Sensor signal processing with kalman-based calibration

A non-transitory computer-readable storage medium with instructions stored thereon for calibrating an analyte sensor inserted into tissue of a subject, wherein a processor is to execute the instructions to:

• intermittently receive, from an analyte sensor placed in interstitial fluid of the subject, current readings yITr(ti) at times ti reflective of an interstitial level of the analyte;
• intermittently receive capillary blood analyte measurements uB(ts) at times ts, wherein the capillary blood analyte measurements are received less frequently than the current readings;
• when an initial measurement of the capillary blood analyte measurements is available to calibrate the current readings, noise filtering the current readings to provide noise filtered current readings yI(ti);
• when a subsequent measurement of the capillary blood analyte measurements is not yet available, estimate a concentration of the analyte in the interstitial fluid as ûI(ti)={yI(ti)−âI2−âI3·Δt}/âI1, where Δt is a time since an insertion of the analyte sensor, and âI1, âI2 and âI3 are interstitial calibration parameters;
• when the subsequent measurement of the capillary blood analyte measurements is available:
• deconvolute the noise filtered current readings yI(ti) to obtain a hypothetical analyte sensor current yB(ts);
• based on the hypothetical analyte sensor current yB(ts) and a prior set of blood calibration parameters, obtain updated blood calibration parameters;
• update the interstitial calibration parameters âI1, âI2 and âI3 based on the updated blood calibration parameters;
• and
• estimate the concentration of the analyte based on the updated interstitial calibration parameters;
• and
• send one or more instructions to an insulin delivery system based on the estimated concentration of the analyte.

A system for estimating an amount of an analyte in a subject, comprising an analyte sensor and a processor in communication with the analyte sensor, wherein the processor is to:

• receive from the analyte sensor a current reflective of an interstitial level of the analyte in the subject;
• noise filter the current to obtain a noise filtered current;
• deconvolute the noise filtered current via a sequential Kalman filter to obtain a predicted blood analyte sensor current;
• estimate blood calibration parameters based on the predicted blood analyte sensor current via a Kalman filter that uses the predicted blood analyte sensor current as a measurement variable, wherein to estimate the blood calibration parameters, the processor is to x initialize a Kalman filter based on an initial blood analyte calibration parameter state estimate and an initial blood analyte calibration parameter covariance;
• update interstitial calibration parameters based on the estimated blood calibration parameters;
• estimate a concentration of the analyte based on the updated interstitial calibration parameters;
• and
• send one or more instructions to an insulin delivery system based on the estimated concentration of the analyte.