In-vivo electrochemical impedance spectroscopy (EIS)-based calibration
First Claim
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1. A method for real-time self-calibration of a glucose sensor, said glucose sensor including sensor electronics, a microcontroller, and at least one working electrode, the method comprising:
- inserting said glucose sensor into subcutaneous tissue of a user;
periodically measuring, by said sensor electronics, a value of the electrode current (Isig) for the working electrode, wherein said Isig is the sum of a Faradaic current component and a non-Faradaic current component;
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;
adjusting, by said microcontroller, a calibration factor for said glucose sensor, based on said variations in the calculated values and on only the Faradaic current component of the Isig, to obtain an adjusted calibration factor; and
using, by said microcontroller, said adjusted calibration factor to calculate a level of glucose in said user'"'"'s body,wherein the calibration factor is adjusted in accordance with the relation CF(t)=CFreference−
m(Rreference−
R(t)), wherein CF(t) is the calibration factor at time t, CFreference is a reference value for the calibration factor, Rreference is the value of membrane resistance when CF=CFreference, R(t) is membrane resistance at time t, and m is the gradient of a correlation between CF and R.
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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.
106 Citations
15 Claims
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1. A method for real-time self-calibration of a glucose sensor, said glucose sensor including sensor electronics, a microcontroller, and at least one working electrode, the method comprising:
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inserting said glucose sensor into subcutaneous tissue of a user; periodically measuring, by said sensor electronics, a value of the electrode current (Isig) for the working electrode, wherein said Isig is the sum of a Faradaic current component and a non-Faradaic current component; 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; adjusting, by said microcontroller, a calibration factor for said glucose sensor, based on said variations in the calculated values and on only the Faradaic current component of the Isig, to obtain an adjusted calibration factor; and using, by said microcontroller, said adjusted calibration factor to calculate a level of glucose in said user'"'"'s body, wherein the calibration factor is adjusted in accordance with the relation CF(t)=CFreference−
m(Rreference−
R(t)), wherein CF(t) is the calibration factor at time t, CFreference is a reference value for the calibration factor, Rreference is the value of membrane resistance when CF=CFreference, R(t) is membrane resistance at time t, and m is the gradient of a correlation between CF and R. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for real-time self-calibration of a glucose sensor, said glucose sensor including sensor electronics, a microcontroller, and at least one working electrode, the method comprising:
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inserting said glucose sensor into subcutaneous tissue of a user; periodically measuring, by said sensor electronics, a value of the electrode current (Isig) for the working electrode, wherein said Isig is the sum of a Faradaic current component and a non-Faradaic current component; 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; adjusting, by said microcontroller, a calibration factor for said glucose sensor, based on said variations in the calculated values and on only the Faradaic current component of the Isig, to obtain an adjusted calibration factor; and using, by said microcontroller, said adjusted calibration factor to calculate a level of glucose in said user'"'"'s body, wherein the calibration factor is adjusted in accordance with the relation CF(t)/CFreference=−
m(R(t)/Rreference), wherein CF(t) is the calibration factor at time t, CFreference is a reference value for the calibration factor, Rreference is the value of membrane resistance when CF=CFreference, R(t) is membrane resistance at time t, and m is the gradient of a correlation between CF and R.
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Specification