Application of electrochemical impedance spectroscopy in sensor systems, devices, and related methods

Patent metadata

Field	Value
Publication number	US-2022133179-A1
Application number	US-202217571723-A
Country	US
Kind code	A1
Filing date	Jan 10, 2022
Priority date	Jun 8, 2012
Publication date	May 5, 2022
Grant date	—

Abstract

A diagnostic Electrochemical Impedance Spectroscopy (EIS) procedure is applied to measure values of impedance-related parameters for one or more sensing electrodes. The parameters may include real impedance, imaginary impedance, impedance magnitude, and/or phase angle. The measured values of the impedance-related parameters are then used in performing sensor diagnostics, calculating a highly-reliable fused sensor glucose value based on signals from a plurality of redundant sensing electrodes, calibrating sensors, detecting interferents within close proximity of one or more sensing electrodes, and testing surface area characteristics of electroplated electrodes. Advantageously, impedance-related parameters can be defined that are substantially glucose-independent over specific ranges of frequencies. An Application Specific Integrated Circuit (ASIC) enables implementation of the EIS-based diagnostics, fusion algorithms, and other processes based on measurement of EIS-based parameters.

First claim

1 - 19 . (canceled)

20 . A method of calibration of a glucose sensor involving low start-up detection, the method comprising:
performing electrochemical impedance spectroscopy (EIS) procedures for a working electrode of the glucose sensor to obtain values of at least one impedance-based parameter for the working electrode; performing a bound check for a Nyquist slope and a real impedance value at 1 kHz based on the at least one impedance-based parameter to calculate a reliability index; performing a first calibration of the glucose sensor in a case where the reliability index is higher than a predetermined threshold; and in a case where the reliability index is not higher than the predetermined threshold:
calculating a length of time for the Nyquist slope and the real impedance value at 1 kHz to be within a respective range;
performing the first calibration of the glucose sensor in a case where the length of time is shorter than a predetermined duration; and
performing a second calibration with an EIS-based calibration factor adjustment in a case where the length of time is not shorter than the predetermined duration.

21 . The method of claim 20 , wherein the reliability index is calculated to be higher than the predetermined threshold when each of the Nyquist slope and the real impedance value at 1 kHz is lower than an upper bound for the Nyquist slope and lower than an upper bound for the real impedance value at 1 kHz, respectively.

22 . The method of claim 21 , further comprising: in a case where the second calibration with the EIS-based calibration factor adjustment is performed, gradually offsetting the Nyquist slope to be lower than the upper bound for the Nyquist slope.

23 . The method of claim 21 , further comprising: in a case where the second calibration with the EIS-based calibration factor adjustment is performed, gradually offsetting the real impedance value at 1 kHz to be lower than the upper bound for the real impedance value at 1 kHz.

24 . The method of claim 20 , wherein the reliability index is calculated to be lower than or equal to the predetermined threshold when at least one of the Nyquist slope or the real impedance value at 1 kHz is not lower than the respective upper bound.

25 . The method of claim 20 , further comprising: calculating the length of time for the Nyquist slope and the real impedance value at 1 kHz to be within the respective range based on a trend of the Nyquist slope and of the real impedance value at 1 kHz.

26 . The method of claim 25 , wherein the trend of the Nyquist slope and of the real impedance value at 1 kHz is measured during a start-up period.

27 . The method of claim 20 , wherein the first calibration is performed after the length of time has passed, in a case where the reliability index is not higher than the predetermined threshold.

28 . The method of claim 20 , wherein the predetermined duration is one hour.

29 . The method of claim 20 , wherein the second calibration with the EIS-based calibration factor adjustment is performed upon determining that the length of time is not shorter than the predetermined duration.

