Sensor model supervisor for a closed-loop insulin infusion system

• US 10,130,767 B2
• Filed: 04/26/2016
• Issued: 11/20/2018
• Est. Priority Date: 08/30/2012
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Grosman, Benyamin, Wu, Di, Roy, Anirban, Parikh, Neha J.
• Primary Examiner(s): Durant, Jonathan
• Application Number:
  US15/138,540
• Publication Number:
  US 20160256629A1
• Time in Patent Office: 938 Days
• CPC Class Codes: A61B 5/14503 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors A61B5/1459, A61B5/1464, A61B5/1473, A61B5/1482, A61B5/14865 take precedence
• 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: A61B 5/746 Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms alarms per se G08B
• CPC Class Codes: A61M 2005/14208 with a programmable infusion control system, characterised by the infusion program
• CPC Class Codes: A61M 2205/52 with memories providing a history of measured variating parameters of apparatus or patient
• 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 5/14244 adapted to be carried by the patient, e.g. portable on the body
• 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 20/17 delivered via infusion or injection
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass

Abstract

An insulin infusion device includes a processor architecture, and a memory element that stores executable instructions to perform a method of controlling delivery of insulin to a user. The method operates the device in a closed-loop mode to deliver insulin, obtains patient-specific parameters for a current time sample, and estimates a plasma insulin value and a blood glucose value for the user based on at least some of the patient-specific parameters. The estimating is also based on a previously estimated plasma insulin value obtained for a previous time sample, and a previously estimated blood glucose value obtained for the previous time sample. A predicted sensor glucose value is generated for the current time sample, and the closed-loop mode or a safe basal mode is selected for controlling operation of the insulin infusion device in accordance with the selected mode.

Claims

1. An insulin infusion device comprising:

a reservoir for insulin to be delivered from the insulin infusion device to a body of a user;

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 delivery of insulin from the insulin reservoir to the body of the user, the method comprising;

automatically operating the insulin infusion device in a closed-loop mode to deliver insulin from the insulin reservoir to the body of the user;

obtaining, for a current time sample, a patient-specific insulin gain value (KI), a patient-specific fasting insulin basal rate value (IBasal), a patient-specific fasting blood glucose value (SGBase), a meter blood glucose value (MBG), and an insulin delivered value (Iin) that represents an amount of insulin delivered since a preceding time sample;

estimating, for the current time sample, an estimated plasma insulin value (Ip_t) and an estimated blood glucose value (G_t) for the user, the estimating based on at least some of the values of KI, IBasal, SGBase, MBG, and (Iin), and the estimating further based on a previously estimated plasma insulin value obtained for a previous time sample (Ip_t-1), and a previously estimated blood glucose value obtained for the previous time sample (G_t-1);

generating, for the current time sample, a predicted sensor glucose value (SGp) for the user, the generating based on the values of G_t and SGBase for the current time sample;

selecting between the closed-loop mode, a first safe basal mode, or a second safe basal mode, based on at least some of the values of SGp, SG, Ip_t, and G_t for the current time sample, the first safe basal mode representing a higher basal rate of insulin relative to the second safe basal mode; and

controlling operation of the insulin infusion device to deliver insulin to the body of the user in accordance with the selected mode;

wherein the closed-loop mode is selected in response to detecting a sensor over-reading condition, the first safe basal mode is selected only in response to detecting a sensor under-reading condition, and the second safe basal mode is selected only in response to detecting a sensor under-reading condition; and

wherein the second safe basal mode, rather than the first safe basal mode, is selected when;

a temporary target glucose value is raised to a threshold set point value;

or SGp is below a specified low glucose threshold;

or Ip_t is above a specified typical basal rate.

2. The insulin infusion device of claim 1, wherein the method performed by the processor architecture further comprises:

calculating a difference (SGpThDiff) between the predicted sensor glucose value (SGp) and a low threshold value in accordance with the expression;

SGpThDiff=SGp−

Low Threshold, wherein the second safe basal mode is selected when SGpThDiff<

0.

3. The insulin infusion device of claim 1, wherein the method performed by the processor architecture further comprises:

collecting, during a predetermined period of time, MBG values, sensor glucose (SG) values from a continuous glucose sensor, meal-related data, insulin history data, and total daily insulin data associated with the user; and

calculating, for each predetermined period of time, the values of KI, IBasal, and SGBase, the calculating based on at least some of the collected MBG values, SG values, meal-related data, insulin history data, and total daily insulin data.

4. The insulin infusion device of claim 3, wherein the method performed by the processor architecture further comprises:

searching the SG values for a fasting glucose value for the user, wherein the values of IBasal and SGBase are calculated based on an identified fasting glucose value.

5. The insulin infusion device of claim 1, wherein:

IBasal represents an estimated basal rate needed to maintain the fasting blood glucose value (SGBase) for the user; and

SGBase represents an estimated fasting blood glucose value for the user when insulin is delivered at the fasting insulin basal rate value (IBasal).

6. The insulin infusion device of claim 1, wherein the method performed by the processor architecture further comprises:

resetting the value of G_t-1 with each new value of MBG in accordance with the expression;

G_t-1=MBG SGBase.

