Blood glucose validation for a closed-loop operating mode of an insulin infusion system

• US 10,496,797 B2
• Filed: 06/04/2015
• Issued: 12/03/2019
• Est. Priority Date: 08/30/2012
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Monirabbasi, Salman, Grosman, Benyamin
• Primary Examiner(s): Lubin, Valerie
• Application Number:
  US14/731,356
• Publication Number:
  US 20160162662A1
• Time in Patent Office: 1,643 Days
• Field of Search: None
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/4839 combined with drug delivery
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: A61M 2230/005 Parameter used as control input for the apparatus
• CPC Class Codes: A61M 2230/201 Glucose concentration
• 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: G16H 10/40 for data related to laboratory analysis, e.g. patient specimen analysis
• CPC Class Codes: G16H 20/17 delivered via infusion or injection
• CPC Class Codes: G16H 40/40 for the management of medical equipment or devices, e.g. scheduling maintenance or upgrades
• CPC Class Codes: G16H 50/50 for simulation or modelling of medical disorders

Abstract

A method of controlling an insulin infusion device is presented here. The method can be implemented in a suitably configured electronic device, on an electronic storage medium, or the like. In accordance with certain embodiments, the method evaluates the operational integrity of a glucose sensor that measures sensor glucose values for a user of the insulin infusion device, and calculates a sensor integrity metric based on the evaluation. The calculated sensor integrity metric is used to adjust the aggressiveness of a closed-loop therapy algorithm that is used to control a closed-loop operating mode of the insulin infusion device. The insulin infusion device is operated in the closed-loop operating mode in accordance with the adjusted therapy setting.

Claims

1. A computer-implemented method of controlling an insulin infusion device, the method comprising:

obtaining electrochemical impedance spectroscopy (EIS) measurement data for a glucose sensor that measures sensor glucose values for a user of the insulin infusion device;

analyzing the obtained EIS measurement data as an initial check for gross sensor errors or operational deficiencies;

determining, based on the analyzing, that the obtained EIS measurement data does not indicate a bad glucose sensor;

in response to determining that the obtained EIS measurement data does not indicate a bad glucose sensor, calculating a sensor integrity metric, wherein the calculating comprises;

obtaining a meter blood glucose value from a blood glucose meter, the meter blood glucose value having a measurement time associated therewith;

obtaining a sensor glucose value from the glucose sensor, the sensor glucose value having the measurement time associated therewith;

comparing the obtained meter blood glucose value to the obtained sensor glucose value; and

calculating the sensor integrity metric as an error value that indicates a difference between the obtained meter blood glucose value and the obtained sensor glucose value;

determining that the calculated sensor integrity metric satisfies a threshold value;

in response to determining that the calculated sensor integrity metric satisfies the threshold value, adjusting aggressiveness of a closed-loop therapy algorithm used for controlling a closed-loop operating mode of the insulin infusion device, resulting in an adjusted therapy setting, wherein the adjusting adjusts the aggressiveness of the closed-loop therapy algorithm as a function of the calculated sensor integrity metric such that the aggressiveness is proportional to the calculated sensor integrity metric, wherein the aggressiveness of the closed-loop therapy algorithm relates to an amount of insulin that the insulin infusion device is allowed to deliver in one delivery cycle, which corresponds to a predetermined period of time; and

operating the insulin infusion device in the closed-loop operating mode in accordance with the adjusted therapy setting.

2. The method of claim 1, wherein:

evaluating operational integrity of the glucose sensor comprises obtaining electrical measurements corresponding to one or more operating parameters of the glucose sensor; and

the sensor integrity metric is calculated based on the obtained electrical measurements.

3. The method of claim 1, wherein:

the closed-loop therapy algorithm utilizes a maximum insulin infusion rate variable (Umax) expressed in Units/hour; and

the adjusting adjusts Umax as a function of the calculated sensor integrity metric such that Umax is adjusted downward in response to lower values of the calculated sensor integrity metric.