30 . A system for calibrating a glucose sensor involving low start-up detection, the system comprising:
a glucose sensor having a working electrode; and control circuitry configured to:
perform electrochemical impedance spectroscopy (EIS) procedures for the working electrode of the glucose sensor to obtain values of at least one impedance-based parameter for the working electrode;
perform a bound check for a Nyquist slope and a real impedance value at 1 kHz based on the at least one impedance-based parameter to calculate a reliability index;
perform a first calibration in a case where the reliability index is higher than a predetermined threshold; and
in a case where the reliability index is not higher than the predetermined threshold:
calculate a length of time for the Nyquist slope and the real impedance value at 1 kHz to be within a respective range;
perform the first calibration in a case where the length of time is shorter than a predetermined duration; and
perform a second calibration with an EIS-based calibration factor adjustment in a case where the length of time is not shorter than the predetermined duration.

31 . The system of claim 30 , wherein the reliability index is calculated to be higher than the predetermined threshold when each of the Nyquist slope and the real impedance value at 1 kHz is lower than an upper bound for the Nyquist slope and lower than an upper bound for the real impedance value at 1 kHz, respectively.

32 . The system of claim 31 , wherein the control circuitry further causes performance of: in a case where the second calibration with the EIS-based calibration factor adjustment is performed, gradually offsetting the Nyquist slope to be lower than the upper bound for the Nyquist slope.

33 . The system of claim 31 , wherein the control circuitry further causes performance of: in a case where the second calibration with the EIS-based calibration factor adjustment is performed, gradually offsetting the real impedance value at 1 kHz to be lower than the upper bound for the real impedance value at 1 kHz.

34 . The system of claim 30 , wherein the reliability index is calculated to be lower than or equal to the predetermined threshold when at least one of the Nyquist slope or the real impedance value at 1 kHz is not lower than the respective upper bound.

35 . The system of claim 30 , wherein the control circuitry further causes performance of: calculating the length of time for the Nyquist slope and the real impedance value at 1 kHz to be within the respective range based on a trend of the Nyquist slope and of the real impedance value at 1 kHz.

36 . The system of claim 35 , wherein the trend of the Nyquist slope and of the real impedance value at 1 kHz is measured during a start-up period.

37 . The system of claim 30 , wherein the first calibration is performed after the length of time has passed, in a case where the reliability index is not higher than the predetermined threshold.

38 . The system of claim 30 , wherein the second calibration with the EIS-based calibration factor adjustment is performed upon determining that the length of time is not shorter than the predetermined duration.

39 . A non-transitory computer-readable medium storing instructions which, when executed by one or more processors, cause performance of operations comprising:
performing electrochemical impedance spectroscopy (EIS) procedures for a working electrode of the glucose sensor to obtain values of at least one impedance-based parameter for the working electrode; performing a bound check for a Nyquist slope and a real impedance value at 1 kHz based on the at least one impedance-based parameter to calculate a reliability index; performing a first calibration in a case where the reliability index is higher than a predetermined threshold; and in a case where the reliability index is not higher than the predetermined threshold:
calculating a length of time for the Nyquist slope and the real impedance value at 1 kHz to be within a respective range;
performing the first calibration in a case where the length of time is shorter than a predetermined duration; and
performing a second calibration with an EIS-based calibration factor adjustment in a case where the length of time is not shorter than the predetermined duration.

Assignees

• Medtronic Minimed Inc

Inventors

• Yang Ning
• Gautham Raghavendhar
• Liang Bradley C
• Shah Rajiv

Classifications

• G08B21/182

  Level alarms, e.g. alarms responsive to variables exceeding a threshold · CPC title

• A61B5/6886

  Monitoring or controlling distance between sensor and tissue · CPC title

• A61B5/0537

  Measuring body composition by impedance, e.g. tissue hydration or fat content · CPC title

• A61B5/7221 Primary

  Determining signal validity, reliability or quality (preventing, reducing or removing noise induced by motion artefacts A61B5/7207; noise originating from a therapeutic or surgical apparatus A61B5/7217) · CPC title

• A61B5/14503

  invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors (A61B5/1459, A61B5/1464, A61B5/1473, A61B5/1482, A61B5/14865 take precedence) · CPC title