SENSOR SYSTEMS, DEVICES, AND METHODS FOR CONTINUOUS GLUCOSE MONITORING

• US 20170181673A1
• Filed: 12/28/2015
• Published: 06/29/2017
• Est. Priority Date: 12/28/2015
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Engel, Taly G., Shah, Rajiv, Liu, Mike C., Tsai, Andy Y., Kim, Jaeho, Nogueira, Keith, Li, Xiaolong, Liang, Bradley C.
• Granted Patent: US 10,327,686 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2560/0204 of power management
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/1451 for interstitial fluid
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/6848 Needles
• CPC Class Codes: A61B 5/6868 Brain
• 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 5/742 using visual displays A61B5/339 takes precedence

Abstract

Electrochemical impedance spectroscopy (EIS) may be used in conjunction with continuous glucose monitoring (CGM) to enable identification of valid and reliable sensor data, as well implementation of Smart Calibration algorithms.

Claims

1. A method for first day calibration (FDC) of a glucose sensor for measuring the level of glucose in a body of a user, said sensor including physical sensor electronics, a microcontroller, and a working electrode, the method comprising:

(a) measuring, by said physical sensor electronics, the electrode current (Isig) for the working electrode;

(b) calculating, by said microcontroller, a calibration ratio (CR);

(c) comparing said calibration ratio to a threshold range; and

(d) based on said comparison, calculating a time interval until the next calibration.

2. The method of claim 1, wherein said threshold range is 4<

CR<

7.

3. The method of claim 1, wherein, if CR is outside of said threshold range, then the time interval until the next calibration is calculated to be 3 hours.

4. The method of claim 1, wherein, if CR is within said threshold range, then the time interval until the next calibration is calculated to be 6 hours.

5. A method for real-time calibration of a glucose sensor for measuring the level of glucose in a body of a user, said glucose sensor including physical sensor electronics, a microcontroller, and a working electrode, the method comprising:

(a) performing, by said microcontroller, an electrochemical impedance spectroscopy (EIS) procedure to obtain imaginary impedance values for said electrode;

(b) calculating, by said microcontroller. a reference range associated with said values of imaginary impedance, said range being a function of the difference between the current imaginary impedance value and prior imaginary impedance values;

(c) comparing the current value of imaginary impedance to the reference range; and

(d) based on said comparison, determining a time interval until the next calibration.

6. The method of claim 5, wherein said imaginary impedance values are filtered imaginary impedance values.

7. The method of claim 5, wherein said imaginary impedance values are 1 kHz imaginary impedance values.

8. The method of claim 5, wherein said reference range is calculated according to the relation range=3×

median(|x_i−

x_j|), wherein where j represents the current imaginary impedance value, and i represents the most recent 2 hours of imaginary impedance values.

9. The method of claim 8, wherein the reference range is clipped to be between 50Ω

and 100Ω

.

10. The method of claim 8, wherein, said imaginary impedance values are filtered 1 kHz imaginary impedance values.

11. The method of claim 10, wherein, if the current filtered 1 kHz imaginary value is outside of the reference range, the time interval until the next calibration is set at 6 hours from the most-recent calibration.