4. The method of claim 1, wherein:

the closed-loop therapy algorithm utilizes a proportional-integral-derivative insulin feedback (PID-IFB) control algorithm having a proportional component, an integral component, and a derivative component;

the integral component has a maximum value (Imax) expressed in Units/hour; and

the adjusting adjusts Imax as a function of the calculated sensor integrity metric such that Imax is adjusted downward in response to lower values of the calculated sensor integrity metric.

5. The method of claim 1, wherein:

the closed-loop therapy algorithm utilizes a proportional-integral-derivative insulin feedback (PID-IFB) control algorithm having an error gain variable; and

the adjusting adjusts the error gain variable as a function of the calculated sensor integrity metric such that the error gain variable is adjusted downward in response to lower values of the calculated sensor integrity metric.

6. The method of claim 1, wherein:

the closed-loop therapy algorithm utilizes a proportional-integral-derivative insulin feedback (PID-IFB) control algorithm having a derivative gain variable; and

the adjusting adjusts the derivative gain variable as a function of the calculated sensor integrity metric such that the derivative gain variable is adjusted downward in response to lower values of the calculated sensor integrity metric.

7. The method of claim 1, wherein:

the closed-loop therapy algorithm utilizes a proportional-integral-derivative insulin feedback (PID-IFB) control algorithm having an integral gain variable; and

the adjusting adjusts the integral gain variable as a function of the calculated sensor integrity metric such that the integral gain variable is adjusted downward in response to lower values of the calculated sensor integrity metric.

8. The method of claim 1, further comprising:

maintaining, at the insulin infusion device, a plurality of different user-specific closed-loop insulin delivery profiles for the user; and

selecting one of the plurality of different user-specific closed-loop insulin delivery profiles to obtain a selected profile, wherein the selecting is based on the calculated sensor integrity metric;

wherein the adjusting adjusts the aggressiveness of the closed-loop therapy algorithm in accordance with the selected profile.

9. An electronic device comprising:

a processor architecture comprising at least one processor device; and

at least one memory element associated with the processor architecture, the at least one memory element storing processor-executable instructions that, when executed by the processor architecture, perform a method of controlling an insulin infusion device for a user, the method comprising;

obtaining electrochemical impedance spectroscopy (EIS) measurement data for a glucose sensor that measures sensor glucose values for the user of the insulin infusion device;

analyzing the obtained EIS measurement data as an initial check for gross sensor errors or operational deficiencies;

determining, based on the analyzing, that the obtained EIS measurement data does not indicate a bad glucose sensor;

in response to determining that the obtained EIS measurement data does not indicate a bad glucose sensor, calculating a sensor integrity metric, wherein the calculating comprises;

obtaining a meter blood glucose value from a blood glucose meter, the meter blood glucose value having a measurement time associated therewith;

obtaining a sensor glucose value from the glucose sensor, the sensor glucose value having the measurement time associated therewith;

comparing the obtained meter blood glucose value to the obtained sensor glucose value; and

calculating the sensor integrity metric as an error value that indicates a difference between the obtained meter blood glucose value and the obtained sensor glucose value;

determining that the calculated sensor integrity metric satisfies a threshold value;

in response to determining that the calculated sensor integrity metric satisfies the threshold value, adjusting aggressiveness of a closed-loop therapy algorithm used for controlling a closed-loop operating mode of the insulin infusion device, resulting in an adjusted therapy setting, wherein the adjusting adjusts the aggressiveness of the closed-loop therapy algorithm as a function of the calculated sensor integrity metric such that the aggressiveness is proportional to the calculated sensor integrity metric, wherein the aggressiveness of the closed-loop therapy algorithm relates to an amount of insulin that the insulin infusion device is allowed to deliver in one delivery cycle, which corresponds to a predetermined period of time; and

operating the insulin infusion device in the closed-loop operating mode in accordance with the adjusted therapy setting.

