Safeguarding measures for a closed-loop insulin infusion system

• US 10,758,674 B2
• Filed: 11/17/2016
• Issued: 09/01/2020
• Est. Priority Date: 08/30/2012
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Keenan, Desmond Barry, Mastrototaro, John J., Grosman, Benyamin, Parikh, Neha J., Roy, Anirban
• Primary Examiner(s): Wise, Olivia M.
• Application Number:
  US15/354,451
• Publication Number:
  US 20170119968A1
• Time in Patent Office: 1,384 Days
• Field of Search: None
• 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 2205/18 with alarm
• CPC Class Codes: A61M 2205/502 User interfaces, e.g. screens or keyboards
• CPC Class Codes: A61M 2205/52 with memories providing a history of measured variating parameters of apparatus or patient
• CPC Class Codes: A61M 2205/582 by tactile feedback
• CPC Class Codes: A61M 2230/201 Glucose concentration
• CPC Class Codes: A61M 5/172 electrical or electronic A61M5/16804, A61M5/16831 take precedence
• 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 50/20 for computer-aided diagnosis, e.g. based on medical expert systems
• CPC Class Codes: G16H 50/50 for simulation or modelling of medical disorders

Abstract

Processor-implemented methods of controlling an insulin infusion device for a user are provided here. A first method obtains a current insulin on board (IOB) value that estimates active insulin in the user, and compensates a calculated insulin infusion rate in response to the obtained IOB value. A second method supervises the operation of a glucose sensor by obtaining and processing insulin-delivered data and glucose sensor data for the user. An alert is generated if the second method determines that a current glucose sensor value has deviated from a predicted sensor glucose value by at least a threshold amount.

Claims

1. A processor-implemented method of controlling an insulin infusion device for a user, the insulin infusion device comprising an insulin reservoir for insulin to be delivered from the insulin infusion device to a body of the user, and further comprising a processor architecture having at least one processor device, the method comprising:

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

operating the processor architecture to obtain current insulin-delivered data that indicates an amount of insulin delivered by the insulin infusion device during a most recent sampling period;

operating the processor architecture to obtain current sensor data that indicates a current sensor glucose value for the user corresponding to the most recent sampling period;

processing historical insulin-delivered data and historical sensor data, for a plurality of historical sampling periods prior to the most recent sampling period, to obtain predicted sensor glucose values for a historical time period, the historical time period including the most recent sampling period, and the predicted sensor glucose values comprising a predicted current sensor glucose value for the most recent sampling period;

calculating a difference between the current sensor glucose value and the predicted current sensor glucose value for the most recent sampling period;

generating an alert when the difference exceeds a threshold error amount; and

operating the processor architecture to switch the insulin infusion device from the closed-loop mode to an open-loop mode in response to generating the alert.

2. The method of claim 1, wherein:

a recent history period corresponds to a period of time from a begin-prediction sampling period to the most recent sampling period, inclusive;

a distant history period corresponds to a period of time from a begin-training sampling period to an end-training sampling period, inclusive;

the distant history period occurred before the recent history period; and

the processing obtains the predicted sensor glucose values as a function of a bounded initial condition that is influenced by a baseline sensor glucose value obtained during the distant history period.

3. The method of claim 2, wherein the begin-prediction sampling period corresponds to the end-training sampling period.

4. The method of claim 2, wherein the baseline sensor glucose value is obtained during the begin-training sampling period.

5. The method of claim 1, wherein the processing comprises:

estimating plasma insulin for the user based on the current insulin-delivered data, the historical insulin-delivered data, and an insulin basal rate for the user; and

obtaining the predicted sensor glucose values based at least in part on the estimated plasma insulin.

6. The method of claim 1, wherein the processing comprises:

calculating a plurality of candidate solutions to a sensor glucose prediction model, wherein each of the plurality of candidate solutions is calculated as a function of a bounded initial condition, and wherein the bounded initial condition is influenced by a baseline sensor glucose value, wherein the historical sensor data includes the baseline sensor glucose value; and

selecting one of the calculated plurality of candidate solutions for use as the predicted sensor glucose values.

7. A processor-implemented method of controlling an insulin infusion device for a user, the insulin infusion device comprising an insulin reservoir for insulin to be delivered from the insulin infusion device to a body of the user, and further comprising a processor architecture having at least one processor device, the method comprising:

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

operating the processor architecture to identify, from historical sensor glucose values for the user, a baseline historical sensor glucose value obtained during a begin-training sampling period;

operating the processor architecture to calculate a plurality of candidate solutions to a sensor glucose prediction model, wherein each of the plurality of candidate solutions is calculated as a function of a bounded initial condition and historical insulin-delivered data for the user, and wherein the bounded initial condition is influenced by the baseline sensor glucose value;

operating the processor architecture to select one of the calculated plurality of candidate solutions, based on a comparison of predicted sensor glucose values from the calculated plurality of candidate solutions to a first portion of the historical sensor glucose values, resulting in a selected solution;

operating the processor architecture to compare at least one predicted sensor glucose value from the selected solution to a second portion of the historical sensor glucose values, wherein the first portion of the historical sensor glucose values corresponds to a distant history period, the second portion of the historical sensor glucose values corresponds to a recent history period, and the distant history period occurred before the recent history period that data samples;

generating an alert, in response to the comparing, when the second portion of the historical sensor glucose values deviates from the selected solution by at least a threshold error amount; and

operating the processor architecture to switch the insulin infusion device from the closed-loop mode to an open-loop mode in response to generating the alert.

8. The method of claim 7, wherein the calculating comprises:

estimating plasma insulin for the user based on at least some of the historical insulin-delivered data for the user, and based on an insulin basal rate for the user, wherein each of the plurality of candidate solutions is calculated based at least in part on the estimated plasma insulin.

9. A processor-implemented method of controlling an insulin infusion device for a user, the insulin infusion device comprising an insulin reservoir for insulin to be delivered from the insulin infusion device to a body of the user, and further comprising a processor architecture having at least one processor device, the method comprising:

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

defining a model training period and a model prediction period for a historical period of time;

operating the processor architecture to find a solution to a sensor glucose prediction model, relative to historical sensor glucose values obtained during the model training period, wherein the solution found is a function of a baseline sensor glucose value obtained during the model training period, and is a function of historical insulin-delivered data for the user obtained during the historical period of time;

operating the processor architecture to compare at least one predicted sensor glucose value from the solution found to at least one historical sensor glucose value corresponding only to the model prediction period;

generating an alert, in response to the comparing, when the at least one historical sensor glucose value deviates from the at least one predicted sensor glucose value by at least a threshold error amount; and

operating the processor architecture to switch the insulin infusion device from the closed-loop mode to an open-loop mode in response to generating the alert.

10. The method of claim 9, wherein the comparing compares a most recent historical sensor glucose value to a most recent predicted sensor glucose value from the solution found.

11. The method of claim 9, wherein the model prediction period immediately follows the model training period.

12. The method of claim 9, wherein finding the solution comprises:

calculating a plurality of candidate solutions to the sensor glucose prediction model;

comparing predicted sensor glucose values from the calculated plurality of candidate solutions to corresponding historical sensor glucose values obtained only during the model training period, to obtain a respective training error for each of the calculated plurality of candidate solutions; and

selecting the solution from the calculated plurality of candidate solutions, based on the training error.