ECAP-based control of electrical stimulation therapy

Abstract

Devices, systems, and techniques for controlling electrical stimulation therapy are described. In one embodiment, a system can be configured to: deliver an electrical stimulation therapy to a patient, the electrical stimulation therapy comprising a plurality of treatment pulses at a predetermined pulse frequency over a period of time; and deliver a plurality of pulses over the period of time, the plurality of control pulses being interleaved with at least some of the plurality of treatment pulses. The system can also be configured to: sense a corresponding evoked compound action potential (ECAP) after one or more control pulses and before an immediately subsequent treatment pulse in the plurality of treatment pulses; adjust one or more parameter values ​​that at least partially define the plurality of treatment pulses based on at least one corresponding ECAP; and deliver the electrical stimulation therapy to the patient according to the adjusted one or more parameter values.

Description

Technical Field

[0001] The present disclosure relates generally to electrical stimulation therapy and, more particularly, to the control of electrical stimulation therapy. Technical Background

[0002] The medical device can be an external device or an implanted device and can be used to deliver electrical stimulation therapy to a patient through various tissue sites to treat various symptoms or conditions, such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis. A medical device can deliver electrical stimulation therapy through one or more leads that include electrodes located near a target location associated with the patient's brain, spinal cord, pelvic nerves, peripheral nerves, or gastrointestinal tract. Stimulation within the brain near the spinal cord, near the sacral nerves, and near the peripheral nerves are commonly referred to as spinal cord stimulation (SCS), sacral neuromodulation (SNM), deep brain stimulation (DBS), and peripheral nerve stimulation (PNS), respectively.

[0003] The electrical stimulation therapy may be delivered by the medical device in a series of electrical stimulation pulses, and the parameters defining the electrical stimulation pulses may include frequency, amplitude, pulse width, and pulse shape. Summary of the Invention

[0004] Systems, devices, and techniques for controlling electrical stimulation therapy by sensing evoked compound action potentials (ECAPs) are described. In some embodiments, electrical stimulation pulses are delivered in the form of informed pulses and control pulses that are at least partially interleaved with each other. Control pulses are those stimulation pulses that are configured to cause a detectable ECAP signal (e.g., an ECAP test pulse). In some embodiments, the control pulses can contribute to the treatment of the patient. In other embodiments, the control pulses do not contribute to the treatment of the patient, e.g., non-therapeutic pulses. In this way, the control pulses may or may not be configured to cause a therapeutic effect on the patient. Informed pulses are those stimulation pulses that are defined at least in part by one or more parameters based on a detectable ECAP signal caused by one or more control pulses. In this way, the informed pulses are "informed" by the ECAP signal detected from the control pulses. The informed pulses are also configured to provide therapy to the patient, such as alleviating paresthesias of pain symptoms.

[0005] A medical device (e.g., an implantable medical device) can deliver one or more control pulses to a patient via one or more leads, and a system can sense the resulting ECAP signals caused by the control pulses—all between consecutive learn pulses. For example, in response to a determination that a characteristic of the ECAP signal (e.g., voltage amplitude) has deviated from a target ECAP characteristic, the system can change one or more stimulation parameters of the next one or more learn pulses and / or control pulses delivered to the patient. For example, the system can increase or decrease the current amplitude of the learn pulse (and in some embodiments, the control pulse) in a predetermined step size or based on a gain value representing a growth curve of the patient. In this way, the system can be configured to maintain a consistent amount of neural activation by adjusting one or more stimulation parameters of the learn pulse and / or control pulse. As discussed herein, since the medical device may not be able to detect the ECAP signal caused by the learn pulse, the value of one or more parameters of the learn pulse can be determined based on the characteristics of the ECAP signal detected from the control pulse.

[0006] In some embodiments, the control pulse can be a non-therapeutic pulse, which is a stimulation pulse with a selected parameter value and whose primary purpose is not to contribute to the patient's treatment. In this embodiment, one or more non-therapeutic pulses can be delivered to the patient, and the system can sense the resulting ECAP signal - all between consecutive therapeutic pulses (e.g., configured as a learning pulse that contributes to the patient's treatment). In response to a determination that a characteristic (e.g., voltage amplitude) of the ECAP signal has deviated from a target ECAP characteristic, the system can change one or more stimulation parameters of the next one or more therapeutic pulses delivered to the patient. For example, the system can increase or decrease the current amplitude of the therapeutic pulse in a predetermined step size or based on a gain value representing a growth curve of the patient. In this way, the system can be configured to maintain a consistent amount of neural activation by adjusting one or more stimulation parameters of the therapeutic pulse.

[0007] In one embodiment, a method includes: delivering an electrical stimulation therapy to a patient, the electrical stimulation therapy comprising a plurality of learned pulses at a predetermined pulse frequency over a period of time, wherein the plurality of learned pulses are at least partially defined by a first set of parameter values; delivering a plurality of control pulses interleaved with at least some of the plurality of learned pulses over the period of time, wherein the plurality of control pulses are at least partially defined by a second set of parameter values ​​different from the first set of parameter values; sensing corresponding evoked compound action potentials (ECAPs) after one or more of the plurality of control pulses and before an immediately subsequent learned pulse in the plurality of learned pulses; adjusting one or more parameter values ​​in the first set of parameter values ​​that at least partially define the plurality of learned pulses of the electrical stimulation therapy based on at least one corresponding ECAP; and delivering the electrical stimulation therapy to the patient according to the adjusted one or more parameter values ​​in the first set of parameter values.

[0008] In another embodiment, a system includes: a stimulation generation circuit configured to: deliver an electrical stimulation therapy to a patient, wherein the electrical stimulation therapy includes a plurality of learned pulses at a predetermined pulse frequency over a period of time, and wherein the plurality of learned pulses are at least partially defined by a first set of parameter values; and deliver a plurality of control pulses over the period of time, wherein the plurality of control pulses are interleaved with at least some of the plurality of learned pulses, and wherein the plurality of control pulses are at least partially defined by a second set of parameter values ​​different from the first set of parameter values; and a processing circuit configured to: receive corresponding sensed evoked compound action potentials (ECAPs) after one or more control pulses in the plurality of control pulses and before a subsequent learned pulse in the plurality of learned pulses; adjust one or more parameter values ​​in the first set of parameter values ​​that at least partially define the plurality of learned pulses of the electrical stimulation therapy based on at least one corresponding ECAP; and deliver the electrical stimulation therapy to the patient via the stimulation generation circuit according to the adjusted one or more parameter values ​​in the first set of parameter values.

[0009] In another embodiment, a computer-readable storage medium comprises instructions that, when executed, cause one or more processors to: control delivery of an electrical stimulation therapy to a patient, the electrical stimulation therapy comprising a plurality of learned pulses at a predetermined pulse frequency over a period of time, wherein the plurality of learned pulses are at least partially defined by a first set of parameter values; control delivery of a plurality of control pulses interleaved with at least some of the plurality of learned pulses over the period of time, wherein the plurality of control pulses are at least partially defined by a second set of parameter values ​​different from the first set of parameter values; receive a corresponding sensed evoked compound action potential (ECAP) after one or more of the plurality of control pulses and before an immediately subsequent learned pulse in the plurality of learned pulses; adjust one or more parameter values ​​in the first set of parameter values ​​that at least partially define the plurality of learned pulses of the electrical stimulation therapy based on at least one corresponding ECAP; and deliver the electrical stimulation therapy to the patient according to the adjusted one or more parameter values ​​in the first set of parameter values.

[0010] In another embodiment, a method includes: delivering a control stimulation pulse to a patient, the control stimulation pulse having a first pulse width; sensing an evoked compound action potential (ECAP) signal caused by the control stimulation pulse; identifying characteristics of the ECAP signal; determining a parameter value that at least partially defines a learned stimulation pulse based on a plurality of learned pulses based on the characteristics and a gain value of the ECAP signal; wherein the plurality of learned pulses have a second pulse width greater than the first pulse width; and delivering the learned pulse based on the determined parameter value.

[0011] In another embodiment, a system includes: a stimulation generation circuit configured to: deliver a control stimulation pulse to a patient, the control stimulation pulse having a first pulse width; and deliver a learned stimulation pulse from a plurality of learned pulses according to a parameter value, wherein the plurality of learned pulses have a second pulse width longer than the first pulse width; and a processing circuit configured to: receive a sensed evoked compound action potential (ECAP) signal caused by the control stimulation pulse; identify characteristics of the ECAP signal; and determine the parameter value that at least partially defines the learned stimulation pulse based on the characteristics of the ECAP signal and a gain value.

[0012] In another embodiment, a computer-readable storage medium includes instructions that, when executed, cause one or more processors to: control the delivery of a control stimulation pulse to a patient, the control stimulation pulse having a first pulse width; sense an evoked compound action potential (ECAP) signal caused by the control stimulation pulse; identify characteristics of the ECAP signal; determine a parameter value that at least partially defines a learned stimulation pulse based on a plurality of learned pulses based on the characteristics and a gain value of the ECAP signal, wherein the plurality of learned pulses have a second pulse width that is longer than the first pulse width; and control the delivery of the learned pulse based on the determined parameter value.

[0013] The details of one or more embodiments of the disclosed technology are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the technology will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a conceptual diagram illustrating an exemplary system including a medical device programmer and an implantable medical device (IMD) configured to deliver spinal cord stimulation (SCS) therapy in accordance with the disclosed technology.

[0015] Figure 2A yes Figure 1 Block diagram of an exemplary IMD.

[0016] Figure 2B yes Figure 1 A block diagram of an exemplary external programmer.

[0017] Figure 3 is a graph of exemplary evoked compound action potentials (ECAPs) sensed for corresponding stimulation pulses.

[0018] Figure 4A is a timing diagram illustrating an embodiment of electrical stimulation pulses and corresponding sensing ECAPs in accordance with one or more techniques of this disclosure.

[0019] Figure 4B is a timing diagram illustrating an embodiment of electrical stimulation pulses and corresponding sensing ECAPs according to the disclosed technology.

[0020] Figure 5 is a timing diagram illustrating another embodiment of electrical stimulation pulses and corresponding ECAPs according to the disclosed technology.

[0021] Figure 6 is a timing diagram illustrating another embodiment of electrical stimulation pulses and corresponding ECAPs according to the disclosed technology.

[0022] Figure 7is a flow chart illustrating an exemplary technique for therapeutic delivery in accordance with the disclosed technology.

[0023] Figure 8 is a flow chart illustrating an exemplary technique for adjusting the delivery of control pulses of an ECAP test stimulus in response to input.

[0024] Figure 9 is a flow chart illustrating an exemplary technique for adjusting stimulation therapy.

[0025] Figure 10A is a graph of an exemplary growth curve of sensed ECAPs as a function of corresponding stimulation pulse amplitudes.

[0026] Figure 10B is a schematic diagram illustrating an exemplary technique for adjusting stimulation therapy.

[0027] Figure 11 is a flow chart illustrating an exemplary technique for adjusting stimulation therapy.

[0028] Figure 12 is a schematic diagram of an exemplary apparatus used in experiments to test the efficacy of a feedback mechanism using a sensing ECAP.

[0029] Figure 13 Included are graphs showing the sensed ECAP voltage amplitude using open loop and different feedback target amplitudes in a closed loop configuration. DETAILED DESCRIPTION

[0030] The present disclosure describes embodiments of medical devices, systems, and techniques for automatically adjusting electrical stimulation therapy delivered to a patient in response to one or more characteristics of an evoked compound action potential (ECAP) received by the medical device in response to a controlled stimulation pulse delivered by the medical device. Electrical stimulation therapy is typically delivered to a patient's target tissue (e.g., one or more nerves or muscles) via two or more electrodes. The parameters of the electrical stimulation therapy (e.g., electrode combination, voltage or current amplitude, pulse width, pulse frequency, etc.) are selected by a clinician and / or patient to relieve various symptoms, such as pain, muscle disorders, etc. However, as the patient moves, the distance between the electrode and the target tissue changes. Since neural recruitment is a function of the intensity of the stimulation and the distance between the target tissue and the electrode, movement of the electrode closer to the target tissue may result in an increased perception by the patient (e.g., possible pain), while movement of the electrode away from the target tissue may result in a reduced efficacy of the treatment for the patient.

[0031] ECAP is a measure of neural recruitment because each ECAP signal represents the superposition of electrical potentials generated by axonal firing in response to an electrical stimulus (e.g., a stimulation pulse). Changes in the characteristics of the ECAP signal (e.g., the amplitude of a portion of the signal, the area below one or more peaks, the frequency content, and / or the timing of the maximum and / or minimum peaks) occur depending on the number of axons activated by the delivered stimulation pulse. The system can monitor changes in the characteristics of the ECAP signal and use the changes in the characteristics to adjust one or more stimulation parameters of the learning pulse and / or control pulse delivered to the patient. For example, the system can reduce the intensity of the stimulation pulse (e.g., reducing the current amplitude and / or pulse width) in response to detecting an increase in the amplitude of the ECAP signal. After the delivered stimulation pulse first depolarizes the nerve, the nerve impulse can be detected as the ECAP signal rapidly propagates along the nerve fiber. Therefore, if the stimulation pulse delivered by the first electrode has a pulse width that is too long, a different electrode configured to sense the ECAP will sense the stimulation pulse itself as an artifact that obscures the lower amplitude ECAP signal. However, the ECAP signal loses fidelity as the potential propagates from the electrical stimulus, as different nerve fibers propagate the potential at different speeds. Thus, sensing the ECAP at a large distance from the stimulation electrode can avoid artifacts caused by stimulation pulses with long pulse widths, but the ECAP signal may lose the fidelity required to detect changes in the ECAP signal as the distance from the electrode to the target tissue changes. In other words, the system may not be able to identify the ECAP at any distance from the stimulation electrode that is configured to deliver a therapeutic stimulation pulse to the patient.

[0032] As described herein, a medical device can be configured to deliver multiple learn pulses and / or control pulses configured to provide treatment to a patient based on one or more parameters of an ECAP signal induced by a previously delivered control pulse. In some cases, a medical device can deliver multiple learn pulses configured to provide treatment to a patient, or at least contribute to treatment of the patient, based on one or more parameters of an ECAP signal induced by a control pulse. In some embodiments, a control pulse can be configured to induce an ECAP signal without contributing to treatment of the patient. However, in other embodiments, a control pulse can provide treatment to the patient alone or in combination with a learn pulse. The control pulses can be interleaved with the delivery of the learn pulses. For example, a medical device can alternately deliver learn pulses and control pulses, such that control pulses are delivered between successive learn pulses and an ECAP signal is sensed from the control pulses. In some embodiments, multiple control pulses are delivered between successive learn pulses, and corresponding ECAP signals are sensed. In some embodiments, multiple learn pulses are delivered between successive control pulses. In any case, the learn pulses can be delivered according to a selected predetermined pulse frequency so that the learn pulses can produce or contribute to a therapeutic outcome for the patient. One or more control pulses are then delivered within one or more time windows between successive learn pulses delivered according to a predetermined pulse frequency, and corresponding ECAP signals are sensed. The predetermined pulse frequency can be a single consistent frequency or a varying frequency that varies over time. The pulse width of the control pulses can be shorter than the pulse width of the learn pulses to enable the medical device to detect ECAP signals arising from the control pulses. In other words, the longer pulse width of the learn pulses may prevent detection of the resulting ECAP signal, for example due to overlap of the learn pulses with the ECAP signal. In this way, the medical device can uninterruptedly manage learn pulses from the medical device while simultaneously sensing ECAP from control pulses delivered during times when no learn pulses were delivered.

[0033] In one embodiment, the control pulses do not contribute to the patient's treatment and may be referred to as non-therapeutic pulses. In this embodiment, the medical device may be configured to deliver: a plurality of therapeutic pulses (e.g., learn pulses) configured to provide treatment to the patient; and a plurality of non-therapeutic pulses configured to induce a detectable ECAP signal whose primary purpose is not to provide treatment to the patient. The non-therapeutic pulses may be interleaved with the delivery of the therapeutic pulses. For example, the medical device may alternate the delivery of therapeutic pulses with the delivery of non-therapeutic pulses, such that non-therapeutic pulses are delivered and ECAP signals are sensed between consecutive therapeutic pulses. In some embodiments, a plurality of non-therapeutic pulses are delivered between consecutive therapeutic pulses, and corresponding ECAP signals are sensed. In some embodiments, a plurality of therapeutic pulses are delivered between consecutive non-therapeutic pulses. In any case, the therapeutic pulses may be delivered according to a predetermined pulse frequency selected so that the therapeutic pulses produce a therapeutic result for the patient. One or more non-therapeutic pulses are then delivered within one or more time windows between consecutive therapeutic pulses delivered according to the predetermined pulse frequency, and corresponding ECAP signals are sensed. In this manner, the medical device can continuously administer therapeutic pulses from the medical device while simultaneously sensing ECAP from non-therapeutic pulses delivered during times when no therapeutic pulses were delivered.

[0034] The system can adjust the values ​​of one or more parameters that at least partially define the learn pulse in response to determining a change in one or more characteristics of a sensed ECAP signal received by the medical device. For example, the medical device can measure the amplitude of the ECAP signal caused by the control pulse and compare it to a target ECAP amplitude previously identified as appropriate for the patient. If the amplitude of the ECAP signal (e.g., the voltage amplitude of one or more peaks in the ECAP signal) is greater than the target ECAP amplitude, the intensity of the control pulse may be too high because the stimulating electrode has moved closer to the nerve. The medical device can responsively reduce the intensity of the learn pulse (e.g., current amplitude, pulse width, pulse frequency, slew rate, or any combination thereof). Conversely, if the amplitude of the ECAP signal is less than the target ECAP amplitude, the intensity of the control pulse may not be strong enough because the stimulating electrode has moved away from the nerve. The medical device can responsively increase the intensity of the learn pulse. In this manner, the medical device can monitor the ECAP signal caused by the control pulse to adjust one or more parameters of the learn pulse to maintain a certain amount of neural activation, thereby providing effective treatment to the patient.

