Methods and Apparatus for Adjusting Neurostimulation Intensity Using Evoked Responses

Abstract

A neurostimulation system provides for capture verification and stimulation intensity adjustment to ensure effectiveness of vagus nerve stimulation in modulating one or more target functions in a patient. In various embodiments, stimulation is applied to the vagus nerve, and evoked responses are detected to verify that the stimulation captures the vagus nerve and to adjust one or more stimulation parameters that control the stimulation intensity.

What is claimed is: 
     
         1 . A method of delivering neurostimulation to a patient, wherein the patient is implanted with an implantable medical device (IMD) comprising an electrode lead comprising a plurality of electrodes, the method comprising:
 using one or more of the plurality electrodes to deliver electrical stimulation to the patient's neural tissue,   using one or more of the plurality of electrodes to sense a neural responses evoked in the patient's tissue by the stimulation,   determining one or more characteristic parameters of the neural responses, and   using the one or more characteristic parameters of the neural responses to adjust the electrical stimulation as the patient changes from a first posture to a second posture.   
     
     
         2 . The method of  claim 1 , wherein determining one or more characteristic parameters of the neural responses comprises determining a waveform for the sensed neural responses, and determining one or more characteristics of the waveform. 
     
     
         3 . The method of  claim 2 , wherein determining the waveform comprises determining an average of a plurality of sensed neural responses. 
     
     
         4 . The method of  claim 2 , wherein the one or more characteristics comprises an amplitude of the waveform. 
     
     
         5 . The method of  claim 2 , wherein the one or more characteristics comprises a frequency of the waveform. 
     
     
         6 . The method of  claim 2 , wherein the one or more characteristics comprises a width of a peak of the waveform. 
     
     
         7 . The method of  claim 1 , wherein adjusting the electrical stimulation comprises adjusting the stimulation to maintain the neural response relative to a threshold value determined for the second posture. 
     
     
         8 . The method of  claim 1 , wherein adjusting a stimulation comprises adjusting an amplitude of the stimulation. 
     
     
         9 . The method of  claim 1 , wherein adjusting a stimulation comprises adjusting one or more of a pulse width, a pulse frequency, a duty cycle, or a duration of the stimulation. 
     
     
         10 . The method of  claim 1 , wherein sensing a neural response comprises detecting the neural response within a time window, wherein the time window begins following the delivery of electrical stimulation. 
     
     
         11 . An implantable medical device (IMD) configured to provide neurostimulation to a patient using a plurality of electrodes implanted in the patient, the IMD comprising:
 stimulation circuitry,   sensor circuitry,   and control circuitry, wherein the control circuitry is configured to:
 cause the stimulation circuitry to deliver electrical stimulation to the patient's neural tissue, 
 cause the sensor circuitry to use one or more of the plurality of electrodes to sense a neural responses evoked in the patient's tissue by the stimulation, 
 determine one or more characteristic parameters of the neural responses, and 
 use the one or more characteristic parameters of the neural responses to adjust the electrical stimulation as the patient changes from a first posture to a second posture. 
   
     
     
         12 . The IMD of  claim 11 , wherein determining one or more characteristic parameters of the neural responses comprises determining a waveform for the sensed neural responses, and determining one or more characteristics of the waveform. 
     
     
         13 . The IMD of  claim 12 , wherein determining the waveform comprises determining an average of a plurality of sensed neural responses. 
     
     
         14 . The IMD of  claim 12 , wherein the one or more characteristics comprises an amplitude of the waveform. 
     
     
         15 . The IMD of  claim 12 , wherein the one or more characteristics comprises a frequency of the waveform. 
     
     
         16 . The IMD of  claim 12 , wherein the one or more characteristics comprises a width of a peak of the waveform. 
     
     
         17 . The IMD of  claim 11 , wherein adjusting the electrical stimulation comprises adjusting the stimulation to maintain the neural response relative to a threshold value determined for the second posture. 
     
     
         18 . The IMD of  claim 11 , wherein adjusting a stimulation comprises adjusting an amplitude of the stimulation. 
     
     
         19 . The IMD of  claim 11 , wherein adjusting a stimulation comprises adjusting one or more of a pulse width, a pulse frequency, a duty cycle, or a duration of the stimulation. 
     
     
         20 . The IMD of  claim 11 , wherein sensing a neural response comprises detecting the neural response within a time window, wherein the time window begins following the delivery of electrical stimulation.