Power supply monitoring for an implantable device

• US 20060025829A1
• Filed: 07/28/2004
• Published: 02/02/2006
• Est. Priority Date: 07/28/2004
• Status: Active Grant

• Current Assignee: LivaNova USA, Inc. (LivaNova Plc)
• Original Assignee: Cyberonics, Inc
• Inventors: Armstrong, Randolph K., Nguyen, Huan D., Guzman, Albert W.
• Granted Patent: US 7,751,891 B2
• Time in Patent Office: Days
• US Class Current: 607/29
• CPC Class Codes: A61N 1/3708 for power depletion
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

A method and an apparatus for projecting an end of service (EOS) and/or an elective replacement indication (ERI) of a component in an implantable device and for determining an impedance experienced by a lead associated with the implantable device. An active charge depletion of an implantable device is determined. An inactive charge depletion of the implantable device is determined. A time period until an end of service (EOS) and/or elective replacement indication (ERI) of a power supply associated with the IMD based upon the active charge depletion, the inactive charge depletion, and the initial and final (EOS) battery charges, is determined. Furthermore, to determine the impedance described above, a substantially constant current signal is provided through a first terminal and a second terminal of the lead. A voltage across the first and second terminals is measured. An impedance across the first and second terminals is determined based upon the constant current signal and the measured voltage.

Claims

7. A method for determining the remaining useful life of an energy storage device in an implantable medical device, said energy storage device having a total available electrical charge that may be obtained from said energy storage device, said method comprising:

determining an active charge depletion of the implantable medical device;

determining an inactive charge depletion of said implantable medical device; and

determining a time period until an end of service of the energy storage device based upon said active charge depletion, said inactive charge depletion, and said total available charge.

8. The method of claim 7, wherein determining an active charge depletion of an implantable medical device further comprises determining a charge depleted during a previous stimulation performed by said implantable device.

9. The method of claim 8, wherein determining an active charge depletion of an implantable medical device further comprises determining an active current usage rate for a future stimulation to be performed by said implantable device.

10. The method of claim 9, wherein determining an active current usage rate for a future stimulation to be performed by said implantable medical device further comprises correlating a first predetermined current usage rate with a first stimulation performed by said implantable device.

11. The method of claim 10, wherein correlating said first predetermined current usage rate with said first stimulation performed by said implantable device further comprises calibrating said first predetermined current usage rate based upon at least one stimulation parameter.

12. The method of claim 10, wherein correlating said first predetermined current usage rate with said first stimulation performed by said implantable device further comprises calibrating said first predetermined current usage rate based upon a lead impedance.

13. The method of claim 10, wherein determining an active current usage rate for a future stimulation to be performed by said implantable medical device further comprises correlating a second predetermined current usage rate with a second stimulation performed by said implantable device.

14. The method of claim 13, wherein correlating said second predetermined current usage rate with said second stimulation performed by said implantable device further comprises calibrating said second predetermined current usage rate based upon at least one stimulation parameter.

15. The method of claim 7, wherein said energy storage device comprises a battery.

16. The method of claim 7, wherein determining an inactive charge depletion of an implantable medical device further comprises determining a charge depleted during a previous idle period of said implantable medical device.

17. The method of claim 7, wherein determining an inactive charge depletion of said implantable medical device further comprises determining an idle current usage rate for a future idle period of said implantable medical device.

18. The method of claim 17, further comprising calibrating said idle current usage rate for a previous idle time period.

19. The method of claim 7, further comprising generating an end of service signal based upon a determination that said time period until said end of service equals zero.

20. The method of claim 7, further comprising generating an end of service signal based upon a determination that said end of service has already occurred.

21. The method of claim 20, further comprising generating an elective replacement indicator signal based upon a determination that said time period until said end of service is less than or equal to a predetermined period.

22. The method of claim 21, wherein said predetermined period is six months.

23. A method for determining a time period until an end of service of an energy storage device in an implantable medical device, said energy storage device comprising an initial charge corresponding to a substantially full charge and a final charge corresponding to an end of useful life, comprising:

determining an idle current usage rate for at least one future idle period of an implantable medical device;

determining charge depleted during at least one previous idle period;

determining a stimulation current usage rate for at least one future stimulation to be performed by said implantable medical device;

determining charge depleted during a previous stimulation performed by said implantable medical device;

determining a total charge depleted by said implantable medical device based upon said charge depleted during said previous idle period and said charge depleted during said previous stimulation by said implantable medical device;

determining a future combined current usage based upon said idle current usage rate and said stimulation current usage rate; and

determining a time period until an end of service of the energy storage device based upon said total charge depleted, said future combined current usage rate, said initial battery charge and said final battery charge.

