Subthreshold stimulation based on ecap detection

Abstract

Systems, devices, and techniques are described that determine stimulation parameters based on one or more stimulation thresholds (e.g., a perception threshold or a detection threshold). In one example, a medical device includes a sensing circuit configured to sense one or more ECAP signals, where the sensing circuit is configured to sense each ECAP signal of the one or more ECAPs elicited by a respective control pulse of a plurality of control pulses, and the medical device includes a processing circuit configured to determine, based on the one or more ECAP signals, a stimulation level of the plurality of control pulses that achieves a stimulation threshold, determine, based on the stimulation level, a value of a stimulation parameter of a plurality of therapy pulses that at least partially define an electrical stimulation therapy, and control a stimulation generation circuit to deliver the electrical stimulation therapy in accordance with the value of the stimulation parameter.

Description

Technical Field

[0001] This disclosure relates generally to electrical stimulation therapy, and more specifically to the control of electrical stimulation therapy. Background Technology

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

[0003] Evoked compound action potentials (ECAPs) are synchronous firings of a population of neurons in response to stimuli (including electrical stimulation in some cases) applied by a medical device. ECAPs can be detectable because they are events separate from the stimulus itself, and they can reveal the characteristics of the stimulus's effect on nerve fibers. Electrical stimulation can be delivered to the patient by a medical device in the form of a train of electrical pulses, and the parameters of these pulses can include frequency, amplitude, pulse width, and pulse shape. The parameters of the electrical pulses may change in response to sensory input, such as the ECAP parameters sensed in response to the electrical pulse train. This change may affect the patient's perception of the electrical pulses, or the absence of such perception. Summary of the Invention

[0004] Generally, systems, apparatuses, and techniques for controlling electrical stimulation based on at least one stimulation threshold are described. For example, the techniques disclosed herein can enable a medical device to determine at least one stimulation threshold based on sensing one or more evoked compound action potential (ECAP) signals, such as a sensing threshold or detection threshold associated with one or more stimulation pulses that elicit these ECAP signals. The sensing threshold may represent a characteristic ECAP value associated with a value of stimulation parameters that define a pulse perceptible to a patient. The detection threshold may represent a characteristic ECAP value associated with a value of stimulation parameters that define a pulse that elicits an ECAP signal measurable by the device. In some examples, the medical device may also adjust stimulation parameters to define a notification pulse based on the stimulation level of a pulse (e.g., a control pulse) that elicits an ECAP signal having characteristics that achieve or approach a stimulation threshold.

[0005] By identifying the stimulation level that elicits an ECAP signal with characteristics similar to a stimulation threshold (such as a perception threshold or detection threshold), the system is able to deliver electrical stimulation therapy to the patient at a level where the patient would not normally perceive the stimulation or where the system cannot detect the ECAP signal. Compared to overthreshold stimulation therapy, this subthreshold stimulation therapy can be configured to provide relief for patient symptoms (such as chronic pain) while reducing or eliminating uncomfortable sensations, unpleasant vibrations, or other side effects. In some examples, subthreshold stimulation therapy may still elicit therapeutic sensory abnormalities or reduce the propagation of pain signals.

[0006] In one example, the medical device includes: a stimulation generation circuit configured to deliver electrical stimulation therapy to a patient, wherein the electrical stimulation therapy includes a plurality of treatment pulses; a sensing circuit configured to sense one or more evoked compound action potential (ECAP) signals, wherein the sensing circuit is configured to sense each of the one or more ECAP signals induced by a corresponding control pulse of a plurality of control pulses; and a processing circuit configured to determine, based on the one or more ECAP signals, a stimulation level for achieving a stimulation threshold of the plurality of control pulses, determine, based on the stimulation level, a value of a stimulation parameter of the plurality of treatment pulses that at least partially defines the electrical stimulation therapy, and control the stimulation generation circuit to deliver the electrical stimulation therapy to the patient according to the value of the stimulation parameter.

[0007] In another example, a method includes: delivering electrical stimulation therapy to a patient by a stimulation generation circuit, wherein the electrical stimulation therapy comprises a plurality of treatment pulses; sensing one or more evoked compound action potential (ECAP) signals by a sensing circuit, wherein the sensing circuit is configured to sense each of the one or more ECAP signals induced by a corresponding control pulse among a plurality of control pulses; determining, by a processing circuit, a stimulation level of the plurality of control pulses to achieve a stimulation threshold based on the one or more ECAP signals; determining, by the processing circuit, values ​​of stimulation parameters that at least partially define the plurality of treatment pulses of the electrical stimulation therapy based on the stimulation level; and controlling the stimulation generation circuit by the processing circuit to deliver the electrical stimulation therapy to the patient according to the values ​​of the stimulation parameters.

[0008] In another example, a computer-readable medium includes instructions that, when executed by a processor, cause the processor to: control a stimulation generation circuit to deliver electrical stimulation therapy to a patient, wherein the electrical stimulation therapy comprises a plurality of treatment pulses; control a sensing circuit to sense one or more evoked compound action potential (ECAP) signals, wherein the sensing circuit is configured to sense each of the one or more ECAP signals induced by a corresponding control pulse among the plurality of control pulses; determine a stimulation level for achieving a stimulation threshold of the plurality of control pulses based on the one or more ECAP signals; determine, based on the stimulation level, a value of a stimulation parameter of the plurality of treatment pulses that at least partially defines the electrical stimulation therapy; and control the stimulation generation circuit to deliver the electrical stimulation therapy to the patient according to the value of the stimulation parameter.

[0009] The summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive interpretation of the systems, apparatus, and methods described in detail in the accompanying drawings and the following detailed description. Further details of one or more examples of this disclosure are set forth in the accompanying drawings and the following detailed description. Other features, objectives, and advantages will be apparent from the specification, drawings, and claims. Attached Figure Description

[0010] Figure 1 This is a conceptual diagram illustrating an exemplary system according to one or more technologies of this disclosure, the exemplary system including an implantable medical device (IMD) configured to deliver spinal cord stimulation (SCS) therapy, and an external programmer.

[0011] Figure 2 This is a block diagram illustrating an exemplary configuration of components of an implantable medical device (IMD) according to one or more technologies of this disclosure.

[0012] Figure 3 This is a block diagram illustrating an exemplary configuration of components of an exemplary external programmer according to one or more technologies disclosed herein.

[0013] Figure 4 It is an exemplary evoked compound action potential (ECAP) curve for sensing a corresponding stimulus pulse according to one or more techniques of this disclosure.

[0014] Figure 5A This is a timing diagram illustrating an example of an electrical stimulation pulse according to one or more techniques of this disclosure and the corresponding sensed ECAP.

[0015] Figure 5B This is a timing diagram illustrating another example of an electrical stimulation pulse according to one or more techniques of this disclosure and the corresponding sensed ECAP.

[0016] Figure 6 This is a timing diagram illustrating another example of an electrical stimulation pulse and a corresponding ECAP according to one or more techniques of this disclosure.

[0017] Figure 7 This is a timing diagram illustrating another example of an electrical stimulation pulse and a corresponding ECAP according to one or more techniques of this disclosure.

[0018] Figure 8 This is a timing diagram illustrating another example of an electrical stimulation pulse according to one or more techniques of this disclosure and the corresponding sensed ECAP.

[0019] Figure 9 This is a flowchart illustrating an exemplary operation of determining stimulation parameters based on a perception threshold according to one or more techniques of this disclosure.

[0020] Figure 10 This is a flowchart illustrating an exemplary operation of determining stimulation parameters based on a detection threshold according to one or more techniques of this disclosure.

[0021] Throughout the specification and drawings, similar reference numerals represent similar elements. Detailed Implementation

[0022] This disclosure describes examples of medical devices, systems, and techniques for automatically modulating the delivery of electrical stimulation therapy to a patient based on one or more characteristics and stimulation thresholds of evoked compound action potentials (ECAPs). In some examples, the ECAP signal can be sensed by the medical device in response to a controlled stimulation pulse delivered by the medical device. The controlled stimulation pulse may or may not contribute to the treatment of the patient (e.g., eliciting a therapeutic effect on the patient). Electrical stimulation therapy is typically delivered to a target tissue of the patient (e.g., nerves in the spinal cord or muscles) via two or more electrodes. Parameters of the electrical stimulation therapy (e.g., electrode combination, voltage or current amplitude, pulse width, pulse frequency, etc.) are selected by the clinician and / or the patient to provide relief for various symptoms (such as pain, neurological disorders, muscle disorders, etc.). However, the distance between the electrodes and the target tissue changes when the patient moves. Since neural recruitment is a function of stimulation intensity and the distance between the target tissue and the electrodes, moving the electrodes closer to the target tissue can lead to increased neural recruitment (e.g., possible pain sensation or impaired motor function), while moving the electrodes further away from the target tissue can lead to decreased therapeutic efficacy for the patient.

[0023] ECAP can be used as a metric for neural recruitment because each ECAP signal represents a superposition of potentials generated in response to electrical stimulation (e.g., a stimulation pulse) by the excitation of a population of axons. Changes in the characteristics of the ECAP signal (e.g., the amplitude of a portion of the signal) occur as a function of the number of axons activated by the delivered stimulation pulse. The system can monitor changes in the characteristics of the ECAP signal and use these changes to adjust one or more stimulation parameters of the pulses delivered to the patient (e.g., control pulses or notification pulses). For example, the system can reduce the intensity of the stimulation pulse (e.g., reduce the current amplitude and / or pulse width) in response to a detected increase in the amplitude of the ECAP signal.

[0024] In some examples, clinicians may wish to deliver electrical stimulation at an intensity that is related to a stimulation threshold. For instance, the perception threshold could represent a characteristic ECAP value associated with the value of a stimulation parameter that defines the pulse that the patient can perceive. Electrical stimulation delivered at a level that is a fraction below the perception threshold could provide some relief of the patient's symptoms without the patient perceiving the stimulation. As another exemplary type of stimulation threshold, the detection threshold could represent a characteristic ECAP value associated with the value of a stimulation parameter that defines the pulse that elicits a detectable ECAP signal. Since a detectable ECAP signal indicates that nerve fibers have been recruited, thus indicating that the patient can perceive the stimulation, clinicians may wish to deliver stimulation at a level that is a fraction below the detection threshold.

[0025] The stimulation levels of the pulses used to achieve or cause a fraction of the perception and detection thresholds required for the patient to perceive the stimulus and for the medical device to detect an ECAP in response to the stimulus can vary over time based on a variety of factors. The distance between the electrodes of the medical device and the patient's target neural tissue can affect the pulse intensity required to achieve the perception and detection thresholds. For example, if the distance between the electrodes and the neural tissue decreases, the stimulation level of the pulses required to achieve the perception and detection thresholds will also decrease. Alternatively, if the distance between the electrodes and the neural tissue increases, the stimulation level of the pulses required to achieve the perception and detection thresholds will also increase. In some examples, the distance between the electrodes and the neural tissue varies over time depending on the patient's posture, patient activity, patient movement, or lead migration. Therefore, it may be beneficial for the medical device to occasionally, repeatedly, or continuously determine the stimulation level required to elicit an ECAP signal that reaches or is similar to the perception and detection thresholds in order to maintain consistent delivery of electrical stimulation. However, when the desired stimulation therapy may not elicit many (if any) patient perceptions and / or ECAP signals, it may be difficult to use the ECAP signal as feedback to control the stimulation therapy.

[0026] As described herein, a system can be configured to deliver stimulation therapy based on one or more stimulation thresholds using one or more techniques. For example, the perception threshold may be less than the patient's detection threshold. In this way, electrical stimulation delivered to the patient by the medical device can be perceived by the patient at an intensity that does not trigger an ECAP detectable by the system. In such examples, it may be difficult to determine the perception threshold based on the sensed ECAP because electrical stimulation delivered at or near the perception threshold does not trigger an ECAP detectable by the medical device. One or more techniques of this disclosure enable the medical device to periodically determine the stimulation level of the pulses required to achieve the detection threshold and deliver sub-perception threshold stimulation to the patient at a fraction of the detection threshold. By periodically determining the stimulation level associated with the detection threshold, the medical device can be configured to maintain a consistent level of sub-perception therapy as the distance between the electrodes of the medical device and the target tissue changes over time and / or as the patient moves. Furthermore, in examples where the perception threshold is greater than the detection threshold, one or more techniques of this disclosure enable the medical device to periodically determine the perception threshold and vary the stimulation level required to achieve the perception threshold. By periodically determining the stimulation level associated with the perception threshold, the medical device can be configured to maintain a consistent level of subsensory therapy as the distance between the device's electrodes and the target tissue changes.

[0027] While the techniques described herein can monitor ECAP induced by one or more pulses (e.g., control pulses that may be therapeutic or non-therapeutic), these techniques can be used to induce ECAP signals in other examples. After the delivered stimulation pulse initially depolarizes the nerve, a synchronized neural pulse, detectable as an ECAP signal, travels rapidly along the nerve fiber. If the stimulation pulse delivered by the first electrode has an excessively long pulse width, the different electrodes configured to sense the ECAP will sense the stimulation pulse itself as an artifact that blurs the lower amplitude ECAP signal. However, the ECAP signal loses fidelity as the potential propagates from the electrical stimulation because different nerve fibers propagate the potential at different speeds. Therefore, sensing the ECAP at a location remote 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 that occur as the distance from the electrode to the target tissue changes. In other words, the system may not be able to identify the ECAP from stimulation pulses configured to provide treatment to a patient at any distance from the stimulation electrode.

[0028] In some examples, the medical device can be configured to deliver control pulses or a combination of multiple control pulses and multiple notification pulses. In some cases, the multiple control pulses may be therapeutic and contribute to the treatment received by the patient. In other examples, the multiple control pulses may be non-therapeutic and do not contribute to the treatment received by the patient. In other words, a control pulse configured to trigger a detectable ECAP may or may not contribute to alleviating the patient's symptoms. A notification pulse, compared to a control pulse, may not trigger a detectable ECAP, or the system may not utilize the ECAP from the notification pulse as feedback for controlling treatment. Therefore, the medical device or other components associated with the medical device may, alternatively, determine the value of one or more stimulation parameters that at least partially define the notification pulse based on the ECAP signal triggered by the control pulse. In this way, the notification pulse can be notified by the ECAP triggered from the control pulse. The medical device or other components associated with the medical device may determine the value of one or more stimulation parameters that at least partially define the control pulse based on the ECAP signal triggered by a previous control pulse.

[0029] In one example described herein, a medical device is configured to deliver multiple notification pulses configured to provide treatment to a patient, and multiple control pulses. At least some of the control pulses can trigger a detectable ECAP signal, the primary purpose of which is not to provide treatment to the patient. The control pulses can be interleaved with the delivery of notification pulses. For example, the medical device can deliver notification pulses and control pulses alternately, such that control pulses are delivered between consecutive notification pulses, and the ECAP signal is sensed. In some examples, multiple control pulses are delivered between consecutive notification pulse deliveries, and the corresponding ECAP signals are sensed. In some examples, multiple notification pulses are delivered between consecutive control pulses. In any case, notification pulses can be delivered according to a selected predetermined pulse frequency, such that the notification pulses can produce a therapeutic outcome for the patient. Then, one or more control pulses are delivered within one or more time windows between consecutive notification pulses delivered according to the predetermined pulse frequency, and the corresponding ECAP signals are sensed. In this way, the medical device can continuously manage notification pulses from the medical device while sensing ECAP from control pulses delivered during periods when notification pulses are not delivered. In other examples described herein, the ECAP is sensed by the medical device in response to a notification pulse delivered by the medical device, and a control pulse is not used to trigger the ECAP.

[0030] Based on one or more characteristics of the detected ECAP, the system can adjust one or more parameters that at least partially define the notification pulses and / or control pulses (if delivered). For example, in some cases, it may be desirable to maintain sub-sensory stimulation therapy delivered to the patient. In other words, it may be beneficial to alleviate the patient's chronic pain while avoiding or reducing the induction of side effects that might not be considered symptom relief. One or more characteristics of the ECAP can provide an indication of whether the patient is able to perceive the electrical stimulation. A perception threshold can define the characteristics of the ECAP signal elicited when a pulse is delivered at a specific stimulation level. This stimulation level can be used by the system to at least partially define the notification pulses, which the patient is able to perceive. For example, the patient may not perceive a notification pulse delivered with a first pulse amplitude below the perception threshold. However, the patient may perceive a notification pulse delivered with a second pulse amplitude greater than the first pulse amplitude, and the second pulse amplitude results in a characteristic ECAP signal greater than the perception threshold. Other parameters besides pulse amplitude can contribute to the stimulation level associated with the perception threshold. Pulse width or pulse frequency can contribute to the level of stimulation perceived by the patient (e.g., stimulation intensity) and can be altered to deliver stimuli above and below the perception threshold.

