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

• US 9,408,567 B2
• Filed: 02/27/2013
• Issued: 08/09/2016
• Est. Priority Date: 06/08/2012
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Wang, Jenn-Hann Larry, Miller, Michael E., Gautham, Raghavendhar, Li, Yiwen, Shah, Rajiv
• Primary Examiner(s): Vazquez, Arleen M
• Assistant Examiner(s): ALLGOOD, ALESA M
• Application Number:
  US13/778,391
• Publication Number:
  US 20130328572A1
• Time in Patent Office: 1,259 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/0214 Capacitive electrodes
• CPC Class Codes: A61B 2562/04 Arrangements of multiple sensors of the same type
• 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 5/14503 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 Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 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 5/4839 combined with drug delivery
• CPC Class Codes: A61B 5/6849 in combination with a needle set
• CPC Class Codes: A61B 5/6852 Catheters
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• 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 5/7242 using integration
• CPC Class Codes: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B
• 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: A61M 5/1723 : using feedback of body parameters, e.g. blood-sugar, pressure measurement of body parameters A61B5/00
• CPC Class Codes: G01N 27/026 : Dielectric impedance spectroscopy electrochemical impedance spectroscopy for measuring corrosion G01N17/02
• CPC Class Codes: G01N 27/028 : Circuits therefor measuring impedance per se G01R27/02
• CPC Class Codes: G01N 27/416 : Systems G01N27/27 takes precedence
• CPC Class Codes: G01N 27/4163 : checking the operation of, or calibrating, the measuring apparatus G01N27/3274, G01N27/4175 and G01N33/0006 take precedence
• CPC Class Codes: G01N 33/49 : Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80
• CPC Class Codes: G01N 33/66 : involving blood sugars, e.g. galactose
• CPC Class Codes: G01N 33/96 : involving blood or serum control standard
• CPC Class Codes: G01R 35/00 : Testing or calibrating of apparatus covered by the other groups of this subclass
• CPC Class Codes: G01R 35/005 : Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

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.

Claims

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

(a) performing a first electrochemical impedance spectroscopy (EIS) procedure to generate a first set of impedance-related data for the at least one working electrode;

(b) after a predetermined time interval, performing a second EIS procedure to generate a second set of impedance-related data for the at least one electrode; and

(c) based on the first and second sets of impedance-related data, deteimining whether the sensor is functioning normally,

wherein each of the first and second sets of impedance-related data includes data for at least one impedance-related parameter that is substantially glucose-independent, wherein said at least one substantially glucose-independent impedance-related parameter is imaginary impedance, and wherein the imaginary impedance is measured at a frequency of at least 1 kHz.

2. The method of claim 1, wherein each of the first and second sets of impedance-related data includes data for at least one of real impedance, imaginary impedance, impedance magnitude, and phase angle.

3. The method of claim 1, wherein the determination as to whether the sensor is functioning normally is made based only on said data for the at least one impedance-related parameter that is substantially glucose-independent.

4. The method of claim 1, wherein the sensor includes between two and five independent working electrodes.

5. The method of claim 1, wherein each of the first and second EIS procedures is performed for a respective range of frequencies.

6. The method of claim 5, wherein the range of frequencies for the first EIS procedure is different from the range of frequencies for the second EIS procedure.

7. The method of claim 1, wherein said at least one substantially glucose-independent impedance-related parameter is real impedance.

8. The method of claim 7, wherein the real impedance is measured at a frequency of at least about 1 kHz.

9. The method of claim 1, wherein each of the first and second sets of impedance-related data includes values for impedance-related parameters, and wherein step (c) comprises comparing the value of at least one impedance-related parameter from the first set of impedance-related data to the value of the same parameter from the second set of impedance-related data.

10. The method of claim 9, wherein the at least one impedance-related parameter is real impedance.

11. The method of claim 9, wherein the at least one impedance-related parameter is imaginary impedance.

12. The method of claim 9, wherein the at least one impedance-related parameter is phase angle.

13. The method of claim 1, wherein, a predetermined time period after the second EIS procedure has been performed and subsequent to step (c), a third EIS procedure is performed to generate a third set of impedance-related data for the at least one electrode, and wherein a determination is made as to whether the sensor is functioning normally based on the second and third sets of impedance-related data.

14. The method of claim 13, wherein the predetermined time period is different from said predetermined time interval.

15. The method of claim 13, wherein the second and third EIS procedures are performed for the same range of frequencies.

16. The method of claim 13, wherein the second EIS procedure is performed for a range of frequencies that is different than the range of frequencies for the third EIS procedure.

17. The method of claim 13, wherein each of the second and third sets of impedance-related data includes values for impedance-related parameters, and wherein the determination as to whether the sensor is functioning normally is made by comparing the value of at least one impedance-related parameter from the second set of impedance-related data to the value of the same parameter from the third set of impedance-related data.