Generation and application of an insulin limit for a closed-loop operating mode of an insulin infusion system

1. An insulin infusion device comprising:

an insulin reservoir for insulin to be delivered from the insulin infusion device to 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 closed-loop delivery of insulin from the insulin reservoir to the user, the method comprising:

calculating a maximum insulin infusion rate for the user based on a fasting blood glucose value associated with the user, a total daily insulin value associated with the user, and fasting insulin delivery data that is indicative of insulin delivered to the user during a fasting period, wherein the maximum insulin infusion rate is applicable during a period of closed-loop operation of the insulin infusion device;

obtaining a first closed-loop insulin infusion rate for the user, wherein the first closed-loop insulin infusion rate is obtained for a current sampling point during the period of closed-loop operation;

providing a second closed-loop insulin infusion rate for the user when the obtained first closed-loop insulin infusion rate is greater than the calculated maximum insulin infusion rate, wherein the second closed-loop insulin infusion rate is less than the first closed-loop insulin infusion rate; and

operating the insulin infusion device in a closed-loop mode to continuously deliver insulin from the insulin reservoir to the user in accordance with either the first closed-loop insulin infusion rate or the second closed-loop insulin infusion rate.

2. The insulin infusion device of claim 1 , wherein the provided second closed-loop insulin infusion rate is equal to the calculated maximum insulin infusion rate.

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

the first closed-loop insulin infusion rate is calculated in accordance with a proportional-integral-derivative insulin feedback (PID-IFB) control algorithm; and

the method performed by the processor-executable instructions further comprises the step of inhibiting windup of an integral component of the PID-IFB control algorithm when the obtained first closed-loop insulin infusion rate is greater than the calculated maximum insulin infusion rate.

4. The insulin infusion device of claim 3 , wherein inhibiting windup of the integral component comprises:

freezing the integral component while permitting continued updating of a proportional component of the PID-IFB control algorithm, and while permitting continued updating of a derivative component of the PID-IFB control algorithm.

5. The insulin infusion device of claim 4 , wherein the method performed by the processor-executable instructions further comprises:

unfreezing the integral component when a third closed-loop insulin infusion rate for the user is less than or equal to the calculated maximum insulin infusion rate, wherein the third closed-loop insulin infusion rate is obtained for a subsequent sampling point during the period of closed-loop operation, the subsequent sampling point occurring after the current sampling point.

6. The insulin infusion device of claim 1 , wherein the fasting insulin delivery data is correlated to the fasting blood glucose value.

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

the maximum insulin infusion rate is calculated in accordance with the expression

Umax

=

I

basal

,

0

+

BG

LBL

-

FBG

0

KI

;

Umax is the maximum insulin infusion rate, expressed in Units/hour;

I basal,0 is an estimated basal rate that results in the fasting blood glucose value for the user, expressed in Units/hour;

BG LBL is a lower blood glucose limit, expressed in mg/dL, and corresponding to operation of the insulin infusion device at Umax;

FBG 0 is the fasting blood glucose value, expressed in mg/dL; and

KI is an insulin gain value, expressed in

mg

dL

⁢

⁢

per

⁢

⁢

⁢

Units

hour

.

8. The insulin infusion device of claim 7 , wherein:

KI

=

-

IS

*

3

⁢

(

mg

dL

⁢

⁢

per

⁢

⁢

Units

hour

)

;

IS is an insulin sensitivity value for the user, expressed in mg/dL/Units; and

IS is derived from the total daily insulin value obtained for the user.

9. The insulin infusion device of claim 8 , wherein:

IS

=

1800

TDI

;

and

TDI is the total daily insulin value obtained for the user, expressed in Units.

10. The insulin infusion device of claim 1 , 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 insulin infusion device of claim 1 , wherein the electronic device comprises the insulin infusion device.

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

the electronic device comprises a portable wireless device; and

the portable wireless device and the insulin infusion device are physically distinct hardware devices.

13. 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 closed-loop delivery of insulin from an insulin reservoir of an insulin infusion device to a user, the method comprising:

calculating a maximum insulin infusion rate for the user based on a fasting blood glucose value associated with the user, a total daily insulin value associated with the user, and fasting insulin delivery data that is indicative of insulin delivered to the user during a fasting period, wherein the maximum insulin infusion rate is applicable during a period of closed-loop operation of the insulin infusion device;

obtaining a first closed-loop insulin infusion rate for the user, wherein the first closed-loop insulin infusion rate is obtained for a current sampling point during the period of closed- loop operation;

providing a second closed-loop insulin infusion rate for the user when the obtained first closed-loop insulin infusion rate is greater than the calculated maximum insulin infusion rate, wherein the second closed-loop insulin infusion rate is less than the first closed-loop insulin infusion rate; and

operating the insulin infusion device in a closed-loop mode to continuously deliver insulin from the insulin reservoir to the user in accordance with either the first closed-loop insulin infusion rate or the second closed-loop insulin infusion rate.

