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Generation of target glucose values for a closed-loop operating mode of an insulin infusion system

  • US 9,878,096 B2
  • Filed: 08/13/2013
  • Issued: 01/30/2018
  • Est. Priority Date: 08/30/2012
  • Status: Active Grant
First Claim
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1. An insulin infusion device comprising:

  • an insulin 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;

    initiating a closed-loop operating mode of the insulin infusion device, wherein during the closed-loop operating mode the insulin infusion device receives sensor glucose values from a continuous glucose sensor, and automatically controls delivery of insulin to the body of the user in response to at least the received sensor glucose values;

    in response to initiating the closed-loop operating mode, obtaining a most recent sensor glucose value for the user;

    calculating a difference between the most recent sensor glucose value and a target glucose setpoint value;

    when the calculated difference is less than or equal to a minimum threshold value, adjusting a closed-loop insulin infusion rate over time, based on a fixed final target glucose value that is derived from the target glucose setpoint value, and operating the insulin infusion device over time to deliver insulin from the insulin reservoir in accordance with the adjusted closed-loop insulin infusion rate; and

    when the calculated difference is greater than the minimum threshold value, adjusting the closed-loop insulin infusion rate over time by;

    calculating a dynamic glucose setpoint value for a current sampling point, wherein the dynamic glucose setpoint value is calculated in accordance with the expression DynSP(n)=cd1·

    DynSP(n−

    1)+cd2·

    DynSP(n−

    2)+cn0·

    DeltaGlu(n)+cn1·

    DeltaGlu(n−

    1), where cd1, cd2, cn0, and cn1 are coefficients of the discretized second order transfer function model, and for an initial calculation of the dynamic glucose setpoint value, DeltaGlu(n) is the difference, at the current sampling point, between the most recent sensor glucose value and the target glucose setpoint value;

    for the current sampling point, adding the calculated dynamic glucose setpoint value to the target glucose setpoint value to obtain a dynamic final target glucose value, wherein the dynamic final target glucose value is calculated in accordance with the expression FinalTarget(n)=Setpoint+DynSP(n), where n represents a current sampling point, FinalTarget(n) is the dynamic final target glucose value at the current sampling point, Setpoint is the target glucose setpoint value, and DynSP(n) is the dynamic glucose setpoint value at the current sampling point;

    for the current sampling point, adjusting the closed-loop insulin infusion rate in accordance with the obtained dynamic final target glucose value;

    for the current sampling point, operating the insulin infusion device to deliver insulin from the insulin reservoir in accordance with the adjusted closed-loop insulin infusion rate; and

    repeating, for subsequent sampling points, the steps of calculating a dynamic glucose setpoint value, adding the calculated dynamic glucose setpoint value to the target glucose setpoint value, adjusting the closed-loop insulin infusion rate, and operating the insulin infusion device, wherein the method decreases the calculated dynamic glucose setpoint value over time such that the obtained dynamic final target glucose value approaches the target glucose setpoint value.

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