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

• US 9,632,060 B2
• Filed: 02/27/2013
• Issued: 04/25/2017
• Est. Priority Date: 06/08/2012
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Shah, Rajiv, Mucic, Robert C., de Barros, Genival D., Callirgos, Carlos A., Sirigiri, Manjunath, Brinson, Joseph Paul
• Primary Examiner(s): Hollington, Jermele M
• Assistant Examiner(s): Pothen, Feba
• Application Number:
  US13/778,473
• Publication Number:
  US 20130328578A1
• Time in Patent Office: 1,518 Days
• 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 testing the surface area characteristics of an electroplated electrode of an electrochemical glucose sensor, comprising:

performing an electrochemical impedance spectroscopy (EIS) procedure to obtain a value of an impedance-related parameter for said glucose sensor electrode, wherein the impedance-related parameter is imaginary impedance;

correlating said obtained value to said glucose sensor electrode'"'"'s electrochemical surface area;

based on said correlation, determining lower and upper threshold values for said value of the imaginary impedance; and

determining whether the glucose sensor electrode is acceptable for measuring glucose in a body of a subject, wherein said determination is made based on whether said value of the imaginary impedance falls within said lower and upper threshold values and is indicative of a number of low start-up events for the glucose sensor that is below a low start-up event threshold.

2. The method of claim 1, wherein the electrode is tested in a sulfuric acid solution.

3. The method of claim 1, wherein the electrode is tested in a Phosphate Buffered saline Solution with zero mg/ml of Glucose (PBS-0).

4. The method of claim 1, wherein said EIS procedure is performed for a range of frequencies between about 5 Hz and about 100 Hz.

5. The method of claim 1, wherein said value of the imaginary impedance is obtained at a frequency of 10 Hz.

6. A method of testing the surface area characteristics of an electroplated electrode of an electrochemical glucose sensor, comprising:

performing an electrochemical impedance spectroscopy (EIS) procedure to obtain a value of an impedance-related parameter for said glucose sensor electrode, wherein the impedance-related parameter is imaginary impedance;

correlating said obtained value to said glucose sensor electrode'"'"'s electrochemical surface area;

based on said correlation, determining lower and upper threshold values for said value of the imaginary impedance; and

determining whether the glucose sensor electrode is acceptable for measuring glucose in a body of a subject, wherein said determination is made based on whether said value of the imaginary impedance falls within said lower and upper threshold values and is indicative of a level of glucose sensor responsiveness that is above a sensor responsiveness threshold.

7. The method of claim 6, wherein the electrode is tested in a sulfuric acid solution.

8. The method of claim 6, wherein the electrode is tested in a Phosphate Buffered saline Solution with zero mg/ml of Glucose (PBS-0).

9. The method of claim 6, wherein said EIS procedure is performed for a range of frequencies between about 5 Hz and about 100 Hz.

10. The method of claim 6, wherein said value of the imaginary impedance is obtained at a frequency of 10 Hz.