24. The method of claim 23, wherein said method further comprises determining a previous idle current usage rate and a previous stimulation current usage rate, and wherein said step of determining charge depleted during a previous idle period comprises multiplying said previous idle current usage rate by the duration of said previous idle period, and said step of determining charge depleted during a previous stimulation comprises multiplying said previous stimulation current usage rate by the duration of said stimulation.

25. The method of claim 23, further comprising generating an end of service signal based upon a determination that said time period until said end of service equals zero.

26. The method of claim 25, wherein further comprising generating an elective replacement indicator signal based upon a determination that said time period until said end of service is less than or equal to a predetermined period.

27. The method of claim 26 wherein said predetermined period is six months.

28. A method for determining the remaining useful life of a battery in an implantable medical device, said battery having a first charge and a second charge less than said first charge comprising:

determining a total available charge for said battery comprising the difference between said first charge and said second charge;

determining a charge depletion of the implantable medical device; and

determining a time period until an end of service of a power supply associated with said implantable medical device based upon said charge depletion and said total available charge.

29. A method for determining a remaining time until the end of service of a battery of an implantable medical device, said battery comprising a total available electrical charge that may be obtained from said battery, said method comprising:

determining a previous active charge depletion of an implantable device;

determining a future active current usage rate of said implantable device;

determining a previous inactive charge depletion of said implantable device;

determining a future inactive current usage rate of said implantable device;

determining a remaining time period until an end of service of said battery based upon said total available electrical charge, said previous active charge depletion, said future active current usage rate, said previous inactive charge depletion, and said future inactive current usage rate.

30. The method of claim 29, further comprising the step of generating an end of service signal based upon a determination that said time period until said end of service equals zero.

31. The method of claim 29, further comprising the step of generating an end of service signal based upon a determination that said end of service has already occurred.

32. The method of claim 29, further comprising the step of generating an elective replacement indicator signal based upon a determination that said time period until said end of service is less than or equal to a predetermined period.

33. The method of claim 30, wherein said predetermined time period is six months.

34. An implantable medical device, comprising:

an energy storage device to provide power for an operation performed by said implantable medical device, characterized by a total available electrical charge defined by the difference between an initial electrical charge and a final electrical charge;

a stimulation unit, operatively coupled to said energy storage device for providing a stimulation signal; and

a controller operatively coupled to said stimulation unit and said energy storage device, said controller comprising;

an active charge depletion determination unit adapted to determine an electrical charge depleted by said energy storage device during stimulation operations of the implantable medical device;

an inactive charge depletion determination unit adapted to determine an electrical charge depleted by said energy storage device during inactive periods of the implantable medical device; and

an end of service determination unit adapted to determine a time period until an end of service of said energy storage device based upon said total available electrical charge, said active charge depletion, and said inactive charge depletion.

35. The implantable device of claim 34, wherein said implantable device is a vagus nerve stimulator device.

36. The implantable device of claim 34, wherein said active charge depletion determination unit is adapted to determine an active charge depletion relating to at least one previous stimulation period performed by said implantable device.

37. The implantable device of claim 34, wherein said active charge depletion determination unit is adapted to determine an active current usage rate for a future stimulation period to be performed by said implantable medical device

38. The implantable medical device of claim 34, wherein said inactive charge depletion determination unit is adapted to determine an idle charge depletion relating to at least one previous idle period of said implantable medical device.

39. The implantable medical device of claim 34, wherein said inactive charge depletion determination unit is adapted to determine an idle current usage rate for a future idle period of said implantable medical device.

40. The implantable medical device of claim 34, wherein said controller is adapted to generate an end of service signal based upon a determination that said time period until said end of service equals zero.

41. The implantable medical device of claim 34, wherein said controller is adapted to generate an elective replacement indicator signal based upon a determination that said time period until said end of service is less than or equal to a predetermined period.

42. The implantable medical device of claim 41, wherein said predetermined period is six months.

43. A system for determining remaining useful life of a battery in an implantable medical device, comprising:

an external monitoring device for performing remote communications with an implantable medical device;

an implantable medical device adapted to communicate with said external device and to deliver a stimulation signal to a patient, said implantable device comprising;

a battery to provide power for an operation performed by said implantable medical device;

a communications unit to provide for communications between said external monitoring device and said implantable medical device;

a stimulation unit, operatively coupled to said battery, to provide a stimulation signal; and

a controller operatively coupled to said stimulation unit and said battery, said controller being adapted to determine;

an active charge depletion of said implantable medical device;

an inactive charge depletion of said implantable medical device; and

a time period until an end of service of said battery based upon said active charge depletion and said inactive charge depletion.

44. The system of claim 43, wherein said controller further comprises an active charge depletion determination unit to determine an active charge depletion relating to a previous stimulation period performed by said implantable medical device.

45. The system of claim 44, wherein said controller further comprises an inactive charge depletion determination unit to determine an inactive charge depletion relating to a previous inactive period of said implantable medical device.

