CALIBRATION FACTOR ADJUSTMENTS FOR INFUSION DEVICES AND RELATED METHODS AND SYSTEMS

• US 20150331418A1
• Filed: 05/19/2014
• Published: 11/19/2015
• Est. Priority Date: 05/19/2014
• Status: Active Application

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Nogueira, Keith, Agrawal, Pratik, Kannard, Brian T., Li, Xiaolong, Liang, Bradley C., Shah, Rajiv, Zhong, Yuxiang
• Granted Patent: US 10,274,349 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61M 2205/70 with testing or calibration facilities
• CPC Class Codes: A61M 2205/702 automatically during use
• CPC Class Codes: A61M 2230/201 Glucose concentration
• CPC Class Codes: A61M 5/14244 adapted to be carried by the patient, e.g. portable on the body
• CPC Class Codes: A61M 5/1452 pressurised by means of pistons
• CPC Class Codes: A61M 5/1723 using feedback of body parameters, e.g. blood-sugar, pressure measurement of body parameters A61B5/00
• CPC Class Codes: G01D 18/00 Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
• CPC Class Codes: G05B 23/00 Testing or monitoring of control systems or parts thereof monitoring of programme-control systems G05B19/048, G05B19/406

Abstract

Infusion systems, infusion devices, and related operating methods are provided. An exemplary method of operating an infusion device capable of delivering fluid to a user involves obtaining one or more uncalibrated measurements indicative of the physiological condition, obtaining one or more reference measurements of the physiological condition, determining a raw calibration factor based on a relationship between the one or more uncalibrated measurements and the one or more reference measurements corresponding to the respective uncalibrated measurements of the one or more uncalibrated measurements, and determining an adjusted calibration factor based at least in part on an expected calibration factor and the raw calibration factor, wherein operation of the infusion device to deliver the fluid is influenced by the adjusted calibration factor.

Claims

1. A method of operating an infusion device operable to deliver fluid to a user, the fluid influencing a physiological condition of the user, the method comprising:

obtaining one or more uncalibrated measurements indicative of the physiological condition;

obtaining one or more reference measurements of the physiological condition, each respective reference measurement of the one or more reference measurements corresponding to a respective uncalibrated measurement of the one or more uncalibrated measurements;

determining a raw calibration factor based on a relationship between the one or more uncalibrated measurements and the one or more reference measurements corresponding to the respective uncalibrated measurements of the one or more uncalibrated measurements; and

determining an adjusted calibration factor based at least in part on an expected calibration factor and the raw calibration factor, wherein operation of the infusion device to deliver the fluid is influenced by the adjusted calibration factor.

2. The method of claim 1, wherein determining the adjusted calibration factor comprises determining the adjusted calibration factor as a weighted sum of the raw calibration factor and the expected calibration factor.

3. The method of claim 2, wherein operating the infusion device using the adjusted calibration factor comprises:

converting a subsequent uncalibrated measurement into a calibrated measurement value for the physiological condition using the adjusted calibration factor; and

determining a delivery command for operating a motor of the infusion device based on a relationship between the calibrated measurement value and a target value for the physiological condition.

4. The method of claim 1, wherein determining the raw calibration factor comprises:

determining a first sum of products of each respective uncalibrated measurement of the one or more uncalibrated measurements, the respective reference measurement corresponding to the respective uncalibrated measurement, and one or more weighting factors associated therewith;

determining a second sum of products of a square of each respective uncalibrated measurement of the one or more uncalibrated measurements and the one or more weighting factors; and

determining the raw calibration factor as a ratio of the first sum to the second sum.

5. The method of claim 4, further comprising determining a first weighting factor of the one or more weighting factors as a function of the respective reference measurement corresponding to the respective uncalibrated measurement.

6. The method of claim 4, wherein determining the adjusted calibration factor comprises determining the adjusted calibration factor as a weighted sum of the raw calibration factor and the expected calibration factor.

7. The method of claim 1, wherein determining the adjusted calibration factor comprises determining the adjusted calibration factor only when the raw calibration factor is within a range of values encompassing the expected calibration factor.

8. The method of claim 1, wherein determining the adjusted calibration factor comprises determining the adjusted calibration factor as a function of the raw calibration factor and an elapsed time, wherein the function is configured to adjust the adjusted calibration factor from the raw calibration factor towards the expected calibration factor as the elapsed time increases.

