ECAP sensing for high frequency nerve stimulation

Abstract

Techniques are disclosed for enabling adaptive adjustment of parameters of high frequency electrical stimulation using electrically evoked compound action potential (ECAP). In one example, a medical device delivers an electrical stimulation therapy including a train of electrical stimulation pulses to a patient, where the train of electrical stimulation pulses includes a pulse frequency greater than or equal to 500 Hertz. After delivering the electrical stimulation pulse train, the medical device stops delivery of the high frequency electrical stimulation therapy for a predetermined period of time. During the predetermined time period, the medical device senses ECAP from the patient and determines a value of a parameter that at least partially defines the electrical stimulation pulse train based on the sensed ECAP. In response to the elapsed predetermined period of time, the medical device resumes delivery of the high frequency electrical stimulation in accordance with the determined parameter.

Description

[0001] This application is a divisional application of PCT international application number PCT / US2020 / 055652, international application date October 15, 2020, and Chinese national phase application number 202080082411.3, entitled "ECAP sensing for high-frequency neural stimulation". Technical Field

[0002] This disclosure generally relates to medical treatments, and more specifically to electrical stimulation therapy. Background Technology

[0003] Medical devices, including implantable medical devices (IMDs), can be used to treat a variety of medical conditions. For example, a medical electrical stimulation device can deliver electrical stimulation therapy to a patient via external and / or implanted electrodes. Electrical stimulation therapy may include stimulating nerve tissue, muscle tissue, the brain, the heart, or other tissues within the patient. In some examples, the electrical stimulation device is fully implanted within the patient. For example, an implantable electrical stimulation device may include an implantable electrical stimulation generator and one or more implantable leads with electrodes. Alternatively, the electrical stimulation device may include a leadless stimulator. In some cases, the implanted electrodes may be coupled to an external electrical stimulation generator via one or more percutaneous leads or a fully implanted lead with a percutaneous lead extension.

[0004] Medical electrical stimulators have been proposed for the relief of a variety of symptoms or conditions, such as chronic pain, tremor, Parkinson's disease, depression, epilepsy, migraine, urinary or fecal incontinence, pelvic pain, sexual dysfunction, obesity, and gastroparesis. The stimulator can be configured to deliver electrical stimulation therapy via leads comprising electrodes that can be implanted near the patient's spinal cord, pelvic nerves, gastrointestinal organs, sacral nerves, peripheral nerves, or within the patient's brain. 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. Summary of the Invention

[0005] Generally, this disclosure describes techniques for adaptively adjusting parameters of defined high-frequency electrical stimulation pulses using electrically evoked compound action potentials (ECAPs). The amplitude titration of a low-frequency spinal nerve stimulation (SCS) system can be controlled using characteristic values ​​of the sensed ECAPs to maintain a desired level of sensory abnormality in the patient. Low-frequency stimulation systems typically deliver stimulation pulses with a pulse frequency less than 500 Hz. However, patients using low-frequency systems may experience inconsistent or uneven sensations due to slight deviations in the distance between the stimulation electrodes and the spinal cord.

[0006] High-frequency stimulation typically involves delivering stimulation pulses with a frequency greater than or equal to 500 Hz. Compared to low-frequency stimulation, high-frequency stimulation may employ different mechanisms of action for therapeutic delivery to the patient. ECAP feedback can still be used to control parameters of high-frequency stimulation. However, high-frequency stimulation pulses may mask the ECAP signal, thus hindering the detection of the ECAP signal from the target nerve. Therefore, techniques used to incorporate ECAP feedback to control low-frequency stimulation parameters may be ineffective for deployment in high-frequency stimulation systems.

[0007] The systems, apparatuses, and techniques disclosed herein provide high-frequency stimulation, which may also employ ECAP to adaptively adjust parameters defining the high-frequency electrical stimulation (e.g., stimulation with a pulse frequency greater than or equal to 500 Hz). In one example, the medical device delivers high-frequency stimulation in the form of a series of electrical stimulation pulses, with pauses in the high-frequency electrical stimulation between each series. By temporarily pausing the high-frequency stimulation for a predetermined amount of time, the medical device can sense an ECAP response from the target nerve during this amount of time without interference from the delivered pulses. In this way, the medical device can use the sensed ECAP to adjust the values ​​of one or more parameters defining the high-frequency stimulation (e.g., for subsequent pulses). In some examples, the last pulse in a series differs from the previous pulses in the series and is configured to elicit a detectable ECAP. Additionally or alternatively, the medical device may deliver low-frequency electrical stimulation during the pauses in the high-frequency stimulation. One or more pulses of low-frequency stimulation may elicit a detectable ECAP signal and / or maintain therapeutic efficacy in the patient during the pauses.

[0008] Therefore, by using the techniques described herein, a medical device can pause the delivery of high-frequency electrical stimulation to allow time for the device to detect an ECAP signal that can be used to modulate the high-frequency electrical stimulation. During pulse delivery, the ECAP signal may otherwise be undetectable because the large amplitude of the delivered pulses from the high-frequency electrical stimulation can mask it. Furthermore, the medical device described herein can deliver low-frequency electrical stimulation while pausing high-frequency electrical stimulation and sensing the ECAP signal resulting from one or more pulses of low-frequency stimulation, thereby maintaining therapeutic efficacy for the patient while sensing the ECAP. The medical device described herein can deliver sufficient pulses for high-frequency electrical stimulation while also detecting the patient's ECAP response during brief pauses in pulse delivery, thereby allowing the titration of one or more parameters defining the pulses for high-frequency electrical stimulation therapy to be controlled using the characteristics of the sensed ECAP.

[0009] In one example, this disclosure describes a method comprising: delivering an electrical stimulation therapy comprising a first electrical stimulation pulse train to a patient via a medical device, wherein the first electrical stimulation pulse train comprises a first pulse frequency greater than or equal to 500 Hz; after delivery of the first electrical stimulation pulse train, stopping delivery of the electrical stimulation therapy via the medical device for a predetermined time period; during the predetermined time period, sensing an evoked compound action potential (ECAP) signal from the patient's tissue via the medical device; determining, via the medical device and based on characteristic values ​​of the ECAP signal, a value of at least one parameter that at least partially defines a second electrical stimulation pulse train, wherein the second electrical stimulation pulse train comprises a second pulse frequency greater than or equal to 500 Hz; and, in response to the elapsed predetermined time period, delivering the second electrical stimulation pulse train according to the value of the at least one parameter that at least partially defines the second set of pulses.

[0010] In another example, this disclosure describes a medical device configured to: deliver to a patient an electrical stimulation therapy comprising a first electrical stimulation pulse train, wherein the first electrical stimulation pulse train comprises a first pulse frequency greater than or equal to 500 Hz; after delivery of the first electrical stimulation pulse train, stop delivery of the electrical stimulation therapy for a predetermined time period; during the predetermined time period, sense an evoked compound action potential (ECAP) signal from the patient's tissue; determine, based on characteristic values ​​of the ECAP signal, the value of at least one parameter that at least partially defines a second electrical stimulation pulse train, wherein the second electrical stimulation pulse train comprises a second pulse frequency greater than or equal to 500 Hz; and in response to the elapsed predetermined time period, deliver the second electrical stimulation pulse train according to the value of the at least one parameter that at least partially defines the second set of pulses.

[0011] In another example, this disclosure describes a non-transitory computer-readable medium comprising instructions configured, when executed, to cause processing circuitry of an implantable medical device to: control a stimulator of the implantable medical device to deliver electrical stimulation therapy to a patient, comprising a first electrical stimulation pulse train, wherein the first electrical stimulation pulse train comprises a first pulse frequency greater than or equal to 500 Hz; after delivery of the first electrical stimulation pulse train, control the stimulator to stop delivery of the electrical stimulation therapy for a predetermined time period; during the predetermined time period, sense an evoked compound action potential (ECAP) signal from the patient's tissue; determine, based on characteristic values ​​of the ECAP signal, the value of at least one parameter that at least partially defines a second electrical stimulation pulse train, wherein the second electrical stimulation pulse train comprises a second pulse frequency greater than or equal to 500 Hz; and in response to the elapsed predetermined time period, control the stimulator to deliver the second electrical stimulation pulse train according to the value of the at least one parameter that at least partially defines the second set of pulses.

[0012] Details of one or more examples of the technology disclosed herein are set forth in the accompanying drawings and the following description. Other features, objectives, and advantages of these technologies will be apparent from the specification, drawings, and claims. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating an exemplary implantable stimulation system comprising a pair of implantable stimulation electrode arrays carried by implantable leads.

[0014] Figure 2 It shows IMD (such as Figure 1 The diagram shows a functional block diagram of an exemplary component of an IMD (Integrated Device Diagram).

[0015] Figure 3 This shows an external programmer (such as) for IMD. Figure 1 The diagram shows a functional block diagram of exemplary components of an external programmer and an IMD.

[0016] Figure 4A , 4B Figures 4 and 4C are diagrams illustrating exemplary electrical stimulation pulse trains according to the technology of this disclosure.

[0017] Figure 5 This is a diagram illustrating an exemplary electrical stimulation pulse train according to the technology of this disclosure and the signals sensed from the patient's response.

[0018] Figure 6 This is a flowchart illustrating the operation of the technology according to this disclosure.

[0019] In all the accompanying drawings and descriptions, similar reference numerals refer to similar elements. Detailed Implementation

[0020] This disclosure includes systems, apparatus, and methods relating to adjusting electrical stimulation parameter values ​​for high-frequency electrical stimulation delivered to a patient. In therapeutic or interventional applications, patients may receive electrical stimulation to relieve a variety of symptoms or conditions. In some cases, physicians or clinicians may manually adjust the electrical stimulation parameters based on patient feedback, such as the patient's perception of a reduction in pain levels or any changes in symptoms. However, patient feedback can be inconsistent and subjective over time. In this way, it may be difficult to determine the most appropriate stimulation parameters to relieve a patient's symptoms or conditions and provide improved system performance (e.g., efficient energy utilization and targeted therapeutic delivery).

[0021] In the past, spinal cord stimulation (SCS) for patients consisted of low-frequency, periodic electrical pulses delivered to the patient's dorsal column for the purpose of inducing sensory abnormalities. As described herein, "low-frequency electrical stimulation" refers to electrical stimulation involving pulse frequencies less than 500 Hz, which typically induces sensory abnormalities in the patient. Sensory abnormalities are used to mask pain felt in specific areas of the body, such as the lower back or legs. Sensory signals, in this case, either the periodic electrical pulses from the spinal cord stimulator or the pain signal itself, are relayed to the brain via the dorsal column of the spinal cord. The dorsal column is composed of various types of sensory nerve fibers, typically classified by fiber thickness and their associated signal propagation velocity. Very thick (13–20 µm) Aα fibers have an action potential propagation velocity of approximately 100 m / s and are associated with proprioception. Thick-diameter (6–12 µm) Aβ fibers are heavily myelinated and have an action potential propagation velocity approaching 60 m / s. Sensory abnormalities induced using SCS are thought to be caused by modulation of Aβ fibers. Thin-diameter (2-5 µm), myelinated Aδ fibers have an action potential propagation speed of approximately 10 m / s. Unmyelinated C fibers (0.2 µm – 1.5 µm) transmit signals at 2 m / s. Both Aδ and C fibers are responsible for transmitting pain signals to the brain, with Aδ and C fibers contributing to the characteristics of intense and burning pain, respectively.

[0022] Many factors can affect signal propagation along the spinal cord. Examples include certain chemical factors, disease states, or the presence or absence of electrical stimulation. In some cases, it is desirable to adjust treatment interventions for patients based on measured characteristics of spinal cord signal propagation. One approach to addressing these factors, which may change over time, involves detecting ECAP signals. In various examples, electrical stimulation is applied to the patient's spinal cord at a specific location, and the resulting ECAP can be detected and recorded. The sensing and measurement of these ECAP signals are not limited to the spinal cord and can also be recorded at other locations besides the spinal cord, such as in the peripheral nerves, or, for example, from within the brain.

