Kalman filter based on-off switch for insulin pump

Patent metadata

Field	Value
Publication number	US-9227014-B2
Application number	US-201414175020-A
Country	US
Kind code	B2
Filing date	Feb 7, 2014
Priority date	Feb 7, 2013
Publication date	Jan 5, 2016
Grant date	Jan 5, 2016

Abstract

Techniques for controlling an insulin pump include determining values for parameters selected from a group including a first prediction time horizon, a predicted glucose threshold (Goff) for turning the insulin pump off, a maximum shut off time within a time window, and duration of the time window. A safety rule is determined based on the maximum shut off time within the duration. Glucose readings are collected up to a current time. An expected current glucose value G and glucose temporal rate of change are determined based only on the glucose readings and a Kalman filter configured for noisy glucose readings. A glucose level (Gh1) is predicted for a future time that is the prediction time horizon after the current time. A command is issued to shut off the insulin pump if it is determined both that Gh1 is less than Goff and that the safety rule is satisfied.

First claim

What is claimed is:

1. A non-transitory computer-readable medium carrying one or more sequences of instructions, wherein execution of the one or more sequences of instructions by one or more processors causes an apparatus to:
determine values for a plurality of parameters for an automatic on-off switch for an insulin pump configured to inject insulin into a subject, wherein the plurality of parameters comprises a first prediction time horizon (H1), a first predicted glucose threshold (Goff) for turning the insulin pump off, a maximum shut off time within a first time window, and duration of the first time window;
determine a safety rule based at least in part on the maximum shut off time within the first time window and the duration of the first time window;
collect a plurality of glucose readings of a glucose level in a bloodstream of the subject up to a current time;
determine an expected current glucose value G and expected current glucose temporal rate of change dG/dt based only on the plurality of glucose readings and a Kalman filter configured for noisy glucose readings of the glucose level in the bloodstream of the subject;
predict a glucose level (Gh1) for a first future time that is the first prediction time horizon after the current time; and
issue a command to shut off the insulin pump if it is determined both that the predicted glucose level (Gh1) is less than Goff and that the safety rule is satisfied.

2. The non-transitory computer-readable medium as recited in claim 1 , wherein:
the group of parameters further comprises a second predicted glucose threshold (Gon) for turning the insulin pump on, and a constant basal rate for the insulin pump when the insulin pump is on; and
the apparatus is further configured to issue a command to turn on the insulin pump at the constant basal rate if it is determined both that the predicted glucose level (Gh1) is more than Gon and that the insulin pump is currently turned off.

3. The non-transitory computer-readable medium as recited in claim 2 , wherein the second predicted glucose threshold (Gon) is in a range from about 90 milligram per deciliter to about 110 milligrams per deciliter.

4. The non-transitory computer-readable medium as recited in claim 1 , wherein:
the group of parameters further comprises a different second prediction time horizon, a predicted glucose threshold (Gon) for turning the insulin pump on, and a constant basal rate for the insulin pump when the insulin pump is on; and
the apparatus is further configured to:
predict a different glucose level (Gh2) for a different second future time that is the second prediction time horizon (H2) after the current time; and
issue a command to turn on the insulin pump at the constant basal rate if it is determined both that the different predicted glucose level (Gh2) is more than Gon and that the insulin pump is currently turned off.

5. The non-transitory computer-readable medium as recited in claim 1 , wherein:
the group of parameters further comprises a maximum shut off time within a second time window and a duration of the second time window; and
to determine the safety rule further comprises to determine the safety rule based at least in part on the maximum shut off time within the second time window and the duration of the second time window.

6. The non-transitory computer-readable medium as recited in claim 1 , wherein:
the group of parameters further comprises at least one of an initial variability of glucose readings, or initial variability in time rate of change of glucose, or a steady state variability of glucose values; and
the Kalman filter is based at least in part on at least one of the values for the initial variability of glucose readings, or the initial variability in time rate of change of glucose, or the steady state variability of glucose values.