14. The electronic storage medium of claim 13 , wherein the provided second closed-loop insulin infusion rate is equal to the calculated maximum insulin infusion rate.

15. The electronic storage medium of claim 13 , wherein:

the first closed-loop insulin infusion rate is calculated in accordance with a proportional-integral-derivative insulin feedback (PID-IFB) control algorithm; and

the method performed by the processor-executable instructions further comprises the step of inhibiting windup of an integral component of the PID-IFB control algorithm when the obtained first closed-loop insulin infusion rate is greater than the calculated maximum insulin infusion rate.

16. The electronic storage medium of claim 15 , wherein inhibiting windup of the integral component comprises:

freezing the integral component while permitting continued updating of a proportional component of the PID-IFB control algorithm, and while permitting continued updating of a derivative component of the PID-IFB control algorithm.

17. The electronic storage medium of claim 16 , wherein the method performed by the processor-executable instructions further comprises:

unfreezing the integral component when a third closed-loop insulin infusion rate for the user is less than or equal to the calculated maximum insulin infusion rate, wherein the third closed-loop insulin infusion rate is obtained for a subsequent sampling point during the period of closed-loop operation, the subsequent sampling point occurring after the current sampling point.

18. The electronic storage medium of claim 13 , wherein the fasting blood glucose value remains constant during the period of closed-loop operation.

19. The electronic storage medium of claim 13 , wherein the total daily insulin value remains constant during the period of closed-loop operation.

20. The electronic storage medium of claim 13 , wherein the fasting insulin delivery data remains constant during the period of closed-loop operation.

21. The electronic storage medium of claim 13 , wherein the fasting insulin delivery data is correlated to the fasting blood glucose value.

22. The electronic storage medium of claim 13 , wherein:

the maximum insulin infusion rate is calculated in accordance with the expression

Umax

=

I

basal

,

0

+

BG

LBL

-

FBG

0

KI

;

Umax is the maximum insulin infusion rate, expressed in Units/hour;

I basal,0 is an estimated basal rate that results in the fasting blood glucose value for the user, expressed in Units/hour;

BG LBL is a lower blood glucose limit, expressed in mg/dL, and corresponding to operation of the insulin infusion device at Umax;

FBG 0 is the fasting blood glucose value, expressed in mg/dL; and

KI is an insulin gain value, expressed in

mg

dL

⁢

⁢

per

⁢

⁢

⁢

Units

hour

.

23. The electronic storage medium of claim 22 , wherein:

KI

=

-

IS

*

3

⁢

(

mg

dL

⁢

⁢

per

⁢

⁢

Units

hour

)

;

IS is an insulin sensitivity value for the user, expressed in mg/dL/Units; and

IS is derived from the total daily insulin value obtained for the user.

24. The electronic storage medium of claim 23 , wherein:

IS

=

1800

TDI

;

and

TDI is the total daily insulin value obtained for the user, expressed in Units.

25. An electronic controller for an insulin infusion device having an insulin reservoir, the electronic controller 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, provide a closed-loop insulin limit module configured to:

obtain a fasting blood glucose value associated with the user, the fasting blood glucose value corresponding to a fasting period for the user;

obtain a total daily insulin value associated with the user;

obtain fasting insulin delivery data that is indicative of insulin delivered to the user during the fasting period;

calculate a maximum insulin infusion rate for the user based on the obtained fasting blood glucose value, the obtained total daily insulin value, and the obtained fasting insulin delivery data, wherein the maximum insulin infusion rate is applicable during a period of closed-loop operation of the insulin infusion device; and

operating the insulin infusion device in a closed-loop mode to continuously deliver insulin from the insulin reservoir to the user in accordance with the maximum insulin infusion rate.

26. The electronic controller of claim 25 , wherein the electronic controller:

obtains a first closed-loop insulin infusion rate for the user, wherein the first closed-loop insulin infusion rate is obtained for a current sampling point during the period of closed-loop operation; and

provides a second closed-loop insulin infusion rate for the user when the obtained first closed-loop insulin infusion rate is greater than the calculated maximum insulin infusion rate, wherein the second closed-loop insulin infusion rate is less than the first closed-loop insulin infusion rate.

27. The electronic controller of claim 26 , wherein the provided second closed-loop insulin infusion rate is equal to the calculated maximum insulin infusion rate.

28. The electronic controller of claim 25 , wherein:

the electronic controller is implemented in a monitor device for the insulin infusion device; and

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

29. The electronic controller of claim 25 , wherein the electronic controller is implemented in the insulin infusion device.

30. The electronic controller of claim 25 , wherein:

the electronic controller is implemented in a portable wireless device; and

the portable wireless device and the insulin infusion device are physically distinct hardware devices.