System and method for providing closed loop infusion formulation delivery

• US 20030060753A1
• Filed: 12/26/2001
• Published: 03/27/2003
• Est. Priority Date: 09/07/2001
• Status: Active Grant

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Shah, Rajiv, Miller, Michael E., Starkweather, Timothy J., Lebel, Ronald J.
• Granted Patent: US 6,740,072 B2
• Time in Patent Office: Days
• US Class Current: 604/66
• CPC Class Codes: A61M 2005/14208 with a programmable infusion control system, characterised by the infusion program
• CPC Class Codes: A61M 2230/201 Glucose concentration
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• 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 20/17 delivered via infusion or injection
• CPC Class Codes: G16H 40/67 for remote operation
• CPC Class Codes: G16H 50/50 for simulation or modelling of medical disorders

Abstract

A system and method for providing closed loop infusion formulation delivery which accurately calculates a delivery amount based on a sensed biological state by adjusting an algorithm'"'"'s programmable control parameters. The algorithm calculates a delivery amount having proportional, derivative, and basal rate components. The control parameters may be adjusted in real time to compensate for changes in a sensed biological state that may result from daily events. Safety limits on the delivery amount may be included in the algorithm. The algorithm may be executed by a computing element within a process controller for controlling closed loop infusion formulation delivery. The biological state is sensed by a sensing device which provides a signal to the controller. The controller calculates an infusion formulation delivery amount based on the signal and sends commands to an infusion formulation delivery device which delivers an amount of infusion formulation determined by the commands.

Claims

1. A method for calculating a delivery rate of an infusion formulation in response to a sensed biological state, the method comprising:

measuring parameters of a sensed biological state at timed intervals;

processing the measured parameters and times at which the measurements are taken in an algorithm;

adjusting control parameters within the algorithm to compensate for changes in the sensed biological state resulting from events affecting the sensed biological state; and

calculating an infusion formulation delivery amount after adjusting the control parameters.

2. The method recited in claim 1, wherein the infusion formulation comprises an insulin formulation and wherein the sensed biological state comprises blood glucose levels in a human body.

3. The method recited in claim 2, wherein measuring parameters of the sensed biological state comprises providing a sensing device for measuring a present blood glucose level and a rising or falling rate of change for the blood glucose level.

4. The method recited in claim 3, wherein measuring parameters of the sensed biological state further comprises generating and providing to a computing element a signal representative of the measured parameters.

5. The method recited in claim 4, further comprising providing a low pass filter for reducing noise in the generated signal.

6. The method recited in claim 5, wherein the filter comprises a finite impulse response (FIR) filter.

7. The method recited in claim 6, wherein an order of the filter is programmable.

8. The method recited in claim 7, wherein the filter is programmed to have a higher order when the blood glucose level is falling.

9. The method recited in claim 1, wherein the measured parameters and the times are processed by a controller comprising a computing element for executing a closed-loop algorithm for calculating an insulin formulation delivery amount having proportional, derivative, and basal rate components.

10. The method recited in claim 9, wherein the derivative component is expressed as (G_(t)−

G<sub>(t−

x)</sub>)/x, wherein G_(t) denotes a blood glucose level at time t, G<sub>(t−

x)</sub> denotes a blood glucose level at time t−

x, and x denotes a numerical value representing an increment of time.

11. The method recited in claim 2, wherein the control parameters comprise at least one of a glucose set point, basal rate, proportional gain, trend term, trend up gain, and trend down gain.

12. The method recited in claim 1, wherein the control parameters are programmable.

13. The method recited in claim 12, wherein the control parameters are programmable in real time.

14. The method recited in claim 11, wherein the trend term is expressed as (G_(t)−

G<sub>(t−

x)</sub>)/x, wherein G_(t) denotes a blood glucose level at time t, G<sub>(t−

x)</sub> denotes a blood glucose level at time t−

x, and x denotes a numerical value representing an increment of time, and wherein adjusting control parameters comprises adjusting the value of x in the trend term to define a timeframe extending back in time from the time t.

15. The method recited in claim 14, wherein the value of x in the trend term is adjusted only when the blood glucose level is falling.

16. The method recited in claim 11, wherein the trend term is multiplied by one of the trend up gain and the trend down gain and wherein adjusting control parameters comprises adjusting at least one of the trend up gain and the trend down gain.

17. The method recited in claim 16, wherein the trend down gain is greater than the trend up gain.

18. The method recited in claim 16, wherein the trend down gain is adjusted such that the calculation of the trend term results in a negative value high enough to substantially cut off further delivery of insulin formulation.

19. The method recited in claim 11, wherein the trend term is enabled only when the blood glucose level is rising and equal to or greater than a set point value for the blood glucose level.

20. The method recited in claim 11, wherein adjusting control parameters comprises adjusting the basal rate.

21. The method recited in claim 20, wherein adjusting the basal rate comprises disabling the basal rate when the blood glucose level is falling and is below a set point value for the blood glucose level.