[0035] The pulse width of the control pulse can be shorter than the pulse width of the learn pulse to reduce or prevent the sensed electrical artifacts from the control pulse from obscuring the ECAP signal (in other words, the pulse width of the learn pulse can be longer than the pulse width of the control pulse). For example, the control pulse can be less than about 300 microseconds (μs). In one embodiment, the control pulse can be a biphasic pulse having a positive phase of about 100 μs and a negative phase of about 100 μs, the positive phase and the negative phase being separated by an interphase interval of about 30 μs. In this way, the stimulation electrode at one end of the lead can deliver the control pulse, while the electrode at the other end of the same lead can sense the ECAP signal without interference from the control pulse itself, or with minimal interference.

[0036] In one embodiment, the system can adjust one or more parameters of a learn pulse based on a sensed ECAP signal. The medical device can determine a representative amplitude of at least one corresponding ECAP signal. The medical device can then compare the representative amplitude to a target ECAP characteristic (e.g., a target ECAP amplitude or other characteristic, such as frequency content, area under one or more peaks, or timing of one or more peaks) and a target ECAP adjustment window. The target ECAP adjustment window can be an amplitude range around the target ECAP amplitude, including an upper and lower limit. In some embodiments, the target ECAP adjustment window can be defined by the target ECAP characteristic plus and minus the variation, such that for smaller oscillations in the ECAP signal, one or more parameters of the learn pulse are not adjusted. In other words, the target ECAP characteristic plus the variation can be the upper limit of the target ECAP adjustment window, and the target ECAP characteristic minus the variation can be the lower limit of the target ECAP adjustment window. The variations above and below the target ECAP characteristic can be the same or different. If the representative amplitude of the at least one corresponding ECAP signal is greater than the upper limit of the target ECAP adjustment window, the medical device can be configured to reduce the amplitude of subsequent learn pulses and control pulses. The control pulse can also be adjusted to determine whether further adjustment is needed based on subsequently detected ECAP signals. If the representative amplitude of the at least one corresponding ECAP signal falls below a lower limit of a target ECAP adjustment window, the medical device can be configured to increase the amplitude of the learning pulse and the control pulse after the at least one corresponding ECAP signal. The amount by which the amplitude of the learning pulse and the control pulse is changed based on the detected change in the representative amplitude of the ECAP signal can be a predetermined amplitude step or a predetermined percentage. In this manner, the feedback loop may require more than one iteration to reach the target ECAP amplitude again.

[0037] In another embodiment, the medical device can employ a dynamic feedback loop. A growth curve can be determined for the patient based on the slope of the relationship between the detected values ​​of a characteristic of the ECAP signal for different stimulation pulse amplitudes. Thus, the medical device can determine the difference between a target ECAP characteristic value (e.g., amplitude value, area under one or more peaks, frequency content, or maximum and / or minimum peak timing) and the measured ECAP value and multiply this difference by a gain value. The resulting value can then be used to increase or decrease the previous parameter value that defined the control pulse that caused the measured ECAP value. The gain value can also be used to similarly adjust the parameter value of the learn pulse. By using the gain value, the system can be able to quickly respond to large ECAP signal changes and reset the learn pulse and control pulse to the target ECAP. This process can reduce the number of learn pulses that produce less effective treatment due to changes in the electrode-tissue distance during patient movement.

[0038] Learn pulses and control pulses are generally described herein as different stimulation pulses reflecting different types of electrical stimulation. However, different attributes can be used to describe different types of electrical stimulation and their respective pulses. For example, a first type of electrical stimulation may include a first pulse configured to primarily assist in patient treatment. The first pulse of the first type of electrical stimulation may also have one or more characteristics (e.g., pulse width) that prevent or reduce the system's ability to detect an ECAP signal induced by the first pulse of the first type of electrical stimulation because an artifact representing the first pulse itself overlaps with and obscures at least a portion of the corresponding induced ECAP signal. A second type of electrical stimulation may include a second pulse defined by one or more parameter values ​​selected to induce an ECAP signal that is sensed and detectable by the system. Because the second pulse is configured to induce a detectable ECAP signal, the second pulse may be referred to as a "control pulse," "sensing pulse," or "test pulse." For example, the second pulse of the second type of electrical stimulation may improve the detectability of the ECAP signal, thereby not generating artifacts that obscure the ECAP signal (or reducing the presence of artifacts) or otherwise preventing or reducing the system's ability to detect an ECAP signal from each of the second pulses. Additionally, the second pulse can be defined by parameter values ​​selected to cause an ECAP signal that is used to modify at least one parameter value of the first pulse of the first type of electrical stimulation (e.g., the learn pulse). Thus, the first pulse can differ from the second pulse in at least one parameter (e.g., current and / or voltage amplitude, pulse width, and / or frequency). As discussed herein, in some embodiments, the pulse width of the second pulse is shorter than the pulse width of the first pulse. The first pulse can be at least partially interleaved with at least some of the second pulses. For example, the system can alternately deliver one first pulse and one second pulse. In another embodiment, the number of first pulses can differ from the number of second pulses in a ratio or percentage. When the first and second pulses are fully interleaved, the ratio can be 1:1. In an embodiment, the ratio of the first pulse to the second pulse can be 10:1, wherein the second pulse is delivered less frequently than the first pulse. In other embodiments, when the second pulse and the corresponding sensed ECAP signal occur more frequently than the first pulse, the ratio of the first pulse to the second pulse can be 1:4. The second pulses may or may not contribute to the treatment or the sensation perceived by the patient, but the primary purpose of the second pulses is to induce a corresponding ECAP signal detectable by the system, separate from any sensing artifacts representing the second pulses themselves. Because the ECAP signals induced by the second pulses are detectable, the system can use the ECAP signals from one or more second pulses to "inform" or adjust one or more parameter values ​​that at least partially define the first pulses (e.g., the learn pulses).

[0039] Although electrical stimulation is generally described herein in terms of electrical stimulation pulses, in other embodiments, electrical stimulation can be delivered in a non-pulsed manner. For example, electrical stimulation can be delivered as a signal having a variety of waveform shapes, frequencies, and amplitudes. Thus, electrical stimulation in the form of a non-pulsed signal can be a continuous signal, rather than having a sinusoidal or other continuous waveform.

[0040] Figure 1 is a conceptual diagram illustrating an exemplary system 100 including an implantable medical device (IMD) 110 configured to deliver electrical stimulation therapy to a patient 105. Figure 1 In the illustrated embodiment, IMD 110 is configured to deliver spinal cord stimulation (SCS) therapy according to the techniques of the present disclosure. Although the techniques described in this disclosure are generally applicable to a variety of medical devices, including external and implantable medical devices (IMDs), for illustrative purposes, these techniques will be described as being applied to IMDs, and more specifically to implantable electrical stimulators (e.g., neurostimulators). More specifically, for illustrative purposes, the present disclosure will relate to implantable spinal cord stimulation (SCS) systems, but is not limited to other types of medical devices or other therapeutic applications of medical devices.

[0041] like Figure 1 As shown, system 100 includes IMD 110, shown with patient 105, which is typically a human patient, leads 130A and 130B, and external programmer 150. Figure 1 In some embodiments, IMD 110 is an implantable electrical stimulator that is configured to generate and deliver electrical stimulation therapy to patient 105 via one or more of the electrodes of leads 130A and / or 130B (collectively, "leads 130"), e.g., to relieve pain or other symptoms. In other embodiments, IMD 110 may be coupled to: a single lead with multiple electrodes; or more than two leads, each with multiple electrodes. In addition to electrical stimulation therapy, IMD 110 may also be configured to generate and deliver control pulses configured to cause ECAP signals that may or may not contribute to the therapy of the pulsed therapy. As discussed herein, in some embodiments, the control pulses may be non-therapeutic. IMD 110 may be a chronic electrical stimulator that may be implanted in patient 105 for weeks, months, or even years. In other embodiments, IMD 110 may be a temporary or trial stimulator used to screen or evaluate the efficacy of electrical stimulation for chronic therapy. In one embodiment, IMD 110 is implanted in patient 105, while in another embodiment, IMD 110 is an external device coupled to percutaneously implanted leads. In some embodiments, IMD 110 uses one or more leads, while in other embodiments, IMD 110 is leadless.

[0042] IMD 110 may be comprised of components sufficient to integrate IMD 110 (e.g., Figure 2A 105 is constructed of any polymer, metal, or composite material that is housed within the body of patient 105, including the components shown in FIG. 10 . In this embodiment, IMD 110 can be constructed of a biocompatible housing (e.g., titanium or stainless steel) or a polymeric material (e.g., silicone, polyurethane, or liquid crystal polymer) and surgically implanted in patient 105 near the pelvis, abdomen, or buttocks. In other embodiments, IMD 110 can be implanted in other suitable locations within patient 105, which can depend, for example, on the target location within patient 105 for delivery of electrical stimulation therapy. The housing of IMD 110 can be configured to provide an airtight seal for components such as a rechargeable or non-rechargeable power source. Additionally, in some embodiments, the housing of IMD 110 can be selected from a material that facilitates receiving energy to charge a rechargeable power source.

[0043] For example, electrical stimulation energy, which may be constant current-based or constant voltage-based pulses, is delivered from IMD 110 to one or more target tissue sites of patient 105 via one or more electrodes (not shown) of implantable leads 130. Figure 1 In some embodiments, lead 130 carries electrodes that are positioned adjacent to target tissue of spinal cord 120. One or more of the electrodes can be located at the distal end of lead 130 and / or at other locations along the midpoint of the lead. Lead 130 can be implanted and coupled to IMD 110. The electrodes can deliver electrical stimulation generated by an electrical stimulation generator in IMD 110 to tissue of patient 105. Although leads 130 can each be a single lead, leads 130 can include lead extensions or other sections that facilitate implantation or positioning of lead 130. In other embodiments, IMD 110 can be a leadless stimulator having one or more electrode arrays disposed on the housing of the stimulator, rather than leads extending from the housing. Additionally, in other embodiments, system 100 can include one lead or more than two leads, each coupled to IMD 110 and directed to similar or different target tissue sites.

[0044] The electrodes of lead 130 can be: electrode pads on a paddle-shaped lead; circular (e.g., ring-shaped) electrodes surrounding the lead body; conformable electrodes; cuff electrodes; segmented electrodes (e.g., electrodes disposed at different circumferential locations around the lead rather than a continuous ring electrode); any combination thereof (e.g., ring electrodes and segmented electrodes); or any other type of electrode capable of forming a monopolar, bipolar, or multipolar electrode combination for treatment. For illustrative purposes, ring electrodes disposed at different axial locations at the distal end of lead 130 will be described.

[0045] For illustrative purposes, the layout of electrodes through lead 130 is described, but the array of electrodes can be arranged in different ways. For example, a housing associated with a leadless stimulator can carry an array of electrodes, such as rows and / or columns (or other patterns), to which a shift operation can be applied. Such electrodes can be arranged as surface electrodes, ring electrodes, or protrusions. As another alternative, the electrode array can be formed by rows and / or columns of electrodes on one or more paddle-shaped leads. In some embodiments, the electrode array can include electrode segments that can be arranged at corresponding positions around the periphery of the lead, for example, in the form of one or more segmented rings around the periphery of a cylindrical lead. In other embodiments, one or more of the leads 130 are linear leads with 8 ring electrodes along the axial length of the lead. In another embodiment, the electrodes are segmented rings arranged in a linear manner along the axial length of the lead and at the periphery of the lead.

[0046] The stimulation parameters of a therapeutic stimulation program, which define the stimulation pulses for electrical stimulation therapy delivered by IMD 110 via the electrodes of leads 130, may include information identifying: which electrodes have been selected for delivering stimulation according to the stimulation program; the polarity of the selected electrodes, i.e., the electrode combination of the program; and the voltage or current amplitude, pulse frequency, pulse width, and pulse shape of the stimulation delivered by the electrodes. These stimulation parameters of the learned pulses are typically predetermined parameter values ​​determined prior to delivering the learned pulses. However, in some embodiments, system 100 may automatically change one or more parameter values ​​based on one or more factors or based on user input.

[0047] In addition to stimulating the learning pulses, the ECAP test stimulation program can also define stimulation parameter values ​​that define the control pulses delivered by the IMD 110 through at least some of the electrodes of the leads 130. These stimulation parameter values ​​may include information identifying which electrodes have been selected to deliver the control pulses; the polarity of the selected electrodes (i.e., the electrode combination used for the program); and the voltage or current amplitude, pulse frequency, pulse width, and pulse shape of the stimulation delivered by the electrodes. The stimulation signals (e.g., one or more stimulation pulses or a continuous stimulation waveform) defined by the parameters of each ECAP test stimulation program are configured to induce compound action potentials from the nerve. In some embodiments, the ECAP test stimulation program can define when the control pulses are delivered to the patient based on the frequency and / or pulse width of the learning pulses. However, not all stimulation defined by each ECAP test stimulation program is intended to provide therapy to the patient or contribute to the patient's treatment. In embodiments where the control pulses contribute to the patient's treatment or provide therapy to the patient, the ECAP test stimulation program can also be used in place of the therapy stimulation program or in the same manner as the therapy stimulation program.

[0048] although Figure 1The invention relates to SCS therapy (e.g., for treating pain), but in other embodiments, the system 100 can be configured to treat any other condition that can benefit from electrical stimulation therapy. For example, the system 100 can be used to treat tremors, Parkinson's disease, epilepsy, pelvic floor disorders (e.g., urinary incontinence or other bladder dysfunction, fecal incontinence, pelvic pain, bowel dysfunction or sexual dysfunction), obesity, gastroparesis, or psychiatric disorders (e.g., depression, mania, obsessive-compulsive disorder, anxiety, etc.). In this way, the system 100 can be configured to provide therapy in the form of deep brain stimulation (DBS), peripheral nerve stimulation (PNS), peripheral nerve field stimulation (PNFS), cortical stimulation (CS), pelvic floor stimulation, gastrointestinal stimulation, or any other stimulation therapy capable of treating the condition of the patient 105.

[0049] In some embodiments, lead 130 may include one or more sensors configured to allow IMD 110 to monitor one or more parameters of patient 105, such as patient activity, pressure, temperature, or other characteristics. The one or more sensors may be provided in addition to or in lieu of therapy delivery via lead 130.

[0050] IMD 110 is configured to deliver electrical stimulation therapy to patient 105 via a selected combination of electrodes carried by one or both leads 130, either alone or in combination with electrodes carried by or confined to the housing of IMD 110. The target tissue for the electrical stimulation therapy can be any tissue that is susceptible to electrical stimulation, which can be in the form of electrical stimulation pulses or a continuous waveform. In some embodiments, the target tissue includes nerves, smooth muscle, or skeletal muscle. Figure 1 In the illustrated embodiment, the target tissue is tissue adjacent to the spinal cord 120, such as within the intrathecal space or epidural space of the spinal cord 120, or in some embodiments, adjacent nerves branching from the spinal cord 120. The lead 130 can be introduced into the spinal cord 120 through any suitable region, such as the thoracic, cervical, or lumbar regions. Stimulation of the spinal cord 120 can, for example, prevent pain signals from traveling through the spinal cord 120 to the brain of the patient 105. The patient 105 can perceive the interruption of the pain signals as a reduction in pain, thereby providing an effective therapeutic outcome. In other embodiments, stimulation of the spinal cord 120 can produce paresthesias that can reduce the patient's 105 perception of pain and thereby provide an effective therapeutic outcome.

[0051] The IMD 110 generates electrical stimulation therapy according to one or more therapeutic stimulation programs and delivers the electrical stimulation therapy to a target stimulation site in the body of the patient 105 via electrodes of the leads 130 to the patient 105. The therapeutic stimulation program defines the values ​​of one or more parameters that define an aspect of the therapy delivered by the IMD 110 according to the program. For example, a therapeutic stimulation program that controls the delivery of stimulation by the IMD 110 in the form of pulses can define the values ​​of the voltage or current pulse amplitude, pulse width, and pulse rate (e.g., pulse frequency) of the stimulation pulses delivered by the IMD 110 according to the program. The therapeutic stimulation program can define the control pulses and / or the learned pulses when they are configured to contribute to a therapeutic effect (e.g., paresthesia, pain block, etc.) for the patient.

[0052] Furthermore, IMD 110 is configured to deliver controlled stimulation to patient 105 via a combination of electrodes of leads 130, either alone or in combination with electrodes carried or defined by the housing of IMD 110. The tissue targeted by the controlled stimulation may be the same tissue targeted by the electrical stimulation therapy, but IMD 110 may deliver the control pulses via the same, at least some of the same, or different electrodes, and is intended to induce a detectable ECAP signal. This controlled stimulation may contribute to the patient's treatment outcome (e.g., therapeutic stimulation) or may not contribute to the patient's treatment outcome (e.g., non-therapeutic stimulation). Because the control pulses can be delivered in an interleaved manner with the learned pulses, the clinician and / or user can select any desired electrode combination for the learned pulses. Like the electrical stimulation therapy, the controlled stimulation may be in the form of electrical stimulation pulses or a continuous waveform. In one embodiment, each control pulse may comprise a balanced biphasic square pulse with an active recharge phase. However, in other embodiments, the control pulse may comprise a monophasic pulse followed by a passive recharge phase. In other embodiments, the control pulse may comprise an unbalanced biphasic portion and a passive recharge portion. Although not required, the biphasic control pulses may include an interphase interval between the positive and negative phases to promote the propagation of the neural pulse in response to the first phase of the biphasic pulse. The control stimulation may be delivered without interrupting the delivery of the electrical stimulation learn pulses (e.g., during a window between consecutive learn pulses). The control pulses may induce an ECAP signal from the tissue, and the IMD 110 may sense the ECAP signal through two or more electrodes on the lead 130. When the control pulses are applied to the spinal cord 120, the IMD 110 may sense the signal from the spinal cord 120. As discussed herein, the control stimulation may contribute, alone or in part, to the therapeutic effect received by the patient. In other words, in some embodiments, the control pulses may be delivered to provide therapy without any additional learn pulses. In embodiments where only the control pulses may provide therapy to the patient, the control stimulation may be a therapeutic stimulation for the patient.