7. The non-transitory computer-readable medium as recited in claim 1 , wherein:
the group of parameters further comprises at least one of a default glucose value, or a prior multiplier, or a sensor dropout time; and
the Kalman filter is based at least in part on at least one of the values for the default glucose value, or the prior multiplier, or the sensor dropout time.

8. The non-transitory computer-readable medium as recited in claim 1 , wherein:
the group of parameters further comprises a current activity level (Aoff) for turning the insulin pump off and a current glucose threshold (Ga) for turning the insulin pump off during activity; and
the apparatus is further configured to
collect a reading of activity level at the current time, and
issue a command to shut off the insulin pump if it is determined both that the reading of activity level is more than Aoff and that the expected current glucose value G is less than Ga.

9. The non-transitory computer-readable medium as recited in claim 8 , wherein the current glucose threshold (Ga) for turning the insulin pump off during activity is in about 180 milligrams per deciliter.

10. The non-transitory computer-readable medium as recited in claim 1 , wherein
the group of parameters further comprises a danger current glucose threshold (Gd) for turning off the insulin pump; and
the safety rule is not satisfied if the expected current glucose value G is less than Gd.

11. The non-transitory computer-readable medium as recited in claim 1 , wherein the first prediction time horizon H1 is in a range from about 50 minutes to about 90 minutes.

12. The non-transitory computer-readable medium as recited in claim 1 , wherein the first predicted glucose threshold (Goff) is in a range from about 70 milligram per deciliter to about 90 milligrams per deciliter.

13. An apparatus comprising:
at least one processor; and
at least one memory including one or more sequences of instructions,
the at least one memory and the one or more sequences of instructions configured to, with the at least one processor, cause the apparatus to perform at least the following,
determining values for a plurality of parameters for an automatic on-off switch for an insulin pump configured to inject insulin into a subject, wherein the plurality of parameters comprises a first prediction time horizon, a predicted glucose threshold (Goff) for turning the insulin pump off, a maximum shut off time within a first time window, and duration of the first time window;
determining a safety rule based at least in part on the maximum shut off time within the first time window and the duration of the first time window;
collecting a plurality of glucose readings of a glucose level in a bloodstream of a subject up to a current time;
determining an expected current glucose value G and expected current glucose temporal rate of change dG/dt based only on the plurality of glucose readings and a Kalman filter configured for noisy glucose readings of the glucose level in the bloodstream of the subject;
predicting a glucose level (Gh1) for a first future time that is the first prediction time horizon (H1) after the current time; and
issuing a command to shut off the insulin pump if it is determined both that the predicted glucose level (Gh1) is less than Goff and that the safety rule is satisfied.

14. A method for operating an insulin pump, comprising:
determining values for a plurality of parameters for an automatic on-off switch for an insulin pump configured to inject insulin into a subject, wherein the plurality of parameters comprises a first prediction time horizon, a predicted glucose threshold (Goff) for turning the insulin pump off, a maximum shut off time within a first time window, and duration of the first time window;
determining

Assignees

• Buckingham Bruce A
• Bequette B Wayne
• Cameron Fraser
• Wilson Darrell M
• Chase H Peter
• Doyle Iii Francis J
• Stenerson Matthew
• Trustees Of The Laland Stanford Junior University Board Of
• Univ California Corp
• Univ Colorado Regents
• Rensselaer Polytech Inst

Inventors

• Buckingham Bruce A
• Bequette B Wayne
• Cameron Fraser
• Wilson Darrell M
• Chase H Peter
• Doyle Iii Francis J
• Stenerson Matthew

Classifications

• A61M5/14244

  adapted to be carried by the patient, e.g. portable on the body · CPC title

• A61M2230/005

  Parameter used as control input for the apparatus · CPC title

• A61M5/1723 Primary

  using feedback of body parameters, e.g. blood-sugar, pressure (measurement of body parameters A61B5/00) · CPC title

• A61M2230/06

  Heartbeat rate only · CPC title

• A61M2005/14296

  Pharmacokinetic models · CPC title