[0023] Given these factors, additional parameters used to deliver SCS treatments that differ from historically applied SCS treatments can provide efficacy in the treatment of specific patients. For example, SCS systems that deliver stimulation at high frequencies utilize pulse frequencies much faster than conventional SCS treatments delivered at, for example, 50 Hz. As described herein, “high-frequency electrical stimulation” refers to electrical stimulation comprising pulse frequencies greater than or equal to 500 Hz. A definite advantage of applying high-frequency electrical stimulation therapy is that patients have reported reduced or eliminated pain and the absence of associated sensory abnormalities typically experienced when using low-frequency SCS therapy. However, at least one disadvantage of these high-frequency pulses is that the high-frequency pulse train delivered to the patient may mask any ECAP signal. Therefore, when a medical device delivers high-frequency electrical stimulation to a patient, the medical device may be unable to detect ECAP, thus preventing the medical device from using the ECAP response to titrate the values ​​of one or more parameters defining the pulses of the high-frequency electrical stimulation.

[0024] As discussed herein, systems, apparatus, and methods for adjusting one or more parameters of high-frequency electrical stimulation based on detected ECAPs are described. ECAPs can be induced in response to the application of one or more electrical stimulation pulses defined according to a set of stimulation parameters. Adjusting electrical stimulation parameters based on detected ECAPs can provide more objective information than patient feedback. Furthermore, ECAP detection allows the system to provide closed-loop stimulation control. Incorporating ECAPs into the adjustment and / or titration of stimulation parameters, compared to techniques without ECAP detection, enables the stimulation system to provide stimulation therapy using less energy, improved patient perception of stimulation, more targeted stimulation delivery to desired tissues, and / or improved therapeutic efficacy. In some examples, dorsal column stimulation therapy (e.g., a type of spinal cord stimulation) or other electrical stimulation therapy is provided according to a treatment procedure defining values ​​for stimulation parameters such as current or voltage amplitude, pulse frequency, pulse width, burst frequency, and / or pulse shape, which are selected to provide a level of therapy, such as a reduction or elimination of pain perceived by the patient. In some examples, spinal cord stimulation may also include stimulation of the dorsal nerve roots. Furthermore, stimulation is not limited to spinal cord stimulation and can be applied to peripheral nerves or their terminal organs. In addition, peripheral stimulators need not be implantable devices, and they may also include non-electrical stimulation (e.g., mechanical, thermal).

[0025] The techniques, systems, and apparatuses disclosed herein can provide high-frequency stimulation using ECAP to adaptively adjust parameters defining high-frequency electrical stimulation (e.g., stimulation with a pulse frequency greater than or equal to 500 Hz). In one example, the medical device delivers high-frequency stimulation in the form of a series of electrical stimulation pulses, with pauses in the high-frequency electrical stimulation between each series. By temporarily pausing the high-frequency stimulation for a predetermined amount of time, the medical device can sense an ECAP response from the target nerve during this amount of time, thereby allowing the medical device to use the sensed ECAP to adjust the values ​​of one or more parameters defining the pulses of the high-frequency stimulation. In some examples, the medical device uses the last pulse in the series, which is different from the other pulses in the series and is configured to elicit a detectable ECAP. Additionally or alternatively, the medical device can deliver low-frequency electrical stimulation (e.g., one or more pulses) during the pauses in the high-frequency stimulation to elicit an ECAP response and / or maintain therapeutic efficacy for the patient during the pauses. Therefore, by using the techniques described herein, a medical device can be enabled to deliver high-frequency electrical stimulation and sense an ECAP response during the pauses in the high-frequency stimulation, allowing the device to use the ECAP signal as feedback to adjust one or more parameters of the high-frequency electrical stimulation for subsequent delivery. Without this pause during the delivery of high-frequency electrical stimulation, the ECAP signal may be undetectable and unusable for feedback.

[0026] Compared to patient feedback, detected ECAP provides more objective information for adjusting parameter values ​​that define subsequent high-frequency stimulation pulses. Furthermore, the techniques described herein enable devices to employ ECAP detection as closed-loop control of a system delivering high-frequency electrical stimulation. By incorporating ECAP signal detection into feedback for adjusting stimulation parameters and / or titrating, medical devices can deliver high-frequency electrical stimulation compared to techniques without ECAP detection, resulting in more targeted stimulation delivery to the desired tissue, improved therapeutic efficacy, and / or less power consumption. Electrosensing systems, such as those within implantable medical devices or electrically connected to such devices, can perform the ECAP detection described herein. The sensing system may include one or more electrodes positioned at a distance from the site of application of electrical stimulation.

[0027] In some examples, the detection or non-detection of the presence of an ECAP in response to stimulation provided with a specific set of treatment parameters is used to program the initial stimulation treatment parameters provided to the patient via an implantable medical device. In other examples, the detection of an ECAP in response to stimulation provided with a specific set of treatment parameters can be used to automatically adjust existing stimulation treatment parameters. The presence or absence of an ECAP or the characteristic value of an ECAP in response to a set of stimulation treatment parameters can be used to control the programming and adjustment of parameters for high-frequency electrical stimulation.

[0028] For example, an IMD (or other medical device) may begin providing stimulation based on an initial set of treatment parameters, such as a relatively high frequency, like 15 kHz. The IMD detects the ECAP signal generated by one or more nerve fibers due to the applied stimulation and compares the characteristic values ​​of the ECAP signal with the target characteristic values ​​of the ECAP. Based on the comparison, the IMD may adjust one or more parameters of the stimulation therapy to reduce the difference between the characteristic values ​​of the ECAP signal and the target characteristic values ​​of the ECAP. For example, the IMD may reduce the amplitude and / or pulse frequency of the applied stimulation pulse to generate a new set of treatment parameters for subsequent treatment. The IMD may then apply the new stimulation therapy to the patient, sense the resulting ECAP generated as a result of the new treatment application, and may further generate a new set of treatment parameters for use in the treatment according to this closed-loop control scheme.

[0029] In some examples, a given stimulation therapy may be applied to a patient, and the resulting ECAP signal may be sensed and analyzed to determine whether the patient's response to the same specific set of stimulation parameters has changed. In some examples, ECAP signal detection in response to the current stimulation therapy procedure may be performed continuously. For example, ECAP signals may be detected every few seconds, once a minute, once every few minutes, once an hour, once a day, or once a week. In some examples, the medical device may trigger and detect ECAP signals in response to a change in another sensed physiological parameter. For example, when there is a change in the patient's activity level or posture that indicates a change in the value of one or more parameters that should be altered (e.g., because the electrode may have moved relative to the target nerve), the medical device may pause high-frequency stimulation to detect an ECAP signal. These changes in the patient's activity level and / or posture may be sensed and / or determined by the same device that provides the stimulation therapy to the patient or by a device that is not the same device that provides the stimulation therapy to the patient.

[0030] As used herein, "patient" generally refers to a human patient, but is not limited to humans and may include animals. Various references to "test patient" as used herein may include animals used to receive test stimulus patterns and to collect data related to stimulus tests according to the various techniques described herein.

[0031] Figure 1This is a schematic diagram illustrating an exemplary implantable stimulation system 10, which includes a pair of implantable electrode arrays in the form of stimulation leads 16A and 16B. While the techniques described in this disclosure are generally applicable to a variety of medical devices, including external and implantable medical devices (IMDs), for illustrative purposes, the application of such techniques to IMDs will be described, and more specifically, to implantable electrical stimulators, such as neurostimulators. More specifically, for illustrative purposes, this disclosure relates to implantable spinal cord stimulation (SCS) systems, but is not limited thereto, and also relates to other types of medical devices.

[0032] like Figure 1 As shown, system 10 includes an IMD 14 and an external programmer 20, which are shown in conjunction with patient 12. Figure 1 In the example, IMD 14 is an implantable electrical stimulator configured for spinal cord stimulation (SCS), for example, to relieve chronic pain or other symptoms. Similarly, although... Figure 1 An implantable medical device is shown, but other embodiments may include an external stimulator, such as an implantable lead with a percutaneous implantation or an implantable lead with a percutaneous lead extension. Stimulation energy is delivered from the IMD 14 to the spinal cord 18 of the patient 12 via one or more electrodes disposed on implantable leads 16A and 16B (collectively, “leads 16”). In some applications, such as spinal cord stimulation (SCS) for the treatment of chronic pain, adjacent implantable leads 16 may have longitudinal axes that are substantially parallel to each other.

[0033] although Figure 1 While involving SCS treatment, system 10 may alternatively target any other condition that may benefit from stimulation therapy. For example, system 10 may be used to deliver stimulation to one or more tissues to treat tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis. In this manner, system 10 may be configured to provide treatment using deep brain stimulation (DBS), pelvic floor stimulation, gastric stimulation, or any other form of stimulation therapy. Furthermore, patient 12 is typically a human patient.

[0034] Each of the leads 16 may include an electrode, and parameters of the procedure for controlling the delivery of stimulation therapy via the IMD 14 may include information identifying which electrodes have been selected to deliver stimulation according to the stimulation procedure, the polarity of the selected electrodes (i.e., the electrode configuration for the procedure), and the voltage or current amplitude, pulse rate, and pulse width of the stimulation delivered by the electrodes. For illustrative purposes, the delivery of stimulation pulses will be described. However, stimulation may be delivered in other forms, such as continuous waveforms. Procedures for controlling the delivery of other treatments via the IMD 14 may include other parameters, such as the dose, rate, etc., for drug delivery.

[0035] exist Figure 1In one example, lead 16 carries one or more electrodes placed adjacent to target tissue of the spinal cord. The one or more electrodes may be positioned at the distal end of lead 16 and / or at other locations along the midpoint of the lead. Lead 16 may be implanted and coupled to IMD 14. Alternatively, as described above, lead 16 may be implanted and coupled to an external stimulator, e.g., via a percutaneous port. In some cases, the external stimulator may be a trial or screening stimulator used temporarily to assess potential efficacy to aid in consideration of chronic implantation for a patient. In another embodiment, IMD 14 may be a leadless stimulator having one or more electrode arrays disposed on the housing of the stimulator, instead of leads extending from the housing.

[0036] The stimulation can be delivered via a selected combination of electrodes carried by one or two of the leads 16, for example, in a bipolar, unipolar, or multipolar combination. The target tissue can be any tissue affected by electrical stimulation energy, such as electrical stimulation pulses or waveforms. Such tissues include nerves, smooth muscle, and skeletal muscle. Figure 1 In the example shown, the target tissue is the spinal cord 18. For example, stimulating the spinal cord 18 can prevent pain signals from traveling through the spinal cord and reaching the patient's brain. The patient 12 can perceive the interruption of the pain signals as a reduction in pain, and therefore as an effective treatment outcome.

[0037] The deployment of electrodes via lead 16 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 carry electrode arrays, such as rows and / or columns (or other patterns), to which multiplexing operations can be applied. Such electrodes can be arranged as surface electrodes, ring electrodes, or protrusions. As an alternative, the electrode array can be formed by rows and / or columns of electrodes on one or more paddle-shaped leads. In some embodiments, the electrode array may include electrode segments arranged at corresponding locations around the periphery of the leads, for example, in the form of one or more segmented rings arranged around the circumference of a cylindrical lead. Other electrode and lead configurations may be adapted for use with this disclosure, provided they enable the IMD 14 to electrically stimulate and sense target tissue therein.

[0038] exist Figure 1In the example, stimulation energy is delivered by IMD 14 to the spinal cord 18 to reduce the amount of pain perceived by the patient 12. As described above, IMD 14 can be used with a variety of different pain treatments, such as peripheral nerve stimulation (PNS), peripheral nerve field stimulation (PNFS), DBS, cortical stimulation (CS), sacral nerve modulation (SNM), pelvic floor stimulation, gastric stimulation, etc. The electrical stimulation delivered by IMD 14 can take the form of electrical stimulation pulses or continuous stimulation waveforms and can be characterized by controlled voltage levels or controlled current levels, as well as pulse width and pulse rate (i.e., pulse frequency) (in the case of stimulation pulses).

[0039] In some examples, the IMD 14 can deliver stimulation therapy according to one or more procedures. A procedure defines one or more parameters that define one aspect of the therapy delivered by the IMD 14 according to the procedure. For example, a procedure controlling the IMD 14 to deliver stimulation in pulse form can define the voltage or current pulse amplitude, pulse width, and pulse rate of the stimulation pulses delivered by the IMD 14 according to the procedure. The procedure can also define the electrode combination used to deliver the stimulation pulses, including electrode polarity. Furthermore, therapy can be delivered according to multiple procedures, wherein multiple procedures are contained within each of multiple groups.