[0031] As discussed above, the distance between the electrodes of a medical device and the target tissue varies over time depending on the patient's posture, activity, movement, or lead migration. Furthermore, the distance between the electrodes and the target tissue can be transiently altered by any of a cough, sneeze, valsalva maneuver, or another transient movement of the patient. The stimulation level required to achieve the perception threshold can vary, and in some cases, can vary drastically as the electrode position moves relative to the target tissue. For example, the stimulation level may increase if the electrode moves away from the target tissue, and decrease as the electrode moves closer to the target tissue. Therefore, it may be beneficial for a medical device to periodically determine the stimulation level associated with the perception threshold and adjust one or more parameters of the notification pulse to provide the patient with sub-sensory therapy.

[0032] In some cases, medical devices may struggle to determine the stimulus level that leads to the perception threshold because stimulus pulses (e.g., notification pulses or control pulses) may be delivered at an amplitude that the medical device cannot detect due to the ECAP signal being too weak or the stimulus failing to elicit an ECAP signal. In this way, the detection threshold for a stimulus pulse can be greater than the perception threshold. The detection threshold can be associated with one or more parameter values ​​of a notification pulse, wherein the ECAP elicited from the notification pulse or a control pulse interleaved with the notification pulse can be detected by the medical device. Similar to the stimulus level associated with the perception threshold, the stimulus level associated with the detection threshold can vary depending on the distance between the electrodes of the medical device and the target tissue. Therefore, to maintain sub-perceptual therapeutic stimulation for the patient when the detection threshold is greater than the perception threshold, the medical device can periodically determine the stimulus level required to reach the detection threshold and deliver notification pulses at a fraction of the stimulus level in an attempt to deliver notification pulses below the perception threshold.

[0033] In some examples, to determine the stimulation level at which a detection threshold is reached, the medical device is configured to determine one or more baseline parameter values ​​for the stimulation pulse, wherein, if the stimulation pulse is delivered at one or more baseline parameter values, the medical device is configured to detect at least a threshold ratio of ECAP (which can be triggered and detected from a notification pulse or a control pulse interleaved with the notification pulse), the threshold ratio representing the patient's desired detection threshold. The detected ECAP ratio is the ratio of detected ECAPs to the total number of stimulation pulses attempting to detect ECAPs. The detectable ECAP ratio by the medical device may increase with increasing one or more parameters that at least partially define the intensity of the stimulation pulse. If the detectable ECAP ratio by the medical device is below the threshold ratio, the medical device may increase the value of one or more stimulation parameters to attempt to increase the detected ECAP signal ratio. Alternatively, if the detectable ECAP ratio by the medical device is greater than the threshold ratio, the medical device may decrease the value of one or more stimulation parameters to attempt to decrease the detected ECAP signal ratio. In this way, the medical device can attempt to maintain the stimulation parameter value at a stimulation level that reaches a detection threshold represented by a threshold ratio of the detected ECAP, or at a stimulation level that is a fraction lower than the detection threshold represented by that threshold ratio. Once the medical device determines the stimulation level, it can deliver stimulation pulses (such as notification pulses and / or control pulses) at a fraction of the stimulation level of the detection threshold, so that the patient does not perceive the notification pulses.

[0034] Notification pulses and control pulses are generally described herein as different stimulation pulses reflecting different types of electrical stimulation. However, different types of electrical stimulation and their corresponding pulses can be described with different properties. For example, a first type of electrical stimulation may include a first pulse (such as a notification pulse) configured to primarily contribute to the treatment of the patient. This first pulse of the first type of electrical stimulation may also have one or more features (e.g., pulse width) that prevent or reduce the system's ability to detect an ECAP signal induced by the first pulse of this first type of electrical stimulation, because artifacts representing the first pulse itself overlap with and obscure at least a portion of the corresponding induced ECAP signal. A second type of electrical stimulation may include a second pulse (such as a control 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, it may be referred to as a "sensing pulse" or a "test pulse." For example, the second pulse of the second type of electrical stimulation may improve the detectability of the ECAP signal to the extent that it does not generate artifacts that obscure the ECAP signal, or otherwise prevent or reduce the system's ability to detect the ECAP signal from each second pulse. Furthermore, the second pulse can be defined by parameter values ​​selected to elicit an ECAP signal that modifies at least one or more parameter values ​​of the first pulse of the first type of electrical stimulation. Therefore, the first and second pulses can differ in at least one parameter (e.g., current and / or voltage amplitude, pulse width and / or frequency). The first pulse can be at least partially interleaved with at least some of the second pulses. For example, the system can deliver one first pulse and one second pulse alternately. In another example, the number of first pulses can differ from the number of second pulses by a certain ratio or percentage. When the first and second pulses are completely interleaved, this ratio can be 1:1. In examples where the second pulse is delivered at a lower frequency than the first pulse, the ratio of the first pulse to the second pulse can be 10:1. In other examples, 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 pulse may or may not contribute to the treatment and / or the sensation perceived by the patient, but the primary purpose of the second pulse is to elicit a corresponding ECAP signal that can be detected by the system, separate from any sensed artifacts representing the second pulse itself.

[0035] Although electrical stimulation is typically described herein as an electrical stimulation pulse, it can be delivered in a non-pulsed form in other examples. For instance, electrical stimulation can be delivered as a signal with various waveform shapes, frequencies, and amplitudes. Thus, electrical stimulation in the form of a non-pulsed signal can be a continuous signal, which can have a sinusoidal waveform or other continuous waveforms.

[0036] Figure 1 This is a conceptual diagram illustrating an exemplary system 100 according to one or more technologies of this disclosure, the exemplary system including an implantable medical device (IMD) 110 configured to deliver spinal cord stimulation (SCS) therapy, and an external programmer 150. While the technologies described in this disclosure are generally applicable to a variety of medical devices, including external devices and IMDs, for illustrative purposes, the application of such technologies to IMDs, and more specifically, to implantable electrical stimulators (e.g., neurostimulators), will be described. More specifically, for illustrative purposes, this disclosure relates to implantable SCS systems, but is not limited thereto, and also to other types of medical devices or other therapeutic applications of medical devices.

[0037] like Figure 1 As shown, system 100 includes IMD 110, leads 130A and 130B, and an external programmer 150, which is illustrated in conjunction with patient 105, typically a human patient. Figure 1 In this example, IMD 110 is an implantable electrical stimulator configured to generate and deliver electrical stimulation therapy to patient 105 via one or more electrodes of leads 130A and / or 130B (collectively, "leads 130"), for example, to relieve chronic pain or other symptoms. In other examples, IMD 110 may be coupled to a single lead carrying multiple electrodes, or more than two leads each carrying multiple electrodes. In addition to electrical stimulation therapy, IMD 110 may also be configured to generate and deliver control pulses configured to trigger an ECAP signal without contributing to the treatment of the notification pulse. IMD 110 may be a long-term electrical stimulator that remains implanted in patient 105 for weeks, months, or even years. In other examples, IMD 110 may be a temporary or experimental stimulator used to screen or evaluate the efficacy of electrical stimulation for long-term treatment. In one example, IMD 110 is implanted in patient 105, while in another example, IMD 110 is an external device coupled to a percutaneously implanted lead. In some examples, IMD 110 uses one or more leads, while in other examples, IMD 110 is leadless.

[0038] IMD 110 can be made of components sufficient to mount IMD 110 (e.g., Figure 2The component shown may be constructed from any polymer, metal, or composite material housed within the patient 105. In this example, the IMD 110 may be constructed with a biocompatible shell, such as titanium or stainless steel, or a polymeric material (such as silicone, polyurethane, or liquid crystal polymer), and surgically implanted into a site near the pelvis, abdomen, or buttocks of the patient 105. In other examples, the IMD 110 may be implanted in other suitable sites within the patient 105, depending on, for example, the target site within the patient 105 for delivering electrical stimulation therapy. The outer shell of the IMD 110 may be constructed to provide a hermetically sealed component, such as a rechargeable or non-rechargeable power source. Furthermore, in some examples, the outer shell of the IMD 110 is selected from materials that facilitate the reception of energy to charge a rechargeable power source.

[0039] The electrical stimulation energy can be, for example, pulses based on a constant current or constant voltage, delivered from the IMD 110 to one or more target tissue sites in the patient 105 via one or more electrodes (not shown) of the implanted lead 130. Figure 1 In this example, lead 130 carries an electrode disposed adjacent to the target tissue of spinal cord 120. One or more electrodes may be disposed at the distal end of lead 130 and / or at other locations along the midpoint of lead 130. Lead 130 may be implanted and coupled to IMD 110. The electrodes may transfer electrical stimulation generated by an electrical stimulation generator in IMD 110 to the tissue of patient 105. Although lead 130 may each be a single lead, lead 130 may include lead extensions or other segments that may facilitate implantation or positioning of lead 130. In some other examples, IMD 110 may be a leadless stimulator having one or more electrode arrays disposed on the housing of the stimulator, rather than leads extending from the housing. Furthermore, in some other examples, system 100 may include one or more leads, each coupled to IMD 110 and pointing to similar or different target tissue sites.

[0040] The electrodes of lead 130 may be electrode pads on a paddle-shaped lead, circular (e.g., annular) electrodes surrounding the lead body, conformal electrodes, cuff electrodes, segmented electrodes (e.g., electrodes disposed at different circumferential positions around the lead, rather than continuous annular electrodes), any combination thereof (e.g., annular electrodes and segmented electrodes), or any other type of electrode capable of forming a combination of monopolar, bipolar, or multipolar electrodes for treatment. For illustrative purposes, annular electrodes disposed at different axial positions at the distal end of lead 130 will be described.

[0041] The deployment of electrodes via lead 130 has been described for illustrative purposes, but electrode arrays can be deployed in different ways. For example, a housing associated with a leadless stimulator can hold electrode arrays, such as rows and / or columns (or other patterns), to which displacement operations can be applied. Such electrodes can be arranged as surface electrodes, ring electrodes, or protrusions. Alternatively, the electrode array can be formed by rows and / or columns of electrodes on one or more paddle-shaped leads. In some examples, the electrode array includes electrode segments arranged at corresponding locations around the periphery of the leads, for example, arranged as one or more segmented rings around the circumference of a cylindrical lead. In other examples, one or more leads in lead 130 are linear leads having eight ring electrodes along the axial length of the lead. In yet another example, the electrodes are segmented rings arranged linearly along the axial length of the lead around the periphery of the lead.

[0042] The stimulation parameters of the therapeutic stimulation program for electrical stimulation therapy via electrodes of lead 130, which defines the stimulation pulses of the IMD 110, may include information identifying which electrodes have been selected to deliver stimulation according to the stimulation program, the polarity of the selected electrodes (i.e., the electrode combination used in 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 notification pulse are typically predetermined parameter values ​​determined before the delivery of the notification pulse. However, in some examples, system 100 automatically changes one or more parameter values ​​based on one or more factors or based on user input.

[0043] In addition to the notification pulse, the ECAP test stimulation procedure may define stimulation parameter values ​​that define the control pulse delivered by the IMD 110 through at least some electrodes of the lead 130. These stimulation parameter values ​​may include information identifying which electrodes have been selected to deliver the control pulse, the polarity of the selected electrodes (i.e., the electrode combination used in the procedure), and the voltage or current amplitude, pulse frequency, pulse width, and pulse shape of the stimulation delivered by the electrodes. The stimulation signal (e.g., one or more stimulation pulses or a continuous stimulation waveform) defined by the parameters of each ECAP test stimulation procedure is configured to evoke a compound action potential from a nerve. In some examples, the ECAP test stimulation procedure defines when to deliver the control pulse to the patient based on the frequency and / or pulse width of the notification pulse. However, the stimulation defined by each ECAP test stimulation procedure is not intended to provide treatment to the patient or contribute to the patient's treatment.

[0044] although Figure 1While involving SCS therapy, such as for pain treatment, in other examples, system 100 can be configured to treat any other condition that can benefit from electrical stimulation therapy. For example, system 100 can be used to treat tremor, Parkinson's disease, epilepsy, pelvic floor abnormalities (e.g., urinary incontinence or other bladder dysfunction, fecal incontinence, pelvic pain, bowel dysfunction, or sexual dysfunction), obesity, gastroparesis, or mental disorders (e.g., depression, mania, obsessive-compulsive disorder, anxiety, etc.). In this way, 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 form of stimulation therapy capable of treating the condition of patient 105.

[0045] In some examples, lead 130 includes 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. One or more sensors may be provided to supplement or replace treatment delivery performed by lead 130.

[0046] The IMD 110 is configured to deliver electrical stimulation therapy to a patient 105, either alone or in combination with electrodes carried or defined by an outer housing of the IMD 110, via a selected combination of electrodes carried by one or two leads 130. The target tissue for the electrical stimulation therapy can be any tissue affected by electrical stimulation, which can be in the form of electrical stimulation pulses or continuous waveforms. In some examples, the target tissue includes nerves, smooth muscle, or skeletal muscle. Figure 1 In the example shown, the target tissue is tissue close to the spinal cord 120, such as within the intrathecal or epidural space of the spinal cord 120, or in some examples, adjacent nerves branching from the spinal cord 120. The lead 130 can be introduced into the spinal cord 120 via any suitable area, such as the thoracic, cervical, or lumbar region. For example, stimulation of the spinal cord 120 can prevent pain signals from traveling through the spinal cord 120 and reaching the brain of the patient 105. The patient 105 can perceive the interruption of the pain signal as pain relief and thus as an effective treatment outcome. In other examples, stimulation of the spinal cord 120 can produce sensory abnormalities, which can reduce the patient 105's perception of pain and thus provide an effective treatment outcome.

[0047] The IMD 110 generates electrical stimulation therapy according to one or more therapeutic stimulation programs and delivers it to a target stimulation site within the patient 105 via electrodes connected to a lead 130 leading to the patient 105. The therapeutic stimulation program defines the values ​​of one or more parameters that define one aspect of the therapy delivered by the IMD 110 according to the program. For example, a therapeutic stimulation program controlling the IMD 110 to deliver stimulation in pulses may 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.

[0048] Furthermore, the IMD 110 can be configured to deliver control stimulation to the patient 105, either alone or in combination with electrodes carried or defined by the outer housing of the IMD 110, via a combination of electrodes of the lead 130. The tissue targeted by the control stimulation can be the same as or similar to the tissue targeted by the electrical stimulation therapy, but the IMD 110 can deliver control stimulation pulses via the same, at least some, or different electrodes. Because the control stimulation pulses can be delivered in an interleaved manner with notification pulses, clinicians and / or users can select any desired electrode combination to generate notification pulses. Similar to electrical stimulation therapy, the control stimulation can be in the form of electrical stimulation pulses or continuous waveforms. In one example, each control stimulation pulse may include a balanced biphasic square pulse employing an active recharge phase. However, in other examples, the control stimulation pulse may include a monophasic pulse followed by a passive recharge phase. In other examples, the control pulse may include an unbalanced biphasic portion and a passive recharge portion. Although not strictly necessary, a biphasic control pulse may include an interphase interval between positive and negative phases to facilitate the propagation of nerve impulses in response to the first phase of the biphasic pulse. Control stimulation can be delivered without interrupting the delivery of electrical stimulation notification pulses, such as during a window between consecutive notification pulses. The control pulses can induce an ECAP signal from the tissue, and the IMD 110 can sense the ECAP signal via two or more electrodes on the lead 130. When control stimulation pulses are applied to the spinal cord 120, the signal can be sensed from the spinal cord 120 by the IMD 110.

[0049] The IMD 110 can deliver control stimulation via electrodes of lead 130 to a target stimulation site within the patient 105 according to one or more ECAP test stimulation programs. One or more ECAP test stimulation programs can be stored in the storage device of the IMD 110. Each of the one or more ECAP test stimulation programs includes values ​​for one or more parameters that define one aspect of the control stimulation delivered by the IMD 110 according to that program, such as current or voltage amplitude, pulse width, pulse frequency, electrode combination, and, in some examples, timing based on a notification pulse to be delivered to the patient 105. In some examples, the IMD 110 delivers control stimulation to the patient 105 according to multiple ECAP test stimulation programs.

[0050] Users (such as clinicians or patients 105) can interact with the user interface of an external programmer 150 to program the IMD 110. Programming the IMD 110 typically refers to the generation and transfer of commands, programs, or other information to control the operation of the IMD 110. In this way, the IMD 110 can receive transmitted commands and programs from the external programmer 150 to control electrical stimulation therapy (e.g., notification pulses) and control stimulation (e.g., control pulses). For example, the external programmer 150 can transmit treatment stimulation programs, ECAP test stimulation programs, stimulation parameter adjustments, treatment stimulation program selection, ECAP test program selection, user input, or other information to control the operation of the IMD 110, for example, via wireless telemetry or a wired connection.

[0051] In some cases, if the external programmer 150 is primarily intended for use by a physician or clinician, it can be characterized as a physician or clinician programmer. In other cases, if the external programmer 150 is primarily intended for use by a patient, it can be characterized as a patient programmer. A patient programmer is typically accessible to the patient 105 and, in many cases, can be a portable device that accompanies the patient 105 throughout their daily life. For example, the patient programmer can receive input from the patient 105 when the patient wishes to terminate or change electrical stimulation therapy, or when the patient perceives the stimulation being delivered. Generally, a physician or clinician programmer can support the selection and generation of programs by a clinician for use by the IMD 110, while a patient programmer can support the adjustment and selection of such programs by the patient during regular use. In other examples, the external programmer 150 may include, or be part of, an external charging device for recharging the power source of the IMD 110. In this way, a user can use one or more devices to program and charge the IMD 110.

