Power supply monitoring for an implantable device

• US 20070179547A1
• Filed: 01/27/2006
• Published: 08/02/2007
• Est. Priority Date: 01/27/2006
• Status: Active Grant

• Current Assignee: LivaNova USA, Inc. (LivaNova Plc)
• Original Assignee: Cyberonics, Inc
• Inventors: Scott, Timothy, Armstrong, Scott, Armstrong, Randolph, Inman, Dana
• Granted Patent: US 7,769,455 B2
• Time in Patent Office: Days
• US Class Current: 607/29
• CPC Class Codes: A61N 1/3708 for power depletion
• CPC Class Codes: A61N 1/378 Electrical supply

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 is provided. The method comprises measuring the measured voltage of the energy storage device, and determining whether the measured voltage is less than a transition voltage. When the measured voltage is less than the transition voltage, determining a time period remaining until an end of service of the energy storage device is based upon a function of the measured voltage. When the measured voltage is greater than or equal to the transition voltage, determining a time period remaining until an end of service of the energy storage device is based upon a function of the total charge depleted. The transition voltage is a voltage associated with the transition point of non-linearity in the battery voltage depletion curve.

Claims

1. A method for determining a time period remaining in a useful life of an energy storage device in an implantable medical device, the energy storage device comprising a total available electrical charge that may be obtained from the energy storage device and a measured voltage, the method comprising:

measuring a measured voltage of the energy storage device;

determining whether the measured voltage is less than a transition voltage; and

when the measured voltage is less than the transition voltage, determining a time period remaining in the energy storage device'"'"'s useful life based upon a function of the measured voltage; and

when the measured voltage is greater than or equal to the transition voltage, determining a time period remaining in the energy storage device'"'"'s useful life based upon a function of charge depleted.

2. The method of claim 1, wherein the transition voltage corresponds to a transition point of non-linearity in a battery voltage depletion curve representing the voltage across the energy storage device over time.

3. The method of claim 2, wherein for voltages less than the transition voltage, the battery voltage depletion curve is approximated by a polynomial equation of degree greater than one.

4. The method of claim 1, wherein the transition voltage is approximately 2.6 volts.

5. The method of claim 1, further comprising generating an indicator signal based upon a determination that the energy storage device'"'"'s useful life has already ended.

6. The method of claim 1, further comprising generating an elective replacement indicator signal based upon a determination that the time period remaining in the energy storage device'"'"'s useful life is less than or equal to a predetermined period.

7. The method of claim 6, wherein the predetermined period is approximately six months.

8. The method of claim 1, wherein when the measured voltage is less than the transition voltage, determining a time period remaining in the energy storage device'"'"'s useful life comprises calculating the time period based upon at least the measured voltage, a voltage associated with an end of the energy storage device'"'"'s useful life, a percentage of energy storage device capacity remaining at a transition point of non-linearity in a function representing the voltage across the energy storage device over time, and at least one of the transition voltage, the total available electrical charge, and a consumption rate.

9. The method of claim 8, wherein the transition voltage comprises a variable value based upon the consumption rate.

10. The method of claim 1, wherein when the measured voltage is greater than or equal to the transition voltage, determining a time period remaining in the energy storage device'"'"'s useful life comprises calculating the time period based upon the total charge depleted, and at least one of the total available electrical charge and a consumption rate.

11. The method of claim 1, further adding a correction used in determining the time remaining, wherein the correction factor comprises at least one of 1) a first factor when the measured voltage is greater than or equal to a predetermined voltage, 2) a second factor associated with the energy storage device impedance, and 3) a third factor associated with a measured temperature.

12. An implantable medical device, comprising:

an energy storage device that provides power for an operation performed by the implantable medical device, characterized by a non-linear battery voltage depletion curve of voltage over time;

a stimulation unit operatively coupled to the energy storage device that provides an electrical signal; and

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

a charge depletion determination unit that determines an electrical charge depleted by the energy storage device during operation of the implantable medical device;

a voltage determination unit that determines whether a measured voltage across the energy storage device has reached a transition voltage; and

a useful life determination unit that determines a time period remaining in the energy storage device'"'"'s useful life based upon at least one of

     1) a function of the electrical charge depleted, and

     2) a function of the measured voltage.

13. The implantable device of claim 12, wherein the transition voltage is a voltage associated with a transition point of non-linearity in the battery voltage depletion curve.

14. The implantable device of claim 13, wherein the transition voltage comprises a variable value based upon a consumption rate.

15. The implantable device of claim 12, wherein the useful life determination unit determines the time period remaining in the energy storage device'"'"'s useful life based on the function of the electrical charge depleted when a measured voltage across the energy storage device is greater than or equal to the transition voltage, and the useful life determination unit determines the time period until the end of service of the energy storage device based on the function of the measured voltage when the measured voltage across the energy storage device is less than the transition voltage.

16. The implantable device of claim 15, wherein when the measured voltage is less than the transition voltage, the useful life determination unit calculates the time period remaining in the energy storage device'"'"'s useful life based upon the measured voltage, an end-of-service voltage, a percentage of energy storage device capacity remaining at a transition point of non-linearity in a battery voltage depletion curve representing the voltage across the energy storage device over time and at least one of the transition voltage, the total available electrical charge, and a consumption rate.

17. The implantable device of claim 15, wherein when the measured voltage is greater than or equal to the transition voltage, the determination unit calculates a time period remaining in the energy storage device'"'"'s useful life based upon the total charge depleted, and at least one of the total available electrical charge and a consumption rate.

20. The implantable medical device of claim 12, further comprising a correction factor unit for adding at least one of (1) a first correction factor when the measured voltage is greater than or equal to a predetermined voltage, (2) a second correction factor associated with the energy storage device impedance, and 3) a third correction factor associated with a measured temperature of the energy storage device.

18. The implantable medical device of 12, wherein the controller generates at least one of (1) an end of service signal based upon a determination that the time period remaining in the energy storage device'"'"'s useful life has already ended and (2) an elective replacement indicator signal based upon a determination that the time period remaining in the energy storage device'"'"'s useful life is less than or equal to a predetermined period of time.

19. The implantable medical device of claim 18, wherein the predetermined period of time is approximately six months.

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

an implantable medical device that delivers an electrical signal to a patient and communicates with an external monitoring device, the implantable device comprising;

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

a controller operatively coupled to the battery that determines an electrical charge depleted by the battery and a voltage across the battery;

wherein;

the external monitoring device determines, depending on whether the voltage across the battery is less than a transition voltage, a remaining useful life of the battery based upon at least one of (1) the electrical charge depleted and (2) the voltage across the battery; and

the external monitoring device displays an indication of the remaining useful life of a battery of the implantable medical device.

22. The system of claim 21, wherein the external monitoring device displays at least one of (1) an end of service signal based upon a determination that the time period remaining in the battery'"'"'s useful life has already ended, and (2) an elective replacement indicator signal based upon a determination that the time period remaining in the battery'"'"'s useful life is less than or equal to a predetermined period.

23. The system of claim 22, wherein the predetermined period is approximately six months.

24. The system of claim 21, further comprising a correction unit that adds a correction factor, wherein the correction factor comprises at least one of 1) a first correction factor when the measured voltage is greater than or equal to a predetermined voltage, 2) a second correction factor associated with the energy storage device impedance, and 3) a third correction factor associated with a measured temperature of the battery