7. The insulin infusion device of claim 1, wherein the method performed by the processor architecture further comprises:

processing at least some of the values of SGp, SG, Ip_t, and G_t for the current time sample to detect the sensor under-reading condition.

8. An insulin infusion system comprising:

a continuous glucose sensor that generates sensor data indicative of sensor glucose values (SG) for a user; and

an insulin infusion device coupled to receive the sensor data generated by the continuous glucose sensor, the insulin infusion device comprising an insulin reservoir for insulin to be delivered from the insulin infusion device to the user, a processor architecture comprising at least one processor device and further comprising 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, cause the insulin infusion device to perform a method comprising;

automatically operating the insulin infusion device in a closed-loop mode to deliver insulin from the insulin reservoir to the body of the user;

obtaining, for a current time sample, a patient-specific insulin gain value (KI), a patient-specific fasting insulin basal rate value (IBasal), a patient-specific fasting blood glucose value (SGBase), a meter blood glucose value (MBG), and an insulin delivered value (Iin) that represents an amount of insulin delivered since a preceding time sample;

estimating, for the current time sample, an estimated plasma insulin value (Ip_t) and an estimated blood glucose value (G_t) for the user, the estimating based on at least some of the values of KI, IBasal, SGBase, MBG, and (Iin), and the estimating further based on a previously estimated plasma insulin value obtained for a previous time sample (Ip_t-1), and a previously estimated blood glucose value obtained for the previous time sample (G_t-1);

generating, for the current time sample, a predicted sensor glucose value (SGp) for the user, the generating based on the values of G_t and SGBase for the current time sample;

selecting between the closed-loop mode, a first safe basal mode, or a second safe basal mode, based on at least some of the values of SGp, SG, Ip_t, and G_t for the current time sample, the first safe basal mode representing a higher basal rate of insulin relative to the second safe basal mode; and

controlling operation of the insulin infusion device to deliver insulin to the body of the user in accordance with the selected mode;

wherein the closed-loop mode is selected in response to detecting a sensor over-reading condition, the first safe basal mode is selected only in response to detecting a sensor under-reading condition, and the second safe basal mode is selected only in response to detecting a sensor under-reading condition; and

wherein the second safe basal mode, rather than the first safe basal mode, is selected when;

a temporary target glucose value is raised to a threshold set point value;

or SGp is below a specified low glucose threshold;

or Ip_t is above a specified typical basal rate.

9. The system of claim 8, wherein the method performed by the processor architecture further comprises:

collecting, during a predetermined period of time, MBG values, sensor glucose (SG) values from a continuous glucose sensor, meal-related data, insulin history data, and total daily insulin data associated with the user; and

calculating, for each predetermined period of time, the values of KI, IBasal, and SGBase, the calculating based on at least some of the collected MBG values, SG values, meal-related data, insulin history data, and total daily insulin data.

10. The system of claim 8, wherein:

IBasal represents an estimated basal rate needed to maintain the fasting blood glucose value (SGBase) for the user; and

SGBase represents an estimated fasting blood glucose value for the user when insulin is delivered at the fasting insulin basal rate value (IBasal).

11. The system of claim 8, wherein the method performed by the processor architecture further comprises:

resetting the value of G_t-1 with each new value of MBG in accordance with the expression;

G_t-1=MBG−

SGBase.

12. The system of claim 8, wherein the method performed by the processor architecture further comprises:

processing at least some of the values of SGp, SG, Ip_t, and G_t for the current time sample to detect the sensor under-reading condition.

13. A method of operating an insulin infusion device to regulate delivery of insulin to a body of a user, the method comprising:

obtaining, from a continuous glucose sensor, sensor glucose (SG) values for the user;

calculating, from the obtained SG values, a patient-specific fasting insulin basal rate value (IBasal) and a patient-specific fasting blood glucose value (SGBase), wherein IBasal represents an estimated basal rate needed to maintain SGBase for the user, and wherein SGBase represents an estimated fasting blood glucose value for the user when insulin is delivered at IBasal;

using the values of IBasal and SGBase to calculate, for a current time sample, an estimated plasma insulin value (I p t) and an estimated blood glucose value (G_t) for the user; and

using the values of Ip_t, G_t, SGBase, and SG to select between a closed-loop mode of operation, a safe nominal basal mode of operation, or a safe low basal mode of operation for the insulin infusion device the safe nominal basal mode of operation representing a higher basal rate of insulin relative to the safe low basal mode of operation; and

automatically operating the insulin infusion device to control delivery of insulin from the insulin infusion device to the body of the user, in accordance with the selected mode of operation;

wherein the closed-loop mode of operation is selected in response to detecting a sensor over-reading condition, the safe nominal basal mode of operation is selected only in response to detecting a sensor under-reading condition, and the safe low basal mode of operation is selected only in response to detecting a sensor under-reading condition; and

wherein the safe low basal mode of operation, rather than the safe nominal basal mode of operation, is selected when;

a temporary target glucose value is raised to a threshold set point value;

or a predicted sensor glucose value (SGp) is below a specified low glucose threshold;

or Ip_t is above a specified typical basal rate.

14. The method of claim 13, further comprising:

processing at least some of the values of Ip_t, G_t, SGBase, and SG for the current time sample to detect the sensor under-reading condition.