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EP-4208250-B1 - PHASE ALIGNMENT OF ECAPS

EP4208250B1EP 4208250 B1EP4208250 B1EP 4208250B1EP-4208250-B1

Inventors

  • DINSMOOR, DAVID A.
  • BINK, Hank
  • HAGEMAN, Kristin N.

Dates

Publication Date
20260506
Application Date
20210824

Claims (15)

  1. A system (100) comprising: processing circuitry (210) configured to: receive a first evoked compound action potential (ECAP) signal elicited by a first polarity configuration of stimulus electrodes; receive a second ECAP signal elicited by a second polarity configuration of the stimulus electrodes opposite the first polarity configuration; characterized in that the processing circuitry is further configured to: generate an adjusted second ECAP signal by temporally aligning at least a portion of the second ECAP signal to at least a portion of the first ECAP signal; generate at least a portion of a composite ECAP signal based on the first ECAP signal and the adjusted second ECAP signal; and output at least the portion of the composite ECAP signal.
  2. The system of claim 1, wherein the processing circuitry is configured to characterize a misalignment of the first ECAP signal and the second ECAP signal, and wherein the processing circuitry is configured to generate the adjusted second ECAP signal by temporally aligning, based on the misalignment.
  3. The system of any of claims 1 and 2, wherein the processing circuitry is configured to generate the adjusted the second ECAP signal by temporally aligning an entire second ECAP signal by shifting the entire second ECAP signal by an amount of time.
  4. The system of claim 3, wherein the processing circuitry is configured to determine the amount of time by comparing a first time of a feature of the first ECAP signal to a second time of a corresponding feature of the second ECAP signal.
  5. The system of any of claims 3 and 4, wherein the processing circuitry is configured to determine the amount of time based on a conduction velocity of at least one nerve and a distance between the stimulus electrodes.
  6. The system of claim 5, wherein the conduction velocity is a patient specific conduction velocity for the at least one nerve.
  7. The system of any pf claims 5 and 6, wherein the conduction velocity is a human average conduction velocity for the at least one nerve.
  8. The system of any of claims 1 through 7, further comprising sensing circuitry (206) to sense the first ECAP signal and second ECAP signal with at least one sensing electrode combination,
  9. The system of claim 8, further comprising an implantable medical device (110) that houses the processing circuitry and the sensing circuitry.
  10. The system of any of claims 8 and 9, wherein the sensing circuitry is configured to sense the first ECAP signal via a first sensing electrode combination and to sense the second ECAP signal via a second sensing electrode different than the first sensing electrode to compensate for a distance between the stimulus electrodes.
  11. The system of any of claims 1 through 10, wherein the processing circuitry is configured to: determine a characteristics value from the portion of the composite ECAP signal; and adjust at least one parameter of a plurality stimulation parameters that define a stimulus to provide therapy.
  12. The system of any of claims 1 through 11, wherein the system comprises an implantable medical device that comprises at least some of the processing circuitry.
  13. The system of any of claims 1 through 12, wherein the system comprises an external programmer (300) that comprises at least some of the processing circuitry.
  14. A computer readable medium comprising instructions that, when executed, cause a processing circuitry to perform functions, the functions including: receive a first evoked compound action potential (ECAP) signal elicited by a first polarity configuration of stimulus electrodes; receive a second ECAP signal elicited by a second polarity configuration of the stimulus electrodes opposite the first polarity configuration; generate an adjusted second ECAP signal by temporally aligning at least a portion of the second ECAP signal to at least a portion of the first ECAP signal; generate at least a portion of a composite ECAP signal based on the first ECAP signal and the adjusted second ECAP signal; output at least the portion of the composite ECAP signal.
  15. The computer readable medium of claim 14, wherein the functions further include: characterize a misalignment of the first ECAP signal and the second ECAP signal, and generate the adjusted second ECAP signal by temporally aligning based on the misalignment.

Description

TECHNICAL FIELD This disclosure generally relates to medical devices, and more specifically, analyzing sensed electrical signals. BACKGROUND Medical devices may be external or implanted and may be used to deliver electrical stimulation therapy to patients via various tissue sites to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis. A medical device may deliver electrical stimulation therapy via one or more leads that include electrodes located proximate to target locations associated with the brain, the spinal cord, pelvic nerves, peripheral nerves, or the gastrointestinal tract of a patient. Stimulation proximate the spinal cord, proximate the sacral nerve, within the brain, and proximate peripheral nerves are often referred to as spinal cord stimulation (SCS), sacral neuromodulation (SNM), deep brain stimulation (DBS), and peripheral nerve stimulation (PNS), respectively. Electrical stimulation may be delivered to a patient by the medical device in a train of electrical pulses, and parameters of the electrical pulses may include a frequency, an amplitude, a pulse width, and a pulse shape. An evoked compound action potential (ECAP) is synchronous firing of a population of neurons which occurs in response to the application of a stimulus including, in some cases, an electrical stimulus by a medical device. Document US 2019/0366094 A1 relates to stimulation devices configured to measure an ECAP and a stimulation artifact SUMMARY The invention is defined in the appended claims and relates to a system and a computer readable medium. Any methods disclosed hereinafter do not form part of the scope of the invention, and are mentioned for illustrative purposes only. In general, systems, devices, and techniques are described for phase misalignment correction for evoked compound action potential (ECAP) measurement from alternating polarity stimulation. Alternating stimulation polarity for sensing ECAPs can be used to reduce the impact of stimulation artifacts and increase signal amplitude when sensing the ECAPs. Using a bi-polar electrode configuration, a system may sense a pair of ECAP signals using an alternating stimulus polarity for a combination of stimulus electrodes. The first polarity may include at least a first electrode as a cathode and at least a second electrode as an anode for a first stimulus, and the second opposite (or alternating) polarity may include at least a first electrode as the anode and at least a second electrode as the cathode. In this manner, the two delivered stimulus alternate polarities. A second set of electrodes is used to sense the resulting ECAPs signals from each respective stimulus polarity. In systems where the stimulus electrodes and sensing electrodes are along the same axis or generally parallel axes, the timing of the first and second ECAP signals resulting from the respective stimulus polarities may be different due to, for example, the distance from the cathode to the sensing electrodes being different between the two opposite stimulus polarities (e.g., neural stimulation is generally initiated at the cathode). As described below, processing circuitry characterizes the phase misalignment between the two ECAP signals. For example, the processing circuitry may use the conduction velocity, the distance between the two electrodes, and/or the timing of a feature (such as, the first negative peak (N1) of the ECAP signal, etc.) on the first ECAP signal with respect to the corresponding feature of the second ECAP signal. The processing circuitry compensates for the misalignment by processing one or both ECAPs to adjust the timing characteristics such that the two ECAP signals are temporally aligned. The processing circuitry averages the two ECAP signals to generate a composite ECAP signal for further analysis, such as determining an effectiveness of stimulation, determining a placement a lead associated with the electrodes, migration of a lead associated with the electrodes, and/or posture of the patient, etc. The processing circuitry may be part of an implantable medical device (IMD), an external programmer, or a remote server (e.g., a cloud server, etc.). An example system includes processing circuitry that receives a first ECAP signal elicited by a first polarity configuration of stimulus electrodes and receives a second ECAP signal elicited by a second polarity configuration of the stimulus electrodes opposite the first polarity configuration. The processing circuitry also generates an adjusted second ECAP signal by temporally aligning at least a portion of the second ECAP signal to at least a portion of the first ECAP signal, and generates a composite ECAP signal based on the first ECAP signal and the adjusted second ECAP signal. Additionally, the processing circuitry outputs at least a portion the composite ECAP signal. An example method include