Methods, systems, and devices for calibration and optimization of glucose sensors and sensor output
A continuous glucose monitoring system may utilize externally sourced information regarding the physiological state and ambient environment of its user for externally calibrating sensor glucose measurements. Externally sourced factory calibration information may be utilized, where the information is generated by comparing metrics obtained from the data used to generate the sensor's glucose sensing algorithm to similar data obtained from each batch of sensors to be used with the algorithm in the future. The output sensor glucose value of a glucose sensor may also be estimated by analytically optimizing input sensor signals to accurately correct for changes in sensitivity, run-in time, glucose current dips, and other variable sensor wear effects. Correction actors, fusion algorithms, EIS, and advanced ASICs may be used to implement the foregoing, thereby achieving the goal of improved accuracy and reliability without the need for blood-glucose calibration, and providing a calibration-free, or near calibration-free, sensor.
1 . A method for external calibration of a sensor, the method comprising:
determining a plurality of sensor glucose (SG) values based on a plurality of sensor currents measured by the sensor;
determining a fused SG value based on the plurality of SG values;
determining a validity of a physiological calibration factor (PCF) generated based on one or more physiological measurements, a validity of an environmental calibration factor (ECF) generated based on one or more environmental measurements, or both;
determining a modification factor based at least on a valid PCF, a valid ECF, or both;
calibrating the fused SG value based on the modification factor to produce a calibrated, fused SG value;
determining a first error in the calibrated, fused SG value; and
correcting the first error in the calibrated, fused SG value.
2 . The method of claim 1 , wherein the one or more physiological measurements comprise status information associated with a user, the status information associated with the user comprising an activity level, heart rate status information, blood pressure status information, body temperature status information, or a combination thereof.
3 . The method of claim 1 , wherein the one or more environmental measurements comprise ambient temperature status, ambient pressure status, relative altitude status, ambient humidity status, or a combination thereof.
4 . The method of claim 1 , wherein the determining of the validity of the PCF or the ECF comprises determining whether a value of the PCF or the ECF falls within a lower threshold and an upper threshold.
5 . The method of claim 4 , further comprising, responsive to the value of the PCF or the ECF falling within the lower threshold and the upper threshold, producing the valid PCF or the valid ECF.
6 . The method of claim 4 , further comprising, responsive to a value of a second PCF generated based on second one or more physiological measurements or a second ECF generated based on second one or more environmental measurements not falling within the lower threshold and the upper threshold, ignoring the second PCF or the second ECF as not being valid for determining the modification factor.
7 . The method of claim 1 , wherein the PCF is generated based on the one or more physiological measurements being valid, and the ECF is generated based on the one or more environmental measurements being valid.
8 . The method of claim 1 , wherein the correcting of the first error in the calibrated, fused SG value is responsive to a determination that the first error is correctable.
9 . The method of claim 1 , further comprising:
determining a second error in the calibrated, fused SG value; and
blanking the calibrated, fused SG value responsive to a determination that the second error is not correctable.
10 . The method of claim 1 , wherein the determining of the modification factor comprises fusing a value of the PCF and a value of the ECF.
11 . The method of claim 10 , wherein the fusing of the value of the PCF and the value of the ECF comprises (i) multiplying the value of the PCF and the value of the ECF, (ii) selecting a maximum value between the value of the PCF and the value of the ECF, or (iii) averaging the value of the PCF and the value of the ECF.
12 . The method of claim 1 , further comprising applying a filter to the fused SG value prior to production of the calibrated, fused SG value.
13 . A system comprising:
a plurality of working electrodes; and
one or more processors communicatively coupled with the plurality of working electrodes and configured to:
determine a plurality of sensor glucose (SG) values based on a plurality of sensor currents measured by the plurality of working electrodes;
determine a fused SG value based on the plurality of SG values;
determine a validity of a physiological calibration factor (PCF) generated based on one or more physiological measurements, a validity of an environmental calibration factor (ECF) generated based on one or more environmental measurements, or both;
determine a modification factor based at least on a valid PCF, a valid ECF, or both;
calibrate the fused SG value based on the modification factor to produce a calibrated, fused SG value;
determine a first error in the calibrated, fused SG value; and
correct the first error in the calibrated, fused SG value.
14 . The system of claim 13 , wherein the one or more processors are further configured to, responsive to a determination that a value of the PCF or the ECF falls within a lower threshold and an upper threshold, produce the valid PCF or the valid ECF.
15 . The system of claim 13 , wherein the one or more processors are further configured to, responsive to a value of a second PCF generated based on second one or more physiological measurements or a second ECF generated based on second one or more environmental measurements not falling within the lower threshold and the upper threshold, discard the second PCF or the second ECF.
16 . The system of claim 13 , wherein the PCF is generated based on the one or more physiological measurements being determined to be valid, and the ECF is generated based on the one or more environmental measurements being determined to be valid.
17 . The system of claim 13 , wherein:
the determination of the modification factor comprises a fusion of a value of the PCF and a value of the ECF; and
the fusion comprises (i) multiplication of the value of the PCF and the value of the ECF, (ii) selection of a maximum value between the value of the PCF and the value of the ECF, or (iii) average of the value of the PCF and the value of the ECF.
18 . A method for external calibration of a sensor, the method comprising:
determining a plurality of sensor glucose (SG) values based on a plurality of sensor currents measured by the sensor;
determining a fused SG value based on the plurality of SG values;
determining a modification factor based at least on a physiological calibration factor (PCF) generated based on status information associated with a user, the status information comprising an activity level, a heart rate, a blood pressure, a body temperature, or a combination thereof;
calibrating the fused SG value based on the modification factor to produce a calibrated, fused SG value;
determining a first error in the calibrated, fused SG value; and
correcting the first error in the calibrated, fused SG value.
19 . The method of claim 18 , wherein the status information comprises the body temperature, and the PCF is generated based on the body temperature.
20 . The method of claim 19 , wherein:
the PCF comprises a factor for the body temperature; and
the method further comprises generating the factor for the body temperature based at least on one or more physiological measurements meeting a threshold range.