USE OF ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) IN CONTINUOUS GLUCOSE MONITORING

• US 20150164382A1
• Filed: 08/22/2014
• Published: 06/18/2015
• Est. Priority Date: 12/16/2013
• Status: Abandoned Application

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: VARSAVSKY, ANDREA, MILLER, MICHAEL E., LIANG, BRADLEY C., YU, FEI, YANG, NING
• Application Number:
  US14/466,126
• Publication Number:
  US 20150164382A1
• 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 for real-time self-calibration of a sensor, said sensor including sensor electronics, a microcontroller, and at least one working electrode, the method comprising:

performing, by said microcontroller, an electrochemical impedance spectroscopy (EIS) procedure for said at least one working electrode to obtain values of at least one impedance-based parameter for the at least one working electrode;

periodically repeating, by said microcontroller, said EIS procedure for said working electrode to obtain additional values of said at least one impedance-based parameter;

calculating, by said microcontroller, values of at least one EIS-based parameter based on said obtained values and additional values of the at least one impedance-based parameter;

monitoring the calculated values of said at least one EIS-based parameter for variations in said calculated values; and

adjusting, by said microcontroller, a calibration factor for said sensor based on said variations in the calculated values.

2. A method for real-time self-calibration of a sensor, said sensor including sensor electronics, a microcontroller, and at least one working electrode and one counter electrode, the method comprising:

performing, by said microcontroller, a plurality of electrochemical impedance spectroscopy (EIS) procedures for said at least one working electrode;

generating, by said microcontroller, a plurality of Nyquist plots based on respective outputs of said plurality of EIS procedures;

setting a baseline Nyquist plot length;

setting a baseline higher-frequency Nyquist slope;

monitoring, by said microcontroller, the Nyquist plot length and the higher-frequency Nyquist slope across said plurality of Nyquist plots to detect changes in said plot length and said slope; and

adjusting a calibration factor for said sensor based on said changes in the Nyquist plot length and in the Nyquist slope.

3. 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.

4. A method for determining the age of a sensor, the method comprising:

performing an electrochemical impedance spectroscopy (EIS) procedure prior to initialization of said sensor;

generating a Nyquist plot based on the output of said EIS procedure; and

based on a lower-frequency Nyquist slope, determining whether the sensor is new.

5. A method of differentiating between different glucose sensors, the method comprising:

performing an electrochemical impedance spectroscopy (EIS) procedure for said sensor;

generating a Nyquist plot based on the output of said EIS procedure; and

based on said Nyquist plot, identifying one or more of said different sensors.