Neural stimulation system providing auto adjustment of stimulus output as a function of sensed impedance

Abstract

A neural stimulation system automatically corrects or adjusts the stimulus magnitude (stimulation energy) in order to maintain a comfortable and effective stimulation therapy. Because the changes in impedance associated with the electrode-tissue interface can indicate obstruction of current flow and positional lead displacement, lead impedance can indicate the quantity of electrical stimulation energy that should be delivered to the target neural tissue to provide corrective adjustment. Hence, a change in impedance or morphology of an impedance curve may be used in a feedback loop to indicate that the stimulation energy needs to be adjusted and the system can effectively auto correct the magnitude of stimulation energy to maintain a desired therapeutic effect.

1 - 24 . (canceled) 
     
     
         25 . A system, comprising:
 stimulation circuitry that delivers stimulation to a patient via electrodes;   impedance measurement circuitry that periodically measures an impedance associated with the electrodes;   a user interface; and   a processor that identifies a plurality of postures of the patient, receives feedback for each of the postures regarding a perceived intensity of the stimulation via the user interface, associates measured impedances and received feedback with each of the postures, and determines a patient-specific relationship between a stimulation parameter and impedance for each of the postures based on the measured impedances and the feedback associated with each of the postures.   
     
     
         26 . The system of  claim 25 , wherein the feedback comprises an adjustment to the stimulation parameter. 
     
     
         27 . The system of  claim 25 , wherein the feedback comprises information identifying at least one of a perception threshold or a tolerance threshold. 
     
     
         28 . The system of  claim 25 , wherein the stimulation parameter comprises amplitude. 
     
     
         29 . The system of  claim 25 , wherein the impedance measurement circuitry periodically measures the impedance during delivery of stimulation via the electrodes. 
     
     
         30 . The system of  claim 25 , further comprising:
 a medical device that includes the stimulation circuitry and the impedance measurement circuitry; and   a programming device that includes the user interface and the processor, wherein the processor communicates with the medical device to control the delivery of the stimulation and to receive the periodically measured impedances.   
     
     
         31 . The system of  claim 30 , wherein the medical device comprises an implantable neurostimulator. 
     
     
         32 . A method comprising:
 delivering stimulation to a patient via electrodes;   periodically measuring an impedance associated with the electrodes;   identifying a plurality of postures of the patient;   receiving feedback for each of the plurality of postures of the patient regarding a perceived intensity of the stimulation from a user;   associating measured impedances and received feedback with each of the postures; and   determining a patient-specific relationship between a stimulation parameter and impedance for each of the postures based on the measured impedances and the feedback associated with each of the postures.   
     
     
         33 . The method of  claim 32 , wherein receiving feedback comprises receiving an adjustment to the stimulation parameter. 
     
     
         34 . The method of  claim 32 , wherein receiving feedback comprises receiving information identifying one of a perception threshold or a tolerance threshold. 
     
     
         35 . The method of  claim 32 , wherein the stimulation parameter comprises amplitude. 
     
     
         36 . The method of  claim 32 , wherein periodically measuring an impedance comprises periodically measuring the impedance during delivery of stimulation via the electrodes. 
     
     
         37 . The method of  claim 32 , wherein delivering stimulation to a patient via electrodes comprises delivering neurostimulation via an implantable neurostimulator. 
     
     
         38 . A system, comprising:
 means for delivering stimulation to a patient via electrodes;   means for periodically measuring an impedance associated with the electrodes;   means for identifying a plurality of postures of the patient;   means for receiving feedback for each of the postures regarding a perceived intensity of the stimulation from a user;   means for associating measured impedances and received feedback with each of the postures; and   means for determining a patient-specific relationship between a stimulation parameter and impedance for each of the postures based on the measured impedances and the feedback associated with each of the postures.