[0053] According to one or more ECAP test stimulation programs, IMD 110 delivers controlled stimulation to target stimulation sites within patient 105 via electrodes of leads 130. The one or more ECAP test stimulation programs may be stored in a memory of IMD 110. Each of the one or more ECAP test stimulation programs includes values ​​for one or more parameters that define aspects of the controlled stimulation delivered by IMD 110 according to the program, such as current or voltage amplitude, pulse width, pulse frequency, electrode combination, and, in some embodiments, timing based on a learn pulse to be delivered to patient 105. In some embodiments, IMD 110 delivers controlled stimulation to patient 105 according to multiple ECAP test stimulation programs.

[0054] A user (e.g., a clinician or patient 105) can interact with a user interface of external programmer 150 to program IMD 110. Programming of IMD 110 can generally refer to the generation and delivery of commands, programs, or other information that control the operation of IMD 110. In this manner, IMD 110 can receive delivered commands and programs from programmer 150 to control electrical stimulation therapy (e.g., learning pulses, and in some embodiments, control pulses) and control stimulation (e.g., control pulses). For example, external programmer 150 can transmit therapy stimulation programs, ECAP test stimulation programs, stimulation parameter adjustments, therapy stimulation program selections, ECAP test program selections, user input, or other information to control the operation of IMD 110, e.g., via wireless telemetry or a wired connection.

[0055] In some cases, if external programmer 150 is primarily intended for use by a physician or clinician, it may be characterized as a physician or clinician programmer. In other cases, if external programmer 150 is primarily intended for use by a patient, it may be characterized as a patient programmer. A patient programmer is typically accessible to patient 105 and, in many cases, may be a portable device that accompanies patient 105 throughout their daily routine. For example, a patient programmer may receive input from patient 105 when the patient wishes to terminate or change electrical stimulation therapy. Typically, during normal use, a physician or clinician programmer may support the clinician in selecting and generating programs for use with IMD 110, while a patient programmer may support the patient in adjusting and selecting such programs. In other embodiments, external programmer 150 may include, or be part of, an external charging device that recharges the power supply of IMD 110. In this manner, a user may program and charge IMD 110 using one or more devices.

[0056] As described herein, information can be transferred between external programmer 150 and IMD 110. Thus, IMD 110 and programmer 150 can communicate via wireless communication using any technology known in the art. Examples of communication technologies may include, for example, radio frequency (RF) telemetry and sense coupling, although other technologies are also contemplated. In some embodiments, programmer 150 may include a communication head that can be placed proximate to the patient's body near the implant site of IMD 110 to improve the quality or safety of communication between IMD 110 and programmer 150. Communication between programmer 150 and IMD 110 may occur during or separate from power transfer.

[0057] In some embodiments, IMD 110 delivers electrical stimulation therapy to target tissue sites of spinal cord 120 of patient 105 via electrodes (not depicted) on leads 130 according to a plurality of therapeutic stimulation programs in response to commands from external programmer 150. In some embodiments, as the therapeutic needs of patient 105 evolve over time, IMD 110 can modify the therapeutic stimulation program. For example, modification of the therapeutic stimulation program can result in adjustment of at least one parameter of the plurality of learned pulses. When patient 105 receives the same treatment for an extended period of time, the efficacy of the treatment may decrease. In some cases, the parameters of the plurality of learned pulses can be automatically updated.

[0058] In the present disclosure, the efficacy of electrical stimulation therapy can be indicated by one or more characteristics (e.g., the amplitude between one or more peaks or the area under the curve of one or more peaks) of action potentials (i.e., characteristics of an ECAP signal) evoked by stimulation pulses delivered by IMD 110. Electrical stimulation therapy delivered via leads 130 of IMD 110 may induce neurons within the target tissue to evoke compound action potentials, which travel up and down the target tissue and ultimately reach the sensing electrodes of IMD 110. Furthermore, controlled stimulation may also induce at least one ECAP, and the number of ECAPs responsive to controlled stimulation may also be an indicator of the effectiveness of the therapy. The number of action potentials evoked (e.g., the number of neurons that propagate an action potential signal) can be based on various parameters of the electrical stimulation pulse, such as amplitude, pulse width, frequency, and pulse shape (e.g., slew rate at the start and / or end of the pulse). Slew rate can be defined as the rate of change of the voltage and / or current amplitude of the pulse at the start and / or end of each pulse, or within each phase of a pulse. For example, a very high slew rate indicates that the edges of the pulse are steep or even nearly vertical, while a lower slew rate indicates that the pulse amplitude has a longer rise (or fall) time. In some embodiments, these parameters can contribute to the intensity of the electrical stimulation.Additionally, the characteristics of the ECAP signal (eg, amplitude) can vary based on the distance between the stimulation electrode and the nerve that is subjected to the electric field generated by the delivered control pulses.

[0059] In one embodiment, each learn pulse can have a pulse width greater than approximately 300 μs, such as approximately 300 μs to 1000 μs (i.e., 1 millisecond) in certain embodiments. At these pulse widths, the IMD 110 may not adequately detect the ECAP signal because the learn pulse is also detected as an artifact that obscures the ECAP signal. If the ECAP is not properly recorded, the ECAP arriving at the IMD 110 cannot be compared with the target ECAP characteristics (e.g., target ECAP amplitude), and the electrical therapy stimulation cannot be modified based on the responsive ECAP. When the learn pulse has these longer pulse widths, the IMD 110 can deliver the control stimulation in the form of control pulses. The control pulse can have a pulse width less than approximately 300 μs, such as a biphasic pulse, each phase of which lasts approximately 100 μs. Because the control pulse can have a shorter pulse width than the learn pulse, the ECAP signal can be sensed and identified after each control pulse and used to notify the IMD 110 of any changes that should be made to the learn pulse (and, in certain embodiments, the control pulse). In some embodiments, at least some of the learned pulses may have a pulse width of less than about 300 μs. In such embodiments, the control pulses interleaved with the learned pulses may have a pulse width shorter than the pulse width of the learned pulses. In other embodiments, the control pulses may have a pulse width greater than the pulse width of the learned pulses. In general, the term "pulse width" refers to the total duration of each phase of a single pulse and, when appropriate, the interphase interval. In some embodiments, a single pulse may include a single phase (i.e., a monophasic pulse), or in other embodiments, a single pulse may include two or more phases (e.g., a biphasic pulse or a triphasic pulse). The pulse width defines a time period that starts at the start time of the first phase of the pulse and ends at the end time of the last phase of the pulse (e.g., a biphasic pulse having a positive phase lasting 100 μs, a negative phase lasting 100 μs, and an interphase interval lasting 30 μs defines a pulse width of 230 μs).

[0060] As described, exemplary techniques for adjusting stimulation parameter values ​​for learned pulses are based on comparing characteristic values ​​of the measured ECAP signal with target ECAP characteristic values. During the delivery of control pulses defined by one or more ECAP test stimulation programs, the IMD 110 senses the electrical potential of tissue of the spinal cord 120 of the patient 105 via two or more electrodes inserted on the lead 130 to measure the electrical activity of the tissue. The IMD 110 senses ECAP from target tissue of the patient 105, for example, using electrodes on one or more leads 130 and associated sensing circuitry. In some embodiments, the IMD 110 receives a signal indicative of ECAP from one or more sensors (e.g., one or more electrodes and circuitry) inside or outside the patient 105. Such exemplary signals may include an ECAP indicative of tissue of the patient 105. Embodiments of the one or more sensors include one or more sensors configured to measure the compound action potential of the patient 105 or to indicate the physiological effects of the compound action potential. For example, to measure the physiological effects of a compound action potential, the one or more sensors may be an accelerometer, a pressure sensor, a bend sensor, a sensor configured to detect the posture of patient 105, or a sensor configured to detect the respiratory function of patient 105. However, in other embodiments, external programmer 150 receives a signal indicative of a compound action potential in the target tissue of patient 105 and transmits a notification to IMD 110.

[0061] exist Figure 1 In an embodiment of the present invention, IMD 110 is described as performing a variety of processing and computing functions. However, external programmer 150 may instead perform one, several, or all of these functions. In this alternative embodiment, IMD 110 is configured to relay sensed signals to external programmer 150 for analysis, and external programmer 150 transmits instructions to IMD 110 to adjust one or more parameters defining the electrical stimulation therapy based on the analysis of the sensed signals. For example, IMD 110 may relay sensed signals representing an ECAP to external programmer 150. External programmer 150 may compare a parameter value of the ECAP to a target ECAP characteristic value, and in response to the comparison, external programmer 150 may command IMD 110 to adjust one or more parameters defining the electrical stimulation learn pulses (and, in some embodiments, control pulses) delivered to patient 105.

[0062] In the exemplary techniques described in the present disclosure, control stimulation parameters and target ECAP characteristic values ​​can be initially set in a clinic, but can be set and / or adjusted by the patient 105 at home. Once the target ECAP characteristic value is set, the exemplary techniques allow for automatic adjustment of learned pulse parameters as the distance from the electrode to the neuron changes to maintain a consistent amount of neural activation and a consistent sense of treatment for the patient. The ability to change stimulation parameter values ​​can also allow for long-term efficacy of the treatment and the ability to maintain consistent stimulation intensity (e.g., as indicated by the ECAP) by comparing the measured ECAP value with the target ECAP characteristic value. The IMD 110 can perform these changes without intervention by a physician or patient 105.

[0063] In some embodiments, the system can change the target ECAP characteristic value over a period of time. The system can be programmed to change the target ECAP characteristic value so as to adjust the intensity of the awareness pulse to provide the patient with a sense of change (e.g., to increase or decrease the amount of neural activation). In one embodiment, the system can be programmed to oscillate the target ECAP characteristic value between the maximum target ECAP characteristic value and the minimum target ECAP characteristic value at a predetermined frequency to provide the patient with a sense of being perceived as a wave or other senses that can provide therapeutic relief for the patient. The maximum target ECAP characteristic value, the minimum target ECAP characteristic value, and the predetermined frequency can be stored in the memory of the IMD 110 and can be updated in response to a signal from an external programmer 150 (e.g., a user request to change the value stored in the memory of the IMD 110). In other embodiments, the target ECAP characteristic value can be programmed to steadily increase or steadily decrease to the baseline target ECAP characteristic value over a period of time. In other embodiments, the external programmer 150 can program the target ECAP characteristic value to automatically change over time according to other predetermined functions or modes. In other words, the target ECAP characteristic value can be programmed to change incrementally by a predetermined amount or percentage, where the predetermined amount or percentage is selected according to a predetermined function (e.g., a sinusoidal function, a ramp function, an exponential function, a logarithmic function, etc.). The increment by which the target ECAP characteristic value changes can be changed for each specific number of pulses or a specific time unit. Although the system can change the target ECAP characteristic value, the system can still use the received ECAP signal to adjust one or more parameter values ​​of the learning pulses and / or the control pulses to meet the target ECAP characteristic value.

[0064] Figure 2A is a block diagram of IMD 200. IMD 200 may be Figure 1 Embodiments of the IMD 110. Figure 2AIn the illustrated embodiment, IMD 200 includes processing circuitry 214, memory 215, stimulation generator 211, sensing circuitry 212, telemetry circuitry 213, sensor 216, and power supply 219. Each of these circuits may be or include programmable or fixed-function circuitry configured to perform the functions attributed to the corresponding circuitry. For example, processing circuitry 214 may include fixed-function or programmable circuitry, stimulation generator 211 may include circuitry configured to generate stimulation signals, such as pulses or continuous waveforms, on one or more channels, sensing circuitry 212 may include sensing circuitry for sensing signals, and telemetry circuitry 213 may include telemetry circuitry for transmitting and receiving signals. Memory 215 may store computer-readable instructions that, when executed by processing circuitry 214, cause IMD 200 to perform various functions. Memory 215 may be a storage device or other non-transitory medium.

[0065] exist Figure 2A In the illustrated embodiment, the memory 215 stores therapeutic stimulation programs 217 and ECAP test stimulation programs 218 in separate memories or separate areas within the memory 215. The memory 215 also stores target ECAP feedback rules 221 and patient ECAP characteristics 222. Each stored therapeutic stimulation program 217 defines a set of electrical stimulation parameters (e.g., a parameter set or a set of parameter values) such as stimulation electrode combination, electrode polarity, current or voltage amplitude, pulse width, pulse rate, and pulse shape. Each stored ECAP test stimulation program 218 defines a set of electrical stimulation parameters (e.g., a control stimulation parameter set) such as stimulation electrode combination, electrode polarity, current or voltage amplitude, pulse width, pulse rate, and pulse shape. The ECAP test stimulation program 218 may also contain other information, such as instructions regarding when to deliver control pulses based on the pulse width and / or frequency of the learned pulses defined in the therapeutic stimulation program 217.

[0066] Thus, in some embodiments, the stimulation generator 211 generates an electrical stimulation signal according to the above-described electrical stimulation parameters. Other ranges of parameter values ​​may also be useful and may depend on the target stimulation site within the patient 105. Although stimulation pulses are described, the stimulation signal may have any form, such as a continuous time signal (e.g., a sine wave). The switching circuit 210 may include: one or more switch arrays, one or more multiplexers, one or more switches (e.g., a switch matrix or other collection of switches), or other circuits configured to direct stimulation signals from the stimulation generator 211 to one or more of the electrodes 232, 234 or to direct directional sensing signals from one or more of the electrodes 232, 234 to the sensing circuit 212. In other embodiments, the stimulation generator 211 and / or the sensing circuit 212 may include sensing circuitry to direct signals to and / or from one or more of the electrodes 232, 234, which may or may not include the switching circuit 210.

[0067] The processing circuitry 214 may include one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), discrete logic circuitry, or any other processing circuitry configured to provide the functionality attributed to the processing circuitry 214 herein, which may be embodied as firmware, hardware, software, or any combination thereof. The processing circuitry 214 controls the stimulation generator 211 to generate stimulation signals according to the therapy stimulation programs 217 and the ECAP test stimulation programs 218 stored in the memory 215, applying stimulation parameter values ​​specified by one or more of the programs, such as the amplitude, pulse width, pulse rate, and pulse shape of each stimulation signal.

[0068] exist Figure 2AIn the illustrated embodiment, the group of electrodes 232 includes electrodes 232A, 232B, 232C, and 232D, and the group of electrodes 234 includes electrodes 234A, 234B, 234C, and 234D. In other embodiments, a single lead may include all eight electrodes 232 and 234 along a single axial length of the lead. Processing circuitry 214 also controls stimulation generator 211 to generate and apply stimulation signals to selected combinations of electrodes 232, 234. In some embodiments, stimulation generator 211 includes switching circuitry (instead of or in addition to switching circuitry 210) that can couple stimulation signals to selected conductors within lead 230, which in turn deliver stimulation signals across selected electrodes 232, 234. Such a switching circuit may be a switch array, a switch matrix, a multiplexer, or any other type of switching circuit configured to selectively couple stimulation energy to selected electrodes 232, 234 and selectively sense bioelectrical neural signals of the patient's spinal cord using the selected electrodes 232, 234 (not shown). Figure 2A shown in ).

[0069] However, in other embodiments, stimulation generator 211 does not include switching circuitry, and switching circuitry 212 does not interface between stimulation generator 211 and electrodes 232, 234. In these embodiments, stimulation generator 211 includes multiple pairs of voltage sources, current sources, voltage sinks, or current sinks connected to each of electrodes 232, 234, such that each pair of electrodes has a unique signal circuit. In other words, in these embodiments, rather than switching signals between electrodes 232, 234, each of electrodes 232, 234 is independently controlled by its own signal circuitry (e.g., by a combination of regulated voltage sources and sinks or regulated current sources and sinks).

[0070] The electrodes 232, 234 on the respective leads 230 can be constructed from a variety of different designs. For example, one or both of the leads 230 can include one or more electrodes at each longitudinal position along the length of the lead, such as one electrode at a different peripheral position around the circumference of the lead at each of positions A, B, C, and D. In one embodiment, the electrodes can be electrically coupled to the stimulation generator 211, for example, via the switching circuit 210 and / or the switching circuit of the stimulation generator 211, through corresponding wires that are straightened or coiled within the housing of the lead and extend to a connector at the proximal end of the lead. In another embodiment, each electrode of the lead can be an electrode deposited on a thin film. The thin film can include a conductive trace for each electrode that extends the length of the film to the proximal connector. The thin film can then be wrapped around the internal member (e.g., a spiral wrap) to form the lead 230. These and other configurations can be used to form leads with complex electrode geometries.

[0071] Despite Figure 2A Sensing circuit 212 is incorporated into a common housing with stimulation generator 211 and processing circuit 214, but in other embodiments, sensing circuit 212 may be in a separate housing from IMD 200 and may communicate with processing circuit 214 via wired or wireless communication techniques.

[0072] In some embodiments, one or more of electrodes 232 and 234 may be adapted to sense ECAP. For example, electrodes 232 and 234 may sense a voltage amplitude of a portion of an ECAP signal, wherein the sensed voltage amplitude is characteristic of the ECAP signal.

[0073] Sensor 216 may include one or more sensing elements that sense the value of a corresponding patient parameter. As described, electrodes 232 and 234 may be electrodes that sense the value of an ECAP parameter. Sensor 216 may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other type of sensor. Sensor 216 may output a patient parameter value that can be used as feedback to control the delivery of therapy. For example, sensor 216 may indicate patient activity, and processing circuitry 214 may increase the frequency of control pulses and ECAP sensing in response to detecting increased patient activity. In one embodiment, processing circuitry 214 may initiate control pulses and corresponding ECAP sensing in response to a signal from sensor 216 indicating that patient activity has exceeded an activity threshold. Conversely, processing circuitry 214 may decrease the frequency of control pulses and ECAP sensing in response to detecting a decrease in patient activity. For example, in response to sensor 216 no longer indicating that the sensed patient activity exceeds the threshold, processing circuitry 214 may pause or stop the delivery of control pulses and ECAP sensing. In this way, processing circuit 214 can dynamically deliver control pulses and sense ECAP signals based on patient activity to reduce the system's power consumption when the distance from the electrode to the neuron is unlikely to change, and increase the system's response to ECAP changes when the distance from the electrode to the neuron is likely to change. IMD 200 may include additional sensors within the housing of IMD 200 and / or coupled via lead 130 or one of the other leads. In addition, for example, IMD 200 can wirelessly receive sensor signals from remote sensors via telemetry circuit 213. In some embodiments, one or more of these remote sensors can be external to the patient's body (e.g., carried on the outer surface of the skin, attached to clothing, or otherwise positioned external to the patient's body). In some embodiments, the signal from sensor 216 can indicate a position or body state (e.g., sleeping, awake, sitting, standing, etc.), and processing circuit 214 can select a target ECAP feature value based on the indicated position or body state.

