SYSTEM AND METHOD FOR MONITORING A POWER SOURCE OF AN IMPLANTABLE MEDICAL DEVICE

• US 20090273349A1
• Filed: 04/30/2008
• Published: 11/05/2009
• Est. Priority Date: 04/30/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Jain, Mukul, Rondoni, John C.
• Granted Patent: US 8,823,382 B2
• Time in Patent Office: Days
• US Class Current: 324/430
• CPC Class Codes: A61N 1/3708 for power depletion
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

Techniques for monitoring a battery of an implantable medical device are disclosed. First and second current sources are provided to draw currents having amplitudes of I₁ and I₂, respectively, from the battery. First and second voltage measurements, V₁ and V₂, are obtained when first and second combinations, respectively, of the first and second current sources are selectively activated. Battery impedance is determined using the current amplitudes I₁ and I₂ and the voltage measurements V₁ and V₂. The impedance measurement may be used to obtain an open-circuit voltage of the battery without the need to disconnect the battery from circuitry to which it provides power. Battery impedance and/or open-circuit battery voltage may then be used to determine an estimated time until an action is required involving the battery, which may include activation of an ERI or EOL indicator, or initiation of a recharge session.

Claims

1. For use in an implantable medical device that contains a battery, a system for monitoring the battery, comprising:

a first current source associated with a current having a first predetermined amplitude;

a second current source associated with a current having a second predetermined amplitude; and

a control circuit coupled to the first current source and the second current source to activate the first current source and obtain a first voltage measurement across the battery while the first current source is activated and to activate a second current source and obtain a second voltage measurement across the battery while the second current source is activated, and whereby impedance of the battery is determined from the first and the second predetermined amplitudes and the first and the second voltage measurements.

2. The system of claim 1, wherein the control circuit is adapted to determine the battery impedance from the first and the second predetermined amplitudes and the first and the second voltage measurements.

3. The system of claim 2, wherein the control circuit is adapted to determine an open-circuit voltage of the battery from the battery impedance.

4. The system of claim 2, further including a measurement circuit to measure at least one of a quiescent current being supplied by the battery and a voltage across the battery while the quiescent current is being supplied by the battery, and wherein the control circuit is adapted to determine an open-circuit battery voltage from the battery impedance, the quiescent current, and the voltage across the battery while the quiescent current is being supplied by the battery.

5. The system of claim 2, further including a measurement circuit to measure the first and the second voltage measurements.

6. The system of claim 1, further including a storage device to store data indicative of characteristics of the battery, and wherein the control circuit is adapted to utilize the battery impedance and the data indicative of characteristics of the battery to determine capacity of the battery.

7. The system of claim 6, wherein the control circuit is adapted to utilized the capacity of the battery to determine at least one of an action that is to be taken regarding the battery and a time remaining until the action is to be taken.

8. The system of claim 7, wherein the action is selected from a group consisting of activating an ERI indicator, activating an EOL indicator, and scheduling a recharge session to recharge the battery.

9. The system of claim 3, further including a storage device to store data indicative of a characteristic of the battery, and wherein the control circuit is adapted to utilize at least one of the battery impedance and the open-circuit battery voltage to reference the data indicative of a characteristic of the battery to thereby determine a time until an action involving the battery is required.

10. The system of claim 1, further comprising a second control circuit communicatively coupled to the implantable medical device to receive at least one of the first and the second predetermined amplitudes and the first and the second voltage measurements.

11. The system of claim 10, wherein at least one of the control circuit and the second control circuit is adapted to determine at least one of the battery impedance and an open-circuit voltage of the battery.

12. The system of claim 11, wherein the second control circuit is adapted to determine at least one of an action that is to be taken involving the battery and a time until the action is to be taken based on at least one of the battery impedance and the open-circuit voltage of the battery.

13. The system of claim 1, wherein the control circuit is adapted to determine the impedance of the battery as

(the first voltage measurement−

the second voltage measurement)/(the second predetermined amplitude−

the first predetermined amplitude).

14. A method of monitoring a battery supplying power to an implantable medical device, comprising:

activating a first current source that sources or sinks a current of a first predetermined amplitude;

obtaining a first voltage measurement while the first current source is activated;

activating a second current source that sources or sinks a current of a second predetermined amplitude;

obtaining a second voltage measurement while the second current source is activated; and

determining impedance of the battery from the first predetermined amplitude, the second predetermined amplitude, the first voltage measurement, and the second voltage measurement.

15. The method of claim 14, further including providing a first control circuit to perform at least one of the steps of claim 14.