10. The electronic device of claim 9, wherein:

the electronic device comprises a monitor device for the insulin infusion device; and

the monitor device and the insulin infusion device are physically distinct hardware devices.

11. The electronic device of claim 9, wherein the electronic device comprises the insulin infusion device.

12. The electronic device of claim 9, wherein:

the closed-loop therapy algorithm utilizes a maximum insulin infusion rate variable (Umax) expressed in Units/hour; and

the adjusting adjusts Umax as a function of the calculated sensor integrity metric such that Umax is adjusted downward in response to lower values of the calculated sensor integrity metric.

13. The electronic device of claim 9, wherein:

the closed-loop therapy algorithm utilizes a proportional-integral-derivative insulin feedback (PID-IFB) control algorithm having a proportional component, an integral component, and a derivative component;

the integral component has a maximum value (Imax) expressed in Units/hour; and

the adjusting adjusts Imax as a function of the calculated sensor integrity metric such that Imax is adjusted downward in response to lower values of the calculated sensor integrity metric.

14. The electronic device of claim 9, wherein:

the closed-loop therapy algorithm utilizes a proportional-integral-derivative insulin feedback (PID-IFB) control algorithm having an error gain variable; and

the adjusting adjusts the error gain variable as a function of the calculated sensor integrity metric such that the error gain variable is adjusted downward in response to lower values of the calculated sensor integrity metric.

15. The electronic device of claim 9, wherein:

the closed-loop therapy algorithm utilizes a proportional-integral-derivative insulin feedback (PID-IFB) control algorithm having a derivative gain variable; and

the adjusting adjusts the derivative gain variable as a function of the calculated sensor integrity metric such that the derivative gain variable is adjusted downward in response to lower values of the calculated sensor integrity metric.

16. The electronic device of claim 9, wherein:

the closed-loop therapy algorithm utilizes a proportional-integral-derivative insulin feedback (PID-IFB) control algorithm having an integral gain variable; and

the adjusting adjusts the integral gain variable as a function of the calculated sensor integrity metric such that the integral gain variable is adjusted downward in response to lower values of the calculated sensor integrity metric.

17. A tangible and non-transitory electronic storage medium having processor-executable instructions that, when executed by a processor architecture comprising at least one processor device, perform a method of controlling an insulin infusion device for a user, the method comprising:

obtaining electrochemical impedance spectroscopy (EIS) measurement data for a glucose sensor that measures sensor glucose values for the user of the insulin infusion device;

analyzing the obtained EIS measurement data as an initial check for gross sensor errors or operational deficiencies;

determining, based on the analyzing, that the obtained EIS measurement data does not indicate a bad glucose sensor;

in response to determining that the obtained EIS measurement data does not indicate a bad glucose sensor, calculating a sensor integrity metric, wherein the calculating comprises;

obtaining a meter blood glucose value from a blood glucose meter, the meter blood glucose value having a measurement time associated therewith;

obtaining a sensor glucose value from the glucose sensor, the sensor glucose value having the measurement time associated therewith;

comparing the obtained meter blood glucose value to the obtained sensor glucose value; and

calculating the sensor integrity metric as an error value that indicates a difference between the obtained meter blood glucose value and the obtained sensor glucose value;

determining that the calculated sensor integrity metric satisfies a threshold value;

in response to determining that the calculated sensor integrity metric satisfies the threshold value, adjusting aggressiveness of a closed-loop therapy algorithm used for controlling a closed-loop operating mode of the insulin infusion device, resulting in an adjusted therapy setting, wherein the adjusting adjusts the aggressiveness of the closed-loop therapy algorithm as a function of the calculated sensor integrity metric such that the aggressiveness is proportional to the calculated sensor integrity metric, wherein the aggressiveness of the closed-loop therapy algorithm relates to an amount of insulin that the insulin infusion device is allowed to deliver in one delivery cycle, which corresponds to a predetermined period of time; and

operating the insulin infusion device in the closed-loop operating mode in accordance with the adjusted therapy setting.