22. The method recited in claim 20, wherein adjusting the basal rate comprises including a programmable table of basal rate values and selecting a basal rate value from the table.

23. The method recited in claim 22, wherein the basal rate value is selected from the table at timed intervals.

24. The method recited in claim 23, wherein the timed intervals are programmable.

25. The method recited in claim 23, wherein adjusting the basal rate further comprises selecting a basal rate value from the table at 30 minute intervals.

26. The method recited in claim 23, wherein the basal rate value is selected at timed intervals based on a user'"'"'s historical physiological data.

27. The method recited in claim 1, wherein the sensed biological state comprises one of a sensed blood oxygen level, a temperature, and motion.

28. The method recited in claim 27, wherein the infusion formulation comprises an insulin formulation.

29. The method recited in claim 1, wherein calculating an infusion formulation delivery amount further comprises storing the calculated infusion formulation delivery amount in an accumulator while a volume of infusion formulation in the accumulator is less than a predefined volume.

30. The method recited in claim 29, wherein the volume of infusion formulation stored in the accumulator is delivered to an infusion site when it is substantially equal to the predefined volume.

31. The method recited in claim 29, further comprising purging the volume of infusion formulation stored in the accumulator when the stored volume is less than the predefined volume and a purge command is generated.

32. The method recited in claim 29, further comprising limiting to a predefined amount the amount of infusion formulation that may be stored in the accumulator at any one timed interval.

33. The method recited in claim 30, wherein the predefined volume is a pump stroke volume.

34. The method recited in claim 30, further comprising limiting the volume of infusion formulation that may be delivered to the infusion site during a predefined interval.

35. The method recited in claim 34, wherein the predefined interval is an hour.

36. A method for delivering a bolus of insulin formulation, the method comprising:

sampling a blood glucose level at predefined timed intervals;

comparing the sampled blood glucose level to a predefined blood glucose level threshold; and

disabling a bolus delivery if the sampled blood glucose level is less than the predefined blood glucose level threshold.

37. The method recited in claim 36, further comprising:

determining if a predefined time interval has been exceeded since a previous bolus delivery; and

disabling the bolus delivery if the predefined time interval has not been exceeded.

38. The method recited in claim 36, further comprising:

determining if the sampled blood glucose level is rising at a predefined rate; and

disabling the bolus delivery if the sampled blood glucose level is rising at a rate less than the predefined rate.

39. A closed loop infusion formulation delivery system for controlling a biological state in the body of a user, comprising

a sensor for measuring parameters of a sensed biological state at timed intervals and generating a signal representative of the measured parameters and times at which the measurements are taken;

a computing element for receiving and processing the generated signal, wherein the computing element

adjusts control parameters within the algorithm to compensate for changes in the sensed biological state resulting from events affecting the sensed biological state;

calculates a delivery rate of an infusion formulation after adjusting the control parameters; and

generates commands based on the calculated delivery rate; and

a delivery device for receiving the generated commands and delivering the infusion formulation based on the generated commands.

40. The closed loop infusion formulation delivery system recited in claim 39, wherein the infusion formulation comprises an insulin formulation and wherein the sensed biological state comprises blood glucose levels in a human body.

41. The closed loop infusion formulation delivery system recited in claim 39, wherein the measured parameters of the sensed biological state comprise a present blood glucose level and a rising or falling rate of change for the blood glucose level.

42. The method recited in claim 40, wherein the control parameters comprise at least one of a glucose set point, basal rate, proportional gain, trend term, trend up gain, and trend down gain.

43. The closed loop infusion formulation delivery system recited in claim 40, wherein the control parameters are programmable.

44. The closed loop infusion formulation delivery system recited in claim 43, wherein the control parameters are programmable in real time.

45. The closed loop infusion formulation delivery system recited in claim 39, wherein the sensed biological state comprises one of a sensed blood oxygen level, a temperature, and motion.

46. The closed loop infusion formulation delivery system recited in claim 45, wherein the infusion formulation comprises an insulin formulation.

47. The closed loop infusion formulation delivery system recited in claim 39, wherein the sensor comprises a sensor for measuring at least one of a blood glucose level, a blood oxygen level, a temperature, and motion.

48. The closed loop infusion formulation delivery system recited in claim 39, wherein the sensor comprises a two or more sensors, each of the two or more sensors measuring at least one of a blood glucose level, a blood oxygen level, a temperature, and motion.

49. A method for disabling a calculation of a delivery rate of an infusion formulation by a computing element in response to a sensed biological state, the method comprising:

determining a time window for disabling a calculation of a delivery rate of an infusion formulation;

sampling a current time;

determining if the current time is within the time window; and

disabling the calculation of the delivery rate of the infusion formulation if the current time is within the time window.

50. The method recited in claim 49, wherein determining a time window further comprises providing programmable start and stop times for the time window.

51. The method recited in claim 50, wherein the programmable start and stop times for the time window are determined from historical physiological data.