[0052] As described herein, information can be transmitted between the external programmer 150 and the IMD 110. Therefore, the IMD 110 and the external programmer 150 can communicate wirelessly using any technology known in the art. Examples of communication technologies may include, for example, radio frequency (RF) telemetry and inductive coupling, but other technologies are also contemplated. In some examples, the external programmer 150 includes a communication head that can be placed near the IMD 110 implantation site close to the patient's body to improve the quality or safety of communication between the IMD 110 and the external programmer 150. Communication between the external programmer 150 and the IMD 110 can occur during power transmission or separately from power transmission.

[0053] In some examples, the IMD 110, in response to commands from an external programmer 150, delivers electrical stimulation therapy via electrodes (not shown) on lead 130 to the target tissue site of the spinal cord 120 of the patient 105 according to multiple therapeutic stimulation programs. In some examples, the IMD 110 modifies the therapeutic stimulation programs as the patient 105's treatment needs evolve over time. For example, modification of the therapeutic stimulation programs may cause adjustment of at least one parameter of multiple notification pulses. The efficacy of the treatment may decrease when the patient 105 receives the same treatment for an extended period. In some cases, the parameters of multiple notification pulses can be updated automatically.

[0054] In this disclosure, the efficacy of electrical stimulation therapy can be indicated by one or more characteristics of the action potentials induced by stimulation pulses delivered by the IMD 110 (e.g., the amplitude of one or more peaks or the amplitude between one or more peaks, or the area under the curve of one or more peaks) (i.e., characteristics of the ECAP signal). Electrical stimulation therapy delivered by the leads 130 of the IMD 110 can induce compound action potentials in neurons within the target tissue, which travel up and down along the target tissue and eventually reach the sensing electrodes of the IMD 110. Furthermore, controlled stimulation can also induce at least one ECAP, and an ECAP in response to controlled stimulation can also be a substitute for therapeutic effect. The amount of induced action potentials (e.g., the number of action potential signals propagating in neurons) can be based on various parameters of the electrical stimulation pulses, such as amplitude, pulse width, frequency, pulse shape (e.g., slew rate at the start and / or end of the pulse), etc. The 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 each phase within a pulse. For example, a very high slew rate indicates a steep edge or even a near-vertical edge of the pulse, while a low slew rate indicates a longer rise (or fall) in the pulse amplitude. In some examples, these parameters contribute to the intensity of the electrical stimulation. Furthermore, the characteristics of the ECAP signal (e.g., amplitude) can vary based on the distance between the stimulating electrode and the nerve affected by the electric field generated by the delivered controlled stimulation pulse.

[0055] In one example, each notification pulse may have a pulse width greater than approximately 300 μs (in some examples, such as between approximately 300 μs and 1200 μs (i.e., 1.2 ms)). At these pulse widths, the IMD 110 may be insufficient to detect the ECAP signal because the notification pulse is also detected as an artifact that obscures the ECAP signal. If the ECAP is not adequately recorded, the ECAP arriving at the IMD 110 cannot be compared with the target ECAP characteristics (e.g., target ECAP amplitude), and the electrical stimulation therapy cannot be altered based on the responsive ECAP. When the notification pulse has these longer pulse widths, the IMD 110 is able to deliver control stimulation in the form of control pulses. Control pulses may have pulse widths less than approximately 300 μs, such as biphasic pulses with a duration of approximately 100 δ μs per phase. Since control pulses can have shorter pulse widths than notification pulses, 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 notification pulse (and, in some examples, the control pulse). Generally, the term "pulse width" refers to the total duration of each phase of a single pulse, and the phase intervals when appropriate. A single pulse may include a single phase in some examples (i.e., a single-phase pulse) or two or more phases in others (e.g., a biphase or triphase pulse). The pulse width defines the time period that begins at the start time of the first phase of the pulse and ends at the end time of the last phase (e.g., a biphase pulse with a 100 μs positive phase, a 100 μs negative phase, and a 30 μs phase interval defines a pulse width of 230 μs).

[0056] As described, exemplary techniques for adjusting stimulation parameter values ​​for notification pulses are based on comparing characteristic values ​​of a measured ECAP signal with target ECAP characteristic values, which may or may not be based on stimulation thresholds (e.g., sensing or detection thresholds). During the delivery of a controlled stimulation pulse defined by one or more ECAP testing stimulation procedures, the IMD 110 senses tissue potentials of the spinal cord 120 of the patient 105 via two or more electrodes inserted on leads 130 to measure the electrical activity of the tissue. The IMD 110, for example, uses electrodes on one or more leads 130 and associated sensing circuitry to sense the ECAP from the target tissue of the patient 105. In some examples, the IMD 110 receives signals indicative of the 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 signals indicative of the ECAP of the tissue of the patient 105. Examples of the one or more sensors include one or more sensors configured to measure a compound action potential of the patient 105 or indicative of the physiological effects of a compound action potential. For example, to measure the physiological effects of a compound action potential, one or more sensors may be an accelerometer, a pressure sensor, a flexure 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 examples, external programmer 150 receives a signal indicating a compound action potential in target tissue of patient 105 and sends a notification to IMD 110.

[0057] exist Figure 1 In this example, IMD 110 is described as performing a variety of processing and computational functions. However, external programmer 150 may alternatively perform one, several, or all of these functions. In this alternative example, IMD 110 is used to relay sensed signals to external programmer 150 for analysis, and external programmer 150 sends instructions to IMD 110 to adjust one or more parameters defining electrical stimulation therapy based on the analysis of the sensed signals. For example, IMD 110 may relay sensed signals indicating ECAP to external programmer 150. External programmer 150 may compare the parameter values ​​of ECAP with target ECAP characteristic values, and in response to the comparison, external programmer 150 may instruct IMD 110 to adjust one or more stimulation parameters that define electrical stimulation notification pulses delivered to patient 105, and in some examples, define control pulses delivered to the patient.

[0058] In the exemplary techniques described in this disclosure, the control of stimulation parameters and target ECAP characteristic values ​​can be initially set in the clinic, but can also be set and / or adjusted by the patient 105 at home. For example, the target ECAP characteristic can be changed to match a stimulation threshold or to become a fraction of the stimulation threshold. Once the target ECAP characteristic value is set, the exemplary techniques allow for automatic adjustment of notification pulse parameters to maintain consistent neural activation volume and consistent treatment perception for the patient as the distance from the electrode to the neuron changes. The ability to change stimulation parameter values ​​also allows for long-term therapeutic efficacy and enables consistency of stimulation intensity (e.g., as indicated by the ECAP) by comparing the measured ECAP value with the target ECAP characteristic value. The IMD110 can perform these changes without the intervention of a physician or the patient 105.

[0059] In some examples, the system modulates the target ECAP characteristic value over a period of time, such as based on changes in a stimulus threshold (e.g., a perception threshold or a detection threshold). The system can be programmed to alter the target ECAP characteristic to adjust the intensity of the notification pulse, thereby providing the patient with a sensation of change (e.g., an increase or decrease in neural activation volume). In one example, the system can be programmed to cause the target ECAP characteristic value to oscillate at a predetermined frequency between a maximum and a minimum target ECAP characteristic value to provide the patient with a sensation that can be perceived as a wave or other sensation that can provide therapeutic relief. The maximum target ECAP characteristic value, the minimum target ECAP characteristic value, and the predetermined frequency can be stored in the storage device 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 storage device of the IMD 110). In other examples, the target ECAP characteristic value can be programmed to steadily increase or steadily decrease to a baseline target ECAP characteristic value over a period of time. In other examples, the external programmer 150 can program the target ECAP characteristic value to change automatically 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, selected based on a predetermined function (e.g., a sine function, ramp function, exponential function, logarithmic function, etc.). The increment of the target ECAP characteristic value change can vary per specific number of pulses or per specific unit of time. Although the system can change the target ECAP characteristic value, it can still use the received ECAP signal to adjust one or more parameter values ​​of the notification pulses and / or control pulses to satisfy the target ECAP characteristic value.

[0060] It may be desirable to maintain a sub-sensory level of treatment in patient 105. To maintain sub-sensory treatment, IMD 110 can periodically determine the stimulation level that achieves a perception threshold for patient 105. The perception threshold can be a characteristic ECAP value from the ECAP signal, which can be associated with the stimulation level, such as the value of one or more parameters of a plurality of notification pulses delivered to patient 105 by IMD 110. For example, one or more parameters may include the combination of stimulating electrodes, electrode polarity, current or voltage amplitude, pulse width, pulse rate, pulse shape, underpulse area, or any combination thereof. ECAP provides a reliable metric for determining the stimulation level that determines the perception threshold of patient 105. In other words, one or more characteristics of the ECAP signal sensed by IMD 110 can indicate whether patient 105 is able to perceive the treatment delivered by IMD 110 or the degree to which patient 105 perceives the treatment. Patient perception of electrical stimulation treatment delivered to patient 105 can change when the distance between lead 130 and the target tissue of spinal cord 120 changes. For example, if one or more parameters of the notification pulse delivered to patient 105 by IMD 110 remain constant and the distance between lead 130 and the target tissue of spinal cord 120 decreases, patient 105 may experience a stronger perception of the notification pulse. Conversely, if one or more parameters of the notification pulse delivered to patient 105 by IMD 110 remain constant and the distance between lead 130 and the target tissue of spinal cord 120 increases, patient 105 may experience a weaker perception of the notification pulse.

[0061] In some examples, the IMD 110 includes a stimulation generation circuit configured to deliver electrical stimulation therapy to the patient 105. The electrical stimulation therapy includes a plurality of notification pulses. The stimulation generation circuit is also configured to deliver a plurality of control pulses, wherein the plurality of control pulses are interleaved with at least some of the notification pulses. In some examples, the IMD 110 includes a sensing circuit configured to detect a plurality of ECAPs, wherein the sensing circuit is configured to detect each of the plurality of ECAPs after one of the control pulses and before a subsequent notification pulse in the plurality of notification pulses. In this manner, the IMD detects ECAPs in response to the delivery of control pulses, and the characteristics of the ECAP signal can indicate the efficacy (e.g., tissue activation volume) of the plurality of notification pulses.

[0062] Furthermore, in some examples, the IMD 110 includes processing circuitry configured to determine at least one of a perception threshold or a detection threshold stimulation level based on a plurality of ECAPs detected by the sensing circuitry of the IMD 110 in response to a plurality of control pulses. Patient 105 is able to perceive the electrical stimulation treatment if the value of a first stimulation parameter of the electrical stimulation therapy is delivered at a level higher than the stimulation level associated with the perception threshold. Additionally, the sensing circuitry of the IMD 110 is configured to detect at least some of the plurality of ECAPs that occur when the magnitude of a second parameter of the electrical stimulation treatment is greater than the detection threshold or otherwise associated with a characteristic ECAP value greater than the detection threshold. In this way, the IMD 110 is able to detect a responsive ECAP if the electrical stimulation treatment is delivered at a level higher than the detection threshold. In some examples, the first and second parameters include current amplitude. In other examples, the first and second parameters include voltage amplitude.

[0063] The IMD 110 can control the stimulation generation circuitry to deliver electrical stimulation therapy to the patient 105 based on at least one of a sensing threshold or a detection threshold. In some examples, to control the stimulation generation circuitry to deliver electrical stimulation therapy to the patient based on a sensing threshold, the IMD 110 is configured to instruct the stimulation generation circuitry to deliver multiple notification pulses at a fraction of the stimulation level associated with the sensing threshold. Furthermore, to control the stimulation generation circuitry to deliver electrical stimulation therapy to the patient based on a detection threshold, the IMD 110 is configured to instruct the stimulation generation circuitry to deliver multiple notification pulses at a fraction of the stimulation level associated with the detection threshold and at levels lower than that stimulation level. In some examples, the fraction of the stimulation level is greater than 0.50 and less than 0.99, and the fraction of the stimulation level of the detection threshold is greater than 0.50 and less than 0.99. In examples where an ECAP signal is detected from a control pulse, the detection threshold and / or sensing threshold can be set as characteristics of the ECAP signal from the control pulse. However, the stimulation parameter values ​​that define the notification pulses can be determined by applying a gain value to scale the parameter values ​​of the control pulses to the stimulation parameters of the notification pulses.

[0064] In some examples, the IMD 110 is configured to periodically determine the stimulation level of the perception threshold at which the patient 105 can perceive notification pulses delivered by the IMD 110. The frequency at which the IMD 110 determines the stimulation level of the perception threshold can be a predetermined frequency (e.g., programmed into the IMD 110's storage device). In some cases, an external programmer 150 can be configured to set or update this predetermined frequency. In other cases, the processing circuitry of the IMD 110 can be configured to set or update the predetermined frequency based on data collected by one or more sensors of the IMD 110 (e.g., electrodes, accelerometers, temperature sensors, pressure sensors, optical sensors, or any combination thereof). In some cases, the IMD 110 is capable of measuring the stimulation level of the patient 105's perception threshold at this predetermined frequency. For example, if the predetermined frequency is once per hour, the IMD 110 can determine the stimulation level of the patient 105's perception threshold once per hour.

[0065] IMD 110 can be configured to deliver a first set of stimulation pulses (e.g., notification pulses or control pulses) with a first pulse amplitude. In some examples, the first set of stimulation pulses is delivered by IMD 110 based on a previous stimulation level measured by a perception threshold. For example, to deliver a sub-perception threshold, IMD 110 is capable of delivering electrical stimulation therapy at a fraction of the stimulation level that results in a characteristic ECAP value at the perception threshold determined by the perception threshold measurement. However, the actual stimulation level resulting in the perception threshold may change over a period of time after the previous perception threshold measurement. To obtain an updated perception threshold, IMD 110 performs another perception threshold measurement. When IMD 110 determines that a perception threshold measurement must be performed, IMD 110 is configured to deliver a second set of stimulation pulses that is a fraction of the first pulse amplitude and smaller than the first pulse amplitude, and iteratively increase (e.g., increase by a predetermined amount) the pulse amplitude to achieve a predetermined increase, a predetermined number of pulses, or until a new stimulation level for the perception threshold is detected. To determine the stimulation level of the perception threshold, the processing circuitry is configured to detect the ECAP signal sensed by the sensing circuitry and determine a characteristic ECAP value based on the ECAP signal. In the case where the stimulation pulse is a control pulse, the ECAP signal is sensed after the stimulation generation circuitry delivers each corresponding control pulse and before the subsequent delivery of any other stimulation pulse. In response to IMD 110 determining that the patient can begin to perceive the stimulation pulse, IMD 110 can determine that the characteristic value of the ECAP signal associated with the patient's perception is the new perception threshold. Furthermore, IMD 110 can determine that the stimulation parameter value that at least partially defines the stimulation pulse that elicits the ECAP signal associated with the new perception threshold is the stimulation parameter value (e.g., stimulation level) to be used as the stimulation parameter value associated with the new perception threshold. IMD 110 can determine the delivery of subsequent stimulation pulses based on this stimulation parameter value. In some examples, at least one characteristic value of the ECAP signal includes one or more of the following: peak current amplitude, peak voltage amplitude, gradient, and area under the ECAP.

[0066] In addition to determining the stimulus level for the perception threshold, the IMD 110 can also be configured to determine the stimulus level for the detection threshold. In some examples, the processing circuitry can determine that the stimulus level for the detection threshold is the stimulus level at which a characteristic value of the ECAP signal is first detectable as the intensity of the stimulus pulse increases with each stimulus pulse. In another example, the processing circuitry can determine the stimulus level for the detection threshold based on a set of consecutive stimulus pulses (e.g., a set of notification pulses or a set of control pulses). The threshold ratio of detected ECAP signals (e.g., detectable characteristic values ​​of the ECAP signal) can refer to the ratio of the number of corresponding ECAP signals detected from a set of consecutively delivered stimulus pulses to the total number of pulses in this set of consecutively determined stimulus pulses. A threshold ratio of 100% would indicate that an ECAP signal was detected after each pulse in this set of consecutive stimulus pulses. When using this threshold ratio to determine whether the stimulus was delivered appropriately relative to the detection threshold, the IMD 110 can determine the percentage of ECAP signals detected from the total number of consecutively delivered stimulus pulses. If the ratio of the ECAP signal is greater than the threshold ratio, the IMD 110 can determine that the stimulation level of the detection threshold has been reduced and / or the stimulation parameter values ​​of subsequent stimulation pulses (e.g., notification pulses and / or control pulses) have been decreased. If the ratio of the ECAP signal is less than the threshold ratio, the IMD 110 can determine that the stimulation level of the detection threshold has been increased and / or the stimulation parameter values ​​of subsequent stimulation pulses (e.g., notification pulses and / or control pulses) have been increased. In this way, the IMD 110 can adjust the stimulation parameter values ​​even when the ECAP signal is undetectable after each stimulation pulse is delivered.

