Implantable Medical Device Charge Balance Assessment

• US 20080015641A1
• Filed: 07/12/2006
• Published: 01/17/2008
• Est. Priority Date: 07/12/2006
• Status: Active Grant

• Current Assignee: LivaNova USA, Inc. (LivaNova Plc)
• Original Assignee: Cyberonics, Inc
• Inventors: Armstrong, Randolph K., Armstrong, Scott A.
• Granted Patent: US 8,478,420 B2
• Time in Patent Office: Days
• US Class Current: 607/2
• CPC Class Codes: A61N 1/36142 for improving safety
• CPC Class Codes: A61N 1/36153 Voltage A61N1/3616 takes precedence
• CPC Class Codes: A61N 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control

Abstract

A method is provided including delivering at least one electrical signal to tissue of a patient through an electrode. The method further includes assessing whether a net charge remains on the electrode a predetermined period of time after the delivery of the electrical signal. Systems for delivering such a signal, and assessing whether a net charge remains on the electrode providing the signal, are also provided.

Claims

1. A method for charge balance assessment in an implantable medical device, the method comprising:

delivering at least one electrical signal to tissue of a patient through an electrode; and

assessing whether a net charge remains on the electrode a predetermined period of time after the delivery of the electrical signal.

2. The method of claim 1, wherein assessing whether a net charge remains on the electrode comprises measuring a voltage differential between a charge balancing capacitor associated with the electrode and a reference voltage, and estimating the net charge remaining based on the measured voltage differential.

3. The method of claim 2, wherein measuring the voltage differential comprises measuring a voltage differential across a resistor coupled to a charge balancing capacitor associated with the electrode and a reference voltage, and estimating the charge balance based on the measured voltage differential.

4. The method of claim 2, wherein measuring the voltage differential between a charge balancing capacity and a reference voltage comprises measuring said differential from at least one of:

a) the proximal side of the charge balancing capacitor; and

b) the distal side of the charge balancing capacitor.

5. The method of claim 2, wherein said reference voltage is selected from the group consisting of:

a) another electrode;

b) a common conductor of the implantable medical device; and

c) ground.

6. The method of claim 1, further comprising generating a response based on the step of assessing whether a net charge imbalance remains on the electrode.

7. The method of claim 6, wherein generating a response comprises at least one of:

a) generating a notification to one of the patient and a physician that a net charge remains on the electrode when the predetermined period of time has elapsed;

b) changing the electrical signal delivered by the electrode;

c) modifying a path by which the electrical signal is delivered such that an electrode other than the electrode carrying a net charge is used for delivering the electrical signal;

d) disabling delivery of the electrical signal by way of the electrode carrying a net charge;

e) switching from passive charge balancing to active charge balancing; and

f) increasing the active charge balancing to eliminate the net charge.

8. The method of claim 1, wherein delivering at least one electrical signal comprises delivering said at least one electrical signal via a plurality of electrodes, and the method further comprising assessing whether a net charge remains on each of said plurality of electrodes.

9. The method of claim 1, further comprising selecting at least one electrode from among a plurality of electrodes through which to deliver the at least one electrical signal to tissue, and assessing whether a net charge remains on each said selected electrode.

10. The method of claim 1, further comprising transmitting from the implantable medical device to an external programming device a signal indicative of whether a net charge remains on the electrode.

11. A system comprising:

a current source that generates an electrical signal;

an electrode that delivers the electrical signal generated by the current source to tissue;

a charge balancing unit coupled to the electrode; and

a charge balance determination unit that detects whether a net charge remains on the electrode a predetermined period of time after the electrical signal is delivered.

12. The system of claim 11, wherein the charge balancing unit comprises one of:

a passive charge balancing capacitor; and

an active charge balancing unit that provides an electrical balancing signal of an opposite polarity to the electrical signal generated by the current source.

13. The system of claim 11, wherein the charge balance determination unit comprises a switch for coupling the electrode to a voltage meter to measure a voltage differential between the electrode and a reference voltage to determine whether a net charge remains on the electrode.

14. The system of claim 13, wherein the reference voltage is selected from the group consisting of:

a) another electrode;

b) a common conductor of the system; and

c) ground.

15. The system of claim 11, wherein the charge balance determination unit comprises:

a resistance coupling the electrode to a reference voltage; and

a voltage meter to measure a voltage differential across the resistance as an indication of the net charge remaining on the electrode.

16. The system of claim 11, further comprising a response module that generates a response based on whether the charge balance determination unit detects a net charge remaining on the electrode.

17. The system of claim 16, wherein the response comprises one of:

a) a notification to one of the patient and a physician that a net charge remains on the electrode;

b) changing the electrical signal generated by the current source;

c) modifying the path by which the electrical signal is delivered such that an electrode other than the electrode carrying a net charge is used for delivering the electrical signal;

d) disabling delivery of the electrical signal by way of the electrode carrying a net charge;

e) switching from passive charge balancing to active charge balancing; and

f) increasing the active charge balancing to eliminate the net charge on the electrode.

18. The system of claim 11, further comprising a plurality of electrodes that may be selected to deliver the electrical signal generated by the current source to tissue;

wherein the charge balance determination unit determines whether a net charge remains on each electrode of said plurality of electrodes a predetermined period of time after the electrical signal is delivered.

19. The system of claim 11, further comprising an external programming device operable to display a notification to one of the patient and a physician that a net charge remains on the electrode.

20. The system of claim 11, further comprising an external programming device, wherein the charge balance determination unit transmits a signal indicative of whether a net charge remains on the electrode to the external programming device, and the external programming device is operable to alter the electrical signal generated by the current source based on the signal transmitted by the charge balance determination unit.