16. The method of claim 14, further including providing a second control circuit capable of being communicatively coupled to the first control circuit to perform at least one of the steps of claim 14.

17. The method of claim 14, wherein the impedance of the battery is determined as

(the first voltage measurement−

the second voltage measurement)/(the second predetermined amplitude−

the first predetermined amplitude).

18. The method of claim 14, further including utilizing data describing characteristics of the battery to determine, based on the battery impedance, at least one of an action to be taken regarding the battery and a time until the action is to be taken.

19. The method of claim 14, and further including providing status to a user via a user interface device, the status being determined, at least in part, based on the battery impedance, the data being indicative of at least one of an action to be taken regarding the battery, a time until the action is to be taken, a capacity associated with the battery, an open-circuit voltage of the battery, and the battery impedance.

20. The method of claim 14, further including determining an open-circuit voltage of the battery from the impedance of the battery.

21. The method of claim 20, further including utilizing data describing characteristics of the battery to determine, based on at least one of the battery impedance and the open-circuit voltage, at least one of an action to be taken regarding the battery, a time until the action is to be taken and a capacity associated with the battery.

22. The method of claim 14, further including:

measuring a quiescent current being provided by the battery while the implantable medical device is in the quiescent state;

measuring a voltage across the battery while the battery is providing the quiescent current; and

determining, an open-circuit voltage of the battery based on the quiescent current, the battery impedance, and the voltage across the battery while the battery is providing the quiescent current.

23. The method of claim 22, further including placing the implantable medical device in the quiescent state.

24. A system for monitoring a battery of an implantable medical device that is implanted in a body, comprising:

a first current source that causes a current of a first predetermined amplitude to be drawn from the battery;

a second current source that causes a current of a second predetermined amplitude to be drawn from the battery; and

a measurement circuit to measure a first voltage across the battery when a first combination of the first and second current sources is activated and to measure a second voltage across the battery when a different combination of the first and the second current sources is activated, whereby impedance of the battery is determined from the first predetermined amplitude, the second predetermined amplitude, the first voltage, and the second voltage.

25. The system of claim 24, further including a control circuit to determine the battery impedance from the first predetermined amplitude, the second predetermined amplitude, the first voltage, and the second voltage.

26. The system of claim 25, further including an external device capable of being electromagnetically coupled to the implantable medical device, and wherein the control circuit is provided by the external device.

27. The system of claim 25, wherein the control circuit is implanted within the living body.

28. The system of claim 24, a storage device to store executable instructions to cause selective activation of at least one of the first current source, the second current source, and the measurement circuit.

29. The system of claim 24, wherein the measurement circuit includes a circuit to measure a quiescent current that is drawn from the battery when the implantable medical device is not delivering therapy and both the first current source and the second current source are deactivated.

30. The system of claim 25, wherein the measurement circuit includes a circuit to measure a quiescent current that is drawn from the battery when the implantable medical device is not delivering therapy and when both the first current source and the second current source are deactivated, and wherein the control circuit is adapted to determine an open-circuit voltage of the battery from the quiescent current and the battery impedance.

31. The system of claim 25, wherein the control circuit is adapted to determine the battery impedance as

(the first voltage measurement−

the second voltage measurement)/(the second predetermined amplitude−

the first predetermined amplitude).

32. The system of claim 24, further including a control circuit to determine, based on the battery impedance, at least one of battery capacity, an action to be performed in association with the battery, and a time until the action is to be performed.

33. A system for monitoring a battery of an implantable medical device, comprising:

first current source means for causing a battery to provide a current of a first predetermined amplitude;

second current source means for causing a battery to provide a current of a second predetermined amplitude;

measurement means for obtaining a first voltage measurement across the battery when a first combination of the first current source means and the second current source means are selectively activated, and for obtaining a second voltage measurement across the battery when a second combination of the first current source means and the second current source means is selectively activated; and

control means for determining impedance of the battery based on the first predetermined amplitude, the second predetermined amplitude, the first voltage measurement, and the second voltage measurement.

34. A method of monitoring a battery supplying power to an implantable medical device that is implanted in a living body, comprising:

generating a first current having a first predetermined amplitude;

obtaining a first voltage measurement across the battery while the first current is being generated;

generating a second current having a second predetermined amplitude;

obtaining a second voltage measurement across the battery while the second current source is activated; and

determining impedance of the battery from the first predetermined amplitude, the second predetermined amplitude, the first voltage measurement, and the second voltage measurement.