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

• US 9,427,183 B2
• Filed: 07/12/2011
• Issued: 08/30/2016
• Est. Priority Date: 08/22/2003
• Status: Expired due to Term

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Goode, Paul V. Jr., Brauker, James H., Kamath, Apurv U., Thrower, James Patrick, Carr-Brendel, Victoria
• Primary Examiner(s): JANG, CHRISTIAN YONGKYUN
• Application Number:
  US13/181,341
• Publication Number:
  US 20110270062A1
• Time in Patent Office: 1,876 Days
• Field of Search: 600/345, 600/347, 600/365
• US Class Current: 1/1
• 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 method for processing data from a continuous glucose sensor, the method comprising:

providing a glucose sensor operably connected to electronic circuitry;

monitoring, using the electronic circuitry, a signal generated by a working electrode of the glucose sensor, the signal comprising a glucose sensor data point;

further monitoring, using the electronic circuitry, an output of a counter electrode of the glucose sensor;

detecting, using the electronic circuitry, a signal artifact associated with the glucose signal based on the monitoring of the output of the counter electrode, wherein the detecting includes determining a first state of severity from a plurality of state of severities of the signal artifact;

selecting a first signal estimation algorithm from a group of one or more signal estimation algorithms based on the determination of the first state of severity of the signal artifact, wherein the first signal estimation algorithm is different from the other plurality of signal estimation algorithms and wherein each of the plurality of signal estimation algorithms use historical and/or present signal data to estimate unknown signal data;

applying using the electronic circuitry, the selected first signal estimation algorithm;

generating an estimated sensor data point based on the application of the selected first signal estimation algorithm; and

replacing, using the electronic circuitry, the sensor data point with the estimated sensor data point.

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

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

4. The method of claim 1, wherein the signal artifact is a transient non-glucose related signal artifact.

5. The method of claim 1, further comprising displaying or transmitting the estimated data point.

6. The method of claim 1, wherein the detecting comprises identifying a drop in the output of the counter electrode to about zero and associating the output drop with the glucose sensor data point.

7. The method of claim 1, wherein the detecting comprises comparing the signal with the output of the counter electrode.

8. The method of claim 1, wherein the electronic circuitry is housed within an electronics unit configured to be physically coupled to the glucose sensor.

9. The method of claim 1, wherein the monitored signal is associated with a biological sample.

10. The method of claim 1, wherein the signal artifact is associated with a change in a pH value of a fluid that is detected by the glucose sensor.

11. The method of claim 1, wherein the signal artifact is associated with a change in available surface area of at least one of the electrodes.

12. The method of claim 1, further comprising measuring a counter electrode voltage, wherein the counter electrode voltage is directly related to current from the working electrode.

13. The method of claim 12, wherein the measured counter electrode voltage is in units of counts.

14. The method of claim 12, wherein the counter electrode has a greater electrochemically reactive surface area than the working electrode.

15. The method of claim 1, wherein the working electrode is an anode and the counter electrode is a cathode of an electrochemical cell.

16. A system for processing data from a glucose sensor, the system comprising:

a glucose sensor comprising a working electrode configured to generate a signal and a counter electrode configured to generate a counter electrode output; and

an artifact replacement module configured to;

monitor the counter electrode output;

detect a signal artifact associated with a portion of the signal based on the monitoring of the counter electrode output, wherein the detection includes determination of a first state of severity from a plurality of state of severities of the signal artifact;

select a first signal estimation algorithm from a group of one or more signal estimation algorithms based on the determination of the first state of severity of the signal artifact, wherein the first signal estimation algorithm is different from the other plurality of signal estimation algorithms and wherein each of the plurality of signal estimation algorithms use historical and/or present signal data to estimate unknown signal data;

apply the selected first signal estimation algorithm;

an estimated data stream portion based on the application of the selected first signal estimation algorithm; and

replace the portion of the signal with the estimated data stream portion.

17. The system of claim 16, wherein the signal comprises a raw signal.

18. The system of claim 16, wherein the signal comprises a calibrated signal of glucose concentration values.

19. The system of claim 16, wherein the signal artifact is a transient non-glucose related signal artifact.

20. The system of claim 16, further comprising an output module configured to display or transmit the information representative of the estimated data stream portion.

21. The system of claim 16, wherein the artifact replacement module is configured to detect by identifying a drop in the counter electrode output to about zero and associating the output drop with the portion of the signal.

22. The system of claim 16, wherein the artifact replacement module is configured to detect by comparing the signal with the counter electrode output.

23. The system of claim 16, wherein the monitored output is associated with a biological sample.

24. The system of claim 16, wherein the signal artifact is associated with a change in a pH value of a fluid that is detected by the glucose sensor.

25. The system of claim 16, wherein the signal artifact is associated with a change in available surface area of at least one of the electrodes.

26. The system of claim 16, further configured to measure a counter electrode voltage, wherein the counter electrode voltage is directly related to current from the working electrode.

27. The system of claim 26, wherein the measured counter electrode voltage is in units of counts.

28. The system of claim 26, wherein the counter electrode has a greater electrochemically reactive surface area than the working electrode.

29. The system of claim 16, wherein the working electrode is an anode and the counter electrode is a cathode of an electrochemical cell.