9. The method of claim 1, further comprising:

determining the expected calibration factor based at least in part on a current uncalibrated measurement indicative of the physiological condition and a recent reference measurement one or more reference measurements, wherein;

determining the adjusted calibration factor comprises determining the adjusted calibration factor as a weighted sum of the expected calibration factor and a preceding calibration factor based at least in part on a derivative metric associated with the current uncalibrated measurement prior to obtaining a recent uncalibrated measurement of the one or more uncalibrated measurements that corresponds to the recent reference measurement.

10. The method of claim 1, wherein determining the adjusted calibration factor comprises dynamically adjusting the raw calibration factor towards the expected calibration factor.

11. The method of claim 10, wherein:

the one or more uncalibrated measurements are based on output signals from a sensing element influenced by the physiological condition; and

dynamically adjusting the raw calibration factor comprises dynamically adjusting the raw calibration factor in response to identifying a recent uncalibrated measurement of the one or more uncalibrated measurements that corresponds to a recent reference measurement of the one or more reference measurements was obtained within a threshold amount of time of initialization of the sensing element.

12. The method of claim 10, wherein:

the one or more uncalibrated measurements are based on output signals from a sensing element influenced by the physiological condition; and

dynamically adjusting the raw calibration factor comprises dynamically adjusting the raw calibration factor in response to identifying a low current condition for the sensing element based on a relationship between a recent uncalibrated measurement of the one or more uncalibrated measurements that corresponds to a recent reference measurement of the one or more reference measurements.

13. The method of claim 1, further comprising identifying an error condition based at least in part on a recent reference measurement of the one or more reference measurements and a current uncalibrated measurement prior to obtaining an uncalibrated measurement that corresponds to the recent reference measurement.

14. A computer-readable medium having computer-executable instructions stored thereon that, when executed by a control module, cause the control module to perform the method of claim 1.

15. An infusion system comprising:

a sensing arrangement including a sensing element to provide output signals influenced by a physiological condition in a body of a user, the sensing arrangement determining uncalibrated measurements of the physiological condition based at least in part on the output signals; and

an infusion device comprising;

a motor operable to deliver fluid to the body of the user, the fluid influencing the physiological condition; and

a control system to determine a delivery command for operating the motor based at least in part on a first uncalibrated measurement of the uncalibrated measurements and a calibration factor for converting the uncalibrated measurements, wherein;

the calibration factor is determined based at least in part on an expected calibration factor and a raw calibration factor calculated based on one or more reference measurements for the physiological condition and one or more of the uncalibrated measurements; and

each of the one or more of the uncalibrated measurements is paired with a respective reference measurement of the one or more reference measurements.

16. The infusion system of claim 15, further comprising a meter for obtaining the one or more reference measurements from the body of the user.

17. The infusion system of claim 15, wherein the calibration factor is determined as a weighted sum of the expected calibration factor and the raw calibration factor.

18. The infusion system of claim 17, wherein:

the raw calibration factor comprises a ratio of a first weighted sum to a second weighted sum;

the first weighted sum comprises a sum of products of each respective uncalibrated measurement of the one or more of the uncalibrated measurements, the respective reference measurement paired with the respective uncalibrated measurement, and one or more weighting factors associated with the respective pairing;

the second weighted sum comprises a sum of products of a square of each respective uncalibrated measurement of the one or more uncalibrated measurements and the one or more weighting factors; and

a first weighting factor of the one or more weighting factors is calculated as a function of the respective reference measurement of the respective pairing.

19. The infusion system of claim 15, wherein the calibration factor is dynamically adjusted from the raw calibration factor towards the expected calibration factor.

20. A device comprising:

a sensing element to provide one or more signals influenced by a physiological condition of a user; and

a control module coupled to the sensing element to;

determine one or more uncalibrated measurements indicative of the physiological condition based on the one or more signals;

obtain one or more reference measurements of the physiological condition, each respective reference measurement of the one or more reference measurements corresponding to a respective uncalibrated measurement of the one or more uncalibrated measurements;

determine a raw calibration factor based on a relationship between the one or more uncalibrated measurements and the one or more reference measurements corresponding to the respective uncalibrated measurements of the one or more uncalibrated measurements; and

determine an adjusted calibration factor based at least in part on an expected calibration factor and the raw calibration factor, wherein delivery of a fluid influencing the physiological condition is influenced by the adjusted calibration factor.