46. The system of claim 45, wherein said controller further comprises an EOS/ERI determination unit to determine said time period until an end of service of said battery based upon said active charge depletion and said inactive charge depletion.

47. The system of claim 46, wherein at least one of said active charge depletion determination unit, said inactive charge depletion determination unit, and said EOS/ERI determination unit comprises of at least one of hardware, software, firmware, and a combination of said hardware, software and firmware.

48. The system of claim 43, wherein said controller is adapted to determine an active current usage rate relating to a potential stimulation to be performed by said implantable device

49. The system of claim 43, wherein said controller is adapted to determine an idle current usage rate relating to a potential idle period of said implantable medical device.

50. The system of claim 43, wherein said controller is adapted to generate an end of service signal based upon a determination that said time period until said end of service equals zero.

51. The system of claim 43, wherein said controller is adapted to generate an end of service signal based upon a determination that said end of service time has already occurred.

52. The system of claim 43, wherein said controller is adapted to generate an elective replacement indicator signal based upon a determination that said time period until said end of service is less than or equal to a predetermined period.

53. The system of claim 52, wherein said predetermined period is 6 months.

54. A computer readable program storage device encoded with instructions that, when executed by a computer, performs a method, comprising:

determining an active charge depletion of an implantable medical device;

determining an inactive charge depletion of said implantable medical device; and

determining a time period until an end of service of an energy storage device associated with said implantable medical device based upon said active charge depletion and said inactive charge depletion.

1. A method for determining a time period until an end of service of an energy storage device in an implantable medical device, said energy storage device comprising a total available electrical charge that may be obtained from said energy storage device, said method comprising:

determining a first current usage rate for a first future current usage period of an implantable medical device;

determining a second current usage rate for a second future current usage period of an implantable medical device;

determining a future combined current usage rate based upon said first future current usage rate and said second current usage rate; and

determining a total charge depleted by said implantable medical device by

determining a charge depleted during at least a first prior current usage period, and

determining a charge depleted during at least a second prior current usage period; and

determining a time period until an end of service of the energy storage device based upon said total available electrical charge, said total charge depleted, and said future combined current usage rate.

2. The method of claim 1, wherein said energy storage devices comprises a battery.

3. The method of claim 1 wherein said first prior current usage period comprises a stimulation period.

4. The method of claim 1 wherein said second prior current usage period comprises an inactive period.

5. The method of claim 1, further comprising the step of determining a third current usage rate for a third future current usage period of an implantable medical device, and wherein said step of determining a future combined current usage rate comprises determining a future combined current usage rate based upon said first future current usage rate, said second current usage rate, and said third current usage rate.

6. The method of claim 5 wherein said first future current usage period comprises an inactive period, said second future current usage period comprises a stimulation period, and said third future current usage period comprises a stimulation period, and wherein said second future current usage rate is different from said third current usage rate.

55. The computer readable program storage device of claim 54, wherein determining an active charge depletion of an implantable medical device comprises determining the charge depleted during a previous stimulation period performed by said implantable medical device.

56. The computer readable program storage device of claim 54, wherein determining an active charge depletion of an implantable medical device comprises determining an active current usage rate for a future stimulation period to be performed by said implantable medical device.

57. The computer readable program storage device of claim 56, wherein determining an active current usage rate for a future stimulation period to be performed by said implantable medical device further comprises correlating a first predetermined current usage rate with a first stimulation performed by said implantable device.

58. The computer readable program storage device of claim 57, wherein correlating said first predetermined current usage rate with said first stimulation performed by said implantable device further comprises calibrating said first predetermined current usage rate based upon at least one stimulation parameter.

59. The computer readable program storage device of claim 57, wherein determining an active current usage rate for a future stimulation period further comprises correlating a second predetermined current usage rate with a second stimulation performed by said implantable device.

60. The computer readable program storage device of claim 59, wherein correlating said second predetermined current usage rate with said second stimulation performed by said implantable device further comprises calibrating said second predetermined current usage rate based upon at least one stimulation parameter.

61. The computer readable program storage device of claim 54, wherein determining an inactive charge depletion of an implantable medical device comprises determining the charge depleted during a previous inactive period of the implantable medical device.

62. The computer readable program storage device of claim 61, wherein determining an inactive charge depletion of an implantable medical device comprises determining an inactive current usage rate for a future inactive period of the implantable medical device.

63. The computer readable program storage device of claim 54, further comprising generating an elective replacement indicator signal based upon a determination that said time period until said end of service is less than or equal to a predetermined period.

61-1. The computer readable program storage device of claim 62, further comprising calibrating said inactive current usage rate for a previous inactive period.

62-2. The computer readable program storage device of claim 54, further comprising generating an end of service signal based upon a determination that said time period until said end of service equals zero.

64. The computer readable program storage device of claim 65, wherein said predetermined period is six months.