[0040] During treatment of patient 12 using the IMD 14, movement of patient 12 between different postural states may affect the IMD 14's ability to deliver consistent, effective, or optimal sensory therapy. For example, when patient 12 bends over, lead 16 may migrate toward the IMD 14, causing electrode displacement and potentially disrupting the delivery of effective therapy. The stimulation energy delivered to the target tissue may decrease due to electrode movement, resulting in reduced efficacy in relieving symptoms such as pain. Similarly, when patient 12 lies down, lead 16 may be compressed toward the spinal cord 18. This compression may lead to an increase in the amount of stimulation energy delivered to the target tissue. In this case, the amplitude of the stimulation therapy may be reduced to avoid causing additional pain or unusual sensations to patient 12, which may be considered adverse side effects detrimental to overall efficacy.

[0041] Additionally, changes in postural state may manifest as changes in symptoms or symptom levels (e.g., pain levels). Due to changes in posture and / or activity levels associated with the patient's postural state, efficacy may be reduced due to increased or decreased coupling of stimulus energy to the target tissue. To avoid or minimize potential disruption to effective treatment caused by changes in postural state, the IMD 14 may include a posture state module that detects the patient's postural state and automatically detects an ECAP signal in response to changes in postural state. Based on the detected ECAP signal, the IMD 14 determines whether adjustments to stimulus parameters are recommended or otherwise appropriate. For example, the posture state module may include a posture state sensor, such as an accelerometer, that detects when the patient 12 lies down, stands, or otherwise changes posture. In some examples, the postural state detected by the posture state sensor may include activity levels, in addition to the patient's posture.

[0042] The posture state module may include, for example, one or more accelerometers that detect when the patient 12 adopts a posture state that may be suitable for reducing the stimulus amplitude, such as when the patient 12 lies down. In some examples, the IMD may automatically reduce the stimulus amplitude so that the patient 12 does not have to do so manually. The IMD may then detect an ECAP signal in response to the adjusted stimulus parameters to determine whether the adjustment is effective. In other examples, the IMD may detect an ECAP signal in response to a stimulus when a change in posture is detected before adjustments are made to the stimulus parameters. The IMD 14 may analyze the detected ECAP signal to determine one or more characteristic values ​​of the ECAP signal (e.g., the amplitude of one or more peaks of the detected ECAP or the area under the curve of one or more peaks of the ECAP), and then determine an appropriate adjustment to one or more values ​​of the stimulus parameters. Exemplary posture states may include “upright,” “upright and active,” “lying down,” etc.

[0043] As will be described in more detail below, in some examples, IMD 14 may be configured to automatically adjust the stimulation amplitude when a change in position of patient 12 is detected. In some examples, in response to the detection of a position change, IMD 14 determines an appropriate adjustment to the stimulation parameters. In some examples, the determination may include detecting an ECAP signal based on the current stimulation parameters and adjusting one or more stimulation parameters based on determined characteristic values ​​of the detected ECAP signal. In other examples, IMD 14 may select a new set of stimulation parameters stored in memory based on previously detected ECAPs at the same location.

[0044] In some examples, the stimulation parameters may be configured to change at a rate suitable for preventing adverse effects, such as those caused by compression of the lead 16 toward the spinal cord 18 when the patient 12 lies down. In some examples, the IMD 14 may be configured to reduce the stimulation amplitude to a first predetermined lower amplitude value substantially immediately upon detection by the IMD 14 of the patient 12 lying down. The IMD 14 may then assess the appropriateness of the new stimulation amplitude based on the ECAP and make further adjustments as needed. In other examples, the IMD 14 may be configured to detect the ECAP signal of the stimulus upon detection of the patient 12 lying down. Based on the detected ECAP signal, the IMD 14 may adjust one or more stimulation parameters until the desired characteristics of the detected ECAP signal are achieved.

[0045] In response to a posture state indication from the posture state module, the IMD 14 can modify program groups, programs, stimulus amplitude, pulse width, pulse rate, and / or one or more other parameters, groups, or programs to maintain therapeutic efficacy. For example, when the patient lies down, the IMD 14 can automatically reduce the stimulus amplitude so that the patient 12 does not need to manually reduce the stimulus amplitude. The amount of automatic reduction can be determined at least in part based on the characteristic values ​​of the ECAP signal detected in the new posture state. In some cases, the IMD 14 can communicate with an external programmer 20 to provide proposed stimulus changes in response to a change in posture state, such as from a first posture state to a second posture state, and to receive approval or rejection of the change from a user (such as the patient 12 or a clinician) before automatically applying the therapeutic change. In some examples, posture state detection can also be used to provide notifications, such as notifying caregivers via a wireless link that a patient may be experiencing a fall.

[0046] In some examples, IMD 14 can periodically detect ECAPs generated in response to current stimulation parameters, and adjust the current stimulation parameters if the characteristic value of the detected ECAP signal changes significantly relative to the target ECAP characteristic value, i.e., the change is greater than a predetermined threshold. For example, IMD 14 can detect and analyze ECAPs hourly, daily, weekly, or monthly. In some examples, IMD 14 can initiate an ECAP signal detection and analysis cycle if a predetermined amount of time has elapsed since the last ECAP detection. IMD 14 can reset this time in response to the detection of an ECAP signal. In some examples, IMD 14 can adjust the rate of ECAP detection based on the patient's posture or in response to changes in the patient's posture. For example, in response to the detection that the patient has changed posture, IMD 14 can increase or decrease the rate of ECAP detection.

[0047] Users (such as clinicians or patients 12) can interact with the user interface of external programmer 20 to program IMD 14. The user interface may include output devices for information presentation and input devices for receiving user input. Programming IMD 14 typically refers to the generation and transmission of commands, programs, or other information to control the operation of IMD 14. For example, external programmer 20 may transmit programs, parameter adjustments, program selections, group selections, or other information to control the operation of IMD 14, such as via wireless telemetry. For example, external programmer 20 may transmit parameter adjustments to support treatment changes caused by changes in the posture of patient 12. As another example, the user may select a program or a group of programs. Similarly, a program can be characterized by electrode combinations, electrode polarity, voltage or current amplitude, pulse width, pulse rate, and / or duration. A group of programs can be characterized by multiple programs delivered simultaneously or in an interleaved or alternating manner.

[0048] During the delivery of stimulation therapy, patient 12 can make patient treatment adjustments, i.e., adjust one or more parameters of the treatment via the input device of the programmer's user interface to customize the treatment after patient 12 moves to a different postural state or when the next postural state is anticipated. As described in more detail below, IMD 14 can detect ECAP in response to treatment adjustments. In some examples, the detected ECAP in response to the adjusted treatment can be stored as an indication of effective treatment for a specific patient state. If the same patient state is detected again, IMD 14 can automatically adjust one or more stimulation parameters to achieve an ECAP feature value corresponding to the stored target ECAP feature value. In an example where IMD 14 is in recording mode to store all patient treatment adjustments associated with a specific patient state, IMD 14 can implement a method to ensure that the patient treatment adjustment is associated with the correct patient state expected by patient 12 when it is made. Patient 12 can adopt the patient state multiple times, resulting in multiple instances of the sensed patient state. For example, the patient state can be a posture or activity level. In some examples, the patient can type one or more treatment adjustments each time patient 12 adopts a postural state.

[0049] In some cases, if the external programmer 20 is primarily intended for use by a physician or clinician, it may be characterized as a physician or clinician programmer. In other cases, if the external programmer 20 is primarily intended for use by a patient, such as for entering patient input to specify patient adjustments to one or more treatment parameters, it may be characterized as a patient programmer. The patient programmer is typically accessible to the patient 12 and, in many cases, may be a portable device that accompanies the patient throughout their daily life. Typically, a physician or clinician programmer allows for the selection and generation of programs by a clinician for use by the stimulator 14, while a patient programmer allows for the adjustment and selection of such programs by the patient manually or via other user input media during routine use.

[0050] The IMD 14 may be constructed with a biocompatible shell, such as titanium or stainless steel, or a polymeric material (such as silicone or polyurethane), and surgically implanted in a location near the pelvis of patient 12. The IMD 14 may also be implanted in patient 12 in a location least noticeable to patient 12. Alternatively, the IMD 14 may be external, with a percutaneously implantable lead. For SCS, the IMD 14 may be located in the lower abdomen, lower back, upper buttock, or other locations used to secure the IMD 14. The lead 16 may tunnel from the IMD 14 through tissue to reach target tissue adjacent to the spinal cord 18 for stimulation delivery.

[0051] At the distal end of lead 16 are one or more electrodes that deliver electrical stimulation from the lead to the tissue. The electrodes may be electrode pads on a paddle-shaped lead, circular (e.g., annular) electrodes surrounding the body of lead 16, conformal electrodes, cuff electrodes, segmented electrodes (e.g., partially annular electrodes positioned at different circumferential locations around the periphery of the lead), or any other type of electrode capable of forming a unipolar, bipolar, or multipolar electrode configuration for therapeutic purposes. The electrodes may be directly punctured or attached to the tissue itself. Typically, for illustrative purposes, annular electrodes positioned at different axial locations at the distal end of lead 16 will be described.

[0052] One or more characteristics of the ECAP are used to control the titration of the amplitude of the low-frequency SCS system in order to maintain even paresthesia in the patient. Low-frequency stimulation typically involves stimulation pulses with a pulse frequency of less than 500 Hz. However, patients using low-frequency stimulation may experience inconsistent or uneven sensations due to slight offsets of the stimulating electrodes relative to the spinal cord. High-frequency stimulation typically involves stimulation pulses with a pulse frequency greater than or equal to 500 Hz. High-frequency stimulation may potentially employ other mechanisms of action, allowing the patient to experience a reduction in pain rather than paresthesia (or a lower level of paresthesia). The efficacy of high-frequency stimulation may also change with patient movement. However, high-frequency stimulation pulses may be delivered too frequently, causing the presence of these pulses to mask the ECAP signal, thereby hindering the detection of the ECAP signal from the target nerve. Therefore, techniques for incorporating ECAP feedback to control or modulate high-frequency stimulation pulses (and, in some examples, low-frequency stimulation parameters) may include pausing for a predetermined period of time during the delivery of high-frequency stimulation to detect at least one ECAP signal.

[0053] According to the technology disclosed herein, the IMD 14 can adaptively determine (e.g., set or adjust) the parameters of high-frequency electrical stimulation using ECAP. In one example, the IMD 14 delivers high-frequency stimulation in the form of a series of electrical stimulation pulses, with pauses in the high-frequency electrical stimulation between each series. By temporarily pausing the high-frequency stimulation for a predetermined amount of time, the IMD 14 can sense ECAP signals from one or more target nerves of the patient 12 during this amount of time without interference from the high-frequency stimulation. Therefore, the IMD 14 can use the sensed ECAP to adjust the parameters of the high-frequency stimulation. In some examples, the IMD 14 delivers the last pulse of the series (e.g., the main pulse) to elicit a detectable ECAP, wherein the last pulse is distinct from previous pulses (e.g., the primary pulse) within the same series. Additionally or alternatively, the IMD 14 can deliver low-frequency electrical stimulation during the pauses in the high-frequency stimulation to elicit an ECAP response during the pauses and / or maintain therapeutic efficacy for the patient.

[0054] Therefore, by using the techniques described herein, IMD 14 can pause the delivery of high-frequency electrical stimulation to allow time for IMD 14 to detect the ECAP response to the high-frequency electrical stimulation, which would otherwise be undetectable by other systems delivering continuous high-frequency electrical stimulation. Furthermore, the medical device described herein can deliver low-frequency electrical stimulation while pausing high-frequency electrical stimulation and sensing the ECAP, thereby maintaining the therapeutic efficacy for patient 12 while sensing the ECAP. Thus, the medical device described herein can prevent one or more high-frequency electrical stimulation pulses from masking the patient's ECAP signal, thereby allowing the sensed ECAP to be used as a control signal for titrating one or more parameters of high-frequency electrical stimulation therapy.

