Systems and methods for calibrating physiological characteristic sensors

• US 8,306,766 B2
• Filed: 06/30/2010
• Issued: 11/06/2012
• Est. Priority Date: 10/31/2007
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Mueller, John C. Jr., Keenan, Desmond Barry, Wang, Lu, Mastrototaro, John J.
• Primary Examiner(s): WACHSMAN, HAL D
• Application Number:
  US12/827,851
• Publication Number:
  US 20100268477A1
• Time in Patent Office: 860 Days
• Field of Search: 702/85, 702/23, 702/32, 702/104
• US Class Current: 702/85
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors

Abstract

A method of calibrating glucose monitor data includes collecting the glucose monitor data over a period of time at predetermined intervals, obtaining reference glucose values from a reference source that temporally correspond with the glucose monitor data obtained at the predetermined intervals, calculating the calibration characteristics using the reference glucose values and corresponding glucose monitor data to regress the obtained glucose monitor data, and calibrating the obtained glucose monitor data using the calibration characteristics. In additional embodiments, calculation of the calibration characteristics includes linear regression and, in particular embodiments, least squares linear regression. Alternatively, calculation of the calibration characteristics includes non-linear regression. Data integrity may be verified and the data may be filtered.

Claims

1. A system to calibrate a glucose sensor, comprising:

a glucose sensor monitor associated with the glucose sensor having

a memory for storing program instructions and a plurality of measured glucose concentrations, the stored measured glucose concentrations received from the glucose sensor,

a processor being integrated into the glucose sensor monitor, the processor executing the stored program instructions to determine

a rate of change of measured blood glucose concentration and

a calibration factor

the calibration factor being based on

a calibration reference value,

a temporally correlated data value, the temporally correlated data value being selected from the plurality of measured glucose concentrations and further being determined by correlating one of the measured glucose concentrations to a threshold parameter such that a first time delay is used if the glucose concentration is less than the threshold parameter and a second time delay is used if the glucose concentration is equal to or exceeds the threshold parameter, and

if the rate of change of measured blood glucose concentration exceeds a threshold limit, a predetermined multiplier is applied to the calibration factor,

wherein the calibration factor is stored in the memory, the calibration factor further being used to convert the plurality of measured glucose concentrations to a plurality of calculated glucose concentrations.

2. The system in claim 1, wherein the measured glucose concentrations are determined by sampling glucose concentrations at a predetermined rate from the glucose sensor and deriving at least two intermediate data values from the sampled glucose concentrations at a predetermined memory storage rate.

3. The system in claim 2, wherein the predetermined memory storage rate is once every five minutes.

4. The system in claim 1, wherein the calibration reference value is determined using a separate characteristic measuring device.

5. The system in claim 1, wherein the second time delay is selected from a plurality of predetermined time delays based on the rate of change in the glucose concentration, each of the plurality of predetermined time delays corresponding to a different predetermined rate of change in glucose concentration.