherein the frequency content analysis comprises monitoring the data stream for high frequency content.

25. The system of claim 18, wherein the system comprises a filter.

26. The system of claim 25, wherein the system comprises a recursive filter.

27. The system of claim 25, wherein the system comprises a high pass filter.

28. The system of claim 18, wherein the signal estimation module is configured to initiate signal estimation in response to positive detection of the signal artifact.

29. The system of claim 18, wherein the signal estimation module is configured to terminate signal estimation in response to a drop in a severity of the signal artifact.

30. The system of claim 18, wherein the signal artifact detection module is housed in at least one of a sensor electronics housing or receiver electronics housing.

31. The system of claim 18, wherein the signal loss has a higher amplitude than system noise.

32. In a glucose sensing system comprising a glucose sensor configured for producing an output representative of glucose concentration in a host and processing circuitry configured to process the output, a method for processing data from the output, the method comprising:

processing the output from the glucose sensor to reduce or replace signal loss caused by transient non-glucose dependent effects and;

displaying the processed output to a user of the glucose sensing system.

33. The method of claim 32, wherein the signal loss has a higher amplitude than system noise.

34. The method of claim 32, comprising:

processing at least a portion of the output with a first processing algorithm;

processing at least a portion of the output with a second, different processing algorithm;

displaying output processed with the first processing algorithm in the absence of a signal artifact, and;

displaying output processed with the second processing algorithm in the presence of a signal artifact.

35. A glucose sensing system comprising;

a continuous glucose sensor;

processing circuitry configured to produce a data stream from an output of the continuous glucose sensor;

means for reducing or replacing signal artifacts in the data stream comprising noise caused by transient non-glucose dependent signal loss.

36. The glucose sensing system of claim 35, wherein the means for compensating for signal artifacts comprises means for detecting signal artifacts and means for replacing at least a portion of the data stream containing the signal artifacts with an estimated data stream.

37. The glucose sensing system of claim 35, wherein the signal loss has a higher amplitude than system noise.