[0074] Telemetry circuit 213 supports IMD 200 and external programmer ( Figure 2A As updates to the program, the processing circuitry 214 of the IMD 200 may receive values ​​for various stimulation parameters (such as amplitude and electrode combinations) from the external programmer via the telemetry circuitry 213. Updates to the therapy stimulation program 217 and the ECAP test stimulation program 218 may be stored in the memory 215. The telemetry circuitry 213 in the IMD 200, as well as the telemetry circuitry in other devices and systems described herein, such as an external programmer, may communicate via radio frequency (RF) communication techniques. Additionally, the telemetry circuitry 213 may communicate with an external medical device programmer (e.g., a computer programmable controller) via proximal sensing interaction between the IMD 200 and the external programmer. Figure 2A The external programmer can be Figure 1 Thus, telemetry circuit 213 may send information to the external programmer continuously, at periodic intervals, or upon request from IMD 110 or the external programmer.

[0075] Power supply 219 delivers operating power to the various components of IMD 200. Power supply 219 may include a rechargeable or non-rechargeable battery and power generation circuitry to generate the operating power. Charging may be accomplished through proximal inductive interaction between an external charger and a sensing charging coil in IMD 200. In other embodiments, conventional primary batteries may be used.

[0076] According to the techniques of the present disclosure, stimulation generator 211 of IMD 200 receives instructions via telemetry circuitry 213 to deliver electrical stimulation therapy to a target tissue site of a patient's spinal cord via a plurality of electrode combinations of electrodes 232 and 234 of leads 230 and / or the housing of IMD 200 according to a therapy stimulation program 217. Stimulation generator 211 can also receive user instructions via telemetry circuitry 213 to deliver control stimulation to the patient according to an ECAP test stimulation program 218. Each of a plurality of control pulses can induce an ECAP sensed by sensing circuitry 212 via some of electrodes 232 and 234. ECAP test stimulation program 218 can instruct stimulation generator 211 to deliver a plurality of control pulses interleaved with at least some of a plurality of learn pulses. Processing circuitry 214 can receive information indicating ECAP signals generated in response to the control stimulation (e.g., numerical values ​​indicating characteristics of the ECAP in electrical units, such as voltage or power) via electrical signals sensed by sensing circuitry 212. The therapeutic stimulation program 217 may be updated based on the ECAPs recorded at the sensing circuit 212 according to the following technique.

[0077] In one embodiment, the plurality of learning pulses each have a pulse width greater than about 300 μs and less than about 2000 μs (i.e., 2 milliseconds). In certain embodiments, the learning pulse width is greater than about 300 μs and less than about 800 μs. In another embodiment, the learning pulse width is greater than about 300 μs and less than about 500 μs. In one embodiment, the learning pulse has a pulse width of about 450 μs and a pulse frequency of about 60 Hz. The amplitude (current and / or voltage) of the learning pulse can be between about 0.5 mA (or volts) and about 10 mA (or volts), however in other embodiments, the amplitude can be lower or higher. In some embodiments, the system can deliver learning pulses from two or more stimulation programs such that the learning pulse from one stimulation program has at least one parameter value that is different from the learning pulse from another stimulation program.

[0078] Each of the multiple control pulses may have a pulse width of less than approximately 300 μs. In one embodiment, each of the multiple control pulses may be a biphasic pulse having a positive phase with a width of approximately 100 μs, a negative phase with a width of approximately 100 μs, and an interphase interval with a width of approximately 30 μs. In some embodiments, the positive and negative phases may each be 90 μs or 120 μs in other embodiments. In other embodiments, the control pulses may each have a pulse width of approximately 60 μs or less. Due to the relatively long pulse widths of the multiple learn pulses, the sensing circuit 212 may not be able to properly register the ECAP signal induced by the learn pulses because the learn pulses themselves will appear during and obscure the ECAP signal. However, stimulation pulses having a pulse width of less than approximately 300 μs (such as the multiple control pulses) may be suitable for inducing ECAP, which can be sensed at the sensing circuit 212 after the control pulses pass through the two or more electrodes 232 and 234. In some embodiments, the control pulses may be non-therapeutic pulses because the control pulses do not contribute to the patient's treatment. In other embodiments, the controlled pulses may fully provide or partially contribute to the treatment being received by the patient by alleviating or eliminating the patient's symptoms and / or condition.

[0079] The control pulses delivered to induce a detectable ECAP signal can have a current amplitude of between about 6 mA and 12 mA in some embodiments, but higher or lower amplitudes can be used in other embodiments. In some embodiments, the frequency of the control pulses can be between about 50 Hz and 400 Hz, which can match the predetermined pulse frequency of the learn pulses when one control pulse is delivered for each therapeutic pulse. The predetermined pulse frequency can be a single frequency or a frequency that varies over time (e.g., the interval between pulses can vary over time according to a predetermined pattern, formula, or plan). In some embodiments, the system can change the predetermined pulse frequency based on patient input or sensed parameters (such as patient posture or activity). This relationship may exist when the control pulses are completely interleaved (e.g., alternating) with the learn pulses. However, when two or more control pulses are delivered between consecutive learn pulses, the frequency of the control pulses can be delivered at a higher frequency than the learn pulses. In other embodiments, when at least some learn pulses are delivered without a control pulse delivered between them, the frequency of the control pulses can be delivered at a lower frequency than the learn pulses. If the system is configured to adjust the delivery of control pulses and the resulting ECAP sensing based on other factors (eg, patient activity), the frequency of the control pulses may be delivered at a frequency that varies over time.

[0080] In one embodiment, the predetermined pulse frequency of the plurality of learn pulses may be less than approximately 400 Hz. In some embodiments, the predetermined pulse frequency of the plurality of learn pulses may be between approximately 50 Hz and 70 Hz. In one embodiment, the predetermined pulse frequency of the plurality of learn pulses may be approximately 60 Hz. However, in other embodiments, the frequency of the learn pulses may be greater than 400 Hz or less than 50 Hz. In some embodiments, the predetermined pulse frequency of the learn pulses may be a single frequency or a frequency that varies over time. Additionally, the learn pulses may be delivered in pulse groups, wherein the inter-group frequency of the pulses is sufficiently low that the control pulses and the sense ECAP may still fit within the window between consecutive learn pulses delivered within the group of learn pulses.

[0081] Since each of the multiple learn pulses can be sensed as an artifact that covers or obscures the sensing of at least one ECAP, multiple control pulses can be delivered to the patient during multiple time events. For example, a time event (e.g., a window) in multiple time events can be the time (e.g., a window) between consecutive learn pulses of multiple learn pulses at a predetermined pulse frequency. One or more control pulses in the multiple control pulses can be delivered to the patient during each time event. Therefore, the control pulses can be interleaved with at least some learn pulses so that multiple control pulses are delivered to the patient without the learn pulses being delivered. In one embodiment, the ECAP caused by the control pulses delivered during the time event can be recorded by the sensing circuit 212 during the same time event. In another embodiment, two or more ECAPs in response to two or more corresponding control pulses delivered during the time event can be recorded by the sensing circuit 212 during the same time event.

[0082] In some embodiments, according to the ECAP test stimulation program 218, the therapy stimulation program 217 can be updated based on multiple ECAPs received in response to multiple control pulses delivered to the patient. For example, the processing circuit 214 can update the therapy stimulation program 217 in real time by comparing one or more characteristics of the ECAP sensed by the sensing circuit 212 with a target ECAP characteristic (e.g., the patient ECAP characteristic 222) stored in the memory 215. For example, the processing circuit 214 is configured to determine the amplitude of each ECAP signal received at the sensing circuit 212, and the processing circuit 214 is further configured to determine a representative amplitude of at least one corresponding ECAP signal and compare the representative amplitudes of a series of ECAP signals to a target ECAP adjustment window (e.g., the target ECAP amplitude plus and minus the variation stored in the patient ECAP characteristic 222). The target ECAP adjustment window can therefore be an amplitude range that deviates from the target ECAP amplitude. For example, the target ECAP adjustment window can span from a lower amplitude value (e.g., the target ECAP amplitude minus the variation) to an upper amplitude value (e.g., the target ECAP amplitude plus the variation). Typically, the lower amplitude value is less than the target ECAP amplitude, and the upper amplitude value is greater than the target ECAP amplitude.

[0083] If the representative amplitude of the at least one corresponding ECAP signal (e.g., the amplitude of a single ECAP signal or the average of the amplitudes of two or more ECAP signals) is greater than the upper amplitude value, the processing circuitry 214 may adjust one or more of the therapy stimulation program 217 and the ECAP test stimulation program 218 to reduce the amplitude of the learn pulse and the control pulse following the at least one corresponding ECAP signal. The amplitude of the learn pulse and the control pulse may be reduced by different predetermined step sizes or different predetermined percentages. Additionally, if the representative amplitude of the at least one corresponding ECAP signal is less than the lower amplitude value, the processing circuitry 214 may adjust the therapy stimulation program 217 and the ECAP test stimulation program 218, and the programs 217 and 218 may instruct the stimulation generator 211 to increase the amplitude of the learn pulse and the control pulse following the at least one corresponding ECAP signal. Additionally, if the representative amplitude of the at least one corresponding ECAP signal is greater than the lower amplitude value and less than the upper amplitude value, the processing circuitry 214 may not change the programs 217 and 218, and the stimulation generator 211 may maintain the amplitude of the learn pulse following the at least one corresponding ECAP signal. In one embodiment, the adjustment procedures 217 and 218 may include changing one or more parameters in the plurality of learn pulses and the plurality of control pulses. In one embodiment, the at least one corresponding ECAP may include a series of four consecutive ECAPs.

[0084] In one embodiment, the processing circuitry 214 may change the amplitude of the learn pulse and the control pulse after the at least one corresponding ECAP inversely proportional to the difference between the target ECAP amplitude and the representative amplitude of the at least one corresponding ECAP. For example, if the representative amplitude of the at least one corresponding ECAP is 20% lower than the target ECAP amplitude, the processing circuitry 214 may update the therapy programs 217 and 218 to increase the amplitude of the learn pulse and the control pulse by 20%. In one embodiment, the representative amplitude may be the mean amplitude of two or more corresponding ECAP signals sensed by the sensing circuitry 212. In other embodiments, the representative amplitude may be the median amplitude of the two or more corresponding ECAP signals, or a moving average of the two or more corresponding ECAP signals.

[0085] In another embodiment, the processing circuit 214 may determine the amplitude of the corresponding ECAP signal sensed by the sensing circuit 212. In response to a comparison between the amplitude of the corresponding ECAP signal and the target ECAP amplitude stored in the patient ECAP profile 222, the processing circuit 214 may determine a percentage difference between the amplitude of the corresponding ECAP signal and the target ECAP amplitude. Accordingly, the processing circuit 214 may adjust the amplitude of a subsequent learn pulse to be inversely proportional to the percentage difference between the amplitude of the corresponding ECAP and the target ECAP amplitude.

[0086] In other embodiments, the processing circuit 214 can use the representative amplitude of the at least one corresponding ECAP to change other parameters of the learning pulse to be delivered, such as pulse width, pulse frequency, and pulse shape. All of these parameters can contribute to the intensity of the learning pulse, and changing one or more of these parameter values ​​can effectively adjust the learning pulse intensity to compensate for the varying distance between the stimulation electrode and the nerve indicated by the representative amplitude of the ECAP signal.

[0087] In some embodiments, the lead 230 can be a linear 8-electrode lead (not shown); sensing and stimulation delivery can each be performed using different sets of electrodes. In a linear 8-electrode lead, each electrode can be numbered consecutively from 0 to 7. For example, electrode 1 can be used as a cathode and electrodes 0 and 2 can be used as anodes (e.g., protected cathodes) to generate control pulses, and electrodes 6 and 7 located at opposite ends of the electrode array can be used to sense the corresponding ECAP signals. This strategy can minimize the interference of stimulation pulses on the sensing of the corresponding ECAP. Other electrode combinations can be implemented, and the electrode combination can be changed using the patient programmer through the telemetry circuit 213. For example, the stimulation electrode and the sensing electrode can be positioned closer together. The shorter pulse width for the control pulse can allow the sensing electrode to be closer to the stimulation electrode.

[0088] The ECAP feedback rules 221 may define how the processing circuitry 214 uses the sensed ECAP signal as feedback to change one or more parameters that define the learned pulses and are stored as the therapeutic stimulation program 217. For example, the ECAP feedback rules 221 may specify that the percentage difference between the representative ECAP amplitude and the target ECAP amplitude is used to inversely adjust the current amplitude of the learned pulse to the same proportion as the percentage difference, such as Figure 9 As another example, Figure 11As described, the ECAP feedback rule 221 can specify that the difference between the target ECAP amplitudes is multiplied by a gain value and added to the previous current amplitudes of the learn pulse and the control pulse. In any case, the ECAP feedback rule 221 can instruct the processing circuit 14 how to adjust the learn pulse and / or the control pulse based on the sensed ECAP signal.

[0089] In one embodiment, sensor 216 can detect changes in patient activity or posture. Processing circuit 214 can receive an indication of a patient's activity level or posture change from sensor 216, and processing circuit 214 can be configured to initiate or change the delivery of multiple control pulses according to ECAP test stimulation program 218. For example, in response to receiving an indication that patient activity has increased, which can indicate that the distance between the electrode and the nerve will likely change, processing circuit 214 can increase the frequency of control pulse delivery and corresponding ECAP sensing. Alternatively, in response to receiving an indication that patient activity has decreased, processing circuit 214 can reduce the frequency of control pulse delivery and corresponding ECAP sensing. In some embodiments, one or more parameters (e.g., frequency, amplitude, slew rate, pulse duration, etc.) can be adjusted (e.g., increased or decreased) in response to receiving an indication that patient activity has changed. Processing circuit 214 can also be configured to update treatment stimulation program 217 and ECAP test stimulation program 218 according to the signal received from sensor 216.

[0090] Figure 2B is a block diagram of an exemplary external programmer 300. The external programmer 300 may be Figure 1 1. Although programmer 300 may generally be described as a handheld device, programmer 300 may be a larger portable device or a more stationary device. Additionally, in other embodiments, programmer 300 may be included as part of an external charging device or include the functionality of an external charging device. Figure 2B As shown, programmer 300 may include processing circuitry 353, memory 354, a user interface 351, telemetry circuitry 352, and a power supply 355. Throughout this disclosure, memory 354 may store instructions that, when executed by processing circuitry 353, cause processing circuitry 353 and external programmer 300 to provide the functionality attributed to external programmer 300. Each of these components, circuits, or modules may include circuitry configured to perform some or all of the functionality described herein. For example, processing circuitry 353 may include processing circuitry configured to perform the processes discussed with respect to processing circuitry 353.

[0091] In general, programmer 300 includes any suitable hardware arrangement, alone or in combination with software and / or firmware, to perform the techniques attributed to programmer 300 and its processing circuitry 353, user interface 351, and telemetry circuitry 352. In various embodiments, programmer 300 may include one or more processors, such as one or more microprocessors; a DSP; an ASIC; an FPGA; or any other equivalent integrated or discrete logic circuitry, as well as any combination of these components. In various embodiments, programmer 300 may also include memory 354, such as RAM, ROM, PROM, EPROM, EEPROM, flash memory, a hard disk, or a CD-ROM, containing executable instructions for causing the one or more processors to perform the actions attributed to them. Furthermore, while processing circuitry 353 and telemetry circuitry 352 are depicted as separate modules, in some embodiments, processing circuitry 353 and telemetry circuitry 352 are functionally integrated. In some embodiments, processing circuitry 353 and telemetry circuitry 352 correspond to separate hardware units, such as an ASIC, DSP, FPGA, or other hardware units.

[0092] Throughout this disclosure, memory 354 (e.g., a storage device) may store instructions that, when executed by processing circuitry 353, cause processing circuitry 353 and programmer 300 to provide functionality attributed to programmer 300. For example, memory 354 may include instructions that cause processing circuitry 353 to obtain a parameter set from memory, select a spatial electrode motion pattern, or receive user input and send a corresponding command to IMD 300, or instructions for any other functionality. Additionally, memory 354 may include multiple programs, each of which includes a parameter set that defines therapeutic stimulation or control stimulation. Memory 354 may also store data received from a medical device (e.g., IMD 110). For example, memory 354 may store ECAP-related data recorded at a sensing module of the medical device, and memory 354 may also store data from one or more sensors of the medical device.

[0093] The user interface 351 may include buttons or a keyboard, lights, a speaker for voice commands, a display such as a liquid crystal (LCD), a light emitting diode (LED), or an organic light emitting diode (OLED). In some embodiments, the display may be a touch screen. The user interface 351 may be configured to display any information related to the delivery of electrical stimulation, identified patient behavior, sensed patient parameter values, patient behavior standards, or any other such information. The user interface 351 may also receive user input through the user interface 351. The input may be in the form of, for example, pressing a button on a keyboard or selecting an icon from a touch screen. The input may request to start or stop electrical stimulation, the input may request a new spatial electrode motion pattern or a change to an existing spatial electrode motion pattern, or the input may request some other change to the delivery of electrical stimulation.

[0094] Telemetry circuitry 352 can support wireless communication between the medical device and programmer 300 under the control of processing circuitry 353. Telemetry circuitry 352 can also be configured to communicate with another computing device via wireless communication techniques, or directly via a wired connection. In some embodiments, telemetry circuitry 352 provides wireless communication via RF or proximal inductive media. In some embodiments, telemetry circuitry 352 includes an antenna, which can take various forms, such as an internal or external antenna.

[0095] Examples of local wireless communication technologies that can be used to facilitate communication between programmer 300 and IMD 110 include RF communication according to the 802.11 or Bluetooth specification sets or other standard or proprietary telemetry protocols. In this manner, other external devices may be able to communicate with programmer 300 without establishing a secure wireless connection. As described herein, telemetry circuitry 352 may be configured to transmit spatial electrode motion patterns or other stimulation parameter values ​​to IMD 110 for delivery of electrical stimulation therapy.