[0067] As described herein, the IMD 110 can be configured to determine the stimulation levels of the perception and detection thresholds based on the ECAP sensed in response to a notification pulse and / or a control pulse (e.g., the ECAP is induced by a control pulse). In practice, where an ECAP signal can be detected from a notification pulse, the IMD 110 can be configured to determine the stimulation levels of the perception and detection thresholds based on the ECAP induced by the notification pulse.

[0068] Although in one example the IMD 110 takes the form of an SCS device, in other examples the IMD 110 takes the form of any combination of the following devices: such as a deep brain stimulation (DBS) device, an implantable cardioverter defibrillator (ICD), a pacemaker, a cardiac resynchronization therapy device (CRT-D), a left ventricular assist device (LVAD), an implantable sensor, an orthopedic device, or a drug pump. Furthermore, the techniques of this disclosure can be used to determine stimulation thresholds (e.g., sensing thresholds and detection thresholds) associated with any of the aforementioned IMDs, and then use these stimulation thresholds to indicate the intensity of treatment (e.g., stimulation level).

[0069] Figure 2 This is a block diagram illustrating an exemplary configuration of components of an IMD 200 according to one or more technologies disclosed herein. The IMD 200 may be... Figure 1 An example of IMD 110. In Figure 2 In the example shown, IMD 200 includes a stimulus generation circuit 202, a switching circuit 204, a sensing circuit 206, a telemetry circuit 208, a processing circuit 210, a storage device 212, a sensor 222, and a power source 224.

[0070] exist Figure 2 In the example shown, storage device 212 stores therapeutic stimulation program 214 and ECAP test stimulation program 216 in a separate memory or a separate area within storage device 212. Storage device 212 also stores threshold 218 and threshold detection parameters 220. Each stored therapeutic stimulation program in therapeutic stimulation program 214 defines values ​​for a set of electrical stimulation parameters (e.g., a set of stimulation parameters), such as stimulation electrode combination, electrode polarity, current or voltage amplitude, pulse width, pulse rate, and pulse shape. Each stored ECAP test stimulation program 216 defines values ​​for a set of electrical stimulation parameters (e.g., a set of control stimulation parameters), such as stimulation electrode combination, electrode polarity, current or voltage amplitude, pulse width, pulse rate, and pulse shape. ECAP test stimulation program 216 may also have additional information, such as instructions on when to deliver control pulses based on the pulse width and / or frequency of the notification pulses defined in therapeutic stimulation program 214.

[0071] Therefore, in some examples, the stimulation generation circuit 202 generates an electrical stimulation signal according to the described electrical stimulation parameters. Other ranges of stimulation 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 can be of any form, such as a continuous-time signal (e.g., a sine wave). The switching circuit 204 may include one or more switch arrays, one or more multiplexers, one or more switches (e.g., a switch matrix or other set of switches), or other circuitry configured to direct the stimulation signal from the stimulation generation circuit 202 to one or more of the electrodes 232, 234, or to direct a sensed signal from one or more of the electrodes 232, 234 to the sensing circuit 206. In other examples, the stimulation generation circuit 202 and / or the sensing circuit 206 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 204.

[0072] Sensing circuit 206 monitors signals from any combination of electrodes 232, 234. In some examples, sensing circuit 206 includes one or more amplifiers, filters, and analog-to-digital converters. Sensing circuit 206 can be used to sense physiological signals, such as ECAP. In some examples, sensing circuit 206 detects ECAP from a specific combination of electrodes 232, 234. In some cases, the specific combination of electrodes used to sense ECAP includes electrodes different from the set of electrodes 232, 234 used to deliver stimulation pulses. Alternatively, in other cases, the specific combination of electrodes used to sense ECAP includes at least one electrode from the same set of electrodes used to deliver stimulation pulses to patient 105. Sensing circuit 206 can provide signals to analog-to-digital converters for conversion into digital signals for processing, analysis, storage, or output by processing circuit 210.

[0073] Under the control of the processing circuit 210, the telemetry circuit 208 supports IMD 200 and external programmers ( Figure 2 Wireless communication between the IMD 200 (not shown) or another computing device. As updates to the program, the processing circuitry 210 of the IMD 200 can receive values ​​of various stimulation parameters (such as amplitude and electrode combinations) from an external programmer via telemetry circuitry 208. Updates to the therapeutic stimulation program 214 and the ECAP test stimulation program 216 can be stored in storage device 212. The telemetry circuitry 208 in the IMD 200, as well as telemetry circuits in other devices and systems described herein (such as external programmers), can communicate via radio frequency (RF) communication technology. Furthermore, the telemetry circuitry 208 can interact with the external medical device programmer (IMD 200) via proximal sensing interaction with the external programmer. Figure 2 (Not shown) communicates. An external programmer can be... Figure 1 An example of an external programmer 150. Thus, the telemetry circuit 208 can continuously, periodically, or upon request from the IMD 110 or the external programmer.

[0074] Processing circuitry 210 may include one or more of the following: 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 functions attributed to processing circuitry 210, which may herein be embodied as firmware, hardware, software, or any combination thereof. Processing circuitry 210 controls stimulation generation circuitry 202 to generate stimulation signals according to therapeutic stimulation program 214 and ECAP test stimulation program 216 stored in storage device 212, to apply stimulation parameter values ​​specified by one or more programs, such as the amplitude, pulse width, pulse rate, and pulse shape of each stimulation signal.

[0075] exist Figure 2 In the example shown, the set of electrodes 232 includes electrodes 232A, 232B, 232C, and 232D, and the set of electrodes 234 includes electrodes 234A, 234B, 234C, and 234D. In other examples, a single lead may include all eight electrodes 232 and 234 along a single axial length of the lead. The processing circuit 210 also controls the stimulation generation circuit 202 to generate stimulation signals and apply these stimulation signals to a selected combination of electrodes 232, 234. In some examples, the stimulation generation circuit 202 includes a switching circuit (instead of or as a supplement to the switching circuit 204) that can couple the stimulation signals to a selected conductor within the lead 230, which in turn delivers the stimulation signals through the selected electrodes 232, 234. Such a switching circuit can be a switch array, a switch matrix, a multiplexer, or any other type of switching circuit, wherein the other type of switching circuit is configured to selectively couple stimulation energy to selected electrodes 232, 234 and selectively sense the patient using the selected electrodes 232, 234. Figure 2 Bioelectric nerve signals of the spinal cord (not shown in the image).

[0076] However, in other examples, the stimulus generation circuit 202 does not include a switching circuit, and the switching circuit 204 is not connected between the stimulus generation circuit 202 and the electrodes 232, 234. In these examples, the stimulus generation circuit 202 includes multiple pairs of voltage sources, current sources, voltage absorbers, or current absorbers connected to each of the electrodes 232, 234, such that each pair of electrodes has a unique signal circuit. In other words, in these examples, each of the electrodes 232, 234 is independently controlled via its own signal circuit (e.g., via a combination of a regulated voltage source and absorber or a regulated current source and absorber), which is the opposite of the switching signal between the electrodes 232, 234.

[0077] The electrodes 232, 234 on the corresponding leads 230 can be constructed using a variety of different designs. For example, one or both of the leads 230 may include one or more electrodes at each longitudinal location along the length of the lead, such as including one electrode at different peripheral locations around the periphery of the lead at each of locations A, B, C, and D. In one example, the electrodes may be electrically coupled to the stimulation generation circuit 202, for example, via a switching circuit of the switching circuit 204 and / or the stimulation generation circuit 202, via corresponding wires of a straight or coiled connector within the lead housing extending to the proximal end of the lead. In another example, each electrode in the leads may be an electrode deposited on a thin film. The thin film may include conductive traces for each electrode extending along the length of the film to the proximal end connector. The thin film may then be wrapped (e.g., spirally wrapped) around an internal component to form the lead 230. These and other configurations can be used to form leads with complex electrode geometries.

[0078] Although the sensing circuit 206 is in Figure 2 The stimulation generation circuit 202 and processing circuit 210 are integrated into a common housing; however, in other examples, the sensing circuit 206 may be located in a separate housing from the IMD 200 and may communicate with the processing circuit 210 via wired or wireless communication technologies. In some examples, one or more of electrodes 232 and 234 are adapted to sense the ECAP. For example, electrodes 232 and 234 may sense a portion of the voltage amplitude of the ECAP signal, wherein the sensed voltage amplitude is characteristic of the ECAP signal.

[0079] Storage device 212 can be configured to store information within IMD 200 during operation. Storage device 212 may include a computer-readable storage medium or a computer-readable storage device. In some examples, storage device 212 includes one or more of short-term memory or long-term memory. Storage device 212 may include, for example, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), magnetic disk, optical disk, flash memory, or electrically programmable memory (EPROM) or electrically erasable programmable memory (EEPROM). In some examples, storage device 212 is used to store data indicating instructions executed by processing circuitry 210. As discussed above, storage device 212 is configured to store therapeutic stimulation procedure 214, ECAP test stimulation procedure 216, threshold 218, and threshold detection parameters 220.

[0080] In some examples, IMD 200 is configured to determine at least one of a stimulation threshold, such as a perception threshold or a detection threshold. The perception threshold may be represented by a first set of values ​​of a characteristic ECAP value and / or a notification pulse delivered to the patient 105 by the stimulation generation circuit 202. If the stimulation generation circuit 202 delivers a notification pulse at or above the first set of values ​​representing the perception threshold, the patient 105 may perceive or feel the notification pulse (e.g., the characteristic ECAP value would indicate that the patient perceives the stimulus). Furthermore, the detection threshold may be represented by a second set of values ​​of a characteristic ECAP value and / or a notification pulse delivered to the patient 105. If the stimulation generation circuit 202 delivers a notification pulse at or above the second set of values ​​representing the detection threshold, the sensing circuit 206 may be configured to detect all or at least a fraction of the ECAP signal triggered by the corresponding stimulation pulse (e.g., a notification pulse and / or a control pulse) delivered to the patient 105. The perception threshold and the detection threshold may be stored in storage device 212 as part of threshold 218. In some examples, the threshold ratio of the ECAP signal can be associated with a detection threshold and is also stored by threshold 218.

[0081] Based on a sensing threshold, a detection threshold, or other single stimulation threshold, or a combination thereof, processing circuitry 210 can set or update treatment stimulation program 214 and ECAP test stimulation program 216 (e.g., associated stimulation levels or parameter values ​​indicating those stimulation levels). In this way, IMD 200 is configured for customized delivery of electrical stimulation therapy to patient 105. For example, in some cases, it may be desirable to deliver sub-sensory therapy to patient 105. In these cases, processing circuitry 210 can set treatment stimulation program 214 such that stimulation generation circuitry 202 delivers notification pulses to patient 105 at a level below the sensing threshold or according to a scaling factor (e.g., gain) against the sensing threshold determined from the ECAP signal triggered by control pulses. In some examples, the distance between electrodes 232, 234 and the target tissue of spinal cord 120 varies over time depending on patient posture, patient activity, patient movement, or lead migration. Furthermore, the distance between electrodes 232, 234 and the target tissue of the spinal cord 120 can be transiently altered by any of a cough, sneeze, valsalva maneuver, or another transient movement of the patient. Any of these movements can affect the patient's perception of the electrical stimulation therapy delivered by the IMD 200. Therefore, to maintain a consistent level of treatment, such as consistent sub-perceptual therapy, it may be beneficial for the IMD 200 to periodically measure the stimulation level of at least one of the perception threshold or detection threshold and update the treatment stimulation program 214 accordingly. For example, since the stimulation parameter values ​​defining the notification pulses can be based on the perception threshold or detection threshold, the IMD 200 can periodically update the stimulation levels of the perception threshold or detection threshold to maintain effective treatment.

[0082] In some examples, IMD 200 is configured to perform a series of perception threshold measurements to periodically determine and update the stimulus level that causes the perception threshold. This series of perception threshold measurements can be performed at a predetermined frequency. In some examples, to perform one perception threshold measurement in this series, stimulus generation circuit 202 is configured to deliver a plurality of notification pulses and a plurality of control pulses, wherein the plurality of control pulses are interleaved with at least some of the notification pulses. Sensing circuit 206 is configured to detect a plurality of ECAP signals, wherein sensing circuit 206 is configured to sense each of the plurality of ECAP signals after one of the control pulses and before a subsequent notification pulse in the plurality of notification pulses. Processing circuit 210 is configured to detect the ECAP signals and determine, based on one or more detected ECAP signals, the stimulus level causing the perception threshold, wherein the stimulus level corresponds to a first stimulus parameter, and control stimulus generation circuit 202 to deliver electrical stimulation therapy to patient 105.

[0083] More specifically, to determine the stimulation level for the perception threshold, the IMD 200 can be configured to deliver a set of stimulation pulses (e.g., a control pulse if an ECAP signal is not detected from a notification pulse) from a plurality of stimulation pulses beginning with a first pulse amplitude, the first pulse amplitude being selected as a fraction of a previous perception threshold, a fraction of a previously used stimulation parameter value, or some other initial amplitude value. The first stimulation pulse in this set of pulses is delivered by the stimulation generation circuit 202 with the initial amplitude, and then the IMD 200 incrementally increases the amplitude of subsequent stimulation pulses by a predetermined amount. In one example, the perception threshold could be 10 microvolts (μV), generated by a stimulation amplitude of 4 milliamperes (mA) (e.g., a first stimulation level). However, the previous stimulation amplitude used for the stimulation pulses could be set to 0.75% of the stimulation amplitude at the perception threshold. If the fraction of the stimulus amplitude is 0.5 and the predetermined amount is 0.1 mA, the IMD 200 can deliver a first stimulus pulse of 1.5 mA, a second stimulus pulse of 1.6 mA, a third stimulus pulse of 1.7 mA, and so on, until the stimulus amplitude of the stimulus pulse increases to the point that the characteristic ECAP value reaches the perception threshold. In response to reaching the perception threshold, the corresponding stimulus level of the pulse that leads to the perception threshold can be set to a new stimulus level that can be associated with the stimulus amplitude of the same pulse. The new stimulus amplitude of subsequent stimulus pulses can then be set to or based on a fraction of the new stimulus level.

[0084] Furthermore, in order to determine the stimulation level of the perception threshold using control pulses, processing circuit 210 is configured to detect at least one characteristic ECAP value of each ECAP signal in a set of ECAP signals received by processing circuit 210 from sensing circuit 206, wherein this set of ECAP signals is sensed after stimulation generation circuit 202 delivers corresponding control pulses interleaved with a second set of notification pulses. In this way, sensing circuit 206 is configured to receive ECAP signals between at least some notification pulses in the second set of notification pulses. Processing circuit 210 is configured to determine the stimulation level of the first pulse when the obtained characteristic ECAP value reaches the perception threshold. This stimulation level can be associated with the perception threshold and stored in storage device 212 as part of threshold 218. Thus, the same stimulation level can be used to determine the electrical stimulation treatment for patient 105. Processing circuit 210 can determine the stimulation parameter value of the pulse that triggers the characteristic ECAP value and associate the stimulation parameter value with the perception threshold. Subsequently, processing circuit 210 can store the stimulation parameter value associated with the perception threshold in storage device 212 as part of threshold 218. In some examples, the characteristic ECAP value includes one or more of the following, or a combination thereof: peak current amplitude, peak voltage amplitude, gradient, and area under ECAP.

[0085] It may be difficult to monitor the ECAP signal in order to identify the stimulus level of the perception threshold using IMD 200. For example, patient 105 may be able to perceive a notification pulse delivered at a level below the detection threshold of the ECAP signal. In other words, in some cases, the detection threshold may be greater than the perception threshold. In these cases, processing circuitry 210 may not be able to accurately determine the precise stimulus level of the perception threshold using the ECAP sensed by sensing circuitry 206 in response to notification pulses and / or control pulses delivered by stimulus generation circuitry 202. However, even if the detection threshold is greater than the perception threshold and processing circuitry 210 cannot determine the perception threshold, IMD 200 can still be enabled to maintain the delivery of subsensory therapy to patient 105. For example, to maintain subsensory therapy, IMD 200 is configured to determine the stimulus level of the detection threshold and deliver a notification pulse to patient 105 at a fraction of that stimulus level, where that fraction of the stimulus level of the detection threshold is less than the perception threshold.

[0086] In some examples, to determine the stimulation level for a detection threshold, IMD 200 is configured to deliver a set of stimulation pulses (e.g., notification pulses, or control pulses when an ECAP signal cannot be detected from a notification pulse) using stimulation generation circuit 202. Stimulation generation circuit 202 is configured to deliver multiple stimulation pulses with pulse amplitude values. Processing circuit 210 is configured to determine whether an ECAP signal is detected after each stimulation pulse. In this way, processing circuit 210 is configured to determine whether sensing circuit 206 senses an ECAP corresponding to each stimulation pulse. Processing circuit 210 is configured to determine how many ECAPs are detected for the total number of stimulation pulses delivered. IMD 200 can then compare this ratio of the ECAP signal to the total number of stimulation pulses with a desired threshold ratio (e.g., a ratio between 25% and 75%, such as 4:7) to determine whether the amplitude value represents a detection threshold for the detected ECAP. In one example, if ECAPs are detected more frequently than they are not detected (e.g., more than 50% of the time), but not at all times (e.g., less than 90% of the time), the amplitude values ​​of these stimulus pulses can be correlated with the detection thresholds for these ECAP signals.