[0055] Figure 2 This is a functional block diagram showing the various components of the IMD 14. Figure 2 In this example, IMD 14 includes processing circuitry 80, memory 82, switching circuitry 83, stimulation generator 84, posture status module 86, telemetry circuitry 88, power source 90, and sensing circuitry 92. Stimulation generator 84 may form a treatment delivery module. Processing circuitry 83 may control switching circuitry 83, which switches signals to and / or from lead 16 to sensing circuitry 92 and / or stimulation generator 84. Memory 82 may store instructions to be executed by processing circuitry 80, stimulation treatment data, ECAP characteristic values, posture status information, posture status indications, and any other information regarding treatment or patient 12. Treatment information may be recorded for long-term storage and retrieval by the user, and treatment information may include any data created by or stored in IMD 14. Memory 82 may include a separate memory for storing instructions (including instructions for ECAP analysis), posture status information, treatment adjustment information, previously detected ECAP signals and / or ECAP characteristic values, program history, and any other relevant data or instructions.

[0056] Processing circuitry 80 controls stimulation generator 84 to deliver electrical stimulation via electrode combinations formed by electrodes in one or more electrode arrays. For example, stimulation generator 84 may deliver therapeutic electrical stimulation via electrodes on one or more leads 16 (e.g., electrodes 94A-94D and 96A-86D of corresponding leads 16A and 16B), such as stimulation pulses or continuous waveforms. Components described as processing circuitry within IMD 14, external programmer 20, or any other device described in this disclosure may each include one or more processors, individually or in any suitable combination, such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), programmable logic circuits, etc.

[0057] The stimulation generator 84 may include stimulation generation circuitry for generating stimulation pulses or waveforms and switching circuitry for switching stimulation between different electrode combinations, for example, in response to control of the processing circuitry 80. Specifically, the processing circuitry 80 may selectively control the switching circuitry such that the stimulation generator 84 delivers electrical stimulation to selected electrode combinations and deflects the electrical stimulation to different electrode combinations in a first or second direction when treatment must be delivered to different locations within the patient 12. In other examples, the stimulation generator 84 may include multiple current sources and current sinks to drive more than one electrode combination at a time. For example, each electrode may have its own current source and current sink, which may be selectively activated such that the electrode can draw or sink a controlled amount of current. Electrode configurations, such as electrode combinations and associated electrode polarities, may be represented by data stored in memory locations, such as memory 82 in IMD 14. The processing circuitry 80 may access the memory locations to determine electrode combinations and control the stimulation generator 84 to deliver electrical stimulation through the indicated electrode combinations. To adjust the electrode combination, amplitude, pulse rate, or pulse width, processing circuitry 80 can instruct stimulation generator 84 to make appropriate changes to the treatment according to instructions stored in memory 82, and rewrite memory locations to indicate the modified treatment. In other examples, processing circuitry 80 may utilize two or more memory locations instead of rewriting a single memory location.

[0058] When stimulation is activated, the processing circuit 80 can access not only the memory location of the specified electrode combination, but also other memory locations specifying various stimulation parameters such as voltage or current amplitude, pulse width, and pulse rate. The stimulation generator 84, for example under the control of the processing circuit 80, then utilizes the electrode combination and parameters in formulating and delivering electrical stimulation to the patient 12.

[0059] According to the examples described herein, processing circuitry 80 may adjust such stimulation parameters to modify the stimulation therapy delivered by IMD 14 based on a detected ECAP signal of patient 12. In some examples, processing circuitry 80 may detect an ECAP signal of patient 12 indicating that modification of the stimulation therapy is appropriate via sensing circuitry 92, for example, according to instructions stored in memory 82. Processing circuitry 80 may access instructions for modifying the stimulation therapy based on the detected ECAP signal, for example, by changing the procedure from the current stimulation program to one that results in a desired characteristic value of ECAP (e.g., a characteristic value that achieves a target ECAP characteristic value).

[0060] According to other examples described herein, such stimulation parameters can be adjusted to modify the stimulation therapy delivered by IMD 14 based on a combination of the detected ECAP signal and the detected postural state. In some examples, processing circuitry 80 may detect the ECAP signal of patient 12 via sensing circuitry 92 and the postural state of patient 12 via postural state module 86. If a change in the ECAP signal (e.g., a change in ECAP characteristic value) has been detected, the detected postural state can be used to help processing circuitry 80 determine an appropriate stimulation program to achieve a target ECAP characteristic value. For example, memory 82 may include stimulation programs associated with detected postural states that have previously resulted in a target ECAP characteristic value.

[0061] Processing circuitry 80 accesses stimulation parameters in memory 82, such as programs and program groups. After selecting a specific program group, processing circuitry 80 can control stimulation generator 84 to deliver stimuli according to the programs in the group, for example, simultaneously or in a time-staggered manner. A group may include a single program or multiple programs. As previously described, each program may specify a set of stimulation parameters, such as amplitude, pulse width, and pulse rate. Furthermore, each program may specify a specific combination of electrodes for delivering the stimulation. Similarly, an electrode combination may specify specific electrodes in a single array or multiple arrays, such as specific electrodes on a single lead or between multiple leads. Processing circuitry 80 can also control telemetry circuitry 88 to send and receive information from an external programmer 20. For example, telemetry circuitry 88 may send information to and receive information from programmer 20.

[0062] In some examples, IMD 14 includes a posture state module 86, which allows IMD 14 to sense or detect the current patient posture state, such as the posture, activity, or any other static position or movement of patient 12. Figure 2 In one example, the posture state module 86 may include one or more accelerometers, such as a triaxial accelerometer, capable of detecting static orientation or vectors in three dimensions. The triaxial accelerometer may be a microelectromechanical accelerometer. In other examples, the posture state module 86 may optionally or additionally include one or more gyroscopes, pressure transducers, or other sensors to sense the current posture state adopted by the patient 12. The posture state information generated by the posture state module 86 and the processing circuitry 80 may correspond to the total level of activities and / or postures or physical activities performed by the patient 12 (e.g., activity counts based on footsteps).

[0063] Posture status information from posture status module 86 can be stored in memory 82 for later review by clinicians for adjusting treatment, presenting posture status indications to patient 12 and / or clinicians, for example, via a user interface display of external programmer 20, or some combination thereof. For example, processing circuitry 80 can record posture status parameter values ​​or outputs from a 3-axis accelerometer and assign these values ​​to specific predefined postures indicated by them. In this way, IMD 14 can track how frequently patient 12 remains in a particular posture state. When patient 12 is in a sensed posture state, IMD 14 can also store which group or procedure is being used to deliver treatment. Furthermore, processing circuitry 80 can adjust treatment for a new posture state when posture status module 86 indicates that patient 12 has actually changed posture. In some examples, a change in posture can trigger the sensing of an ECAP signal. Based on the sensed ECAP from sensing circuitry 92, processing circuitry 80 can determine appropriate adjustments to one or more current stimulation treatment parameters to achieve a target ECAP characteristic value. In some examples, the current feature value of the ECAP signal can be compared with the target ECAP feature value corresponding to an effective treatment (e.g., the value of the feature or ECAP signal template).

[0064] Processing circuitry 80 can analyze the sensed ECAP signal to determine the values ​​of different types of features according to the techniques described herein. For example, the sensed ECAP signal may include a first peak amplitude, a second peak amplitude, and a third peak amplitude representing the propagation action potential from the ECAP. An exemplary duration of each peak is approximately 1 millisecond (ms). For example, a feature of the ECAP may be the amplitude between the first and second peaks. This amplitude can be easily detected even in the presence of artifacts or electron drift in the sensed signal. In other examples, the feature may be the amplitude relative to one of the first, second, or third peaks, or a neutral point voltage or zero voltage. In some examples, the feature may be the sum of two or more of the first, second, or third peaks. In other examples, the feature may be the area under one or more of the first, second, or third peaks. In other examples, a feature of the ECAP may be the ratio of one of the first, second, or third peaks to another of the peaks. In some examples, a feature of the ECAP may be the slope between two points in the ECAP signal, such as the slope between two of the first, second, or third peaks. In other examples, a characteristic of the ECAP can be the time between two points in the ECAP, such as the time between two of the first, second, or third peaks. The time between the delivery of the stimulus pulse and a point in the ECAP signal can be referred to as the ECAP delay and can indicate the type of fiber captured by the control stimulus pulse. The ECAP delay can also be a characteristic evaluated by the processing circuit 80. An ECAP signal with a lower delay (e.g., a smaller delay value) indicates a higher percentage of nerve fibers with faster signal propagation, while an ECAP signal with a higher delay (e.g., a larger delay value) indicates a higher percentage of nerve fibers with slower signal propagation. Other characteristics of the ECAP signal can be used in other examples.

[0065] As long as the amplitude of the stimulation 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. Target ECAP characteristics (e.g., target ECAP amplitude) can be determined based on the ECAP signal detected from the stimulation pulse to deliver effective treatment to the patient. Therefore, the ECAP signal represents the distance between the stimulating electrode and the nerve that is suitable for the stimulation parameter values ​​of the stimulation pulse being delivered at that time. Thus, the processing circuit 80 can attempt to modify the stimulation pulse parameter values ​​using the detected changes in the measured ECAP characteristic values ​​and maintain the target ECAP characteristic values ​​during the delivery of the primary and main stimulation pulses.

[0066] Therefore, IMD 14 can be configured to provide ECAP-responsive stimulation therapy to patient 12. Stimulus adjustments in response to changes in ECAP signals or patient status can be automatic or semi-automatic (subject to patient approval). In many cases, fully automatic adjustments may be desirable, allowing IMD 14 to respond more quickly to changes in patient status or to changes in therapeutic efficacy that may be unrelated to changes in patient status. In some examples, ECAP sensing and analysis can be used to refine stimulation therapy procedures based on sensed posture selection.

[0067] Memory 82 may include a definition of each posture state of patient 12. In one example, the definition of each posture state may be shown as a cone in three-dimensional space. Whenever a posture state parameter value (e.g., a vector) from a triaxial accelerometer of posture state module 86 resides within a predefined cone or volume, processing circuitry 80 indicates that patient 12 is in the posture state of said cone or volume. In other examples, posture state parameter values ​​from the triaxial accelerometer may be compared with values ​​in a lookup table or equation to determine the posture state currently in which patient 12 resides. Exemplary techniques for detecting patient posture states include those described in U.S. Patent No. 8,708,934, filed April 30, 2009 and granted April 29, 2014, entitled “REORIENTATION OF PATIENT POSTURE STATES FOR POSTURE-RESPONSIVE THERAPY,” the entire contents of which are incorporated herein by reference.

[0068] Although the posture status module 86 is described as containing a 3-axis accelerometer, it may contain multiple single-axis accelerometers, dual-axis accelerometers, 3-axis accelerometers, or some combination thereof. In some examples, the accelerometer or other sensor may be located within or on the IMD 14, on one of the leads 16 (e.g., at the distal end or in the middle), as an additional sensor lead located somewhere within the patient 12, within a separate implantable sensor, or even worn on the patient 12. For example, one or more microsensors may be implanted within the patient 12 to wirelessly transmit posture status information to the IMD 14. In this way, the posture status of the patient 12 can be determined from multiple motion sensors placed at various locations on or within the patient 12's body.

[0069] In some examples, the posture status module 86 may additionally or alternatively be configured to sense one or more physiological parameters of the patient 12. For example, physiological parameters may include heart rate, electromyography (EMG), electroencephalography (EEG), electrocardiography (ECG), body temperature, respiratory rate, or pH. In some embodiments, processing circuitry 80 may use these physiological parameters to confirm or reject sensed changes in posture status that may be caused by vibration, patient movement (e.g., in an airplane, car, or train), or other false positives. In some examples, one or more physiological parameters may be used to determine patient status other than posture. Furthermore, ECAP sensing and analysis may be used to confirm changes in the relationship between the stimulus source and the stimulus target within the patient 12.