[0096] In some embodiments, the selection of parameters or therapeutic stimulation programs can be transmitted to the medical device for delivery to the patient. In other embodiments, the treatment may include medication, activities, or other instructions that the patient must perform themselves or a caregiver may perform for the patient. In some embodiments, programmer 300 may provide visual, auditory, and / or tactile notifications indicating the presence of new instructions. In some embodiments, programmer 300 may need to receive user input confirming that the instructions have been completed.

[0097] According to the technology of the present disclosure, the user interface 351 of the external programmer 300 receives an instruction from a clinician that instructs the processor of the medical device to update one or more therapeutic stimulation programs or to update one or more ECAP test stimulation programs. Updating the therapeutic stimulation programs and the ECAP test stimulation programs may include changing one or more parameters of the stimulation pulses delivered by the medical device according to the program, for example, the amplitude, pulse width, frequency, and pulse shape of the learning pulse and / or control pulse. The user interface 351 may also receive instructions from the clinician that instruct any electrical stimulation (including therapeutic stimulation and control stimulation) to start or stop.

[0098] Figure 2B The architecture of the programmer 300 shown in FIG is shown as an example. The techniques set forth in this disclosure may be used in Figure 2B The exemplary programmer 300 of FIG. 1 and other types of systems not specifically described herein are implemented in this disclosure. Nothing in this disclosure should be interpreted as limiting the technology of this disclosure to Figure 2B An exemplary architecture is shown.

[0099] Figure 3 FIG3 is a graph 390 of exemplary evoked compound action potentials (ECAPs) sensed for corresponding stimulation pulses. Figure 3 As shown, graph 390 shows an exemplary ECAP signal 392 (dashed line) and an ECAP signal 394 (solid line). Each of ECAP signals 392 and 394 can be sensed from the following pulses: a control pulse delivered from a protected cathode; and a biphasic pulse, wherein the biphasic pulse includes an interphase interval between each positive and negative phase of the pulse. The protected cathode of the stimulation electrode can be located at one end of an 8-electrode lead, while two sensing electrodes are provided at the other end of the 8-electrode lead. ECAP signal 392 shows the voltage amplitude sensed due to the subthreshold stimulation pulse. Peak 396 of ECAP signal 392 is detected and represents an artifact of the delivered control pulse. However, no propagation signal is detected after the artifact in ECAP signal 392 because the control pulse is subthreshold.

[0100] In contrast to ECAP signal 392, ECAP signal 394 represents the voltage amplitude detected from a suprathreshold control pulse. Peak 396 of ECAP signal 394 is detected and represents an artifact of the delivered control pulse. Following peak 396, ECAP signal 394 also includes peaks P1, N1, and P2, which are three typical peaks representing a propagating action potential from an ECAP. An exemplary duration of the artifact and peaks P1, N1, and P2 is approximately 1 millisecond (ms). When an ECAP is detected in ECAP signal 394, different characteristics can be identified. For example, the ECAP can be characterized by an amplitude between N1 and P2. Even if the artifact impinges on the relatively large signal P1, this N1-P2 amplitude is easily detected, and electronic drift in the signal may minimally affect the N1-P2 amplitude. In other embodiments, the ECAP for a control learn pulse can be characterized by the amplitude of P1, N1, or P2 relative to neutral or zero voltage. In some embodiments, the ECAP for a control learn pulse can be characterized by the sum of two or more of peaks P1, N1, or P2. In other embodiments, the ECAP signal 394 may be characterized by the area below one or more of the peaks P1, N1, and / or P2. In other embodiments, the ECAP signal may be characterized by the ratio of one of the peaks P1, N1, or P2 to another of the peaks. In some embodiments, the ECAP signal may be characterized by the slope between two points in the ECAP signal, such as the slope between N1 and P2. In other embodiments, the ECAP signal may be characterized by the time between two points in the ECAP signal, such as the time between N1 and P2. The time between two points in the ECAP signal may be referred to as the ECAP delay and may indicate the type of fiber captured by the control pulse. An ECAP signal with a lower delay (i.e., a smaller delay value) indicates a higher percentage of nerve fibers with faster signal propagation, while an ECAP signal with a higher delay (i.e., a larger delay value) indicates a higher percentage of nerve fibers with slower signal propagation. Other characteristics of the ECAP signal may be used in other embodiments.

[0101] As long as the pulse amplitude is greater than the threshold, the amplitude of the ECAP signal increases as the control pulse amplitude increases, thereby depolarizing the nerve and propagating the signal. When a learning pulse is determined to deliver effective treatment to the patient, a target ECAP characteristic (e.g., a target ECAP amplitude) can be determined from the ECAP signal detected from the control pulse. Therefore, the ECAP signal represents the distance between the stimulation electrode and the nerve, which is appropriate for the stimulation parameter value of the learning pulse delivered at that time. Therefore, the IMD 110 can attempt to use the detected change in the measured ECAP characteristic value to change the learning pulse parameter value and maintain the target ECAP characteristic value during the delivery of the learning pulse.

[0102] Figure 4A is a timing diagram 400A illustrating an embodiment of an electrical stimulation pulse and a corresponding sensed ECAP signal according to one or more techniques of the present disclosure. For example, referring to the IMD 200 of FIG. Figure 4A As shown, timing diagram 400A includes: a first channel 402; a plurality of control pulses 404A-404N (collectively referred to as "control pulses 404"); a second channel 406; a plurality of corresponding ECAPs 408A-408N (collectively referred to as "ECAPs 408"); and a plurality of stimulus interference signals 409A-409N (collectively referred to as "stimulus interference signals 409"). Figure 4A In an embodiment, the control pulse 404 may also provide therapy to the patient, with the knowledge that the pulse is not necessary for therapy.

[0103] First channel 402 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of electrodes 232 and 234. In one embodiment, the stimulation electrode of first channel 402 may be located on opposite sides of the lead from the sensing electrode of second channel 406. Control pulses 404 may be electrical pulses delivered to the patient's spinal cord via at least one of electrodes 232 and 234, and may be balanced biphasic square pulses with an interphase interval. In other words, each control pulse 404 is shown as having a negative phase and a positive phase separated by an interphase interval. For example, a control pulse 404 may have a negative voltage for the same amount of time and amplitude that it has a positive voltage. Note that the negative voltage phase may precede or follow the positive voltage phase. Control pulses 404 may be delivered according to an ECAP test stimulation program 218 stored in the memory device 212 of IMD 200, and the ECAP test stimulation program 218 may be updated based on user input via an external programmer and / or based on signals from sensor 222. In one embodiment, the control pulse 404 may have a pulse width of less than about 300 microseconds (e.g., the total time of the positive phase, negative phase, and interphase interval is less than 300 microseconds). In another embodiment, the control pulse 404 may have a pulse width of about 100 μs for each phase of the biphasic pulse. Figure 4A As shown, control pulses 404 can be delivered via one or more electrodes that deliver or sense signals corresponding to channel 402. Delivery of control pulses 404 can be delivered by lead 230 in a protected cathode electrode combination. For example, if lead 230 is a linear 8-electrode lead, the protected cathode combination is a central cathode electrode with an anode electrode immediately adjacent to the cathode electrode. For some patients, control pulses 404 may be sufficient to provide treatment for the patient's condition and / or symptoms. Therefore, for these patients, or for at least some aspects of their treatment, additional awareness pulses may not be necessary.

[0104] The second channel 406 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In one embodiment, the electrodes of the second channel 406 can be located on the opposite side of the lead from the electrodes of the first channel 402. In response to the control pulse 404, an ECAP 408 can be sensed from the patient's spinal cord at the electrodes 232, 234. The ECAP 408 is an electrical signal that can propagate along the nerve away from the origin of the control pulse 404. In one embodiment, the ECAP 408 is sensed by a different electrode than the electrode used to deliver the control pulse 404. Figure 4A As shown, the ECAP 408 may be recorded on the second channel 406 .

[0105] Stimulation interference signals 409A, 409B, and 409N (e.g., artifacts of the stimulation pulses) can be sensed by lead 230 and can be sensed during the same time period as the delivery of control pulse 404. Because the amplitude and strength of the interference signals can be greater than ECAP 408, any ECAP that reaches IMD 200 during the occurrence of stimulation interference signals 409 may not be adequately sensed by sensing circuitry 206 of IMD 200. However, as each ECAP 408 falls after each control pulse 404 is completed, the ECAP 408 can be adequately sensed by sensing circuitry 206. Figure 4A As shown, the stimulation interference signal 409 and the ECAP 408 may be recorded on the channel 406 .

[0106] Figure 4B is a timing diagram 400B illustrating one embodiment of an electrical stimulation pulse and a corresponding sensing ECAP according to some techniques of the present disclosure. Figure 2A IMD 200 to describe Figure 4B As shown, timing diagram 400B includes a first channel 410; a plurality of control pulses 412A-412N (collectively, “control pulses 412”); a second channel 420; a plurality of learn pulses 424A-424N (collectively, “learn pulses 424”) including passive recharge phases 426A-426N (collectively, “passive recharge phases 426”); a third channel 430; a plurality of corresponding ECAPs 436A-436N (collectively, “ECAPs 436”); and a plurality of stimulation interference signals 438A-438N (collectively, “stimulation interference signals 438”).

[0107] First channel 410 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of electrodes 232 and 234. In one embodiment, the stimulation electrode of first channel 410 may be located on opposite sides of the lead from the sensing electrode of third channel 430. Control pulses 412 may be electrical pulses delivered to the patient's spinal cord via at least one of electrodes 232 and 234, and may be balanced biphasic square pulses with an interphase interval. In other words, each control pulse 412 is shown as having a negative phase and a positive phase separated by an interphase interval. For example, a control pulse 412 may have a negative voltage for the same amount of time and amplitude that it has a positive voltage. Note that the negative voltage phase may precede or follow the positive voltage phase. Control pulses 412 may be delivered according to an ECAP test stimulation program 218 stored in memory 250 of IMD 200, and the ECAP test stimulation program 218 may be updated based on user input via an external programmer and / or based on signals from sensor 216. In one embodiment, the control pulse 412 may have a pulse width of less than about 300 microseconds (e.g., the total time of the positive phase, negative phase, and interphase interval is less than 300 microseconds). In another embodiment, the control pulse 412 may have a pulse width of about 100 μs for each phase of the biphasic pulse. As shown in FIG4 , the control pulse 412 may be delivered by one or more electrodes that deliver or sense a signal corresponding to the channel 410. The delivery of the control pulse 412 may be delivered by the lead 230 in a protected cathode electrode combination. For example, if the lead 230 is a linear 8-electrode lead, the protected cathode combination is the central cathode electrode, wherein the anode electrode is immediately adjacent to the cathode electrode.

[0108] The second channel 420 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234 used for the learn pulse. In one embodiment, the electrodes of the second channel 420 may partially or completely share common electrodes with the electrodes of the first channel 410 and the third channel 430. The learn pulse 424 may also be delivered by the same lead 230 configured to deliver the control pulse 412. The learn pulse 424 may be interleaved with the control pulse 412 so that the two types of pulses are not delivered during overlapping time periods. However, the learn pulse 424 may or may not be delivered by the same electrode that delivers the control pulse 412. The learn pulse 424 may be a monophasic pulse having a pulse width greater than approximately 300 μs and less than approximately 1000 μs. In practice, the learn pulse 424 may be configured to have a longer pulse width than the control pulse 412. As shown in FIG. 4 , the learn pulse 424 may be delivered on the channel 420.

[0109] The learn pulse 424 can be configured for passive recharging. For example, each learn pulse 424 can be followed by a passive recharge phase 426 to balance the charge on the stimulation electrode. Unlike pulses configured for active recharging - where the residual charge on the tissue after the stimulation pulse is immediately removed from the tissue by an oppositely applied charge - passive charging allows the tissue to discharge naturally to a reference voltage (e.g., ground voltage or mains voltage) after the learn pulse is terminated. In some embodiments, the electrodes of the medical device can be grounded at the medical device body. In this case, after the learn pulse 424 is terminated, the charge on the tissue surrounding the electrode can be dissipated to the medical device, thereby forming a rapid decay of the residual charge at the tissue after the pulse is terminated. This rapid decay is shown in the passive recharge phase 426. In addition to the pulse width of the previous learn pulse 424, the passive recharge phase 426 can also have a duration. In other embodiments (not shown in FIG. 4 ), the learn pulse 424 may be a biphasic pulse having a positive phase and a negative phase (and, in some embodiments, an interphase interval between each phase), which may be referred to as including active recharging. A learn pulse that is a biphasic pulse may or may not have a subsequent passive recharging phase. The learn pulse 424 may be defined by and part of one or more stimulation programs. Although each learn pulse 424 is illustrated as having the same parameter values ​​(e.g., the same pulse width, amplitude, and pulse shape), some learn pulses 424 may have one or more parameters that have different values ​​from one another.

[0110] The third channel 430 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In one embodiment, the electrodes of the third channel 430 may be located on the opposite side of the lead from the electrodes of the first channel 410. In response to the control pulse 412, an ECAP 436 may be sensed from the patient's spinal cord at the electrodes 232, 234. The ECAP 436 is an electrical signal that may propagate along the nerve away from the origin of the control pulse 412. In one embodiment, the ECAP 436 is sensed by an electrode different from the electrode used to deliver the control pulse 412. As shown in FIG. 4 , the ECAP 436 may be recorded on the third channel 430.

[0111] Stimulation interference signals 438A, 438B, and 438N (e.g., artifacts of the stimulation pulses) can be sensed by lead 230 and can be sensed during the same time period as the delivery of control pulse 412 and learn pulse 424. Because the amplitude and strength of the interference signals can be greater than ECAP 436, any ECAP that arrives at IMD 200 during the occurrence of stimulation interference signals 438 may not be properly detected by detection circuitry 212 of IMD 200. However, as each ECAP 436 falls after each control pulse 412 is completed and before the delivery of the next learn pulse 424, ECAP 436 can be adequately sensed by sensing circuitry 212. As shown in FIG4 , stimulation interference signals 438 and ECAP 436 can be recorded on channel 430.

[0112] Figure 5 is a timing diagram 500 illustrating another embodiment of electrical stimulation pulses and corresponding ECAPs according to the techniques of the present disclosure. Figure 2A Description of IMD 200 Figure 5 As shown, timing diagram 500 includes: a first channel 510; a plurality of control pulses 512A-512N (collectively, “control pulses 512”); a second channel 520; a plurality of learn pulses 524A-524N (collectively, “learn pulses 524”) including passive recharge phases 526A-526N (collectively, “passive recharge phases 526”); a third channel 530; a plurality of corresponding ECAPs 536A-536N (collectively, “ECAPs 536”); and a plurality of stimulation interference signals 538A-538N (collectively, “stimulation interference signals 538”). Figure 5 It may be substantially similar to FIG. 4 , except for the differences detailed below.

[0113] Two or more (e.g., two) control pulses 512 may be delivered during each time event (e.g., window) of the plurality of time events, and each time event represents the time between two consecutive learn pulses 524. For example, during each time event, a first control pulse may be directly followed by a first corresponding ECAP, and after the first corresponding ECAP is completed, a second control pulse may be directly followed by a second corresponding ECAP. The learn pulse may begin after the second corresponding ECAP. In other embodiments not shown herein, three or more control pulses 512 may be delivered during each time event of the plurality of time events, and corresponding ECAP signals may be sensed.

[0114] Figure 6 is a timing diagram 600 illustrating another embodiment of an electrical stimulation pulse and a corresponding ECAP according to the techniques of the present disclosure. Figure 2AIMD 200 to describe Figure 6 As shown, timing diagram 600 includes: a first channel 610; a plurality of control pulses 612A-612N (collectively, “control pulses 612”); a second channel 620; a plurality of learn pulses 624A-624N (collectively, “learn pulses” 624 ) including passive recharge phases 626A-626N (collectively, “passive recharge phases 626 ”); a third channel 630; a plurality of corresponding ECAPs 636A-636N (collectively, “ECAPs 636 ”); and a plurality of stimulus interference signals 438A-438N (collectively, “stimulus interference signals 438 ”). Figure 6 It may be substantially similar to FIG. 4 , except for the differences detailed below.

[0115] In Figures 4 and Figure 5 In the previous embodiment shown, at least one control pulse is delivered and interleaved between each pair of consecutive learn pulses. However, in some embodiments, no control pulse 612 is delivered during each time event (or window) of a plurality of time events, wherein each time event represents the time between two consecutive learn pulses 624. Figure 6 As shown in the embodiment of , the control pulse 612 is not delivered after the learn pulse 624A and before the learn pulse 624B. In other words, consecutive learn pulses 624A and 624B can be delivered without an intermediate control pulse. In any case, the learn pulses are delivered according to a predetermined frequency, and the control pulses can be delivered at any time between the learn pulses. In some embodiments, the parameter values ​​of the learn pulse 624A and the learn pulse 624B can be the same because they are defined by the same stimulation program. In other embodiments, the learn pulse 624A and the learn pulse 624B can have at least one stimulation parameter with a different value, such as a different amplitude, pulse width, pulse frequency, or electrode combination. In this way, the learn pulse 624A can be part of a first stimulation program, and the learn pulse 624B can be part of a second stimulation program that is different from the first stimulation program. Thus, the processing circuit 214 can deliver learn pulses from two or more different stimulation programs, wherein the processing circuit 214 uses the detected ECAP signal from the same control pulse (e.g., control pulse 612A) to "inform" or otherwise adjust one or more parameter values ​​of the learn pulses (e.g., both learn pulses 624A and 624B) in the multiple stimulation programs. The concept of multiple stimulation programs can be applied to any learn pulse described herein.

[0116] Control pulses can be applied according to the ECAP test stimulation program 218. Processing circuit 214 can be configured to update the ECAP test stimulation program according to the user input by telemetry circuit 213 and also by the signal from sensor 216. For example, a clinician can operate a patient programmer and send a signal comprising an instruction for updating the ECAP test stimulation program 218 to the telemetry circuit 213. The clinician can set the control stimulation to any embodiment shown in Figures 4 to 6, and the clinician can also customize the control stimulation to a configuration not shown in Figures 4 to 6. The clinician can select to stop control stimulation or start control stimulation at any time. In certain embodiments, detecting that the patient's posture or activity level have changed will start control stimulation.