[0087] In response to determining that the ratio of the detected ECAP signal to the total number of stimulus signals is greater than a threshold ratio, processing circuit 210 may instruct stimulus generation circuit 202 to decrease the amplitude value of subsequent stimulus pulses. In response to determining that the ratio of the detected ECAP signal to the total number of stimulus signals is less than a threshold ratio, processing circuit 210 may instruct stimulus generation circuit 202 to increase the amplitude value of subsequent stimulus pulses. In some cases, processing circuit 210 may determine that the ratio of the detected ECAP signal to the total number of stimulus signals is equal to the threshold ratio, or within an acceptable range of the threshold ratio plus or minus an offset. In these cases, processing circuit 210 may determine that the pulse amplitude of this set of stimulus pulses is appropriately set to the stimulation level of the detection threshold. In some examples, the threshold ratio is greater than 0.25 and less than 0.75. The threshold ratio value may be stored in storage device 212 as part of threshold detection parameter 220.

[0088] Although in some examples, sensing circuit 206 senses an ECAP signal that occurs in response to a control pulse delivered according to ECAP test stimulation procedure 216, in other examples, sensing circuit 206 senses an ECAP signal that occurs in response to a notification pulse delivered according to treatment stimulation procedure 214. The technology disclosed herein enables IMD to detect perception thresholds and detection thresholds using any combination of ECAPs corresponding to notification pulses and ECAPs corresponding to control pulses.

[0089] Sensor 222 may include one or more sensing elements that sense the value of a corresponding patient parameter. As described above, electrodes 232 and 234 may be electrodes that sense the parameter value of ECAP. Sensor 222 may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other type of sensor. Sensor 222 may output patient parameter values ​​that can be used as feedback to control treatment delivery. For example, sensor 222 may indicate patient activity, and processing circuitry 210 may increase the frequency of control pulses and ECAP sensing in response to the detection of increased patient activity. In one example, processing circuitry 210 may initiate control pulses and corresponding ECAP sensing in response to a signal from sensor 222 indicating that patient activity has exceeded an activity threshold. Conversely, processing circuitry 210 may decrease the frequency of control pulses and ECAP sensing in response to the detection of decreased patient activity. For example, in response to sensor 222 no longer indicating that the sensed patient activity exceeds a threshold, processing circuitry 210 may pause or stop the delivery of control pulses and ECAP sensing. In this manner, processing circuitry 210 can dynamically deliver control pulses and sense ECAP signals based on patient activity to reduce system power consumption when the distance between the electrode and the neuron cannot be changed, and to increase the system's response to changes in ECAP when the distance between the electrode and the neuron may change. IMD 200 may include additional sensors coupled within the housing of IMD 200 and / or via one of the leads 130 or other leads. Furthermore, for example, IMD 200 may wirelessly receive sensor signals from remote sensors via telemetry circuitry 208. In some examples, one or more of these remote sensors may be located outside the patient's body (e.g., supported on an external surface of the skin, attached to clothing, or otherwise positioned outside the patient 105). In some examples, signals from sensor 222 indicate location or body state (e.g., sleep, wakefulness, sitting, standing, etc.), and processing circuitry 210 can select a target ECAP feature value based on the indicated location or body state.

[0090] Power source 224 is configured to deliver operating power to components of IMD 200. Power source 224 may include a battery and power generation circuitry for generating operating power. In some examples, the battery is rechargeable to allow for long-term operation. In some examples, recharging is achieved through near-side inductive interaction between an external charger and an inductive charging coil within IMD 200. Power source 224 may include any one or more of a variety of battery types, such as nickel-cadmium batteries and lithium-ion batteries.

[0091] Figure 3 This is a block diagram of an exemplary external programmer 300. The external programmer 300 can be... Figure 1An example of an external programmer 150. Although the external programmer 300 is generally described as a handheld device, it can be a larger portable device or a more fixed device. Furthermore, in other examples, the external programmer 300 may be included as part of an external charging device or include the functionality of an external charging device. Figure 3 As shown, the external programmer 300 may include processing circuitry 352, storage device 354, user interface 356, telemetry circuitry 358, and power source 360. Storage device 354 may store instructions that, when executed by processing circuitry 352, cause processing circuitry 352 and external programmer 300 to provide the functions attributed to external programmer 300 throughout this disclosure. Each of these components, circuits, or modules may include circuitry configured to perform some or all of the functions described herein. For example, processing circuitry 352 may include processing circuitry configured to perform the processes discussed with respect to processing circuitry 352.

[0092] Generally, the external programmer 300 includes any suitable hardware arrangement that executes the technology belonging to the external programmer 300 and its processing circuitry 352, user interface 356, and telemetry circuitry 358, either alone or in combination with software and / or firmware. In various examples, the external programmer 300 may include one or more processors, such as one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuits, and any combination of such components. In various examples, the external programmer 300 may also include a storage device 354, such as RAM, ROM, PROM, EPROM, EEPROM, flash memory, hard disk, CD-ROM, containing executable instructions for causing one or more processors to perform actions belonging to those instructions. Furthermore, although the processing circuitry 352 and telemetry circuitry 358 are described as separate modules, in some examples, they are functionally integrated. In some examples, the processing circuitry 352 and telemetry circuitry 358 correspond to individual hardware units, such as ASICs, DSPs, FPGAs, or other hardware units.

[0093] Storage device 354 (e.g., a storage device) may store instructions that, when executed by processing circuitry 352, cause processing circuitry 352 and external programmer 300 to provide the functions attributed to external programmer 300 throughout this disclosure. For example, storage device 354 may include instructions that cause processing circuitry 352 to retrieve a parameter set from memory, select a spatial electrode movement mode, or receive user input and send a corresponding command to IMD 200, or instructions for any other function. Furthermore, storage device 354 may include multiple programs, each including a parameter set defining therapeutic or control stimulation. Storage device 354 may also store data received from a medical device (e.g., IMD 110). For example, storage device 354 may store ECAP-related data recorded at the sensing module of the medical device, and storage device 354 may also store data from one or more sensors of the medical device.

[0094] User interface 356 may include buttons or a keypad, lights, a speaker for voice commands, and a display such as a liquid crystal display (LCD), a light-emitting diode (LED) display, or an organic light-emitting diode (OLED) display. In some examples, the display includes a touchscreen. User interface 356 may be configured to display any information related to the delivery of electrical stimulation, identified patient behavior, sensed patient parameter values, patient behavior criteria, or any other such information. User interface 356 may also receive user input (e.g., an indication of when the patient perceives a stimulation pulse). Input may be in the form of, for example, pressing a button on a keypad or selecting an icon from a touchscreen. Input may request to start or stop electrical stimulation, may request a new spatial electrode movement pattern or a change to an existing spatial electrode movement pattern, or may request other changes to the delivery of electrical stimulation.

[0095] Under the control of processing circuitry 352, telemetry circuitry 358 can support wireless communication between the medical device and external programmer 300. Telemetry circuitry 358 can also be configured to communicate with another computing device via wireless communication technology, or directly with another computing device via a wired connection. In some examples, telemetry circuitry 358 provides wireless communication via RF or near-side sensing media. In some examples, telemetry circuitry 358 includes an antenna, which can take various forms, such as an internal antenna or an external antenna.

[0096] Examples of local wireless communication technologies that can be used to facilitate communication between the external programmer 300 and the IMD 110 include those based on 802.11 or... Radio frequency communication using a specification set or other standard or proprietary telemetry protocol. In this way, other external devices can be able to communicate with the external programmer 300 without establishing a secure wireless connection. As described herein, the telemetry circuit 358 can be configured to transmit spatial electrode movement patterns or other stimulation parameter values ​​to the IMD 110 for the delivery of electrical stimulation therapy.

[0097] In some examples, the selection of stimulation parameters or therapeutic stimulation procedures is transmitted to a medical device for delivery to the patient (e.g., Figure 1 (Patient 105). In other examples, the treatment may include medication, activity, or other instructions that patient 105 must perform themselves or that a caregiver must perform for patient 105. In some examples, the external programmer 300 provides visual, auditory, and / or tactile notifications indicating the presence of new instructions. In some examples, the external programmer 300 requires receiving user input to confirm that the instruction has been completed.

[0098] According to the technology disclosed herein, the user interface 356 of the external programmer 300 receives instructions from a clinician to instruct 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 program and the ECAP test stimulation program may include changing one or more parameters of the stimulation pulses delivered by the medical device according to the program, such as the amplitude, pulse width, frequency, and pulse shape of the notification pulse and / or control pulse. The user interface 356 may also receive instructions from the clinician to start or stop any electrical stimulation (including therapeutic and control stimuli).

[0099] Power source 360 ​​is a component configured to deliver operating power to external programmer 300. Power source 360 ​​may include a battery and power generation circuitry for generating operating power. In some examples, the battery is rechargeable to allow for long-term operation. Recharging can be achieved by electrically coupling power source 360 ​​to a bracket or plug connected to an alternating current (AC) outlet. Alternatively, recharging can be achieved through near-side inductive interaction between an external charger and an inductive charging coil within external programmer 300. In other examples, conventional batteries (e.g., nickel-cadmium or lithium-ion batteries) may be used. Furthermore, external programmer 300 may be directly coupled to an AC outlet for operation.

[0100] Figure 3 The architecture of the external programmer 300 shown in this disclosure is illustrated as an example. The techniques described in this disclosure can be used in... Figure 3 This includes the exemplary external programmer 300 and other types of systems not specifically described herein. Nothing in this disclosure should be construed as limiting the technology of this disclosure to... Figure 3 An exemplary architecture is shown.

[0101] Figure 4 This is a graph 402 showing an exemplary evoked compound action potential (ECAP) signal sensed for a corresponding stimulus pulse according to one or more techniques of this disclosure. Figure 4 As shown, graph 402 illustrates exemplary ECAP signals 404 (dashed line) and 406 (solid line). In some examples, each of ECAP signals 404 and 406 is sensed by a control pulse delivered from the protected cathode, wherein the control pulse is a biphase pulse that includes an interphase interval between each positive and negative phase of the pulse. In some such examples, the protected cathode includes an 8-electrode lead (e.g., ...). Figure 1 The stimulation electrode is located at one end of the lead 130, while two sensing electrodes are located at the other end of the 8-electrode lead. The ECAP signal 404 shows the voltage amplitude sensed as a result of the sub-detection threshold stimulation pulse. A peak 408 is detected in the ECAP signal 404, which represents an artifact of the delivered control pulse. However, no propagation signal is detected after the artifact in the ECAP signal 404 because the control pulse is sub-detection threshold.

[0102] Compared to ECAP signal 404, ECAP signal 406 represents the voltage amplitude detected from the over-detection threshold control pulse. A peak 408 of ECAP signal 406 is detected, representing an artifact of the delivered control pulse. Following peak 408, ECAP signal 406 also includes peaks P1, N1, and P2, which are three typical peaks representing the propagation action potential from ECAP. The exemplary duration of the artifacts and peaks P1, N1, and P2 is approximately 1 millisecond (ms). When the ECAP of ECAP signal 406 is detected, different characteristics can be identified. For example, a characteristic of ECAP could be an amplitude between N1 and P2. This N1-P2 amplitude can be easily detected even if the artifact is projected onto a relatively large signal P1, and the N1-P2 amplitude can be minimally affected by electronic drift in the signal. In other examples, the characteristic of ECAP used for controlling the notification pulse could be the amplitude of P1, N1, or P2 relative to the neutral voltage or zero voltage. In some examples, the ECAP used to control the notification pulse is characterized by the sum of two or more of the peaks P1, N1, or P2. In other examples, the ECAP signal 406 may be characterized by the area under one or more of the peaks P1, N1, and / or P2. In other examples, the ECAP may be characterized by the ratio of one of the peaks P1, N1, or P2 to another of these peaks. In some examples, the ECAP may be characterized by the slope between two points in the ECAP signal, such as the slope between N1 and P2. In other examples, the ECAP may be characterized by the time between two points in the ECAP, such as the time between N1 and P2. The time between the delivery of the stimulus pulse and a point in the ECAP signal may be referred to as the delay of the ECAP and may indicate the type of fiber captured by the stimulus pulse (e.g., 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. Delay can also refer to the time between detecting an electrical feature at one electrode and then detecting it again at a different electrode. This time (or delay) is inversely proportional to the conduction velocity of the nerve fiber. In other examples, other features of the ECAP signal may be used.

[0103] As long as the amplitude of the control pulse is greater than a threshold, the amplitude of the ECAP signal increases with the increase of the pulse amplitude, causing nerve depolarization and signal propagation. The target ECAP characteristic (e.g., target ECAP amplitude) can be determined based on the ECAP signal detected from the control pulse when determining effective treatment delivery of the notification pulse to the patient 105. Therefore, the ECAP signal represents the distance between the stimulating electrode and the nerve suitable for the stimulation parameter values ​​of the notification pulse delivered at that time. Thus, the IMD 110 can attempt to modify the notification pulse parameter values ​​using detected changes in the measured ECAP characteristic values ​​and maintain the target ECAP characteristic value during notification pulse delivery.

[0104] Figure 5A This is a timing diagram 500A illustrating an example of an electrical stimulation pulse according to one or more techniques of this disclosure and the corresponding sensed ECAP. For convenience, refer to... Figure 2 IMD 200 pairs Figure 5A The following description is provided. As shown in the figure, timing diagram 500A includes a first channel 502, multiple control pulses 504A–504N (collectively referred to as "control pulses 504"), a second channel 506, multiple corresponding ECAPs 508A–508N (collectively referred to as "ECAP 508"), and multiple stimulus interference signals 509A–509N (collectively referred to as "stimulus interference signals 509"). Figure 5A In this example, the IMD 200 can use control pulses instead of notification pulses to deliver treatment.

[0105] The first channel 502 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In one example, the stimulating electrode of the first channel 502 may be located on the side of the lead opposite to the sensing electrode of the second channel 506. The control pulse 504 may be an electrical pulse delivered to the patient's spinal cord through at least one of the electrodes 232, 234, and the control pulse 504 may be a balanced biphasic square pulse with phase intervals. In other words, each of the control pulses 504 is shown to have a negative phase and a positive phase separated by phase intervals. For example, the control pulse 504 may have a negative voltage, the same amount of time and amplitude as when it has a positive voltage. Note that the negative voltage phase may precede or follow the positive voltage phase. Control pulse 504 can be delivered according to ECAP test stimulus program 216 stored in storage device 212 of IMD 200, and ECAP test stimulus program 216 can be updated according to user input via an external programmer and / or according to signals from sensor 222. In one example, control pulse 504 can have a pulse width of less than about 300 microseconds (e.g., the total time of positive phase, negative phase, and phase interval is less than 300 microseconds). In another example, for each phase of a biphasic pulse, control pulse 504 can have a pulse width of about 100 μs. Figure 5A As shown, control pulse 504 can be delivered via channel 502. The delivery of control pulse 504 can be delivered via lead 230 in the protected cathode electrode assembly. For example, if lead 230 is a linear 8-electrode lead, the protected cathode assembly consists of a center cathode electrode and an anode electrode immediately adjacent to that cathode electrode.

[0106] The second channel 506 is a time / voltage (and / or current) graph indicating the voltage (or current) at at least one of the electrodes 232, 234. In one example, the electrode of the second channel 506 may be located on the side of the lead opposite to the electrode of the first channel 502. In response to a control pulse 504, an ECAP 508 can be sensed from the patient's spinal cord at electrodes 232, 234. The ECAP 508 is an electrical signal that can propagate along the nerve away from the origin of the control pulse 504. In one example, the ECAP 508 is sensed by an electrode different from the electrode used to deliver the control pulse 504. Figure 5A As shown, the ECAP 508 can record on the second channel 506.

[0107] Stimulus interference signals 509A, 509B, and 509N (e.g., artifacts of the stimulation pulse) can be sensed by lead 230 and can be sensed during the same time period as the delivery of control pulse 504. Because the amplitude and intensity of these interference signals may be greater than ECAP 508, any ECAP arriving at IMD 200 during the occurrence of stimulation interference signal 509 may not be sufficiently sensed by sensing circuitry 206 of IMD 200. However, ECAP 508 can be sufficiently sensed by sensing circuitry 206 because each ECAP 508, or at least a portion of ECAP 508 used as feedback for control pulse 504, decreases after each control pulse 504 ends. Figure 5A As shown, the stimulus interference signals 509 and ECAP 508 can be recorded on channel 506.