[0070] Adjusting one or more stimulation parameters in response to sensed changes in ECAP allows the IMD 14 to automate a level of treatment adjustment. Specifically, the IMD 14 can continuously or periodically adjust stimulation parameters to maintain target ECAP characteristic values ​​corresponding to effective treatment. Automatic stimulation adjustment frees the patient 12 from the fixed task of manually adjusting treatment whenever the patient 12 changes posture. Automatic stimulation adjustment based on sensed ECAP signals can also correct for natural drift of the lead 16, regardless of postural state. For example, by detecting ECAP signals over time, the processing circuit 80 can determine that the position of the stimulated nerve has changed over time and automatically adjust the treatment according to the changing conditions without receiving changes in patient state from the patient 12 via the programmer 20.

[0071] Furthermore, the IMD 14 can store input from the patient 12 regarding perceived physiological conditions (e.g., symptoms) not detected by any implemented sensors. For example, the patient 12 can provide the programmer 20 with input indicating the location where the patient perceives any symptoms and the characteristics of said particular type of symptom. The processing circuitry 80 can correlate this physiological condition information with currently detected postural states, stimulus parameters, and / or timestamps to provide a complete picture of the treatment to the patient or clinician at a later time. Such information can be stored in the memory 82 of the IMD 14, the memory of the programmer 20, and / or the memory of some other device.

[0072] Wireless telemetry in the IMD 14 using an external programmer 20, such as a patient programmer, clinician programmer, or another device, can be achieved through radio frequency (RF) communication or proximal induction interaction between the IMD 14 and the external programmer 20. The telemetry circuit 88 can send and receive information to and from the external programmer 20 continuously, at periodic intervals, at non-periodic intervals, or upon request from the stimulator or programmer. To support RF communication, the telemetry circuit 88 may include appropriate electronic components such as amplifiers, filters, mixers, encoders, decoders, etc.

[0073] Power source 90 delivers operating power to components of IMD 14. Power source 90 may include a small rechargeable or non-rechargeable battery and power generation circuitry to generate operating power. Recharging is achieved via proximal inductive interaction between an external charger and an inductive charging coil within IMD 14. In some embodiments, the power requirement may be small enough to allow IMD 14 to utilize patient movement and implement kinetic energy clearance devices to trickle charge the rechargeable battery. In other embodiments, conventional batteries may be used for a limited time period. As an alternative, an external inductive power source may power IMD 14 percutaneously when needed or desired.

[0074] Sensing circuitry 92 can be configured to detect ECAP signals. In other examples, sensing circuitry 92 may be located on lead 16 and may include one or more electrodes in lead 16, for example, in combination with suitable amplification, filtering, and / or signal processing circuitry. In some examples, sensing circuitry 92 may include additional electrodes on the housing of IMD 14. In some examples, sensing circuitry 92 may be carried by additional sensor leads located somewhere within patient 12, provided as a stand-alone implantable sensor or even worn on patient 12. For example, one or more microsensors may be implanted within patient 12 to wirelessly transmit the sensed ECAP signal or characteristic value to IMD 14. In this way, ECAP signals can be obtained independently of the location of the electrodes delivering electrical stimulation therapy.

[0075] According to the technology disclosed herein, the IMD 14 can adaptively adjust the parameter values ​​of high-frequency electrical stimulation using ECAP. In one example, the processing circuit 80 controls the stimulation generator 84 to generate high-frequency stimulation in the form of high-frequency electrical stimulation pulse trains for delivery to the patient 12 via lead 16, wherein there are pauses between each train where no high-frequency electrical stimulation is delivered.

[0076] In some examples, each pulse in the pulse train is defined by the same stimulation parameter value. In other examples, the electrical stimulation pulse train includes multiple primary electrical stimulation pulses followed by a master electrical stimulation pulse, wherein the master electrical stimulation pulse is different from the primary electrical stimulation pulses. For example, the primary electrical stimulation pulses may be configured to provide treatment to patient 12. The master electrical stimulation pulses may be configured to induce an ECAP response from the tissues of patient 12 during a pause in high-frequency electrical stimulation. The master electrical stimulation pulses may or may not provide some therapeutic effect to patient 12.

[0077] Exemplary ranges for the electrical stimulation parameters are listed below. However, other parameter values ​​are contemplated. Although stimulation pulses are described, the stimulation signal can be any of many forms, such as a sine wave.

[0078] Each electrical stimulation pulse train may be at least partially defined by a plurality of pulses, a pulse frequency, and a burst frequency. The pulse frequency defines the frequency at which each pulse within the train is delivered to the patient. The burst frequency defines the frequency at which each train of one or more pulses is delivered to the patient. Typically, the pulse frequency is higher than the burst frequency. In some examples, each train of electrical stimulation pulses includes pulse frequencies selected from a range greater than or equal to 500 Hz and less than or equal to 20 kHz. In some examples, each train of electrical stimulation pulses includes pulse frequencies of approximately 1.2 kHz. In some examples, the burst frequency defining the frequency of the pulse train is selected from a range of approximately 1 Hz to approximately 200 Hz. In some examples, the pause between each train is greater than or equal to 1 millisecond.

[0079] In some examples, each pulse in a sequence includes a pulse amplitude selected from the range of about 1 mA to about 25 mA. In some examples, each pulse in a sequence includes a pulse width selected from the range of about 30 microseconds to about 300 microseconds. In some examples, each primary pulse in a sequence includes a pulse width selected from the range of about 90 microseconds. In some examples, each main pulse in a sequence includes a pulse width selected from the range of about 60 microseconds to about 0.5 milliseconds.

[0080] Typically, the number of pulses in a pulse train is a function of the pulse frequency. For example, a pulse train containing high pulse frequencies may include hundreds or more pulses. Conversely, a pulse train containing low pulse frequencies may include only a few pulses. In some examples, each pulse train may include two or more, five or more, or ten or more pulses. In another example, an electrical stimulation train may include 10 electrical stimulation pulses (e.g., nine primary electrical stimulation pulses and one master electrical stimulation pulse).

[0081] Typically, the master electrical stimulation pulse includes one or more parameter values ​​that differ from those defining the primary electrical stimulation pulse. For example, the master electrical stimulation pulse includes one or more of the current amplitude or pulse width that are greater than those of the primary electrical stimulation pulse. In some examples, each of the primary electrical stimulation pulses includes a current amplitude of about 0.4 mA, and the master electrical stimulation pulse includes a current amplitude of about 1.0 mA.

[0082] In some examples, when adjusting one or more parameters of the electrical stimulation therapy, the processing circuit 80 maintains a ratio of the value of one or more parameters of the primary electrical stimulation pulse to the value of one or more parameters of the master electrical stimulation pulse. For example, the processing circuit 80 controls the stimulation generator 84 to generate a pulse train of multiple primary electrical stimulation pulses followed by a master electrical stimulation pulse. Each of the primary electrical stimulation pulses includes a current amplitude of about 0.4 mA, and the master electrical stimulation pulse includes a current amplitude of about 1.0 mA (e.g., the ratio of the amplitudes of the primary electrical stimulation pulses to the master electrical stimulation pulses is 0.4 mA to 1.0 mA, or 1:2.5). The processing circuit 80 may adjust the current amplitude of the pulse train in increments based on a sensed ECAP signal while maintaining the ratio of the primary electrical stimulation pulses to the master electrical stimulation pulses.

[0083] For example, when the amplitude of the pulse train is increased by a step increment of 10%, the processing circuit 80 controls the stimulator 84 to increase the current amplitude of the primary electrical stimulation pulse from 0.4 mA to approximately 0.44 mA, and to increase the current amplitude of the main electrical stimulation pulse from 1.0 mA to approximately 1.1 mA (e.g., a ratio of 1:2.5). Similarly, when the amplitude of the pulse train is decreased by a step increment of 10%, the processing circuit 80 controls the stimulator 84 to decrease the current amplitude of the primary electrical stimulation pulse from 0.4 mA to approximately 0.36 mA, and to decrease the current amplitude of the main electrical stimulation pulse from 1.0 mA to approximately 0.9 mA (e.g., a ratio of 1:2.5).

[0084] By temporarily pausing the high-frequency stimulation for a predetermined amount of time, the sensing circuit 92 can sense the ECAP signal from the target nerve of the patient 12 during this time period without interference from the high-frequency stimulation. Therefore, the processing circuit 80 can use the sensed ECAP to adjust the values ​​of one or more parameters of the high-frequency electrical stimulation pulse train. In some examples, the processing circuit 80 controls the stimulation generator 84 to modify one or more parameters of the last electrical stimulation pulse of the train to elicit a detectable ECAP.

[0085] Additionally or alternatively, the processing circuitry 80 may control the stimulation generator 84 to deliver low-frequency electrical stimulation during pauses in a high-frequency electrical stimulation pulse train, in order to elicit an ECAP response and / or maintain the therapeutic efficacy of the patient 12 during the pause. For example, the low-frequency electrical stimulation may comprise multiple electrical stimulation pulses delivered at a pulse frequency of less than 500 Hz. In some examples, the low-frequency electrical stimulation comprises multiple electrical stimulation pulses delivered at approximately 50 Hz. In this manner, during a pause in high-frequency stimulation, the patient 12 may experience no or minimal interruption to treatment, and the sensing circuitry 92 senses the ECAP from the patient 12's tissues.

[0086] In some examples, processing circuitry 80 can use the posture of patient 86 sensed via posture state module 86 to adjust the rate at which ECAP of patient 12 is sensed. For example, processing circuitry 80 can control stimulation generator 84 to deliver a first high-frequency electrical stimulation pulse train to patient 12. Each of the first electrical stimulation pulse trains includes a plurality of primary pulses configured to provide treatment to patient 12. In some examples, processing circuitry 80 may not include pauses in the electrical stimulation delivery between the first high-frequency electrical stimulation pulse trains. Periodically and in a time-staggered manner, processing circuitry 80 can control stimulation generator 84 to deliver a second high-frequency electrical stimulation pulse train to patient 12, followed by a pause in the delivery of high-frequency electrical stimulation treatment. The second electrical stimulation pulse train includes a plurality of primary pulses configured to provide treatment to patient 12, followed by a main pulse configured to induce an ECAP signal in the patient. Processing circuitry 80 can control the rate at which ECAP of patient 12 is sensed by controlling the rate at which the second high-frequency electrical stimulation treatment train is delivered to patient 12. For example, in response to a change in the posture of the patient 12, the processing circuit 80 can adjust the rate at which the second high-frequency electrical stimulation therapy string is delivered to the patient 12.

[0087] For example, processing circuit 80 may deliver only the first high-frequency electrical stimulation treatment string to patient 12, while patient 12's posture is constant. In response to detecting a change in patient 12's posture, processing circuit 80 controls stimulation generator 84 to deliver a second high-frequency electrical stimulation treatment string, then pauses the delivery of high-frequency electrical stimulation treatment to induce an ECAP signal. Processing circuit 80 can use the ECAP signal as feedback to adjust the values ​​of one or more parameters of the electrical stimulation treatment to take into account patient 12's new posture. In this way, when patient 12's posture is constant, processing circuit 80 can deliver continuous electrical stimulation including the first high-frequency electrical stimulation treatment string to patient 12, and in response to detecting a change in posture, use the second high-frequency electrical stimulation treatment string to induce an ECAP response to adjust one or more parameters of the high-frequency electrical stimulation treatment to adapt to patient 12's new assumed posture.

[0088] Therefore, using the techniques described herein, processing circuitry 80 can pause the delivery of high-frequency electrical stimulation to allow time for stimulation generator 84 to induce ECAP and for sensing circuitry 92 to sense the ECAP signal. Otherwise, ECAP might not be detectable by a system delivering, for example, continuous high-frequency electrical stimulation. Thus, the medical device as described herein avoids high-frequency electrical stimulation masking the patient's ECAP signal, thereby allowing the use of the sensed ECAP characteristics as a control signal for titrating one or more parameters of high-frequency electrical stimulation therapy.

[0089] Figure 3 This is a functional block diagram showing the various components of the external programmer 20 of the IMD 14. (Example) Figure 3 As shown, the external programmer 20 is an external device including processing circuitry 104, memory 108, telemetry circuitry 110, user interface 106, and power source 112. The external programmer 20 can be implemented as a patient programmer or a clinician programmer. The clinician or patient 12 interacts with the user interface 106 to manually change the stimulation parameters of the program, change the program within a group, turn ECAP responsive stimulation on or off, view treatment information, view patient status information, view posture status indicators, or otherwise communicate with the IMD 14.