[0117] Figure 7 is a flow chart illustrating exemplary operations 700 for therapeutic delivery according to the presently disclosed techniques. Figure 1 Description of IMD 110 Figure 7 .However, Figure 7 The techniques may be performed by different components of IMD 110 or by additional or alternative medical devices.

[0118] exist Figure 7 In an embodiment of the present invention, an IMD 110 may deliver an electrical stimulation therapy to a patient 105, the electrical stimulation therapy comprising a plurality of learn pulses at a predetermined pulse frequency over a period of time (710). In addition, the IMD 110 may deliver a plurality of control pulses interleaved with at least some of the plurality of learn pulses over a period of time (720). As described herein, the control pulses may or may not be configured to facilitate treatment of the patient. For example, one or more control pulses may be delivered between consecutive learn pulses. As another embodiment, one or more learn pulses may be delivered between consecutive control pulses. After one or more of the plurality of control pulses and before an immediately subsequent learn pulse in the plurality of learn pulses, the IMD 110 may sense a corresponding ECAP (730). After sensing, the IMD 110 may adjust one or more parameter values ​​that at least partially define the plurality of learn pulses of the electrical stimulation therapy based on at least one corresponding ECAP (740). For example, the IMD 110 may compare a characteristic value of the sensed ECAP with a target ECAP characteristic value and adjust the learn pulses, and in some embodiments, adjust the control pulses to maintain the target ECAP characteristic value. IMD 110 may deliver electrical stimulation therapy to spinal cord 120 of patient 105 via electrodes 130 according to the adjusted one or more parameter values ​​( 750 ).

[0119] Figure 8is a flow chart illustrating exemplary operations 800 for delivering control pulses in response to sensor input. Figure 2A Description of IMD 200 Figure 8 .However, Figure 8 The techniques may be performed by different components of IMD 200 or by additional or alternative medical devices.

[0120] exist Figure 8 In an embodiment, processing circuitry 214 can deliver electrical stimulation therapy (e.g., a learn pulse) and ECAP test stimulation with a control pulse (810). Processing circuitry 214 monitors patient activity (820) during the delivery of the electrical stimulation therapy. Patient activity can include changes in patient movement, switching to a different posture, or any other type of activity that can cause movement of the electrode relative to target tissue (e.g., neurons).

[0121] If the processing circuit 214 does not detect any change in patient activity (the "No" branch of block 830), the processing circuit 214 may continue to deliver the electrical stimulation therapy (810). If the processing circuit 214 does detect a change in patient activity (the "Yes" branch of block 830), the processing circuit 214 may update the ECAP test stimulation program (840) based on the change in patient activity. For example, in response to detecting an increase in patient activity, the processing circuit 214 may increase the frequency of delivering control pulses and sensing ECAP signals. In some embodiments, this increase in frequency may continue for a specified period of time or indefinitely. The processing circuit 214 may then control the stimulation generator 211 to deliver control pulses (850) to the patient and continue to deliver the electrical stimulation therapy (810) based on the updated ECAP test stimulation program. In other embodiments, the processing circuit 214 may update the ECAP test stimulation program in response to receiving user input indicating that activity has changed or will soon change. Alternatively, if the patient believes that the stimulation therapy has not adapted to the activity or posture change within an appropriate amount of time, the patient may request an increase in the frequency of ECAP sensing.

[0122] Figure 9 is a flow chart illustrating exemplary operations 900 for therapeutic delivery according to the disclosed technology. Figure 2A Description of IMD 200 Figure 9 .However, Figure 9 The techniques may be performed by different components of IMD 200 or by additional or alternative medical devices. Operation 900 is an example feedback mechanism for controlling stimulation therapy using sensed ECAP signals.

[0123] like Figure 9As shown, the processing circuit 214 of the IMD 200 can determine a target ECAP amplitude (910). The target ECAP amplitude can be indicated in the patient ECAP characteristics 222 stored in the IMD 200. An exemplary target ECAP amplitude can be the N1-P2 amplitude detectable in the ECAP signal. In other embodiments, the processing circuit 214 can automatically change the target ECAP amplitude over a period of time according to a predetermined function (e.g., a sine function, a step function, an exponential function, or other schedule). The processing circuit 920 then delivers a learning pulse and a control pulse and senses the resulting ECAP caused by the control pulse (920). The processing circuit 214 then determines a representative amplitude of one or more sensed ECAPs (930). For example, the representative amplitude can be the average amplitude of the last four sensed ECAP signals. However, the representative amplitude may come from fewer or more ECAPs.

[0124] The processing circuitry 214 then determines whether the representative amplitude of the one or more corresponding ECAPs is greater than an upper limit of a target ECAP adjustment window (940). As discussed herein, the target ECAP adjustment window can be defined by the target ECAP amplitude plus and minus the variation. Thus, the target ECAP amplitude plus the variation can define the upper limit of the target ECAP adjustment window. Similarly, the target ECAP amplitude minus the variation can define the lower limit of the target ECAP adjustment window. In this manner, the target ECAP adjustment window can be determined such that one or more parameters of the learn pulse are not adjusted for smaller oscillations in the sensed ECAP amplitude. If the processing circuitry 214 determines that the representative amplitude of the one or more ECAPs is greater than the target ECAP amplitude value plus the adjustment window ("yes" branch of block 940), the processing circuitry 214 reduces the amplitudes of the learn pulses and the control pulses by the corresponding values ​​(950). For example, the respective amplitudes of the learn pulses and the control pulses can be reduced by a predetermined step size. As another example, the respective amplitudes of the learn pulses and the control pulses can be reduced by an amount proportional to the difference between the representative amplitude and the target ECAP amplitude. If the processing circuitry 214 determines that the representative amplitude is less than the upper limit of the target ECAP adjustment window (“no” branch of block 940 ), the processing circuitry 214 moves to block 960 .

[0125] At block 960, the processing circuit 214 determines whether the representative amplitude of the one or more corresponding ECAPs is greater than the lower limit of the target ECAP adjustment window. If the representative amplitude of the one or more corresponding ECAPs is less than the lower limit of the target ECAP adjustment window (the "yes" branch of block 960), the processing circuit 214 increases the amplitude of the learning pulse and the control pulse by a corresponding value (970). For example, the respective amplitudes of the learning pulse and the control pulse can be increased by a predetermined step size. As another embodiment, the respective amplitudes of the learning pulse and the control pulse can be increased by an amount proportional to the difference between the representative amplitude and the target ECAP amplitude. The processing circuit 214 then continues to deliver the learning pulse and the control pulse according to the increased or decreased amplitude. In some embodiments, the reduction or increase applied to the learning pulse and / or control pulse in step 950 or 970 can be applied to the amplitude or other parameters of the next planned learning pulse or control pulse. In this way, even if a reduction is applied to the next learn pulse, the overall new amplitude of the following learn pulse can still be greater than the previous learn pulse if the planned amplitude of the next learn pulse minus the reduction is still greater than the amplitude of the previous learn pulse.

[0126] While the process of operation 900 for adjusting the amplitude of the learning pulse and the control pulse is described, other parameter values ​​may be changed in other embodiments. For example, sensing the ECAP signal can be used to increase or decrease the pulse width of the learning pulse and the control pulse to adjust the amount of charge delivered to the tissue to maintain a consistent amount of neural activation. In other embodiments, the electrode combination can be adjusted to deliver different amounts of charge and modify the number of neurons recruited by each learning pulse. In other embodiments, the processing circuit 214 can be configured to adjust the slew rate of the learning pulse (i.e., the rate of change of the voltage and / or amplitude at the beginning and / or end of the pulse or at each phase of the pulse) in response to the characteristics of the ECAP signal being greater than or less than the target ECAP adjustment window. For example, if the representative amplitude of the ECAP signal is greater than the upper limit of the target ECAP adjustment window, the processing circuit 214 can reduce the slew rate of the next learning pulse (i.e., causing the amplitude of the pulse to rise more slowly). If the representative amplitude of the ECAP signal is lower than the lower limit of the target ECAP adjustment window, the processing circuit 214 can increase the slew rate of the next learning pulse (i.e., causing the amplitude of the pulse to rise more quickly). The slew rate can contribute to pulse intensity. Processing circuitry 214 may change one or more parameters defining the learn pulse according to the process of operation 900 .

[0127] In other embodiments, the processing circuit 214 can perform operation 900 without adjusting the amplitude of the control pulse. In this manner, the processing circuit 214 can maintain the same amplitude of the control pulse and adjust the amplitude (or other parameter) in response to a change in the representative amplitude of the sensed ECAP signal compared to the last or most recent representative amplitude of the sensed ECAP signal to detect a change in the electrode-to-nerve distance. In other embodiments where only control pulses are used to provide therapy to the patient, the system can employ Figure 9 The technology does not require adjustment or delivery of any aware pulses.

[0128] Figure 10A FIG1 is a graph 1000 of an exemplary growth curve 1002 of a sensed ECAP from corresponding stimulation pulse amplitudes. Graph 1000 illustrates exemplary ECAPs shown as points for corresponding different current amplitudes of the stimulation pulse. Typically, an ECAP is not generated until the stimulation pulse amplitude reaches a threshold, at which Figure 10A In the embodiment of FIG, the threshold is about 4.5 mA. Then, as the current amplitude increases, the ECAP amplitude also increases approximately linearly. This linear relationship is shown by the growth curve 1002. Figure 10A In an embodiment of the present invention, the slope may be approximately 32 μV / mA. However, the slope may vary for each patient due to the type of electrodes implanted, the location of the implanted electrodes, the sensitivity of the patient's neurons to stimulation, neural dysfunction, or other factors.

[0129] The slope of the linear growth of the growth curve may be referred to herein as "gain" because it indicates the relationship between the sensed ECAP amplitude and the pulse amplitude. In other words, the gain value may represent the slope of the growth curve of the value of a characteristic (e.g., amplitude, such as the N1-P2 amplitude or the amplitude of any peak of the ECAP signal) of the ECAP signal resulting from a corresponding calibrated stimulation pulse delivered to the patient and defined at least in part by different values ​​of a stimulation parameter (e.g., current amplitude, voltage amplitude, or pulse width). For example, the gain value for a patient may be used to dynamically adjust the learned pulse amplitude and the control amplitude based on the sensed ECAP amplitude. In some embodiments, the gain may be approximated for the patient based on historical data of similar patients. In other embodiments, the system may generate a customized growth curve and gain specific to the patient before treatment with the system is initiated.

[0130] Figure 10B is a schematic diagram illustrating an exemplary technique for adjusting stimulation therapy. Figure 10BAs shown in the embodiments of FIG, a system such as IMD 200 or any other device or system described herein can dynamically adjust the learning pulse and control pulse amplitude (or other parameters) based on a gain value representing the patient's sensitivity to stimulation. The processing circuit 214 of IMD 200 can control the stimulation generator 211 to deliver the control pulse to the patient. The processing circuit 214 can then control the sensing circuit 212 to sense the ECAP signal caused by the control pulse and then identify the characteristics of the ECAP signal (e.g., the amplitude of the ECAP signal). The processing circuit 214 can then determine parameter values ​​(e.g., amplitude, pulse width value, pulse frequency value, and / or slew rate value) that at least partially define the learning pulse based on the characteristics of the ECAP signal and the gain value. The processor 214 can then control the stimulation generator 211 to deliver the learning pulse according to the determined learning pulse.

[0131] like Figure 10B As shown, a control pulse 1016 is delivered to the patient via an electrode assembly 1024, which is shown as a protected cathode of three electrodes. The resulting ECAP is sensed by two electrodes at opposite ends of the leads of an electrode assembly 1028, which is fed into a differential amplifier 1030. For each sensed ECAP, the processing circuit 214 can measure the amplitude of a portion of the ECAP signal, such as the N1-P2 voltage amplitude from a portion of the ECAP signal. The processing circuit 214 can average the most recently measured ECAP amplitudes, for example, averaging the most recent and consecutive 2, 3, 5, 6, or more ECAP amplitudes. In some embodiments, the average value can be a mean or median. In some embodiments, if an amplitude value is determined to be an error, one or more ECAP amplitudes can be omitted from the calculation. The measured amplitude (or averaged measured amplitude) is then subtracted from the selected target ECAP amplitude 1010 to generate a differential amplitude. The selected target ECAP amplitude 1010 can be determined from the ECAP sensed when the physician or patient initially found effective treatment from the learning pulse. This target ECAP amplitude 1010 may substantially represent a reference distance between the stimulation electrode and the target neuron (eg, the spinal cord in the case of SCS).

[0132] The differential amplitude is then multiplied by the patient's gain value to generate an initial differential value 1012. The initial differential value is added to the ECAP pulse amplitude (eg, the control pulse amplitude) to generate a new or adjusted ECAP pulse amplitude that at least partially defines the next control pulse 1016.

[0133] To adjust the learned pulse amplitude, the differential value is multiplied by a scaling factor 1018 to generate a treatment differential value. For example, the scaling factor can be the ratio of the previously delivered learned pulse amplitude to the previously delivered control pulse amplitude. The treatment differential value is then added to the previously delivered learned pulse amplitude 1020 to generate a new or adjusted learned pulse amplitude that at least partially defines the next learned pulse 1022. This process can be applied to learned pulses from multiple stimulation programs. For example, if learned pulses from two different stimulation programs are delivered as part of a stimulation therapy, the system can multiply the differential value by the corresponding scaling factor to obtain a corresponding treatment differential value for the learned pulse for each stimulation program. The next learned pulse 1022 (or pulses in the case of multiple stimulation programs involved in the therapy) is then delivered to the patient via the electrode combination 1026, interleaved with the control pulse 1016. In some embodiments, at least two control pulses can be delivered between consecutive learned pulses, and at least two corresponding ECAP signals can be sensed. This increased frequency of control pulses can allow the system to quickly adjust the learned pulse amplitude for any changes in the distance between the electrode and the neuron. Although electrode combination 1026 is different from electrode combinations 1024 and 1028, electrode combination 1026 can be any set of electrodes on the lead required for treatment because the learn pulses are delivered in a non-overlapping manner by controlling the pulses and sensing the ECAP signals. In some embodiments, the next control pulse or learn pulse can be planned to have a higher or lower amplitude (or other parameter) than the previous learn pulse or control pulse. Therefore, the system can apply the differential value of the control pulse and / or learn pulse to the planned amplitude (or other parameter) of the next control pulse and / or learn pulse, rather than just applying the corresponding differential value to the previous amplitude or other parameter of the previous control pulse or learn pulse.

[0134] In some embodiments, the pulse width of the learn pulse can be greater than approximately 300 μs and less than approximately 1000 μs. In other embodiments, the pulse width of the learn pulse can be less than approximately 300 μs or greater than 1000 μs. The learn pulse can be a monophasic pulse following a passive recharge phase. However, in other embodiments, the learn pulse can be a biphasic pulse comprising a positive phase and a negative phase. In some embodiments, the control pulse width can be less than approximately 300 μs. In some embodiments, the control pulse is a biphasic pulse comprising a positive phase and a negative phase. For example, a biphasic control pulse can include a positive phase with a duration of approximately 100 μs, a negative phase with a duration of approximately 100 μs, and an interphase interval with a duration of approximately 30 μs. In this manner, the control pulse can be completed before the resulting ECAP signal is detected. In some embodiments, the learn pulse can be less than 300 μs, but the subsequent passive recharge phase or even the active charging phase (of the biphasic pulse) may still obscure the detectable ECAP signal in the learn pulse. Additionally, sensing the ECAP signal generated by the control pulse is beneficial regardless of the pulse width of the learning pulse so that the learning pulse can have parameter values ​​(e.g., amplitude, pulse width, frequency, pulse shape, electrode combination, etc.) that would otherwise interfere with sensing of the resulting ECAP signal or generation of a detectable ECAP signal.

[0135] exist Figure 10BIn one embodiment, multiple stimulation programs can define a learn pulse that is informed by an ECAP signal detected from a control pulse. For example, using a lead with eight electrodes labeled 1 to 8, a control pulse can be initially delivered at 10.0 milliamperes (mA) with a pulse width of 210 μs (90 μs for the positive phase, 30 μs for the interphase interval, and 90 μs for the negative phase). The control pulse can be delivered in a protected cathode configuration with the cathode on electrode 7 and the anode on electrodes 6 and 8 on either side of electrode 7. One stimulation program can define a first learn pulse of 4.0 mA with a pulse width of 800 μs (400 μs for the positive phase and 400 μs for the negative phase), with a cathode on electrode 6 and an anode on electrode 4. Another stimulation program can define a second learn pulse of 5.0 mA with a pulse width of 400 μs (200 μs for the positive phase and 200 μs for the negative phase), with a cathode on electrode 2 and an anode on electrode 3. For each of the first and second learn pulses relative to the control pulse, the first and second learn pulses can be staggered over time, and both the first and second learn pulses from each corresponding stimulation program can be adjusted or notified based on the ECAP signal detected from the control pulse and the scaling factor or ratio. For example, the scaling factor for the first learn pulse can be 40% (e.g., 4.0 mA divided by 10 mA), and the scaling factor for the second learn pulse can be 50% (e.g., 5.0 mA divided by 10 mA). Therefore, if it is determined that the determined 2 mA differential value 1012 is added to the next control pulse, the system will determine that the next first learn pulse from the first stimulation program should be increased by 0.8 mA (to 4.8 mA), and the next second learn pulse from the second stimulation program should be increased by 1.0 mA (to 6.0 mA). In this way, the system can adjust the learn pulses from two or more stimulation programs based on the ECAP signal detected from a single control pulse.