[0108] Figure 5B This is a timing diagram 500B illustrating another example of an electrical stimulation pulse according to one or more techniques of this disclosure and the corresponding sensed ECAP. For convenience, refer to... Figure 2 IMD 200 pairs Figure 5B The timing diagram 500B is described as follows: As shown in the figure, the timing diagram 500B includes a first channel 510, multiple control pulses 512A–512N (collectively referred to as “control pulses 512”), a second channel 520, multiple notification pulses 524A–524N (collectively referred to as “notification pulses 524”) including passive recharge phases 526A–526N (collectively referred to as “passive recharge phases 526”), a third channel 530, multiple corresponding ECAPs 536A–536N (collectively referred to as “ECAP 536”), and multiple stimulus interference signals 538A–538N (collectively referred to as “stimulus interference signals 538”).

[0109] The first channel 510 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In one example, the stimulating electrode of the first channel 510 may be located on the side of the lead opposite to the sensing electrode of the third channel 530. The control pulse 512 may be an electrical pulse delivered to the patient's spinal cord through at least one of the electrodes 232, 234, and the control pulse 512 may be a balanced biphasic square pulse with phase intervals. In other words, each of the control pulses 512 is shown to have a negative phase and a positive phase separated by the phase intervals. For example, the control pulse 512 may have a negative voltage, the same amount of time and amplitude as when it has a positive voltage. Note that the negative voltage phase may precede or follow the positive voltage phase. Control pulse 512 can be delivered according to ECAP test stimulus program 216 stored in storage device 212 of IMD 200, and ECAP test stimulus program 216 can be updated according to user input via an external programmer and / or according to signals from sensor 222. In one example, control pulse 512 can have a pulse width of less than about 300 microseconds (e.g., the total time of positive phase, negative phase, and phase interval is less than 300 microseconds). In another example, for each phase of a biphasic pulse, control pulse 512 can have a pulse width of about 100 μs. Figure 5B As shown, control pulse 512 can be delivered via channel 510. The delivery of control pulse 512 can be achieved via lead 230 in the protected cathode electrode assembly. For example, if lead 230 is a linear 8-electrode lead, the protected cathode assembly consists of a center cathode electrode and an anode electrode immediately adjacent to that cathode electrode.

[0110] The second channel 520 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234 that generate the notification pulse. In one example, the electrode of the second channel 520 may partially or completely share a common electrode with the electrodes of the first channel 510 and the third channel 530. The notification pulse 524 may also be delivered by the same lead 230 configured to deliver the control pulse 512. The notification pulse 524 may be interleaved with the control pulse 512 such that neither type of pulse is delivered during the overlapping time period. However, the notification pulse 524 may be delivered by, or may not be delivered by, the exact same electrode that delivers the control pulse 512. The notification pulse 524 may be a single-phase pulse with a pulse width greater than about 300 μs and less than about 1200 μs. In practice, the notification pulse 524 may be configured to have a longer pulse width than the control pulse 512. Figure 5B As shown, notification pulse 524 can be delivered on channel 520.

[0111] Notification pulse 524 can be configured for passive recharging. For example, each notification pulse 524 can be followed by a passive recharging phase 526 to equalize the charge on the stimulating electrodes. Unlike pulses configured for active recharging, where residual charge on the tissue is immediately removed from the tissue by the opposite applied charge after the stimulating pulse, passive recharging allows the tissue to discharge naturally to a reference voltage (e.g., ground or line voltage) after the notification pulse terminates. In some examples, the electrodes of the medical device may be grounded at the body of the medical device. In this case, after the notification pulse 524 terminates, the charge on the tissue surrounding the electrodes can dissipate to the medical device, resulting in a rapid decay of residual charge at the tissue after the pulse terminates. This rapid decay is demonstrated in the passive recharging phase 526. The passive recharging phase 526 may have a duration in addition to the pulse width of the preceding notification pulse 524. In other examples ( Figure 5B In (not shown), the notification pulse 524 can be a biphase pulse having a positive phase and a negative phase (and, in some examples, the phase interval between the phases), which can be referred to as a pulse that includes active recharging. The notification pulse as a biphase pulse may or may not have a subsequent passive recharging phase.

[0112] The third channel 530 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In one example, the electrode of the third channel 530 may be located on the side of the lead opposite to the electrode of the first channel 510. In response to the control pulse 512, an ECAP 536 can be sensed from the patient's spinal cord at electrodes 232, 234. The ECAP 536 is an electrical signal that can propagate along the nerve away from the origin of the control pulse 512. In one example, the ECAP 536 is sensed by an electrode different from the electrode used to deliver the control pulse 512. Figure 5B As shown, ECAP 536 can be recorded on the third channel 530.

[0113] Stimulus interference signals 538A, 538B, and 538N (e.g., artifacts of the stimulation pulse) can be sensed by lead 230 and can be sensed during the same time period as the delivery of control pulse 512 and notification pulse 524. Because the amplitude and intensity of these interference signals may be greater than ECAP 536, any ECAP arriving at IMD 200 during the occurrence of stimulation interference signal 538 may not be sufficiently sensed by sensing circuitry 206 of IMD 200. However, ECAP 536 can be sufficiently sensed by sensing circuitry 206 because each ECAP 536 decreases after the end of each control pulse 512 and before the delivery of the next notification pulse 524. Figure 5BAs shown, the stimulus interference signals 538 and ECAP 536 can be recorded on channel 530.

[0114] Figure 6 This is a timing diagram 600 illustrating another example of an electrical stimulation pulse and a corresponding ECAP according to one or more techniques of this disclosure. For convenience, refer to... Figure 2 IMD 200 pairs Figure 6 The following description is provided. As shown in the figure, the timing diagram 600 includes a first channel 610, multiple control pulses 612A–612N (collectively referred to as “control pulses 612”), a second channel 620, multiple notification pulses 624A–624N (collectively referred to as “notification pulses 624”) including passive recharge phases 626A–626N (collectively referred to as “passive recharge phases 626”), a third channel 630, multiple corresponding ECAPs 636A–636N (collectively referred to as “ECAP 636”), and multiple stimulus interference signals 638A–638N (collectively referred to as “stimulus interference signals 638”). Figure 6 It can be basically similar to Figure 5B Except for the differences detailed below.

[0115] Two or more control pulses 612 can be delivered during each of multiple time events (e.g., windows), and each time event represents the time between two consecutive notification pulses 624. For example, during each time event, a first control pulse may be followed directly by a first corresponding ECAP, and a second control pulse may be followed directly by a second corresponding ECAP after the end of the first corresponding ECAP. The notification pulse may begin after the second corresponding ECAP. In other examples not shown here, three or more control pulses 612 may be delivered during each of multiple time events, and a corresponding ECAP signal may be sensed.

[0116] Figure 7 This is a timing diagram 700 illustrating another example of an electrical stimulation pulse and a corresponding ECAP according to one or more techniques of this disclosure. For convenience, refer to... Figure 2 IMD 200 pairs Figure 7The timing diagram 700 is described as follows: As shown in the figure, the timing diagram 700 includes a first channel 710, multiple control pulses 712A–712N (collectively referred to as “control pulses 712”), a second channel 720, multiple notification pulses 724A–724N (collectively referred to as “notification pulses 724”) including a passive recharge phase 726A–726N (collectively referred to as “passive recharge phase 726”), a third channel 730, multiple corresponding ECAPs 736A–736N (collectively referred to as “ECAP 736”), and multiple stimulus interference signals 738A–738N (collectively referred to as “stimulus interference signals 738”). Figure 7 It can be basically similar to Figure 5B Except for the differences detailed below.

[0117] exist Figure 5B and Figure 6 In the previous examples shown, at least one control pulse is delivered and interleaved between each pair of consecutive notification pulses. However, in some examples, the control pulse 712 is not delivered during each time event (or window) of multiple time events, where each time event represents the time between two consecutive notification pulses 724. Figure 7 As this example demonstrates, control pulse 712 is delivered neither after notification pulse 724A nor before notification pulse 724B. In other words, consecutive notification pulses 724A and 724B can be delivered without an intervening control pulse. In any case, notification pulses are delivered at a predetermined frequency, and control pulses can be delivered at any time between notification pulses.

[0118] Control pulses can be applied according to the ECAP test stimulation program 216. Processing circuitry 210 can be configured to update the ECAP test stimulation program based on user input via telemetry circuitry 208 and signals from sensor 222. For example, a clinician can operate a patient programmer and send a signal to telemetry circuitry 208 including instructions for updating the ECAP test stimulation program 216. The clinician can set the control stimulation as shown in Figures 5 to... Figure 7 Any of the examples shown, and clinicians can also customize the control stimulus as shown in Figures 5 to 6. Figure 7 Configurations not shown in the text. Clinicians can choose to stop or start controlled stimulation at any time. In some examples, detecting a change in the patient's posture or activity level will initiate controlled stimulation. As described herein, the stimulation level of the stimulation threshold (e.g., the perception threshold and / or detection threshold) can be configured from Figure 5 to... Figure 7The ECAP signal detected by the control pulse is used to determine, and one or more stimulation parameter values ​​that define the notification pulse can be determined based on the stimulation level of the determined stimulation threshold. For example, the processing circuit 210 can determine the stimulation parameter value directly from the stimulation level or based on stimulation parameter values ​​that define the control pulse and are selected from the stimulation level (e.g., the gain value of the stimulation parameter value applied to the control pulse).

[0119] Figure 8 This is a timing diagram 800 illustrating another example of an electrical stimulation pulse according to one or more techniques of this disclosure and the corresponding sensed ECAP signal. For convenience, refer to... Figure 2 IMD 200 pairs Figure 8 The following description is provided. As shown in the figure, the timing diagram 800 includes a first channel 810, multiple notification pulse bursts 812A–812N (collectively referred to as “notification pulse bursts 812”), a second channel 820, multiple sensed artifacts 822A–822N (collectively referred to as “sensed artifacts 822”), multiple corresponding ECAPs 824A–824N (collectively referred to as “ECAP 824”), multiple N1 ECAP peaks 826A–826N (collectively referred to as “N1 ECAP peaks 826”), and multiple P2 ECAP peaks 828A–828N (collectively referred to as “P2 ECAP peaks 828”).

[0120] The first channel 810 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In some examples, the first channel 810 may represent the voltage of at least one of the stimulating electrodes 232, 234 that delivers a plurality of notification pulse bursts 812. Figure 8 In this example, each of the plurality of notification pulse bursts 812 comprises five notification pulses. Alternatively, in other examples, each of the plurality of notification pulse bursts 812 may comprise more than five or fewer notification pulses. In one example, the stimulation electrode delivering the notification pulse burst 812 may be located on the side of the lead 230 opposite to the sensing electrode recording the signal of the second channel 820. The notification pulses in the notification pulse burst 812 may be balanced biphasic square pulses with phase intervals. In other words, each notification pulse in the notification pulse burst 812 is shown to have a negative phase and a positive phase separated by phase intervals. For example, the notification pulse may have a negative voltage, the same amount of time and amplitude as when it has a positive voltage. Note that the negative voltage phase may precede or follow the positive voltage phase.

[0121] The notification pulse burst 812 can be delivered according to a therapeutic stimulation program 214 stored in the storage device 212 of the IMD 200, and the therapeutic stimulation program 214 can be updated according to user input via an external programmer and / or according to signals from the sensor 222. In one example, each notification pulse of the notification pulse burst 812 can have a pulse width of less than about 400 microseconds (e.g., the total time of the positive phase, negative phase, and phase interval is less than 400 microseconds). In another example, for each phase of a biphasic pulse, each notification pulse of the notification pulse burst 812 can have a pulse width of about 150 μs. In some examples, the frequency of the notification pulses within each notification pulse burst 812 can be greater than 500 Hz and less than 1500 Hz. In other examples, the frequency of the notification pulses within each burst can be greater than 1500 Hz. Figure 8 As shown, the notification pulse burst 812 can be delivered via the first channel 810. The delivery of the notification pulse burst 812 can be delivered via lead 230 in the protected cathode electrode assembly. For example, if lead 230 is a linear 8-electrode lead, the protected cathode assembly consists of a center cathode electrode and an anode electrode immediately adjacent to that cathode electrode.

[0122] The second channel 820 is a time / voltage (and / or current) graph that indicates the voltage (or current) of at least one of the electrodes 232, 234. In one example, the electrode of the second channel 820 may be located on the side of the lead opposite to the electrode of the first channel 810. Figure 8In this example, the second channel 820 is the sensing channel of lead 230. In this manner, the second channel 820 is configured to record sensed artifacts 822A, 822B, and 822N (collectively, “Sensed Artifacts 822”) and ECAPs 824A, 824B, and 824N (collectively, “ECAP 824”). In some examples, the frequency of each notification pulse burst in notification pulse burst 812 is high enough that channel 820 cannot sense a fully or nearly fully manifested ECAP after each notification pulse in notification pulse burst 812 because the next pulse in the burst overlaps temporally with that ECAP signal. However, after each notification pulse burst in notification pulse burst 812 (e.g., during a pause in delivering a notification pulse burst), the second channel 820 can sense the corresponding ECAP in ECAP 824. Since in some cases, the first channel 810 does not apply any stimulation for a period of time after each notification pulse burst, the channel 820 can sense ECAP 824, including the N1 ECAP peak 826 and the P2 ECAP peak 828, for a period of time after each notification pulse burst 812. In some examples, to determine the ECAP amplitude of each ECAP 824, the IMD 200 determines the difference between the amplitudes of the corresponding N1 peak and the corresponding P2 peak. For example, the IMD 200 can determine that the amplitude of ECAP 824A is the difference between the amplitude of the N1 peak 826A and the amplitude of the P2 peak 828A. By delivering such... Figure 8 The notification pulses demonstrated by the IMD 200 can deliver high-frequency therapeutic stimulation to the patient 105 while still recording the ECAP that can be used to determine the treatment. In some examples, the patient 105 may not perceive the “interruption” that occurs after each notification pulse burst 812. Instead, in some such examples, the patient 105 may perceive continuous high-frequency stimulation. In other examples, although the patient 105 may perceive the interruption between notification pulse bursts 812, this perceived interruption may not significantly reduce the therapeutic efficacy.

[0123] In some examples, all stimulation pulses within a single burst 812 may be identical (e.g., defined by the same stimulation parameters). In other examples, the last pulse in a burst may differ from the previous pulses to improve the induced ECAP signal and / or provide a pulse that does not interfere with ECAP detection. For example, the last pulse in each burst (or bursts) may have one or more different stimulation parameter values, such as different amplitudes, pulse widths, pulse shapes, or other characteristics. In one example, the last pulse in each burst 812 may have a larger amplitude than other pulses in the same burst. The last pulse may have a longer or shorter pulse width. In some examples, a shorter pulse width may reduce the likelihood of artifacts being generated on the detected ECAP. In any case, the last pulse may have a larger or smaller charge or phase than other pulses in the same burst, and the last pulse may be referred to as the control pulse. Earlier pulses in the same burst may be referred to as notification pulses because they are notified by the ECAP induced by the previous control pulse (e.g., the last pulse in the previous burst).

[0124] The sensed artifacts 822 (e.g., notification pulse artifacts) can be sensed by lead 230 and can be sensed during the same time period as the delivery of notification pulse burst 812. Because the amplitude and intensity of these interference signals may be greater than ECAP 824, any ECAP arriving at IMD 200 during the occurrence of sensed artifact 822 may not be sufficiently sensed by the sensing circuitry 206 of IMD 200. However, ECAP 824 can be sufficiently sensed by the sensing circuitry 206 because each ECAP of ECAP 824 decreases near or after the end of each notification pulse burst 812 and before the delivery of subsequent notification pulse bursts 812. Figure 8 As shown, the sensed artifacts 822 and ECAP 824 can be recorded on the second channel 820.

[0125] Figure 9 This is a flowchart illustrating an exemplary operation for determining a stimulus level based on a perception threshold according to one or more techniques of this disclosure. For convenience, relative to... Figure 2 IMD 200 pairs Figure 9 To describe. However, Figure 9 The technology can be performed by different components of the IMD 200 or by additional or alternative medical devices.

[0126] IMD 200 can deliver stimulation therapy to a patient (e.g., patient 105). In some cases, IMD 200 delivers the stimulation therapy based on a perception threshold. The perception threshold may be associated with one or more parameter values ​​(e.g., stimulation level) of a stimulation pulse that at least partially defines the level at which patient 105 can perceive the stimulation pulse. For example, patient 105 may not perceive a stimulation pulse delivered with a first pulse amplitude below the notification pulse level associated with the perception threshold. However, patient 105 may perceive a notification pulse delivered with a pulse amplitude (and / or pulse width or pulse frequency) greater than the pulse amplitude (and / or pulse width or pulse frequency) associated with the perception threshold. In this way, stimulation pulses can be delivered at a level of pulse amplitude and / or other stimulation parameter levels associated with or below the level of pulse amplitude and / or other stimulation parameter levels associated with the perception threshold. To maintain a consistent level of treatment delivered by IMD 200, it may be beneficial to periodically determine which stimulation level (e.g., pulse amplitude or pulse width) results in the detection of a characteristic ECAP value at the perception threshold. In some cases, the actual perception threshold may also be redefined. Figure 9 An exemplary system will be described that uses a control pulse to detect an ECAP signal and determine the pulse amplitude that produces a characteristic ECAP value at a sensing threshold. Since the control pulse and the notification pulse can provide different levels of sensing intensity, the stimulation parameter value of the notification pulse can be selected directly from the control pulse level that achieves the sensing threshold or scaled as needed. Similar techniques can be used in other examples where the ECAP signal can be detected from the notification pulse. Figure 9 It replaces control pulses with notification pulses. In some cases, control pulse triggering can be analyzed by IMD 200 to determine one or more characteristics of future control pulses and / or notification pulses delivered by IMD 200.