[0090] User interface 106 may include a screen that allows external programmer 20 to receive input from a user and one or more input buttons, as in the example of the programmer. Alternatively, user interface 106 may additionally or solely utilize a touchscreen display, as in the example of the clinician programmer. The screen may be a liquid crystal display (LCD), a dot matrix display, an organic light-emitting diode (OLED) display, a touchscreen, or any other device capable of delivering and / or receiving information. For visible gesture status indications, a display screen may be sufficient. For auditory and / or tactile gesture status indications, programmer 20 may further include one or more audio speakers, a speech synthesizer chip, a piezoelectric buzzer, etc. Input buttons for user interface 106 may include a touchpad, increase and decrease buttons, an emergency stop button, and other buttons for controlling stimulation therapy, as described above with respect to programmer 20. Processing circuitry 104 controls user interface 106, retrieves data from memory 108, and stores data within memory 108. Processing circuitry 104 also controls the transmission of data via telemetry circuitry 110 to IMD 14 or 26. The memory 108 includes operating instructions for processing circuit 104 and data related to the treatment of patient 12.

[0091] Telemetry circuit 110 allows data to be transmitted to and from IMD 14. Telemetry circuit 110 can communicate with IMD 14 automatically in real time, at predetermined times, or when the telemetry circuit detects the proximity of a stimulator. User interface 106 can then update the displayed information accordingly. Alternatively, telemetry circuit 110 can communicate with IMD 14 when a user sends a signal through user interface 106. To support RF communication, telemetry circuit 110 may include suitable electronic components such as amplifiers, filters, mixers, encoders, decoders, etc. Power source 112 may be a rechargeable battery, such as a lithium-ion or nickel-metal hydride battery. Other rechargeable or conventional batteries may also be used. In some cases, an external programmer 20 may be used when directly or via an AC / DC adapter coupled to an AC outlet (i.e., AC line power).

[0092] In some examples, in addition to programming IMD 14, the external programmer 20 can be configured to also recharge IMD 14. Alternatively, the recharging device can communicate with IMD 14. The recharging device can then transfer programming information, data, or any other information described herein to IMD 14. In this way, the recharging device can act as an intermediate communication device between the external programmer 20 and IMD 14. In other cases, the programmer can integrate recharging functionality into a combined programming / recharging device. The techniques described herein can be used to transfer data between IMD 14 via any type of external device capable of communicating with IMD 14.

[0093] Figure 4A , 4B Figures 4C and 4C are diagrams illustrating exemplary electrical stimulation pulse trains according to the technology of this disclosure. For convenience, relative to... Figure 1 and 2 IMD 14 pairs Figure 4A –4C is used for description.

[0094] Figure 4A An exemplary stimulation signal 430 is shown, comprising a first pulse train 410A and a second pulse train 410B. Each of the pulse trains 410A, 410B (collectively referred to as "train 410") includes a plurality of primary electrical stimulation pulses 400 followed by a main electrical stimulation pulse 408. This can be achieved, for example, by... Figure 2 The IMD 14's stimulation generator 84 generates stimulation signals 430.

[0095] Primary electrical stimulation pulse 400 may be configured to provide treatment to patient 12. In contrast, master electrical stimulation pulse 408 may be configured to induce an ECAP response from the tissue of patient 12, the ECAP response being sensed by IMD 14 during a pause 416 between two consecutive strings 410A, 410B of high-frequency electrical stimulation pulses. IMD 14 may use the ECAP induced by master electrical stimulation pulse 408 to adjust one or more parameters (e.g., amplitude or pulse width of pulses 400, 408) of either or both of the primary electrical stimulation pulse 400 and master electrical stimulation pulse 408. In some examples, IMD 14 adjusts both primary electrical stimulation pulse 400 and master electrical stimulation pulse 408 in a ratio manner (e.g., to maintain a ratio of one or more parameters of the primary electrical stimulation pulse 400 to one or more parameters of the master electrical stimulation pulse 408).

[0096] The primary electrical stimulation pulse 408 is defined by parameter values ​​that differ from those of the primary electrical stimulation pulse 400. For example... Figure 4A As shown, the primary electrical stimulation pulse 408 has a larger pulse width 414 and a larger pulse amplitude 412 compared to the primary electrical stimulation pulse 400's pulse width 404 and pulse amplitude 406. Although the pulses 400 and 408 forming the series 410A are depicted as having a rectangular shape, the shape of the pulses can be triangular, sinusoidal, Gaussian, exponential, ramp, or any shape or combination thereof used to deliver charge to and from target tissues of the patient 12.

[0097] In some examples, the number of primary electrical stimulation pulses 400 is selected from a range of 2 or greater and 50 or less. In some examples, the number of primary electrical stimulation pulses 400 is 9, followed by a single master electrical stimulation pulse 408.

[0098] The primary pulse interval 402 and pulse width 404 of the primary electrical stimulation pulses 400 can be fixed or variable. Each of the primary electrical stimulation pulses 400 may have an asymmetric primary pulse width 402 for the anodic and cathodic phases.

[0099] The stimulation signal 430 further includes an inter-pulse interval 416 (also referred to herein as a “pause”), during which no charge is delivered to the patient 12. The sensing circuitry 92 of the IMD 14 can sense the ECAP response of the patient 12 induced by the primary electrical stimulation pulse 408 during the pause interval 416. The use of the pause interval 416 reduces the possibility that the primary electrical stimulation pulse 400 masks or interferes with the patient 12's ECAP response, allowing the IMD 14 to use one or more characteristic values ​​of the ECAP response to adjust one or more parameters of either or both of the primary electrical stimulation pulse 400 or the primary electrical stimulation pulse 408.

[0100] Figure 4B An exemplary stimulation signal 440 is shown, comprising a first pulse train 410A and a second pulse train 410B. Each of the pulse trains 410A and 410B includes a plurality of primary electrical stimulation pulses 400 followed by a main electrical stimulation pulse 408. This can be achieved, for example, by... Figure 2 The IMD 14's stimulus generator 84 generates a stimulus signal 440. The stimulus signal 440 can be substantially similar to... Figure 4A The stimulation signal 430. However, the stimulation signal 440 further includes an inter-pulse interval 418 during which no charge is delivered to the patient 12. The inter-pulse interval 418 is interposed between the last primary electrical stimulation pulse 400 and the main electrical stimulation pulse 408.

[0101] As mentioned above, in contrast to Figure 4A The sensing circuit 92 of the IMD 14 senses a first ECAP signal induced by the main electrical stimulation pulse 408 in the patient 12 during a pause interval 416. Furthermore, the sensing circuit 92 of the IMD 14 senses a second ECAP signal induced by the last primary electrical stimulation pulse 400 in the patient 12 during a pause interval 418. The use of pause intervals 416 and 418 reduces the possibility of the primary electrical stimulation pulse 400 masking or interfering with the patient 12's ECAP signal, allowing the IMD 14 to use one or more characteristic values ​​of the first and second ECAP signals to control the adjustment of one or more parameters of either the primary electrical stimulation pulse 400 or the main electrical stimulation pulse 408, or both.

[0102] Furthermore, the first ECAP signal in response to the last primary electrical stimulation pulse 400 may exhibit a different morphology than the second ECAP response to the main electrical stimulation pulse 408. IMD 14 or clinicians reviewing the first and second ECAP signals may use the morphological differences between the first and second ECAP signals to further adjust the values ​​of one or more parameters defining either or both of the primary electrical stimulation pulse 400 or the main electrical stimulation pulse 408.

[0103] Figure 4C Exemplary high-frequency stimulation signal 450 and low-frequency stimulation signal 460 are shown. High-frequency stimulation signal 450 includes a first high-frequency pulse train 410A and a second pulse train 410B. Each of the trains 410 includes a plurality of primary electrical stimulation pulses 400 followed by a main electrical stimulation pulse 408. Low-frequency stimulation signal 460 includes a low-frequency pulse train 420 of one or more low-frequency electrical stimulation pulses. Stimulation signals 450 and 460 can be, for example, generated by... Figure 2 The stimulation generator 84 of the IMD 14 generates a stimulation signal 450 that is essentially similar to... Figure 4A The stimulus signal is 430.

[0104] like Figure 4C As depicted in the example, during interval 416, the IMD delivers a series 420 of low-frequency electrical stimulation pulses to the patient 12. After pause 416 has passed, the IMD 14 may stop delivering the series 420 of low-frequency electrical stimulation pulses and resume delivery of a series 410B of high-frequency electrical stimulation pulses. In some examples, the electrical stimulation pulses 420 include pulse frequencies less than 500 Hz. In some examples, the electrical stimulation pulses 420 include pulse frequencies of approximately 50 Hz.

[0105] The series 420 of low-frequency electrical stimulation pulses can substantially not mask or substantially not interfere with the ECAP signal sensed from the patient 12. For example, the electrical stimulation pulses 420 can be configured to elicit an ECAP response from the patient 12. Additionally or alternatively, the electrical stimulation pulses 420 can be configured to maintain the therapeutic efficacy of the patient 12 during a pause 416 between the series of high-frequency electrical stimulation pulses 410A and 410B. Thus, by delivering the series 420 of low-frequency electrical stimulation pulses during the pause 416 between the series of high-frequency electrical stimulation pulses 410A and 410B, the IMD 14 can avoid treatment interruption for the patient 12 during the pause 416 while sensing the ECAP from the tissues of the patient 12.

[0106] Figure 5 This is a diagram illustrating an exemplary stimulation train 502 of electrical stimulation pulses according to the technology of this disclosure and an ECAP signal 504 sensed from the patient. For convenience, relative to... Figure 1 and 2 IMD 14 pairs Figure 5 Describe it.

[0107] Compared to low-frequency stimulation, high-frequency stimulation can employ mechanisms of action other than sensory abnormalities. However, the effectiveness of high-frequency stimulation may change if the electrode position is altered relative to the target nerve. Therefore, incorporating a feedback control system into a high-frequency SCS system can provide patients with more consistent and uniform treatment. However, high-frequency electrical stimulation pulses may mask the patient's ECAP response. For example, resolving ECAP signals in the presence of high-frequency stimulation is particularly challenging because high-frequency stimulation induces larger stimulation artifacts compared to low-frequency stimulation. Stimulation artifacts are sources of nonlinear interference that manifest simultaneously with the delivery of high-frequency electrical stimulation pulses. Stimulation artifacts are used to impair the ability of medical device systems (such as the IMD 14) to resolve ECAP signals from 12 tissues in patients. Therefore, a high-frequency SCS system may be unable to resolve ECAP signals in the presence of high-frequency stimulation.

[0108] According to the technology disclosed herein, the medical device system temporarily pauses the delivery of high-frequency electrical stimulation pulses. This pause in high-frequency electrical stimulation provides a brief window for the manifestation and detection of the ECAP signal before the delivery of the next high-frequency electrical stimulation pulse. In some examples, the high-frequency stimulation is a sequence of two or more stimulation pulses with a pulse frequency greater than or equal to 500 Hz. The sequence can be repeated at burst frequencies from 1 Hz to 200 Hz, wherein the IMD 14 inserts a pause of at least 1 millisecond between the end of the first stimulation sequence and the beginning of the second stimulation sequence. Therefore, using the technology disclosed herein, the IMD 14 can titrate the high-frequency stimulation using the ECAP without any masking of the ECAP by the high-frequency electrical stimulation pulse.

[0109] like Figure 5 As depicted, the processing circuit 80 controls the stimulation generator 84 to generate a series 502 of electrical stimulation pulses for delivery to the patient 12. Figure 5 In the example, the stimulator 84 generates a series 502 of 10 balanced biphasic pulses, comprising a pulse frequency of 1,000 Hz, a pulse amplitude of 5.75 mA, and a pulse width of 90 microseconds. The processing circuitry 80 controls the stimulator 84 to deliver each series 502 every 12 milliseconds (e.g., a burst rate of 83.3 Hz). The processing circuitry 80 also controls the stimulator 84 to pause the delivery of high-frequency electrical stimulation for a 2-millisecond pause interval 506.