[0136] although Figure 10BThe techniques described herein are used to adjust the amplitude of the learned pulses and the control pulses, but other parameter values ​​may be changed in other embodiments. For example, sensing the ECAP signal may be used to increase or decrease the pulse width of the learned pulses and the control pulses to adjust the amount of charge delivered to the tissue to maintain a consistent amount of neural activation. In other embodiments, the electrode combination may be adjusted to deliver different amounts of charge and modify the number of neurons recruited by each learned pulse. In other embodiments, the processing circuit 214 may be configured to adjust the slew rate (i.e., the rate of change of voltage and / or amplitude at the beginning and / or end of a pulse or each phase of a pulse) of the learned pulses and / or control pulses in response to characteristics of the ECAP signal, such as the amplitude of the most recent ECAP amplitude. For parameters other than amplitude, it may be necessary to determine a gain value specific to each type of parameter in order to appropriately adjust that type of parameter. The processing circuit 214 may be configured to adjust the slew rate of the learned pulses and / or control pulses in response to characteristics of the ECAP signal, such as the amplitude of the most recent ECAP amplitude. Figure 10B The process of changing one or more parameters that define the learning pulse and / or the control pulse. For example, the ECAP signal can be used to simultaneously control multiple concurrent feedback mechanisms for corresponding pulse parameters. In other embodiments, when the processing circuit 214 reaches the adjustment limit for a particular parameter, the processing circuit 214 can switch between two or more feedback mechanisms. For example, the processing circuit 214 can be configured to use a feedback control mechanism to adjust the amplitude as long as the amplitude remains within a certain range (e.g., a range defined by a clinician), and then switch to a different feedback control mechanism in response to the amplitude exceeding the range to adjust different parameters (e.g., pulse width or slew rate) of the learning pulse and / or the control pulse.

[0137] In other embodiments, the processing circuit 214 may execute Figure 10B In this manner, the processing circuit 214 can maintain the same amplitude of the control pulses and adjust the amplitude of the learning pulses (or other parameters) in response to a change in the average amplitude of the sensed ECAP signal compared to the last or most recent average amplitude of the sensed ECAP signal to detect a change in electrode-to-nerve distance. In this case, for example, the target ECAP amplitude 1010 can be adjusted by the difference between the target ECAP amplitude and the most recently sensed ECAP amplitude (or average amplitude). In other embodiments where only control pulses provide therapy to the patient, Figure 10B The technique can be employed by the system without adjusting or delivering any aware pulses.

[0138] Figure 11 is a flow chart illustrating exemplary operations 1100 for adjusting stimulation therapy. Figure 11Although IMD 200 and processing circuit 214 are described in the embodiment of FIG, other IMDs (such as IMD 110) or other devices or systems may also perform or partially perform operation 1100. Operation 1100 may be similar to that described in Figure 10B Related diagrams and discussion.

[0139] exist Figure 11 In some embodiments, the processing circuit 214 determines a target ECAP amplitude (1102). The target ECAP amplitude can be determined based on a sample stimulus initially delivered to the patient. The target ECAP amplitude can be the N1-P2 amplitude of the ECAP signal, but other measures of amplitude can be used instead, such as the amplitude of one or more different peaks in the ECAP signal. Alternatively, the target ECAP amplitude can be a different characteristic of the ECAP signal, such as the area under one or more peaks of the ECAP signal, the frequency content of the ECAP signal, the maximum and / or minimum peak timing of the ECAP signal, or any other characteristic of the ECAP signal. In some embodiments, the processing circuit 214 is configured to automatically change the target ECAP amplitude over a period of time according to a predetermined function (e.g., a sinusoidal function) so as to change the amount of neuronal activation and, in some embodiments, change the perceived sensation of the learned pulse.

[0140] The processing circuit 214 receives a measured amplitude from a previously sensed ECAP signal. In order to use the ECAP signal as feedback to control the learned pulse for the patient's electrical stimulation therapy, the processing circuit 214 subtracts the measured amplitude from the target ECAP amplitude to generate a differential amplitude (1104). In some embodiments, or when additional measured amplitudes are available from the process, the processing circuit 214 can average a certain number of recent measured amplitudes (e.g., two or more) to create a rolling average of the measured ECAP amplitudes and subtract the average measured amplitude from the target ECAP amplitude to eliminate variations between the ECAP signals. Thus, the differential amplitude indicates how much the electrode has moved relative to the neuron and can be used to adjust the amplitudes of the learned pulses and control pulses to maintain a consistent amount of neuronal neural activation, thereby providing relief to the patient.

[0141] The processing circuit 214 then multiplies the differential amplitude by the patient's gain value to generate an initial differential value (1106). The gain value can represent the slope of the patient's growth curve. The processing circuit 214 then uses the initial differential value to adjust the amplitude of subsequent learning pulses and control pulses (e.g., ECAP test pulses). The processing circuit 214 adds the initial differential value to the control pulse amplitude to generate a new control pulse amplitude (1108). The processing circuit 214 then controls the stimulation generator 211 to deliver subsequent control pulses defined by the new control pulse amplitude at the scheduled time, for example, based on the frequency of the control pulses or based on the next available window (1110) between learning pulses. The processing circuit 214 also controls the sensing circuit 212 to measure the amplitude of the sensed ECAP caused by the most recently delivered control pulse (1112) to be used again as feedback in block 1104.

[0142] In addition to adjusting the amplitude of the control pulse, the processing circuit 214 also uses the initial amplitude to adjust the learning pulse amplitude. The processing circuit 214 multiplies the differential value by a scaling factor to generate a new treatment differential value (1114). The scaling factor can be determined as the ratio between the amplitude of the most recently delivered learning pulse and the amplitude of the most recently delivered control pulse that caused the ECAP signal used to generate the measurement amplitude used in block 1104. The scaling factor can scale the differential amplitude for the learning pulse because the differential amplitude is generated based on the amplitude of the control pulse. The processing circuit 214 then adds the treatment differential value to the most recently learned pulse amplitude to generate a new learning pulse amplitude (1116). The processing circuit 214 then controls the stimulation generator 211 to deliver the next learning pulse with the newly adjusted learning pulse amplitude at the scheduled time (1118) based on the predetermined pulse frequency of the learning pulse.

[0143] Although operation 1100 is described for adjusting the amplitude of the learning pulse and the control pulse, in other embodiments, similar operations can be used to adjust other stimulation parameters. For example, parameters that contribute to the intensity of the learning pulse and the control pulse can affect the amount of neural activation, such as pulse width, pulse frequency, and even pulse shape (e.g., the amount of charge per pulse). Therefore, the processing circuit 214 can use the sensed ECAP signal caused by the control pulse to adjust different parameters instead of or in addition to the amplitude. For example, in response to detecting a decreased ECAP amplitude, the processing circuit 214 can increase the pulse width of the learning pulse and the control pulse.

[0144] Figure 12 Schematic diagram of an exemplary apparatus used in experiments to test the efficacy of the feedback mechanism using a sensing ECAP. Figure 12As shown, system 1000 may include: a lead 1204, a stimulation generator 1206, an ECAP amplifier 1208, a feedback control device 1210, a signal digitizer 1212, an analog-to-digital converter 1214, and a data storage device 1216. The feedback control device 1210 can control the stimulation generator 1206 to deliver stimulation pulses (e.g., control pulses) to the patient 1202 (e.g., a sheep) via electrodes on the lead 1204. The ECAP amplifier 1208 senses the resulting ECAP signal, which is digitized and stored in the data storage device 1216 for later review. Additionally, for example, the ECAP signal is received by the feedback control device 1210 and used to generate a signal according to a feedback control mechanism (such as Figure 10B and 11 ) to measure the ECAP amplitude and adjust the control pulse. Figure 12 This experimental setup can be used to evaluate the efficacy of feedback control mechanisms such as Figure 13 As shown in the curve graph.

[0145] Figure 13 Included in Figure 12 The graph of the ECAP voltage amplitude sensed by the feedback mechanism used in the experiment is shown. Figure 13 As shown, graphs 1300, 1304, 1308, and 1312 illustrate measured N1-P2 amplitudes of detected ECAP signals over time. Graphs 1302, 1306, 1310, and 1314 group similar N1-P2 amplitudes together to illustrate how closely or dispersed the measured N1-P2 amplitudes are grouped relative to one another. More consistent or more closely grouped measured amplitudes from the ECAP signal indicate that the feedback mechanism is maintaining the target ECAP amplitude and providing adequate feedback for the patient (e.g., Figure 12 of sheep) provide a consistent amount of neural activation.

[0146] Graphs 1300 and 1302 illustrate how the measured ECAP amplitude changes over time in an open-loop system, or when no feedback mechanism is employed to adjust the amplitude of the control pulses. In other words, because the distance from the electrode to the neuron changes, the measured ECAP amplitude changes as the sheep moves. In contrast, employing a feedback mechanism produces: graphs 1304 and 1306, which indicate ECAP amplitudes with a target ECAP amplitude of 0.15 mV; graphs 1308 and 1310, which indicate ECAP amplitudes with a target ECAP amplitude of 0.20 mV; and graphs 1312 and 1314, which indicate ECAP amplitudes with a target ECAP amplitude of 0.25 mV. As shown in these graphs—where a feedback mechanism is employed to control pulse amplitude—the ECAP amplitude remains relatively consistent over time with minimal variation compared to open-loop delivery. These graphs demonstrate that the feedback control mechanism described herein can effectively maintain a constant amount of neural activation, resulting in consistent therapeutic efficacy for the patient even during movement and activity.

[0147] The following embodiments are exemplary systems, devices, and methods described herein. Embodiment 1: A method comprising: delivering an electrical stimulation therapy to a patient, the electrical stimulation therapy comprising a plurality of learn pulses at a predetermined pulse frequency over a period of time, wherein the plurality of learn pulses are at least partially defined by a first set of parameter values; delivering a plurality of control pulses interleaved with at least some of the plurality of learn pulses over the period of time, wherein the plurality of control pulses are at least partially defined by a second set of parameter values ​​different from the first set of parameter values; sensing corresponding evoked compound action potentials (ECAPs) after one or more control pulses in the plurality of control pulses and before an immediately subsequent learn pulse in the plurality of learn pulses; adjusting one or more parameter values ​​in the first set of parameter values ​​that at least partially define the plurality of learn pulses of the electrical stimulation therapy based on at least one corresponding ECAP; and delivering the electrical stimulation therapy to the patient according to the adjusted one or more parameter values ​​in the first set of parameter values.

[0148] Embodiment 2: The method of embodiment 1, wherein a pulse width of each learn pulse of the plurality of learn pulses is greater than approximately 300 microseconds and less than approximately 1000 microseconds.

[0149] Embodiment 3: The method of any combination of Embodiments 1 to 2, wherein the frequency of the plurality of learning pulses is less than about 400 Hz.

[0150] Embodiment 4: The method according to any combination of Embodiments 1 to 3, wherein the pulse width of each control pulse in the plurality of control pulses is less than about 300 microseconds.

[0151] Example 5: A method according to any combination of Examples 1 to 4, wherein delivering the multiple control pulses includes: delivering one control pulse of the multiple control pulses during each time event of a plurality of time events; wherein each time event of the multiple time events includes the time between consecutive learning pulses of the multiple learning pulses at the predetermined pulse frequency within the period of time.

[0152] Example 6: A method according to any combination of Examples 1 to 5, wherein delivering the multiple control pulses includes: delivering two or more of the multiple control pulses during each time event of a plurality of time events, wherein each time event of the multiple time events includes the time between consecutive learning pulses of the multiple learning pulses at the predetermined pulse frequency within the period of time.

[0153] Example 7: The method according to any combination of Examples 1 to 6 further includes, for each sensed corresponding ECAP: determining a representative amplitude of at least one corresponding ECAP; and comparing the representative amplitude of the at least one corresponding ECAP with a target ECAP amplitude, wherein adjusting the one or more parameter values ​​includes adjusting the one or more parameter values ​​based on the comparison of the representative amplitude with the target ECAP amplitude.

[0154] Example 8: The method according to any combination of Examples 1 to 7 further includes: in response to a determination that the representative amplitude is greater than an upper limit of a target ECAP adjustment window, reducing the amplitude of one or more of the multiple learning pulses after the at least one corresponding ECAP; and in response to a determination that the representative amplitude is greater than an upper limit of a target ECAP adjustment window, reducing the amplitude of one or more of the multiple control pulses after the at least one corresponding ECAP.

[0155] Example 9: The method according to any combination of Examples 1 to 8 further includes: in response to a determination that the representative amplitude is less than a lower limit of the target ECAP adjustment window, increasing the amplitude of one or more learning pulses among the multiple learning pulses after the at least one corresponding ECAP; and in response to a determination that the representative amplitude is less than a lower limit of the target ECAP adjustment window, increasing the amplitude of one or more control pulses among the multiple control pulses after the at least one corresponding ECAP.

[0156] Example 10: The method according to any combination of Examples 1 to 9 further includes, for each sensed corresponding ECAP: determining the amplitude of the corresponding ECAP; and determining the percentage difference between the amplitude of the corresponding ECAP and the target ECAP amplitude, wherein adjusting the one or more parameter values ​​includes changing the amplitude value of a subsequent learning pulse to be inversely proportional to the percentage difference between the amplitude of the corresponding ECAP and the target ECAP amplitude.

[0157] Example 11: The method according to any combination of Examples 1 to 10 further includes: receiving a signal from a sensor indicating that the patient's activity level has changed; and increasing or decreasing the frequency of the multiple control pulses delivered to the patient in response to receiving the signal.

[0158] Embodiment 12: The method of any combination of embodiments 1 to 11, wherein each of the plurality of learn pulses is a monophasic pulse followed by a passive recharge phase, and wherein each of the plurality of control pulses is a biphasic pulse including a positive phase and a negative phase.

[0159] Example 13: A method according to any combination of Examples 1 to 12, wherein each of the multiple learning pulses is a first biphasic pulse including a first positive phase and a first negative phase, and wherein each of the multiple control pulses is a second biphasic pulse including a second positive phase and a second negative phase.

[0160] Embodiment 14: The method of any combination of Embodiments 1 to 13, wherein the plurality of control pulses comprises a plurality of non-therapeutic pulses, and wherein the plurality of learn pulses comprises a plurality of therapeutic pulses.

[0161] Example 15: A system comprising: a stimulation generating circuit configured to: deliver an electrical stimulation therapy to a patient, wherein the electrical stimulation therapy includes a plurality of learned pulses at a predetermined pulse frequency over a period of time, and wherein the plurality of learned pulses are at least partially defined by a first set of parameter values; and deliver a plurality of control pulses over the period of time, wherein the plurality of control pulses are interleaved with at least some of the plurality of learned pulses, and wherein the plurality of control pulses are at least partially defined by a second set of parameter values ​​different from the first set of parameter values; and a processing circuit configured to: receive corresponding sensed evoked compound action potentials (ECAPs) after one or more control pulses in the plurality of control pulses and before a subsequent learned pulse in the plurality of learned pulses; adjust one or more parameter values ​​in the first set of parameter values ​​that at least partially define the plurality of learned pulses of the electrical stimulation therapy based on at least one corresponding ECAP; and deliver the electrical stimulation therapy to the patient via the stimulation generating circuit according to the adjusted one or more parameter values ​​in the first set of parameter values.

[0162] Embodiment 16: The system of Embodiment 15, wherein a pulse width of each learn pulse in the plurality of learn pulses is greater than approximately 300 microseconds and less than approximately 1000 microseconds.

[0163] Embodiment 17: The system of any combination of Embodiments 15-16, wherein the predetermined pulse frequency of the plurality of learn pulses is less than about 400 Hz.

[0164] Embodiment 18: The system of any combination of Embodiments 15 to 17, wherein the pulse width of each control pulse in the plurality of control pulses is less than approximately 300 microseconds.

[0165] Example 19: A system according to any combination of Examples 15 to 18, wherein the stimulation generator is further configured to: deliver one of the multiple control pulses during each of a plurality of time events, wherein each of the multiple time events includes time between consecutive learn pulses of the multiple learn pulses at the predetermined pulse frequency within the period of time.

[0166] Example 20: A system according to any combination of Examples 15 to 19, wherein the stimulation generator is further configured to: deliver two or more of the multiple control pulses during each time event of a plurality of time events, wherein each time event of the plurality of time events includes time between consecutive learned pulses of the plurality of learned pulses at the predetermined pulse frequency within the period of time.

[0167] Embodiment 21: The system of any combination of Embodiments 15 to 20, wherein the one or more parameter values ​​include at least one of: pulse amplitude, pulse width, pulse frequency, and pulse shape.

[0168] Example 22: The system according to any combination of Examples 15 to 21, further comprising: a target ECAP amplitude; and an ECAP adjustment window ranging from a lower limit to an upper limit, wherein the target ECAP amplitude is within the ECAP adjustment window, and wherein the one or more processors are further configured to: determine the amplitude of the corresponding ECAP after each of the one or more control pulses in the multiple control pulses; and calculate a representative amplitude of at least one corresponding ECAP.

[0169] Embodiment 23: A system according to any combination of Embodiments 15 to 22, wherein the one or more processors are further configured to: reduce the amplitude of one or more learning pulses among the multiple learning pulses after the at least one corresponding ECAP if the representative amplitude is greater than the upper limit of the ECAP adjustment window; and reduce the amplitude of one or more control pulses among the multiple control pulses after the at least one corresponding ECAP if the representative amplitude is greater than the upper limit of the target ECAP adjustment window.

[0170] Embodiment 24: A system according to any combination of Embodiments 15 to 23, wherein the one or more processors are further configured to: increase the amplitude of one or more learning pulses among the multiple learning pulses after the at least one corresponding ECAP if the representative amplitude is less than the lower limit of the ECAP adjustment window; and increase the amplitude of one or more control pulses among the multiple control pulses after the at least one corresponding ECAP if the representative amplitude is less than the lower limit of the target ECAP adjustment window.

[0171] Example 25: The system according to any combination of Examples 15 to 24, further comprising: a sensor; and wherein the one or more processors are further configured to: receive a signal from the sensor indicating that the patient's activity level has changed; and in response to receiving the signal, increase or decrease the frequency of the multiple control pulses delivered to the patient by the stimulation generating circuit.

[0172] Embodiment 26: The system of any combination of Embodiments 15 to 25, wherein each learn pulse of the plurality of learn pulses is a monophasic pulse followed by a passive recharge phase, and wherein each control pulse of the plurality of control pulses is a biphasic pulse.

