USE OF ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) IN GROSS FAILURE ANALYSIS

• US 20150164371A1
• Filed: 08/22/2014
• Published: 06/18/2015
• Est. Priority Date: 12/16/2013
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: VARSAVSKY, ANDREA, YANG, NING, YU, FEI
• Granted Patent: US 10,945,630 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1468 using chemical or electrochemical methods, e.g. by polarographic means A61B5/1486 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 5/6849 in combination with a needle set
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61M 2005/1726 the body parameters being measured at, or proximate to, the infusion site
• CPC Class Codes: A61M 5/14244 adapted to be carried by the patient, e.g. portable on the body
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: A61M 5/1582 Double lumen needles
• CPC Class Codes: G01N 27/026 Dielectric impedance spectroscopy electrochemical impedance spectroscopy for measuring corrosion G01N17/02

Abstract

Electrochemical Impedance Spectroscopy (EIS) is used in conjunction with continuous glucose monitors and continuous glucose monitoring (CGM) to enable in-vivo sensor calibration, gross (sensor) failure analysis, and intelligent sensor diagnostics and fault detection. An equivalent circuit model is defined, and circuit elements are used to characterize sensor behavior.

Claims

1. A method of performing diagnostics on a subcutaneous or implanted sensor having at least one working electrode, comprising:

defining a vector containing values associated with one or more electrochemical impedance spectroscopy (EIS)-based parameters and values associated with one or more non-EIS-based parameters;

defining a respective threshold value for each of said EIS-based parameters and each of said non-EIS-based parameters;

performing a first EIS procedure to generate a first set of data for said values associated with the one or more EIS-based parameters;

after a calculated time interval, performing a second EIS procedure to generate a second set of data for said values associated with the one or more EIS-based parameters;

updating the vector with said first and second sets of data; and

monitoring said vector values to determine whether the sensor has lost sensitivity.

2. The method of claim 1, wherein said one or more EIS-based parameters include at least one of membrane resistance (Rmem), membrane capacitance (Cmem), and double layer capacitance (Cdl).

3. The method of claim 1, wherein said one or more non-EIS-based parameters include at least one of variability in sensor current (Isig), rate of change of Isig, and a period of time during which Isig is low.

4. The method of claim 1, further including periodically updating the vector values for each of said non-EIS-based parameters.

5. The method of claim 4, wherein said determination of sensitivity loss is made based on comparison of one of the vector values to a corresponding threshold value.

6. The method of claim 4, wherein the sensor is determined to have lost sensitivity when a plurality of the vector values have crossed their corresponding threshold values.

7. The method of claim 6, wherein said plurality of vector values include values for at least one EIS-based parameter and at least one non-EIS-based parameter.

8. The method of claim 1, wherein each of said threshold values is an absolute threshold value.

9. The method of claim 1, wherein each of said threshold values is a relative threshold value.

10. The method of claim 1, further including a second threshold value for a combination of said EIS-based parameters, wherein the sensor is determined to have lost sensitivity if a combined vector value of said combination of EIS-based parameters crosses said second threshold value.

11. The method of claim 1, further including a second threshold value for a combination of said EIS-based and non-EIS-based parameters, wherein the sensor is determined to have lost sensitivity if a combined vector value of said combination of EIS-based and non-EIS-based parameters crosses said second threshold value.

12. The method of claim 1, further including applying a weighting factor to each of the vector values to generate weighted vector values, and determining sensitivity loss based on said weighted vector values.

13. The method of claim 12, wherein said weighting factor is different for each of the EIS-based parameters and for each of the non-EIS-based parameters.

14. The method of claim 13, wherein, for each said EIS-based parameter and each said non-EIS-based parameter, a respective weighting factor is calculated based on each parameter'"'"'s said respective threshold value.

15. The method of claim 14, further including a second threshold value for a combination of said EIS-based parameters, wherein the sensor is determined to have lost sensitivity if a combined weighted vector value of said combination of EIS-based parameters crosses said second threshold value.

16. The method of claim 15, wherein said second threshold value is an absolute threshold value.

17. The method of claim 15, wherein said second threshold value is a relative threshold value.

18. The method of claim 14, further including a second threshold value for a combination of said EIS-based and non-EIS-based parameters, wherein the sensor is determined to have lost sensitivity if a combined weighted vector value of said combination of EIS-based and non-EIS-based parameters crosses said second threshold value.

19. The method of claim 18, wherein said second threshold value is an absolute threshold value.

20. The method of claim 18, wherein said second threshold value is a relative threshold value.