[0110] During pause interval 506, sensing circuit 92 senses a signal from patient 12 indicating the ECAP response to series 502. For example... Figure 5 As shown, during the delivery of the electrical stimulation string 502, the electrical stimulation delivered by the stimulation generator 84 causes noise 510. Noise 510 has a much larger magnitude than the ECAP response of the patient 12 and can render the sensing circuit 92 unable to detect the patient 12's ECAP response. By using a pause interval 506, the sensing circuit 92 is able to sense a clean, artifact-free ECAP response 508 of the patient 12. The pause interval 506 is selected to allow sufficient time for the ECAP response 508 to manifest, since otherwise the ECAP response 508 might be undetectable in the presence of high-frequency electrical stimulation. The processing circuit 80 can then use the ECAP response 508 to adjust one or more parameters of the delivered high-frequency electrical stimulation as described above.

[0111] Figure 6 This is a flowchart illustrating the operation of the technology according to this disclosure. Specifically, Figure 6 The flowchart depicts the operation of adjusting one or more parameters of an electrical stimulation therapy, including a high-frequency electrical stimulation pulse train, using the patient's ECAP response. For convenience, relative to... Figure 1 and 2 IMD 14 and processing circuit 80 pairs Figure 6 Describe it.

[0112] like Figure 6 As depicted in the example, processing circuitry 80 controls stimulation generator 84 to deliver electrical stimulation therapy (602) to patient 12, comprising a first electrical stimulation therapy pulse train. In some examples, the first electrical stimulation therapy pulse train comprises a pulse frequency greater than or equal to 500 Hz. In some examples, the electrical stimulation pulse train comprises multiple primary electrical stimulation pulses followed by a master electrical stimulation pulse. The primary electrical stimulation pulses may be configured to provide therapy to patient 12. The master electrical stimulation pulse may be configured to induce an ECAP response from the tissues of patient 12 during a pause in high-frequency electrical stimulation. However, in some examples, the master electrical stimulation pulse may provide some therapeutic benefit to patient 12.

[0113] After the delivery of the first electrical stimulation pulse train, the processing circuit 80 controls the stimulation generator 84 to stop the delivery of electrical stimulation therapy for a predetermined period of time (604). In some examples, the predetermined period of time is greater than or equal to 1 millisecond.

[0114] During a predetermined time period, sensing circuit 92 senses ECAP signals (606) from the tissue of patient 12. Additionally or alternatively, processing circuit 80 may control stimulation generator 84 to deliver low-frequency electrical stimulation during the predetermined time period to elicit an ECAP response and / or maintain therapeutic efficacy for patient 12 while suspending high-frequency electrical stimulation treatment. For example, low-frequency electrical stimulation may comprise multiple electrical stimulation pulses delivered at a pulse frequency of less than 500 Hz. In some examples, low-frequency electrical stimulation comprises multiple electrical stimulation pulses delivered at approximately 50 Hz. In this manner, patient 12 may not experience treatment interruption during pauses while sensing circuit 92 senses ECAP from the tissue of patient 12. Processing circuit 80 may also determine characteristic values ​​of the sensed ECAP signals and compare them with target ECAP characteristic values.

[0115] The processing circuit 80 determines (608) the value of at least one parameter that at least partially defines the second electrical stimulation pulse train based on the characteristic value of the sensed ECAP signal. In some examples, the second electrical stimulation treatment pulse train includes a pulse frequency greater than or equal to 500 Hz. For example, the sensed ECAP signal may indicate the distance between the electrode positioned along lead 16 and the target nerve of the patient 12. The processing circuit 80 compares the characteristic value of the ECAP signal with the target characteristic value of the ECAP. If the characteristic value of the ECAP signal is greater than the target characteristic value of the ECAP, the ECAP signal may indicate that the electrode positioned along lead 16 has been offset closer to the target nerve, and a corresponding reduction in one or more parameters (such as amplitude) of the high-frequency electrical stimulation pulse is required to maintain a constant level of treatment for the patient 12.

[0116] Conversely, if the characteristic value of the ECAP signal is less than the target characteristic value of the ECAP, the ECAP signal may indicate that the electrode positioned along lead 16 has shifted away from the target nerve, and a corresponding increase in one or more parameters (such as amplitude) of the high-frequency electrical stimulation pulse is required to maintain a constant level of treatment for the patient 12. Based on the comparison results, the processing circuit 80 determines the value of at least one parameter defining the second electrical stimulation treatment pulse train in order to reduce the difference between the characteristic value of the ECAP signal and the target characteristic value of the ECAP.

[0117] In response to the passage of a predetermined time period, the processing circuit 80 controls the stimulation generator 84 to deliver a second electrical stimulation pulse train (610) according to the value of at least one parameter. Thus, the medical device as described herein avoids masking of the patient 12's ECAP response by high-frequency electrical stimulation, thereby allowing the titration of one or more parameters of high-frequency electrical stimulation therapy to be controlled using one or more characteristic values ​​of the sensed ECAP.

[0118] The following examples illustrate one or more aspects of this disclosure.

[0119] Example 1: A method comprising: delivering an electrical stimulation therapy comprising a first electrical stimulation pulse train to a patient via a medical device, wherein the first electrical stimulation pulse train comprises a first pulse frequency greater than or equal to 500 Hz; after delivery of the first electrical stimulation pulse train, stopping the delivery of the electrical stimulation therapy via the medical device for a predetermined time period; during the predetermined time period, sensing an evoked compound action potential (ECAP) signal from the patient's tissue via the medical device; determining, via the medical device and based on characteristic values ​​of the ECAP signal, a value of at least one parameter that at least partially defines a second electrical stimulation pulse train, wherein the second electrical stimulation pulse train comprises a second pulse frequency greater than or equal to 500 Hz; and, in response to the elapsed predetermined time period, delivering the second electrical stimulation pulse train according to the value of the at least one parameter that at least partially defines the second set of pulses.

[0120] Example 2: According to the method of Example 1, wherein the ECAP signal includes a first ECAP signal, and wherein the method further includes: after delivering the second electrical stimulation pulse train, stopping the delivery of the electrical stimulation treatment for a predetermined time period via the medical device; during the predetermined time period, sensing a second ECAP signal from the patient's tissue via the medical device; determining, via the medical device and based on characteristic values ​​of the second ECAP signal, the value of at least one parameter that at least partially defines a third electrical stimulation pulse train, wherein the third electrical stimulation pulse train includes a pulse frequency greater than or equal to 500 Hz; and in response to the passing of the predetermined time period, delivering the third electrical stimulation pulse train according to the value of the at least one parameter that at least partially defines the second set of pulses.

[0121] Example 3: The method according to any one of Examples 1 to 2, wherein: the first electrical stimulation pulse train includes a plurality of primary electrical stimulation pulses followed by a master electrical stimulation pulse, the plurality of primary electrical stimulation pulses being defined by a primary parameter set and configured to aid in the treatment of the patient, and the master electrical stimulation pulse being defined by a master parameter set and configured to induce the ECAP signal from the patient's tissue, wherein the values ​​of the master parameter set are different from the values ​​of the primary parameter set.

[0122] Example 4: According to the method described in Example 3, the main electrical stimulation pulse in the first series includes a current amplitude that is greater than the pulse amplitude of the plurality of primary electrical stimulation pulses in the first series.

[0123] Example 5: According to any one of Examples 3 to 4, wherein the plurality of primary electrical stimulation pulses in the first string are first primary current amplitudes, wherein the main electrical stimulation pulses in the first string include a first main current amplitude, wherein the plurality of primary electrical stimulation pulses in the second string include a second primary current amplitude, wherein the main electrical stimulation pulses in the second string include a second main current amplitude, and wherein determining the value of the at least one parameter defining the second electrical stimulation pulse string includes: determining a value of a second primary current amplitude that is different from the value of the first primary current amplitude; determining a value of a second main current amplitude that is different from the value of the first main current amplitude, wherein the ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

[0124] Example 6: According to the method described in Example 5, the value of the second primary current amplitude is greater than the value of the first primary current amplitude, the value of the second main current amplitude is greater than the value of the first main current amplitude, and the ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

[0125] Example 7: According to any one of Examples 5 to 6, the value of the second primary current amplitude is less than the value of the first primary current amplitude, the value of the second main current amplitude is less than the value of the first main current amplitude, and the ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

[0126] Example 8: The method according to any one of Examples 1 to 7, wherein the method further comprises: during the predetermined time period, delivering an electrical stimulation therapy comprising a third electrical stimulation pulse train to the patient via the medical device, wherein the third electrical stimulation pulse train comprises a third pulse frequency of less than 500 Hz; and stopping the delivery of the electrical stimulation therapy comprising the third electrical stimulation pulse train in response to the passing of the predetermined time period.

[0127] Example 9: The method according to any one of Examples 1 to 8 further includes delivering an electrical stimulation therapy comprising a plurality of primary electrical stimulation pulses to the patient; detecting postural changes of the patient via the medical device, wherein: delivering the electrical stimulation therapy comprising the first electrical stimulation pulse train to the patient comprises, in response to the detected postural changes of the patient, delivering the first electrical stimulation pulse train comprising a plurality of primary electrical stimulation pulses followed by a master electrical stimulation pulse, the plurality of primary electrical stimulation pulses being configured to provide therapy to the patient, and the master electrical stimulation pulse being configured to induce the ECAP signal from the patient's tissue.

[0128] Example 10: The method according to any one of Examples 1 to 9, wherein the electrical stimulation therapy includes a burst frequency greater than or equal to 1 Hz and less than or equal to 200 Hz, wherein the burst frequency includes the frequency at which the first electrical stimulation pulse train and the second electrical stimulation pulse train are delivered to the patient.

[0129] Example 11: The method according to any one of Examples 1 to 10, wherein the medical device is an implantable medical device.

[0130] Example 12: A medical device configured to: deliver an electrical stimulation therapy to a patient comprising a first electrical stimulation pulse train, wherein the first electrical stimulation pulse train comprises a first pulse frequency greater than or equal to 500 Hz; after delivery of the first electrical stimulation pulse train, stop delivery of the electrical stimulation therapy for a predetermined time period; during the predetermined time period, sense an evoked compound action potential (ECAP) signal from the patient's tissue; determine, based on characteristic values ​​of the ECAP signal, the value of at least one parameter that at least partially defines a second electrical stimulation pulse train, wherein the second electrical stimulation pulse train comprises a second pulse frequency greater than or equal to 500 Hz; and in response to the elapsed predetermined time period, deliver the second electrical stimulation pulse train according to the value of the at least one parameter that at least partially defines the second set of pulses.

[0131] Example 13: The medical device according to Example 12, wherein the ECAP signal includes a first ECAP signal, and wherein the medical device is further configured to: after delivering the second electrical stimulation pulse train, stop the delivery of the electrical stimulation treatment for a predetermined time period; during the predetermined time period, sense a second ECAP signal from the tissue of the patient; determine, based on characteristic values ​​of the second ECAP signal, the value of at least one parameter that at least partially defines a third electrical stimulation pulse train, wherein the third electrical stimulation pulse train includes a pulse frequency greater than or equal to 500 Hz; and in response to the elapsed predetermined time period, deliver the third electrical stimulation pulse train according to the value of the at least one parameter that at least partially defines the second set of pulses.

[0132] Example 14: The medical device according to Example 12, wherein: the first electrical stimulation pulse train includes a plurality of primary electrical stimulation pulses followed by a main electrical stimulation pulse, the plurality of primary electrical stimulation pulses being defined by a primary parameter set and configured to aid in the treatment of the patient, and the main electrical stimulation pulse being defined by a master parameter set and configured to induce the ECAP signal from the patient's tissue, wherein the values ​​of the master parameter set are different from the values ​​of the primary parameter set.

[0133] Example 15: The medical device according to Example 14, wherein the first series of main electrical stimulation pulses includes a current amplitude greater than the pulse amplitude of the plurality of primary electrical stimulation pulses in the first series.