[0127] like Figure 9As illustrated in this example, the processing circuitry 210 of the IMD 200 delivers a notification pulse (902) based on a stimulus parameter value previously determined from a perception threshold. For example, the perception threshold could be a characteristic ECAP value of approximately 10 mV triggered by a control pulse with a current amplitude of 4 mA (e.g., a stimulus level). If the IMD 200 would deliver a notification pulse with an amplitude 75% of the control pulse amplitude that reaches the characteristic ECAP value of the perception threshold, then the IMD 200 could deliver a notification pulse with a current amplitude of 3 mA. The IMD 200 then determines whether it is time to remeasure or determine the control pulse level that has reached the known perception threshold (904). The IMD 200 can follow a perception threshold measurement frequency, which represents the rate at which the IMD 200 re-determines the control pulse level that has reached the perception threshold. The measurement frequency can include any frequency value or range of frequency values. In some cases, the measurement frequency may be once per hour. In other cases, the measurement frequency may be twice per hour. In still other cases, the measurement frequency may be sixty times per hour or even continuous measurements. Alternatively, the IMD 200 can update the control pulse level of the sensing threshold in response to a change in patient posture or activity detected by the sensor 222. The IMD 200 can receive instructions from the external programmer 150 via the telemetry circuit 208 that sets the measurement frequency. Furthermore, the IMD 200 can receive instructions from the external programmer 150 to the command processing circuit 210 to update the measurement frequency.

[0128] If the time for measurement has not yet arrived (the "No" branch of box 904), the IMD 200 maintains the delivery of therapeutic stimulation to the patient 105 (906). If the time for measurement has arrived (the "Yes" branch of box 904), the processing circuitry 210 of the IMD 200 reduces the amplitude of the control pulse by a first amount (908). In other words, before measurement, the IMD 200 delivers the control pulse at a first level, and when measurement begins, the IMD 200 delivers the control pulse at a second level below the first level. The control pulse may still be interleaved with the notification pulse as the process continues. In some cases, the "level" at which the IMD 200 delivers the control pulse may depend on a set of parameter values, which may include one or more of amplitude, pulse width, or pulse frequency. Therefore, when the IMD 200 reduces the control pulse level by a first amount, the IMD 200 reduces at least one stimulation parameter value by a first amount. In some examples, the IMD 200 reduces the pulse amplitude by a first amount. In other examples, IMD 200 reduces both the pulse amplitude and the pulse width, with the combined reduction of the pulse amplitude and pulse width defining a first amount.

[0129] After the therapeutic stimulus is reduced by a first amount, processing circuitry 210 delivers a control pulse and determines a characteristic ECAP value (910) based on the ECAP signal. In some examples, the control pulse delivered by IMD 200 directly triggers the ECAP signal after the processing circuitry reduces the level (e.g., amplitude) of the control pulse. The characteristic ECAP value may include the ECAP amplitude (e.g., P1 amplitude, N1 amplitude, P2 amplitude, or any combination thereof), the ECAP duration, the ECAP slope, or the area under one or more curves of the ECAP.

[0130] At box 912, the processing circuitry determines whether the characteristic ECAP value is greater than a perception threshold. The perception threshold can represent the characteristic ECAP value at which the patient 105 can perceive the delivery of the corresponding stimulus pulse. If the characteristic ECAP value is not greater than the ECAP parameter threshold (the "No" branch of box 912), the processing circuitry 210 increases the level of the next control pulse by a second amount (914). In other words, if the characteristic ECAP value remains below the perception threshold, the processing circuitry 210 can determine that the current control pulse delivered by the IMD 200 is below the perception threshold. The processing circuitry 210 can then increase the level of the control pulse by a second amount, causing the process to return to box 910. Therefore, the processing circuitry 210 can iteratively increase the stimulus level (e.g., amplitude) by a second amount until the control pulse elicits a characteristic ECAP value greater than the perception threshold. In some cases, the second amount can be significantly smaller than the first amount. In this way, when the processing circuitry 210 decreases the stimulus level by a first amount and then increases the stimulus level by a second amount, the process can return the stimulus to its original value. Figure 9 The process begins before the level is reached, and the stimulation level is increased by a second amount several times before the process begins.

[0131] If the characteristic ECAP value is greater than the perception threshold (the "Yes" branch of box 912), processing circuitry 210 can determine the level (e.g., amplitude) of the control pulse that elicits a characteristic ECAP value greater than the perception threshold (916). In some examples, processing circuitry 210 determines the level of stimulation delivered before detecting a first characteristic ECAP value greater than the perception threshold as a determining level for determining the stimulation parameter value. Subsequently, processing circuitry 210 can update treatment stimulation program 214 (918) based on the stimulation level that reaches the perception threshold. In some examples, processing circuitry 210 sets treatment stimulation program 214 such that IMD 200 delivers a notification pulse with a level (e.g., amplitude) that has reached a certain fraction of the control pulse level that has reached the perception threshold. In some examples, this fraction is greater than 0.50 and less than 0.99. For example, if this fraction is 0.75 (or 75% of the stimulation level), then in the case where a 6mA control pulse results in a characteristic ECAP value that has reached the perception threshold, processing circuitry 210 can determine that the notification pulse has a level or amplitude of 4.5mA.

[0132] Figure 10 This is a flowchart illustrating an exemplary operation for determining stimulus parameter values ​​based on a detection threshold according to one or more techniques of this disclosure. For convenience, relative to... Figure 2 IMD 200 pairs Figure 10 To describe. However, Figure 10 The technology can be performed by different components of the IMD 200 or by additional or alternative medical devices. Figure 10 The description will use control pulses to trigger a detectable ECAP signal, where the control pulses may be therapeutic or non-therapeutic to the patient. For example, the IMD 200 may use the detected ECAP signal to determine one or more parameters of the control pulse, one or more parameters of a set of notification pulses, one or more parameters of other pulses that do not trigger an ECAP, or any combination thereof.

[0133] exist Figure 10 In this exemplary operation, the IMD 200 delivers pulses (1002) to the patient via electrodes 232, 234 (e.g., Figure 1 Patient 105). In some examples, the pulse is a control pulse among multiple control pulses delivered by IMD 200 according to ECAP test stimulation program 216 stored in storage device 212. In other examples, the pulse is a notification pulse among multiple notification pulses delivered by IMD 200 according to treatment stimulation program 214 stored in storage device 212. In examples where the pulse is a control pulse, the control pulse may be at least partially interleaved with the notification pulse among the multiple notification pulses. Based on the pulse delivered by IMD 200, processing circuit 210 may increment the pulse count (M) by 1 (processing circuit 210 performs the operation M = M + 1) (1004). Thus, IMD 200 maintains the pulse count, which may be incremented by 1 each time IMD 200 delivers another pulse. In some examples, when the ECAP signal is sensed only outside of the control pulse, processing circuit 210 increments the pulse count by 1 only when IMD 200 delivers a control pulse. In other examples, when the IMD 200 delivers any pulses from the ECAP signal it senses and attempts to detect the ECAP signal from it, the processing circuit 210 increments the pulse count by 1.

[0134] Processing circuit 210 determines whether sensing circuit 206 senses a responsive ECAP (1006) corresponding to the pulse delivered by IMD 200 in step 1002. Detection of the ECAP may include characteristics of when processing circuit 210 can detect the ECAP signal. For example, to determine whether sensing circuit 206 senses a responsive ECAP, processing circuit 210 may receive a signal from sensing circuit 206 representing an electrical signal sensed via at least some of electrodes 232, 234. If processing circuit 210 can identify the waveform and distinguish it from noise in the signal received from sensing circuit 206, processing circuit 210 may identify the waveform as an ECAP in response to the pulse delivered by IMD 200. Alternatively, in some examples, if processing circuit 210 cannot identify the waveform and distinguish it from noise in the signal received from sensing circuit 206, processing circuit 210 may determine that sensing circuit 206 has not sensed an ECAP in response to the pulse delivered by IMD 200. In some cases, the processing circuit 210 "searches" for the responsive ECAP in a portion of the signal received by the sensing circuit 206 that occurs within a period of time after the IMD 200 delivers its pulse in step 1002. In the example where the pulse is a control pulse, this period occurs after the IMD 200 delivers its pulse and before the IMD 200 delivers a subsequent notification or control pulse. Furthermore, in the example where the pulse is a notification pulse, this period occurs after the IMD 200 delivers its pulse and before the IMD 200 delivers a subsequent notification or control pulse.

[0135] If IMD 200 senses a responsive ECAP (the "Yes" branch of box 1006), processing circuit 210 increments the responsive ECAP count (N) by 1 (processing circuit 210 performs the operation N = N + 1) (1008). Alternatively, if IMD 200 does not sense a responsive ECAP (the "No" branch of box 1006), processing circuit 210 maintains the responsive ECAP count (processing circuit 210 performs the operation N = N) (1010). In this way, the responsive ECAP count represents a record of how many pulses delivered by IMD 200 caused sensing circuit 206 to sense a responsive ECAP. Processing circuit 210 may reset the responsive ECAP count N at any time. In some examples, if processing circuit 210 resets the responsive ECAP count N, it also resets the pulse count M.

[0136] After processing circuit 210 increments the responsive ECAP count by 1 or maintains the responsive ECAP count, processing circuit 210 determines whether the pulse count M is greater than a threshold pulse count value (1012). The threshold pulse count value may be stored in storage device 212 as part of threshold detection parameter 220. In some examples, the threshold pulse count value is greater than 7 and less than 10,000. In any case, the pulse count value may be predetermined and represents the number of pulses required to determine whether a representative number of ECAPs has been detected. It may be beneficial for processing circuit 210 to determine whether the pulse count is greater than the threshold pulse count value, such that IMD 200 determines a stimulation level with a sufficient number of pulses based on a threshold ratio (e.g., a detection threshold). If processing circuit 210 determines that the pulse count is not greater than the threshold pulse count value (the "No" branch of block 1012), the operation may return to block 1002, and IMD 200 may deliver an additional pulse. In some examples where the pulse is a control pulse, the additional pulse may also be a control pulse. In some examples where the pulse is a notification pulse, the additional pulse may also be a notification pulse. If processing circuit 210 determines that the pulse count is greater than a threshold pulse count value (the "Yes" branch of block 1012), processing circuit 210 may continue to calculate the ratio of the responsive ECAP count N to the pulse count M (e.g., calculate N / M) (1014). In this way, processing circuit 210 calculates the ratio or percentage of pulses delivered by IMD 200, which correspond to the responsive ECAP sensed by sensing circuit 206. The stimulation level of one or more parameters representing the control pulses delivered by IMD 200 may be determined in part based on the ratio N / M calculated in step 1014.

[0137] If processing circuit 210 determines that the ratio N / M is greater than the sum of the threshold ratio (representing the perception threshold) and the variance value (the "Yes" branch of box 1016), then processing circuit 210 may reduce the amplitude of the notification pulse delivered to patient 105 by IMD 200 (1018). In some examples, processing circuit 210 may also reduce the amplitude of the control pulse. In some examples, the amplitude of the control pulse and the amplitude of the notification pulse may be correlated by a gain factor. Subsequently, Figure 10The operation returns to box 1002, and IMD 200 delivers an additional control pulse. A threshold ratio value can represent the ratio of the sensed responsive ECAP to the delivered pulse, indicating a detection threshold where the notification pulse delivered by IMD 200 creates an environment where the responsive ECAP can be detected by sensing circuitry 206. A variance value can represent an error value where processing circuitry 210 determines that ratio N / M is "sufficiently close" to the threshold ratio value if the difference between ratio N / M and threshold ratio value is less than this error value. In some examples, the threshold ratio value is greater than 0.25 and less than 0.5. Furthermore, in some examples, the variance value is greater than or equal to 0 and less than or equal to 0.1. The threshold ratio value and variance value can be stored in storage device 212 as part of threshold detection parameter 220.

[0138] If processing circuit 210 determines that the ratio N / M is not greater than the sum of the threshold ratio value and the variance value (the "No" branch of box 1016), then processing circuit 210 determines whether the ratio N / M is less than the threshold ratio value minus the variance value (1020). If processing circuit 210 determines that the ratio N / M is less than the threshold ratio value minus the variance value (the "Yes" branch of box 1020), then processing circuit 210 increases the amplitude of the notification pulse delivered by IMD 200 to patient 105 (1022). Figure 10 The operation returns to box 1002, and IMD 200 delivers an additional pulse. In some examples where the pulse is a control pulse, the additional pulse is also a control pulse. In some examples where the pulse is a notification pulse, the additional pulse is also a notification pulse. If processing circuit 210 determines that the ratio N / M is not less than the threshold ratio value minus the variance value (the "No" branch of box 1020), processing circuit 210 maintains the amplitude of the notification pulse (1024) and continues to deliver the additional pulse (1002). The upper bound of the threshold ratio value window is given by the sum of the threshold ratio value and the variance value, and the lower bound of the threshold ratio value window is given by the threshold ratio value minus the variance value.

[0139] As discussed above, the amplitude of the notification pulse can be set to a fraction of the stimulus level at which the pulse elicits a detectable ECAP at a threshold ratio. In some examples, the stimulus level can be the amplitude of the control pulse that elicits the detected ECAP signal. For example, this fraction can be greater than 0.50 and less than 0.99.

[0140] although Figure 10The operation is described as adjusting the amplitude of the notification pulse, but other parameter values ​​can be changed in other examples. For example, the sensed ECAP signal can be used to increase or decrease the pulse width of the notification pulse to regulate the amount of charge delivered to the tissue, thereby maintaining a consistent volume of neural activation. In other examples, the electrode combination can be adjusted to deliver different amounts of charge and modify the number of neurons recruited by each notification pulse. In other examples, processing circuitry 210 can be configured to adjust the slew rate of the notification pulse (i.e., the rate of change of voltage and / or amplitude at the beginning and / or end of the pulse or each phase of the pulse) in response to a ratio N / M being greater than or less than a threshold ratio value window. For example, if the representative amplitude of the ECAP signal is above the upper bound of the threshold ratio value window, processing circuitry 210 can reduce the slew rate of subsequent notification pulses (i.e., ramp up the pulse amplitude more slowly). If the representative amplitude of the ECAP signal is below the lower bound of the threshold ratio value window, processing circuitry 210 can increase the slew rate of subsequent notification pulses (i.e., ramp up the pulse amplitude more quickly). The slew rate can contribute to the pulse intensity. Processing circuit 210 can be based on Figure 10 The operation is used to change one or more parameters that define the notification pulse.

[0141] The following examples are exemplary systems, apparatuses, and methods described herein.

[0142] Example 1: A medical device comprising: a stimulation generation circuit configured to deliver electrical stimulation therapy to a patient, wherein the electrical stimulation therapy includes a plurality of treatment pulses; a sensing circuit configured to sense one or more evoked compound action potential (ECAP) signals, wherein the sensing circuit is configured to sense each of the one or more ECAP signals induced by a corresponding control pulse of a plurality of control pulses; and a processing circuit configured to: determine, based on the one or more ECAP signals, a stimulation level for achieving a stimulation threshold of the plurality of control pulses; determine, based on the stimulation level, values ​​of stimulation parameters of the plurality of treatment pulses that at least partially define the electrical stimulation therapy; and control the stimulation generation circuit to deliver the electrical stimulation therapy to the patient according to the values ​​of the stimulation parameters.

[0143] Example 2: According to the medical device of Example 1, the plurality of treatment pulses include a plurality of notification pulses, and at least some of the plurality of notification pulses are interleaved with at least some of the plurality of control pulses.

[0144] Example 3: The medical device according to Example 2, wherein the processing circuit is configured to determine the value of the stimulation parameter by applying a fractional value to the stimulation level, so as to determine the value of the stimulation parameter that at least partially defines the plurality of notification pulses.

[0145] Example 4: A medical device according to any one of Examples 2 to 3, wherein the processing circuit is configured to determine that the value of the stimulation parameter is less than 100% of the stimulation level.

[0146] Example 5: The medical device according to Example 4, wherein the value of the stimulation parameter is determined by a range of about 40% to about 99% of the stimulation level.

[0147] Example 6: A medical device according to any one of Examples 2 to 5, wherein the stimulation level and the stimulation parameter are corresponding current amplitudes.

