Impedance-based stimulation adjustment

• US 20060259079A1
• Filed: 04/28/2006
• Published: 11/16/2006
• Est. Priority Date: 04/30/2005
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: King, Gary W.
• Granted Patent: US 8,108,049 B2
• Time in Patent Office: Days
• US Class Current: 607/2
• CPC Class Codes: A61N 1/36185 Selection of the electrode configuration
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36535 controlled by body position or posture

Abstract

Techniques for adjusting stimulation are disclosed. A medical device measures an impedance associated with one or more electrodes, e.g., the impedance presented to the medical device by a total electrical circuit that includes the one or more electrodes, the conductors associated with the electrodes, and tissue proximate to the electrodes. The medical device stores at least one patient-specific relationship between impedance and a stimulation parameter, and adjusts the value of the stimulation parameter based on the measured impedance according to the relationship. The medical device may store multiple relationships, and select one the relationships based on, for example, an activity level of the patient, posture of the patient, or a current stimulation program or electrode combination used to deliver stimulation. By adjusting a stimulation parameter, such as amplitude, according to such a relationship, the stimulation intensity as perceived by the patient may be kept substantially constant.

Claims

1. A system comprising:

stimulation circuitry that delivers electrical stimulation to a patient via electrodes;

a memory that stores a predetermined patient-specific relationship between a parameter of the stimulation and impedance;

impedance measurement circuitry that measures an impedance associated with the electrodes; and

a processor that adjusts the stimulation parameter based on the measured impedance according to the predetermined patient-specific relationship, and controls the stimulation circuitry to deliver the stimulation to the patient via the electrodes according to the adjusted parameter.

2. The system of claim 1,

wherein the memory stores a plurality of predetermined patient-specific relationships between the parameter and impedance, and

wherein the processor selects one of the relationships, and adjusts the stimulation parameter according to the selected relationship.

3. The system of claim 2,

wherein the stimulation circuitry delivers the stimulation via current combination of electrodes from among a plurality of electrodes, and

wherein the processor identifies the current electrode combination, and selects one of the relationships based on the current stimulation program.

4. The system of claim 2, wherein the processor identifies at least one of an activity level or a posture of the patient, and selects one of the relationships based on the activity level or posture.

5. The system of claim 4, further comprising a sensor that generates a signal as a function of at least one of activity or posture of the patient, wherein the processor identifies the at least one of the activity level or the posture of the patient based on the signal.

6. The system of claim 1, wherein the parameter comprises amplitude.

7. The system of claim 1, wherein impedance measurement circuit measures the impedance during delivery of the stimulation via the electrodes.

8. The system of claim 1, wherein the stimulation circuitry delivers neurostimulation to the patient via the electrodes.

9. The system of claim 1, wherein the electrodes are implanted proximate to a spinal cord of the patient, and the stimulation circuitry delivers spinal cord stimulation via the electrodes.

10. The system of claim 1, further comprising an implantable medical device, wherein the implantable medical device includes the stimulation circuitry;

the memory, the impedance measurement circuitry, and the processor.

11. A method comprising:

measuring an impedance associated with electrodes that deliver electrical stimulation to a patient; and

adjusting a parameter of the stimulation based on the measured impedance according to a predetermined patient-specific relationship between the parameter and impedance.

12. The method of claim 11, further comprising selecting one of a plurality of predetermined patient-specific relationships between the parameter and impedance, wherein adjusting a parameter comprises adjusting the parameter according to the selected relationship.

13. The method of claim 12, further comprising identifying a current combination of electrodes from among a plurality of electrodes, wherein selecting one of a plurality of relationships comprises selecting one of the relationships based on the current electrode combination.

14. The method of claim 12, further comprising identifying at least one of an activity level or a posture of the patient, wherein selecting one of a plurality of relationships comprises selecting one of the relationships based on the activity level or posture.

15. The method of claim 14, wherein identifying at least one of an activity level or a posture of the patient comprises identifying the at least one of the activity level of the posture based on a signal generated by a sensor as a function of at least one of activity or posture of the patient.

16. The method of claim 11, wherein adjusting a parameter of the stimulation comprises adjusting an amplitude of the stimulation.

17. The method of claim 11, wherein measuring an impedance associated with electrodes that deliver stimulation to a patient comprises measuring the impedance during delivery of the stimulation to the patient via the electrodes.

18. The method of claim 11, wherein the stimulation comprises neurostimulation.

19. The method of claim 11, wherein the stimulation comprises spinal cord stimulation.

20. A system comprising:

means for delivering stimulation to a patient;

means for measuring an impedance during the delivery of the stimulation; and

means for adjusting a parameter of the stimulation based on the measured impedance according to a predetermined patient-specific relationship between the parameter and impedance.

21. The system of claim 20, wherein the adjusting means comprises means for selecting one of a plurality of predetermined patient-specific relationships between the parameter and impedance, and adjusting the stimulation parameter according to the selected relationship.

22. The system of claim 20, wherein the adjusting means comprises means for adjusting an amplitude of the stimulation.