[0134] Example 16: A medical device according to any one of Examples 14 to 15, wherein the plurality of primary electrical stimulation pulses in the first string are first primary current amplitudes, wherein the main electrical stimulation pulses in the first string include a first main current amplitude, wherein the plurality of primary electrical stimulation pulses in the second string include a second primary current amplitude, wherein the main electrical stimulation pulses in the second string include a second main current amplitude, and wherein, in order to determine the value of the at least one parameter defining the second electrical stimulation pulse string, the medical device is configured to: determine a value of a second primary current amplitude that is different from the value of the first primary current amplitude; and determine a value of a second main current amplitude that is different from the value of the first main current amplitude, wherein the ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

[0135] Example 17: The medical device according to Example 16, wherein the value of the second primary current amplitude is greater than the value of the first primary current amplitude, wherein the value of the second main current amplitude is greater than the value of the first main current amplitude, and wherein the ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

[0136] Example 18: A medical device according to any one of Examples 16 to 17, wherein the value of the second primary current amplitude is less than the value of the first primary current amplitude, wherein the value of the second main current amplitude is less than the value of the first main current amplitude, and wherein the ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

[0137] Example 19: A medical device according to any one of Examples 12 to 18, wherein the medical device is further configured to: deliver electrical stimulation therapy comprising a third electrical stimulation pulse train to the patient during the predetermined time period, wherein the third electrical stimulation pulse train comprises a third pulse frequency of less than 500 Hz; and stop the delivery of the electrical stimulation therapy comprising the third electrical stimulation pulse train in response to the passing of the predetermined time period.

[0138] Example 20: A non-transitory computer-readable medium comprising instructions, which, when executed, are configured to cause processing circuitry of an implantable medical device to: control a stimulator of the implantable medical device to deliver electrical stimulation therapy to a patient, comprising a first electrical stimulation pulse train, wherein the first electrical stimulation pulse train comprises a first pulse frequency greater than or equal to 500 Hz; after delivery of the first electrical stimulation pulse train, control the stimulator to stop delivery of the electrical stimulation therapy for a predetermined time period; during the predetermined time period, sense an evoked compound action potential (ECAP) signal from the patient's tissue; determine, based on characteristic values ​​of the ECAP signal, a value of at least one parameter that at least partially defines a second electrical stimulation pulse train, wherein the second electrical stimulation pulse train comprises a second pulse frequency greater than or equal to 500 Hz; and, in response to the elapsed predetermined time period, control the stimulator to deliver the second electrical stimulation pulse train according to the value of the at least one parameter that at least partially defines the second set of pulses.

[0139] It should be understood that the various aspects disclosed herein can be combined in combinations different from those specifically presented in the specification and drawings. It should also be understood that, depending on the example, certain actions or events of any process or method described herein may be performed in a different order, and may be completely added, combined, or omitted (e.g., performing the described technique may not require all the described actions or events). Furthermore, although for clarity some aspects of this disclosure are described as being performed by a single module or unit, it should be understood that the techniques of this disclosure can be performed by combinations of units or modules associated with, for example, a medical device.

[0140] In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functionality may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable media, which correspond to tangible media such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and is accessible by a computer).

[0141] The instructions can be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Therefore, as used herein, the term "processor" can refer to any of the aforementioned structures or any other physical structures suitable for implementing the described technology. Furthermore, this technology can be fully implemented in one or more circuit or logic elements.

[0142] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method, the method comprising: Electrical stimulation therapy, comprising a first electrical stimulation pulse train and a second electrical stimulation pulse train, is delivered to a patient via a medical device. The first electrical stimulation pulse train includes a first pulse frequency, and the first electrical stimulation pulse train and the second electrical stimulation pulse train are spaced apart by a predetermined time period. After delivering the first electrical stimulation pulse train, the medical device stops the delivery of the electrical stimulation treatment for the predetermined time period. During the predetermined time period, the medical device senses evoked compound action potential (ECAP) signals from the patient's tissues; The value of at least one parameter that at least partially defines the second electrical stimulation pulse train is determined by the medical device and based on the characteristic value of the ECAP signal, wherein the second electrical stimulation pulse train includes a second pulse frequency; as well as In response to the passing of the predetermined time period, the second electrical stimulation pulse train is delivered according to the value of at least one parameter that at least partially defines the second electrical stimulation pulse train.

2. The method according to claim 1, The ECAP signal mentioned above includes a first ECAP signal, and The method further includes: After the delivery of the second electrical stimulation pulse train, the delivery of the electrical stimulation treatment is stopped for the predetermined time period by the medical device; During the predetermined time period, a second ECAP signal from the patient's tissue is sensed by the medical device; The value of at least one parameter that at least partially defines the third electrical stimulation pulse train is determined by the medical device based on the characteristic value of the second ECAP signal, wherein the third electrical stimulation pulse train includes a third pulse frequency; as well as In response to the passing of the predetermined time period, the third electrical stimulation pulse train is delivered according to the value of at least one parameter that at least partially defines the second electrical stimulation pulse train.

3. The method according to claim 1, wherein: The first electrical stimulation pulse train includes multiple primary electrical stimulation pulses followed by a main electrical stimulation pulse. The plurality of primary electrical stimulation pulses are defined by a primary parameter set and configured to aid in the treatment of the patient, and The master electrical stimulation pulse is defined by a master parameter set and configured to induce the ECAP signal from the patient's tissue, wherein the values ​​of the master parameter set are different from the values ​​of the primary parameter set.

4. The method of claim 3, wherein the first series of master electrical stimulation pulses includes a current amplitude greater than the pulse amplitude of the plurality of primary electrical stimulation pulses in the first series.

5. The method according to claim 3, The plurality of primary electrical stimulation pulses in the first sequence are primary current amplitudes. The first series of main electrical stimulation pulses includes a first main current amplitude. The second series of primary electrical stimulation pulses includes a second primary current amplitude. The second series of main electrical stimulation pulses includes a second main current amplitude, and Determining the value of at least one parameter that defines the second electrical stimulation pulse train includes: Determine the value of the second primary current amplitude, which is different from the value of the first primary current amplitude; Determine the value of the second main current amplitude, which is different from the value of the first main current amplitude. The ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

6. The method according to claim 5, The value of the second primary current amplitude is greater than the value of the first primary current amplitude. The value of the second main current amplitude is greater than the value of the first main current amplitude, and The ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

7. The method according to claim 5, The value of the second primary current amplitude is less than the value of the first primary current amplitude. The value of the second main current amplitude is less than the value of the first main current amplitude, and The ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

8. The method according to claim 1, wherein the method further comprises: During the predetermined time period, electrical stimulation therapy comprising a third electrical stimulation pulse train is delivered to the patient via the medical device, wherein the third electrical stimulation pulse train comprises a third pulse frequency of less than 500 Hz; and In response to the passing of the predetermined time period, the delivery of the electrical stimulation therapy, including the third electrical stimulation pulse train, is stopped.

9. The method according to claim 1, further comprising: Electrical stimulation therapy comprising multiple primary electrical stimulation pulses is delivered to the patient; The medical device detects changes in the patient's posture, wherein: The electrical stimulation therapy, which delivers the first electrical stimulation pulse train to the patient, comprises delivering the first electrical stimulation pulse train, which includes a plurality of primary electrical stimulation pulses followed by a main electrical stimulation pulse, to the patient in response to a detected change in the patient's posture. The plurality of primary electrical stimulation pulses are configured to provide treatment to the patient, and The master electrical stimulation pulse is configured to induce the ECAP signal from the patient's tissue.

10. The method of claim 1, wherein the electrical stimulation therapy comprises a burst frequency greater than or equal to 1 Hz and less than or equal to 200 Hz, wherein the burst frequency comprises the frequency at which the first electrical stimulation pulse train and the second electrical stimulation pulse train are delivered to the patient.

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

12. A medical device configured as follows: The patient is delivered an electrical stimulation therapy comprising a first electrical stimulation pulse train and a second stimulation pulse train, wherein the first electrical stimulation pulse train comprises a first pulse frequency, and wherein the first electrical stimulation pulse train and the second electrical stimulation pulse train are spaced apart by a predetermined time period. After delivering the first electrical stimulation pulse train, the delivery of the electrical stimulation therapy is stopped for the predetermined time period. During the predetermined time period, evoked compound action potential (ECAP) signals from the patient's tissues are sensed; Based on the characteristic values ​​of the ECAP signal, the value of at least one parameter that at least partially defines the second electrical stimulation pulse train is determined, wherein the second electrical stimulation pulse train includes a second pulse frequency; and In response to the passing of the predetermined time period, the second electrical stimulation pulse train is delivered according to the value of at least one parameter that at least partially defines the second electrical stimulation pulse train.

13. The medical device according to claim 12, The ECAP signal mentioned above includes a first ECAP signal, and The medical device is further configured as follows: After delivering the second electrical stimulation pulse train, the delivery of the electrical stimulation treatment is stopped for the predetermined time period; During the predetermined time period, a second ECAP signal from the patient's tissue is sensed; The value of at least one parameter that at least partially defines the third electrical stimulation pulse train is determined based on the characteristic values ​​of the second ECAP signal; and the third electrical stimulation pulse train includes a pulse frequency; and In response to the passing of the predetermined time period, the third electrical stimulation pulse train is delivered according to the value of at least one parameter that at least partially defines the second electrical stimulation pulse train.

14. The medical device according to claim 12, wherein: The first electrical stimulation pulse train includes multiple primary electrical stimulation pulses followed by a main electrical stimulation pulse. The plurality of primary electrical stimulation pulses are defined by a primary parameter set and configured to aid in the treatment of the patient, and The master electrical stimulation pulse is defined by a master parameter set and configured to induce the ECAP signal from the patient's tissue, wherein the values ​​of the master parameter set are different from the values ​​of the primary parameter set.

15. The medical device of claim 14, wherein the first series of primary electrical stimulation pulses comprises a current amplitude greater than the pulse amplitude of the plurality of primary electrical stimulation pulses in the first series.

16. The medical device according to claim 14, The plurality of primary electrical stimulation pulses in the first sequence are primary current amplitudes. The first series of main electrical stimulation pulses includes a first main current amplitude. The second series of primary electrical stimulation pulses includes a second primary current amplitude. The second series of main electrical stimulation pulses includes a second main current amplitude, and In order to determine the value of at least one parameter defining the second electrical stimulation pulse train, the medical device is configured to: Determine the value of the second primary current amplitude, which is different from the value of the first primary current amplitude; and Determine the value of the second main current amplitude, which is different from the value of the first main current amplitude. The ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

17. The medical device according to claim 16, The value of the second primary current amplitude is greater than the value of the first primary current amplitude. The value of the second main current amplitude is greater than the value of the first main current amplitude, and The ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

18. The medical device according to claim 16, The value of the second primary current amplitude is less than the value of the first primary current amplitude. The value of the second main current amplitude is less than the value of the first main current amplitude, and The ratio of the second primary current amplitude to the second main current amplitude is the same as the ratio of the first primary current amplitude to the first main current amplitude.

19. The medical device of claim 12, wherein the medical device is further configured to: During the predetermined time period, electrical stimulation therapy comprising a third electrical stimulation pulse train is delivered to the patient, wherein the third electrical stimulation pulse train comprises a third pulse frequency of less than 500 Hz; and In response to the passing of the predetermined time period, the delivery of the electrical stimulation therapy, including the third electrical stimulation pulse train, is stopped.

20. A non-transitory computer-readable medium comprising instructions that, when executed, are configured to cause processing circuitry of an implantable medical device to: The stimulator of the implantable medical device is controlled to deliver electrical stimulation therapy to the patient, including a first electrical stimulation pulse train and a second electrical stimulation pulse train, wherein the first electrical stimulation pulse train includes a first pulse frequency, and wherein the first electrical stimulation pulse train and the second electrical stimulation pulse train are spaced apart by a predetermined time period. After the first electrical stimulation pulse train is delivered, the stimulation generator is controlled to stop the delivery of the electrical stimulation therapy for a predetermined period of time. During the predetermined time period, evoked compound action potential (ECAP) signals from the patient's tissues are sensed; Based on the characteristic values ​​of the ECAP signal, the value of at least one parameter that at least partially defines the second electrical stimulation pulse train is determined, wherein the second electrical stimulation pulse train includes a second pulse frequency; and In response to the elapsed predetermined time period, the stimulation generator is controlled to deliver the second electrical stimulation pulse train according to the value of at least one parameter that at least partially defines the second electrical stimulation pulse train.

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