[0148] Example 7: A medical device according to any one of Examples 1 to 6, wherein, in order to determine the stimulation level, the processing circuit is configured to: control the stimulation circuit to deliver a set of control pulses from the plurality of control pulses, the set of control pulses having values ​​that at least partially define an iteratively increasing stimulation parameter of a corresponding control pulse from the set of control pulses; and determine the stimulation level as at least partially defining the value of the stimulation parameter of the control pulses from the set of control pulses, the control pulses causing the ECAP signal to reach the stimulation threshold.

[0149] Example 8: According to the medical device of Example 7, the characteristics of the ECAP signal include at least one of the following: peak current amplitude, peak voltage amplitude, gradient, or area under at least one peak of the ECAP signal.

[0150] Example 9: A medical device according to any one of Examples 1 to 8, wherein the stimulation threshold is a perception threshold associated with a characteristic of the ECAP signal indicating that the patient can perceive the control pulse.

[0151] Example 10: A medical device according to any one of Examples 1 to 9, wherein the stimulation threshold is a detection threshold associated with a characteristic of the ECAP signal detectable from the delivered control pulse.

[0152] Example 11: The medical device according to Example 10, wherein the processing circuit is configured to determine the stimulation level as a value of a stimulation parameter at which a threshold ratio of the number of times the corresponding ECAP signal is detected for a set of consecutive control pulses among the plurality of control pulses.

[0153] Example 12: A medical device according to Example 11, wherein the set of consecutive control pulses includes a first set of consecutive control pulses, the value of the stimulation parameter is a first value of the stimulation parameter, and the number of times the corresponding ECAP signal is detected is a first number of times the corresponding ECAP signal is detected, and wherein the processing circuit is configured to: determine a second number of times the corresponding ECAP signal is detected from a second set of consecutive control pulses at least partially defined by the first value of the stimulation parameter; determine a ratio of the second number of times the corresponding ECAP signal is detected to the number of pulses in the second set of consecutive control pulses; determine whether the ratio is greater than a threshold ratio or less than the threshold ratio; in response to determining that the ratio is greater than the threshold ratio, select a decreased value of the stimulation parameter for a subsequent treatment pulse; and in response to determining that the ratio is less than the threshold ratio, select an increased value of the stimulation parameter for the subsequent treatment pulse.

[0154] Example 13: The medical device according to Example 12, wherein the threshold ratio value is greater than 0.25 and less than 0.75.

[0155] Example 14: A medical device according to any one of Examples 1 to 13, wherein the plurality of treatment pulses includes the plurality of control pulses.

[0156] Example 15: A medical device according to any one of Examples 1 to 14, wherein the medical device is an implantable medical device.

[0157] Example 16: A method comprising: delivering electrical stimulation therapy to a patient by a stimulation generation circuit, wherein the electrical stimulation therapy comprises a plurality of treatment pulses; sensing one or more evoked compound action potential (ECAP) signals by a sensing circuit, wherein the sensing circuit is configured to sense each of the one or more ECAP signals induced by a corresponding control pulse of a plurality of control pulses; determining, by a processing circuit, a stimulation level of the plurality of control pulses to achieve a stimulation threshold based on the one or more ECAP signals; determining, by the processing circuit, values ​​of stimulation parameters of the plurality of treatment pulses at least partially defining the electrical stimulation therapy based on the stimulation level; and controlling the stimulation generation circuit by the processing circuit to deliver the electrical stimulation therapy to the patient according to the values ​​of the stimulation parameters.

[0158] Example 17: According to the method of Example 16, the plurality of treatment pulses include a plurality of notification pulses, and the delivery of the electrical stimulation treatment includes the delivery of at least some of the plurality of notification pulses interleaved with at least some of the plurality of control pulses.

[0159] Example 18: According to the method of Example 17, determining the value of the stimulation parameter includes applying a fractional value to the stimulation level to determine the value of the stimulation parameter that at least partially defines the plurality of notification pulses.

[0160] Example 19: The method according to any one of Examples 17 to 18, wherein determining the value of the stimulation parameter includes determining that the value of the stimulation parameter is less than 100% of the stimulation level.

[0161] Example 20: According to the method of Example 19, the value of the stimulation parameter is determined by a range of about 40% to about 99% of the stimulation level.

[0162] Example 21: The method according to any one of Examples 17 to 20, wherein the stimulation level and the stimulation parameter are corresponding current amplitudes.

[0163] Example 22: The method according to any one of Examples 16 to 21, wherein determining the stimulation level comprises: controlling the stimulation circuit to deliver a set of control pulses from the plurality of control pulses, the set of control pulses having values ​​that at least partially define an iteratively increasing stimulation parameter of a corresponding control pulse from the set of control pulses; and determining the stimulation level as at least partially defining the value of the stimulation parameter of the control pulse from the set of control pulses, the control pulses causing a characteristic of the ECAP signal that reaches the stimulation threshold.

[0164] Example 23: The method according to any one of Examples 16 to 22, wherein the stimulation threshold is a perception threshold associated with a characteristic of the ECAP signal indicating that the patient is able to perceive the control pulse.

[0165] Example 24: The method according to any one of Examples 16 to 23, wherein the stimulation threshold is a detection threshold associated with a characteristic of the ECAP signal detectable from the delivered control pulse.

[0166] Example 25: According to the method of Example 24, determining the stimulation level includes determining the stimulation level as a value of the stimulation parameter at which a threshold ratio of the number of times the corresponding ECAP signal is detected for a set of consecutive control pulses in the plurality of control pulses.

[0167] Example 26: According to the method of Example 25, wherein the set of consecutive control pulses includes a first set of consecutive control pulses, the value of the stimulation parameter is a first value of the stimulation parameter, and the number of times the corresponding ECAP signal is detected is a first number of times the corresponding ECAP signal is detected, and wherein the method further includes: determining, by the processing circuit, a second number of times the corresponding ECAP signal is detected from a second set of consecutive control pulses at least partially defined by the first value of the stimulation parameter from the plurality of control pulses; determining, by the processing circuit, a ratio of the second number of times the corresponding ECAP signal is detected to the number of pulses in the second set of consecutive control pulses; determining, by the processing circuit, whether the ratio is greater than a threshold ratio or less than the threshold ratio; in response to determining that the ratio is greater than the threshold ratio, selecting a decreased value of the stimulation parameter for a subsequent notification pulse; and in response to determining that the ratio is less than the threshold ratio, selecting an increased value of the stimulation parameter for the subsequent notification pulse.

[0168] Example 27: The method according to Example 26, wherein the threshold ratio value is greater than 0.25 and less than 0.75.

[0169] Example 28: The method according to any one of Examples 26 to 27, wherein the implantable medical device includes the stimulation generation circuit, the sensing circuit, and the processing circuit.

[0170] Example 29: A computer-readable medium comprising instructions that, when executed by a processor, cause the processor to: control a stimulation generation circuit to deliver electrical stimulation therapy to a patient, wherein the electrical stimulation therapy comprises a plurality of treatment pulses; control a sensing circuit to sense one or more evoked compound action potential (ECAP) signals, wherein the sensing circuit is configured to sense each of the one or more ECAP signals induced by a corresponding control pulse of the plurality of control pulses; determine a stimulation level for achieving a stimulation threshold of the plurality of control pulses based on the one or more ECAP signals; determine, based on the stimulation level, values ​​of stimulation parameters of the plurality of treatment pulses that at least partially define the electrical stimulation therapy; and control the stimulation generation circuit to deliver the electrical stimulation therapy to the patient according to the values ​​of the stimulation parameters.

[0171] The techniques described in this disclosure can be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, aspects of the techniques can 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 circuitry, and any combination of such components. The terms "processor" or "processing circuitry" can generally refer to any of the aforementioned logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry. A control unit, including hardware, can also perform one or more of the techniques disclosed herein.

[0172] Such hardware, software, and firmware may be implemented within the same device or in separate devices to support the various operations and functions described in this disclosure. Furthermore, any described unit, circuit, or component may be implemented together or individually as discrete but interoperable logic devices. Describing different features as circuits or units is intended to highlight different functional aspects and does not necessarily imply that such circuits or units must be implemented by separate hardware or software components. Rather, the functionality associated with one or more circuits or units may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

[0173] The techniques described in this disclosure can also be embodied or encoded in a computer-readable medium (such as a computer-readable storage medium) containing instructions, which can be described as a non-transitory medium. Instructions embedded or encoded in a computer-readable storage medium can cause a programmable processor or other processor to perform the method, for example, when executing those instructions. Computer-readable storage media may include random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, hard disk, CD-ROM, floppy disk, magnetic tape cassette, magnetic media, optical media, or other computer-readable media.

Claims

1. A medical device comprising: A stimulation generation circuit configured to deliver electrical stimulation therapy to a patient, wherein the electrical stimulation therapy comprises a plurality of treatment pulses, and wherein the stimulation generation circuit is configured to deliver a plurality of control pulses at least partially interleaved with the plurality of treatment pulses; A sensing circuit configured to sense an evoked compound action potential (ECAP) signal triggered by the plurality of control pulses rather than the plurality of treatment pulses, wherein the plurality of control pulses are different from the plurality of treatment pulses; and Processing circuit, the processing circuit being configured to: The stimulation level of the plurality of control pulses to achieve the stimulation threshold is determined based on at least one of the ECAP signals. The values ​​of stimulation parameters that at least partially define the plurality of treatment pulses for the electrical stimulation therapy are determined based on the stimulation level. as well as The stimulation generation circuit is controlled to deliver the electrical stimulation therapy to the patient according to the value of the stimulation parameter.

2. The medical device of claim 1, wherein the plurality of treatment pulses comprises a plurality of notification pulses.

3. The medical device of claim 2, wherein the processing circuitry is configured to determine the value of the stimulation parameter by applying a fractional value to the stimulation level, thereby determining the value of the stimulation parameter that at least partially defines the plurality of notification pulses.

4. The medical device of claim 2, wherein the processing circuitry is configured to determine that the value of the stimulation parameter is less than 100% of the stimulation level.

5. The medical device of claim 4, wherein the value of the stimulation parameter is determined by a range of about 40% to about 99% of the stimulation level.

6. The medical device of claim 2, wherein the stimulation level and the stimulation parameter are corresponding current amplitudes.

7. The medical device of claim 1, wherein, in order to determine the stimulation level, the processing circuit is configured to: The stimulus generation circuit is controlled to deliver a set of control pulses from the plurality of control pulses, the set of control pulses having values ​​that at least partially define the iteratively increasing stimulus parameters of the respective control pulses from the set of control pulses; and The stimulation level is determined to at least partially define the value of the stimulation parameter of the control pulses from the set of control pulses, the control pulses causing the ECAP signal to reach the stimulation threshold.

8. The medical device of claim 7, wherein the characteristic of the ECAP signal includes at least one of the following: peak current amplitude, peak voltage amplitude, gradient, or area under at least one peak of the ECAP signal.

9. The medical device of claim 1, wherein the stimulation threshold is a perception threshold associated with a characteristic of the ECAP signal indicating that the patient can perceive the control pulse.

10. The medical device of claim 1, wherein the stimulation threshold is a detection threshold associated with a characteristic of the ECAP signal that can be detected from the delivered control pulse.

11. The medical device of claim 10, wherein the processing circuitry is configured to determine the stimulation level as a value of a stimulation parameter at which a threshold ratio of the number of times the corresponding ECAP signal is detected for a set of consecutive control pulses among the plurality of control pulses.

12. The medical device of claim 11, wherein the set of continuous control pulses includes a first set of continuous control pulses, the value of the stimulation parameter is a first value of the stimulation parameter, and the number of times the corresponding ECAP signal is detected is a first number of times the corresponding ECAP signal is detected, and wherein the processing circuit is configured to: The second number of times the corresponding ECAP signal was detected was determined from a second set of consecutive control pulses, at least partially defined by the first value of the stimulation parameter, from the plurality of control pulses; Determine the ratio of the second number of times the corresponding ECAP signal is detected to the number of pulses in the second group of consecutive control pulses; Determine whether the ratio is greater than or less than the threshold ratio; in response to determining that the ratio is greater than the threshold ratio, select a reduced value of the stimulation parameter for subsequent treatment pulses; and In response to determining that the ratio is less than the threshold ratio, an increased value of the stimulation parameter is selected for the subsequent treatment pulse.

13. The medical device of claim 12, wherein the threshold ratio is greater than 0.25 and less than 0.

75.

14. The medical device according to claim 1, wherein the medical device is an implantable medical device.

15. A medical device, the medical device comprising: Processing circuitry; A storage device storing instructions, which, when executed by the processing circuit, cause the processing circuit to perform a method comprising: The stimulation generation circuitry controls the delivery of electrical stimulation therapy to the patient, wherein the electrical stimulation therapy includes multiple treatment pulses; The stimulation generation circuit is controlled to deliver a plurality of control pulses that are at least partially interwoven with the plurality of treatment pulses; The control sensing circuit senses an evoked compound action potential (ECAP) signal triggered by the plurality of control pulses rather than the plurality of treatment pulses, wherein the plurality of control pulses are different from the plurality of treatment pulses; The stimulation level of the plurality of control pulses to achieve the stimulation threshold is determined based on at least one of the ECAP signals. Based on the stimulation level, the values ​​of the stimulation parameters that at least partially define the plurality of treatment pulses for the electrical stimulation therapy are determined; and The stimulation generation circuit is controlled to deliver the electrical stimulation therapy to the patient according to the value of the stimulation parameter.

16. The medical device of claim 15, wherein the plurality of treatment pulses comprises a plurality of notification pulses.

17. The medical device of claim 16, wherein determining the value of the stimulation parameter comprises applying a fractional value to the stimulation level to determine the value of the stimulation parameter that at least partially defines the plurality of notification pulses.

18. The medical device of claim 16, wherein determining the value of the stimulation parameter includes determining that the value of the stimulation parameter is less than 100% of the stimulation level.

19. The medical device of claim 18, wherein the value of the stimulation parameter is determined by a range of about 40% to about 99% of the stimulation level.

20. The medical device of claim 16, wherein the stimulation level and the stimulation parameter are corresponding current amplitudes.

21. The medical device of claim 15, wherein determining the stimulation level comprises: The stimulation generation circuit is controlled to deliver a set of control pulses from the plurality of control pulses, the set of control pulses having values ​​that at least partially define the iteratively increasing stimulation parameters of the respective control pulses from the set of control pulses; as well as The stimulation level is determined to at least partially define the value of the stimulation parameter of the control pulses from the set of control pulses, the control pulses causing the ECAP signal to reach the stimulation threshold.

22. The medical device of claim 15, wherein the stimulation threshold is a perception threshold associated with a characteristic of the ECAP signal indicating that the patient is able to perceive the control pulse.

23. The medical device of claim 15, wherein the stimulation threshold is a detection threshold associated with a characteristic of the ECAP signal that can be detected from the delivered control pulse.

24. The medical device of claim 23, wherein determining the stimulation level comprises determining the stimulation level as a value of a stimulation parameter at which a threshold ratio of the number of times the corresponding ECAP signal is detected for a set of consecutive control pulses of the plurality of control pulses.

25. The medical device of claim 24, wherein the set of continuous control pulses includes a first set of continuous control pulses, the value of the stimulation parameter is a first value of the stimulation parameter, and the number of times the corresponding ECAP signal is detected is a first number of times the corresponding ECAP signal is detected, and wherein the method further comprises: The processing circuit determines, from a second set of consecutive control pulses, at least partially defined by the first value of the stimulation parameter, the second number of times the corresponding ECAP signal is detected; The processing circuit determines the ratio of the second number of times the corresponding ECAP signal is detected to the number of pulses in the second group of consecutive control pulses; The processing circuit determines whether the ratio is greater than or less than the threshold ratio. In response to determining that the ratio is greater than the threshold ratio, the processing circuit selects a reduced value of the stimulation parameter for subsequent notification pulses; as well as In response to determining that the ratio is less than the threshold ratio, the processing circuit selects an increased value of the stimulation parameter for the subsequent notification pulse.

26. The medical device of claim 25, wherein the threshold ratio is greater than 0.25 and less than 0.

75.

27. The medical device of claim 25, wherein the implantable medical device includes the stimulation generation circuit, the sensing circuit, and the processing circuit.

28. A computer-readable medium comprising instructions that, when executed by a processor, cause the processor to: The stimulation generation circuitry controls the delivery of electrical stimulation therapy to the patient, wherein the electrical stimulation therapy includes multiple treatment pulses; The stimulation generation circuit is controlled to deliver a plurality of control pulses that are at least partially interwoven with the plurality of treatment pulses; The control sensing circuit senses an evoked compound action potential (ECAP) signal triggered by the plurality of control pulses rather than the plurality of treatment pulses, wherein the plurality of control pulses are different from the plurality of treatment pulses; The stimulation level of the plurality of control pulses to achieve the stimulation threshold is determined based on at least one of the ECAP signals. The values ​​of stimulation parameters that at least partially define the plurality of treatment pulses for the electrical stimulation therapy are determined based on the stimulation level. as well as The stimulation generation circuit is controlled to deliver the electrical stimulation therapy to the patient according to the value of the stimulation parameter.

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