[0173] Example 27: The system according to any combination of Examples 15 to 26, further comprising: a memory configured to store a target ECAP amplitude and an ECAP adjustment window; and one or more electrodes, wherein the stimulation generating circuit is further configured to: deliver the electrical stimulation therapy to the patient through the one or more electrodes; and deliver the multiple control pulses to the patient through the one or more electrodes.

[0174] Embodiment 28: The system of any combination of Embodiments 15 to 27, wherein the plurality of control pulses comprises a plurality of non-therapeutic pulses, and wherein the plurality of learn pulses comprises a plurality of therapeutic pulses.

[0175] Example 29: A computer-readable storage medium comprising instructions that, when executed, cause one or more processors to: control the delivery of an electrical stimulation therapy to a patient, the electrical stimulation therapy comprising a plurality of learned pulses at a predetermined pulse frequency over a period of time, wherein the plurality of learned pulses are at least partially defined by a first set of parameter values; control the delivery of a plurality of control pulses interleaved with at least some of the plurality of learned pulses over the period of time, wherein the plurality of control pulses are at least partially defined by a second set of parameter values ​​different from the first set of parameter values; receive a corresponding sensed evoked compound action potential (ECAP) after one or more of the plurality of control pulses and before an immediately subsequent learned pulse in the plurality of learned pulses; adjust one or more parameter values ​​in the first set of parameter values ​​that at least partially define the plurality of learned pulses of the electrical stimulation therapy based on at least one corresponding ECAP; and control the delivery of the electrical stimulation therapy to the patient based on the adjusted one or more parameter values ​​in the first set of parameter values.

[0176] Example 30: A method comprising: delivering a controlled stimulation pulse to a patient, the controlled stimulation pulse having a first pulse width; sensing an evoked compound action potential (ECAP) signal caused by the controlled stimulation pulse; identifying characteristics of the ECAP signal; determining a therapeutic parameter value that at least partially defines the learned stimulation pulse based on a plurality of learned pulses based on the characteristics and a gain value of the ECAP signal, wherein the plurality of learned pulses have a second pulse width greater than the first pulse width; and delivering the learned stimulation pulse based on the determined therapeutic parameter value.

[0177] Example 31: The method of Example 30, wherein the gain value represents the slope of a growth curve of characteristic values ​​of the ECAP signal resulting from corresponding calibration stimulation pulses delivered to the patient and defined at least in part by different values ​​of stimulation parameters.

[0178] Example 32: A method according to any combination of Examples 30 to 31, wherein the characteristic of the ECAP signal is a measured amplitude of a portion of the ECAP signal, wherein the treatment parameter value includes a new learned amplitude value, and wherein determining the new learned amplitude value includes: subtracting the measured amplitude from the patient's target ECAP amplitude value to generate a differential amplitude; multiplying the differential amplitude by the gain value to generate an initial differential value; multiplying the initial differential value by a proportional factor to generate a learned differential value, wherein the proportional factor represents a ratio of a previous learned amplitude value that defines a previous learned stimulation pulse delivered before the control stimulation pulse to a control amplitude value that defines the control stimulation pulse; and adding the learned differential value to the previous learned amplitude value to generate the new learned amplitude value that at least partially defines the learned stimulation pulse.

[0179] Example 33: A method according to any combination of Examples 30 to 32, wherein the control pulse is a first control pulse, and wherein the method further comprises: generating a new control amplitude value defining a second control stimulation pulse by adding the initial differential value to a previous control amplitude value defining the first control stimulation pulse, the second control stimulation pulse to be delivered to the patient after delivery of the first control stimulation pulse.

[0180] Example 34: A method according to any combination of Examples 30 to 33, wherein the learned stimulation pulse is a first learned stimulation pulse, and wherein the method further comprises: delivering a second learned stimulation pulse at least partially defined by the new learned amplitude value after delivery of the first learned stimulation pulse.

[0181] Embodiment 35: The method of any combination of Embodiments 30 to 34, wherein the measured amplitude of a portion of the ECAP signal comprises a voltage amplitude between an N1 peak and a P2 peak of the ECAP signal.

[0182] Example 36: A method according to any combination of Examples 30 to 35, wherein determining the treatment parameter value that at least partially defines the learned stimulation pulse based on the characteristics of the ECAP signal and the gain value includes: determining the treatment parameter value based on the average value of the characteristics of multiple continuously sensed ECAP signals and the gain value, the treatment parameter value at least partially defining the learned stimulation pulse, and the multiple continuously sensed ECAP signals including the ECAP signal.

[0183] Example 37: A method according to any combination of Examples 30 to 36, wherein a plurality of control stimulation pulses include the control stimulation pulses, wherein a plurality of learned stimulation pulses include the learned stimulation pulses, and wherein the method further comprises: interleaving the plurality of control stimulation pulses with at least some of the plurality of learned stimulation pulses.

[0184] Example 38: A method according to any combination of Examples 30 to 37, wherein interleaving the multiple control stimulation pulses within at least some of the multiple learned stimulation pulses includes: delivering at least two control stimulation pulses of the multiple control stimulation pulses between consecutive learned stimulation pulses; and sensing at least two ECAP signals caused by corresponding control stimulation pulses of the at least two control stimulation pulses between the consecutive learned stimulation pulses.

[0185] Embodiment 39: The method of any combination of Embodiments 30 to 38, wherein the pulse width of the learned stimulation pulse is greater than about 300 microseconds and less than about 1000 microseconds.

[0186] Embodiment 40: The method according to any combination of Embodiments 30 to 39, wherein the pulse width of the control stimulation pulse is less than about 300 microseconds.

[0187] Embodiment 41: The method of any combination of Embodiments 30 to 40, wherein the learned stimulation pulse is a monophasic pulse followed by a passive recharge phase, and wherein the control stimulation pulse is a biphasic pulse including a positive phase and a negative phase.

[0188] Example 42: A method according to any combination of Examples 30 to 41, wherein the learned stimulation pulse is a first biphasic pulse including a first positive phase and a first negative phase, and wherein the control stimulation pulse is a second biphasic pulse including a second positive phase and a second negative phase.

[0189] Embodiment 43: The method of any combination of Embodiments 30 to 42, wherein the plurality of control pulses comprises a plurality of non-therapeutic pulses, and wherein the plurality of learn pulses comprises a plurality of therapeutic pulses.

[0190] Example 44: A system comprising: a stimulation generation circuit configured to: deliver a control stimulation pulse to a patient, the control stimulation pulse having a first pulse width; and deliver a learned stimulation pulse from a plurality of learned pulses according to a therapeutic parameter value, wherein the plurality of learned pulses have a second pulse width longer than the first pulse width; and a processing circuit configured to: receive a sensed evoked compound action potential (ECAP) signal caused by the control stimulation pulse; identify characteristics of the ECAP signal; and determine, based on the characteristics of the ECAP signal and a gain value, the therapeutic parameter value that at least partially defines the learned stimulation pulse.

[0191] Example 45: The method of Example 44, wherein the gain value represents the slope of a growth curve of characteristic values ​​of the ECAP signal resulting from corresponding calibration stimulation pulses delivered to the patient and defined at least in part by different values ​​of stimulation parameters.

[0192] Example 46: A system according to any combination of Examples 44 to 45, wherein the characteristic of the ECAP signal is a measured amplitude of a portion of the ECAP signal, wherein the treatment parameter value includes a new learned amplitude value, and wherein the processing circuit is configured to determine the new treatment parameter value by: subtracting the measured amplitude from the patient's target ECAP amplitude value to generate a differential amplitude; multiplying the differential amplitude by the gain value to generate an initial differential value; multiplying the initial differential value by a scaling factor to generate a learned differential value, wherein the scaling factor represents a ratio of a previous learned amplitude value that defines a previous learned stimulation pulse delivered before the control stimulation pulse to a control amplitude value that defines the control stimulation pulse; and adding the learned differential value to the previous learned amplitude value to generate the new learned amplitude value that at least partially defines the learned stimulation pulse.

[0193] Example 47: A system according to any combination of Examples 44 to 46, wherein the control pulse is a first control pulse, and wherein the processing circuit is configured to generate a new control amplitude value defining a second control stimulation pulse by adding the initial differential value to a previous control amplitude value defining the first control stimulation pulse, the second control stimulation pulse to be delivered to the patient after delivery of the first control stimulation pulse.

[0194] Example 48: A system according to any combination of Examples 44 to 47, wherein the learned stimulation pulse is a first learned stimulation pulse, and wherein the processing circuit is configured to control the stimulation generation circuit to deliver a second learned stimulation pulse at least partially defined by the new learned amplitude value after delivery of the first learned stimulation pulse.

[0195] Embodiment 49: The system of any combination of Embodiments 44 to 48, wherein the measured amplitude of a portion of the ECAP signal comprises a voltage amplitude between an N1 peak and a P2 peak of the ECAP signal.

[0196] Example 50: A system according to any combination of Examples 44 to 49, wherein the processing circuit is configured to determine the treatment parameter value that at least partially defines the learned stimulation pulse based on the characteristics of the ECAP signal and the gain value in the following manner: determining the treatment parameter value based on an average value of the characteristics of multiple continuously sensed ECAP signals and the gain value, the treatment parameter value at least partially defining the learned stimulation pulse, and the multiple continuously sensed ECAP signals include the ECAP signal.

[0197] Example 51: A system according to any combination of Examples 44 to 50, wherein a plurality of control stimulation pulses include the control stimulation pulses, wherein a plurality of learned stimulation pulses include the learned stimulation pulses, and wherein the processing circuit is configured to control the stimulation generation circuit to interleave the plurality of control stimulation pulses with at least some of the plurality of learned stimulation pulses.

[0198] Example 52: A system according to any combination of Examples 44 to 51, wherein the processing circuit is configured to control the stimulation generation circuit to interleave the multiple control stimulation pulses within at least some of the multiple learned stimulation pulses in the following manner: controlling the stimulation generation circuit to deliver at least two control stimulation pulses of the multiple control stimulation pulses between consecutive learned stimulation pulses; and controlling the sensing circuit to sense at least two ECAP signals caused by corresponding control stimulation pulses of the at least two control stimulation pulses between the consecutive learned stimulation pulses.

[0199] Embodiment 53: The system of any combination of Embodiments 44 to 52, wherein the pulse width of the learned stimulation pulse is greater than about 300 microseconds and less than about 1000 microseconds.

[0200] Embodiment 54: The system of any combination of Embodiments 44 to 53, wherein the pulse width of the control stimulation pulse is less than about 300 microseconds.

[0201] Embodiment 55: The system of any combination of Embodiments 44 to 54, wherein the learned stimulation pulse is a monophasic pulse followed by a passive recharge phase, and wherein the control stimulation pulse is a biphasic pulse including a positive phase and a negative phase.

[0202] Embodiment 56: A system according to any combination of embodiments 44 to 55, wherein the learned stimulation pulse is a first biphasic pulse including a first positive phase and a first negative phase, and wherein the control stimulation pulse is a second biphasic pulse including a second positive phase and a second negative phase.

[0203] Embodiment 57: The system of any combination of Embodiments 44 to 56, wherein the plurality of control pulses comprises a plurality of non-therapeutic pulses, and wherein the plurality of learn pulses comprises a plurality of therapeutic pulses.

[0204] Example 58: A computer-readable storage medium comprising instructions that, when executed, cause one or more processors to: control the delivery of a controlled stimulation therapy to a patient, the controlled stimulation pulse having a first pulse width; sense an evoked compound action potential (ECAP) signal caused by the controlled stimulation pulse; identify characteristics of the ECAP signal; determine a therapeutic parameter value that at least partially defines the learned stimulation pulse based on a plurality of learned pulses based on the characteristics and a gain value of the ECAP signal, wherein the plurality of learned pulses have a second pulse width that is longer than the first pulse width; and control the delivery of the learned pulse based on the determined therapeutic parameter value.

[0205] The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, the corresponding aspects of the described techniques may be implemented within one or more processors or processing circuits, including one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuits, as well as any combination of such components. The terms "processor" or "processing circuit" may generally refer to any of the aforementioned logic circuits, alone or in combination with other logic circuits or any other equivalent circuits. A control unit including hardware may also perform one or more techniques of the present disclosure.

[0206] Such hardware, software, and firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. In addition, any units, modules, or components described may be implemented together or separately as discrete but interoperable logic devices. Descriptions of different features such as circuits or units are intended to highlight different functional aspects and do not necessarily imply that such circuits or units must be implemented by separate hardware or software components. Rather, the functions associated with one or more circuits or units may be performed by separate hardware or software components, or may be integrated within common or separate hardware or software components.

[0207] The techniques described in this disclosure may also be implemented or encoded in a computer-readable medium (such as a computer-readable storage medium) containing instructions, which may be described as a non-transitory medium. The instructions embedded or encoded in the computer-readable storage medium may cause a programmable processor or other processor to perform the method, for example, when the instructions are executed. The computer-readable storage medium may include a random access memory (RAM), a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electronically erasable programmable read-only memory (EEPROM), a flash memory, a hard disk, a CD-ROM, a floppy disk, a cassette, a magnetic medium, an optical medium, or other computer-readable medium.

Claims

1. A system comprising: A stimulus generating circuit, the stimulus generating circuit being configured to: delivering a controlled stimulation pulse to a patient, the controlled stimulation pulse having a first pulse width; as well as delivering a first learned stimulation pulse of a plurality of learned stimulation pulses, wherein each learned stimulation pulse of the plurality of learned stimulation pulses has a second pulse width, wherein the second pulse width is longer than the first pulse width; and A processing circuit, the processing circuit being configured to: receiving a sensed compound action potential ECAP signal induced by the control stimulation pulse; Identify a characteristic of the ECAP signal; determining, based on the characteristic of the ECAP signal and the gain value, a therapeutic parameter value that at least partially defines a second learned stimulation pulse of the plurality of learned stimulation pulses, the second learned stimulation pulse being a next learned stimulation pulse of the plurality of learned stimulation pulses to be delivered after delivery of the first learned stimulation pulse; as well as The stimulation production circuit is controlled to deliver the second learned stimulation pulse of the plurality of learned stimulation pulses in accordance with the determined therapy parameter value.

2. The system according to claim 1, wherein: The gain value represents the slope of a growth curve of characteristic values ​​of the ECAP signal resulting from respective control stimulation pulses delivered to the patient and defined at least in part by different values ​​of stimulation parameters.

3. The system according to any one of claims 1 to 2, wherein: The characteristic of the ECAP signal is a measured amplitude of a portion of the ECAP signal, wherein the treatment parameter value comprises a new learned amplitude value, and wherein the processing circuit is configured to determine the new treatment parameter value by: subtracting the measured amplitude from a target ECAP amplitude value for the patient to generate a differential amplitude; multiplying the differential amplitude by the gain value to generate an initial differential value; multiplying the initial difference value by a scaling factor to generate a learned difference value, wherein the scaling factor represents a ratio of a previously learned amplitude value defining a previously learned stimulation pulse delivered prior to the control stimulation pulse to a control amplitude value defining the control stimulation pulse; and The learned difference value is added to the previous learned amplitude value to generate the new learned amplitude value that at least partially defines the learned stimulation pulse.

4. The system according to claim 3, wherein: The controlled stimulation pulse is a first controlled stimulation pulse, and wherein the processing circuit is configured to generate a new control amplitude value defining a second controlled stimulation pulse by adding the initial differential value to a previous control amplitude value defining the first controlled stimulation pulse, the second controlled stimulation pulse to be delivered to the patient subsequent to delivery of the first controlled stimulation pulse.

5. The system according to claim 4, wherein: The learned stimulation pulse is a first learned stimulation pulse, and wherein the processing circuit is configured to control the stimulation generation circuit to deliver a second learned stimulation pulse defined at least in part by the new learned amplitude value subsequent to delivery of the first learned stimulation pulse.

6. The system according to claim 3, wherein: The measured amplitude of a portion of the ECAP signal includes a voltage amplitude between an N1 peak and a P2 peak of the ECAP signal.

7. The system according to any one of claims 1 to 2, wherein: The processing circuit is configured to determine the therapy parameter value that at least partially defines the learned stimulation pulse based on the characteristic of the ECAP signal and the gain value by: The therapeutic parameter value is determined based on an average value of characteristics of a plurality of continuously sensed ECAP signals and the gain value, the therapeutic parameter value at least partially defining the learned stimulation pulse, the plurality of continuously sensed ECAP signals including the ECAP signal based on which the therapeutic parameter value that at least partially defines the second learned stimulation pulse is determined.

8. The system according to any one of claims 1 to 2, wherein: A plurality of control stimulation pulses comprises the control stimulation pulses, wherein a plurality of learned stimulation pulses comprises the learned stimulation pulses, and wherein the processing circuit is configured to control the stimulation generation circuit to interleave the plurality of control stimulation pulses with at least some of the plurality of learned stimulation pulses.

9. The system according to claim 8, wherein: The processing circuit is configured to control the stimulation generation circuit to interleave the plurality of control stimulation pulses within at least some of the plurality of learned stimulation pulses by: controlling the stimulation generation circuit to deliver at least two control stimulation pulses of the plurality of control stimulation pulses between consecutive learned stimulation pulses; as well as The control sensing circuit senses at least two ECAP signals caused by respective ones of the at least two control stimulation pulses between the consecutive learn stimulation pulses.

10. The system according to any one of claims 1 to 2, wherein: The pulse width of the learning stimulation pulse is greater than 300 microseconds and less than 1000 microseconds.

11. The system according to any one of claims 1 to 2, wherein: The pulse width of the controlled stimulation pulse is less than 300 microseconds.

12. The system according to any one of claims 1 to 2, wherein: The learned stimulation pulse is a monophasic pulse followed by a passive recharge phase, and wherein the control stimulation pulse is a biphasic pulse including a positive phase and a negative phase.

13. The system according to any one of claims 1 to 2, wherein: The learned stimulation pulse is a first biphasic pulse including a first positive phase and a first negative phase, and wherein the control stimulation pulse is a second biphasic pulse including a second positive phase and a second negative phase.

14. The system according to any one of claims 1 to 2, wherein: The plurality of control stimulation pulses comprises a plurality of non-therapy pulses, and wherein the plurality of learned stimulation pulses comprises a plurality of therapy pulses.

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