Control pulses and postures for ecap

Abstract

Systems, devices, and techniques for adjusting electrical stimulation based on a posture state of a patient are described. For example, processing circuitry is configured to control delivery of a first notification stimulation pulse defined by at least a first value of a notification stimulation parameter; control delivery of a control stimulation pulse to a patient, the control stimulation pulse defined by at least a first value of a control stimulation parameter; determine a characteristic value of the ECAP signal evoked from the control stimulation pulse; receive, from a sensor, a posture state signal representative of a posture state of the patient; and adjust the first value of the notification stimulation parameter to a second value of the notification stimulation parameter based on the characteristic value of the ECAP signal and the posture state signal.

Description

Technical Field

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

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

[0003] In general, systems, devices, and techniques for managing the delivery of electrical stimulation based on evoked compound action potential (ECAP) signals sensed from a patient are described. When a patient moves, the distance between the implanted electrode and the target nerve changes. For example, when the subject is in a supine position compared to a standing position, the electrode implanted along the spine is closer to the spinal cord. Similarly, when the subject coughs or sneezes, the implanted electrode can move closer to the spinal cord. This changing distance between the electrode and the target tissue affects neural recruitment for a given intensity of delivered stimulation and may also alter the patient's perception and / or therapeutic benefit. Therefore, a characteristic value of the ECAP signal can represent the change in distance, and the system can use this characteristic value as feedback to modulate the electrical stimulation.

[0004] When in different postural states (e.g., sitting compared to a supine position), varying distances between the electrodes and the target tissue result in patients exhibiting different levels of sensitivity to changes in the stimulation parameters defining the electrical stimulation. In this way, the growth curve of the ECAP signal (e.g., the relationship between the eigenvalues ​​of the ECAP and the amplitude of the stimulation pulse) can depend at least in part on the patient's postural state. In one example, the closer the distance between the electrodes and the target tissue, the greater the sensitivity and the steeper the slope of the growth curve. As described herein, the system can use the detected patient postural state to inform how to use the ECAP signal in a control strategy that defines changes in the values ​​of stimulation parameters (such as frequency, amplitude, pulse width, and pulse shape) of subsequent pulses. Typically, the notification stimulation pulses can be configured to contribute to the patient's therapeutic effect, but the ECAP signal may not be detectable from these notification stimulation pulses. Therefore, control stimulation pulses with a pulse width shorter than the notification stimulation pulses can be delivered to the patient to detect the induced ECAP signal. The control stimulation pulses may or may not contribute to the patient's therapeutic effect. In one example, the system can select a gain value associated with the detected postural state to adjust the parameter values ​​of one or both of the control and notification stimulation pulses. The gain value can be correlated with the corresponding growth curve of the detected posture state. Alternatively, the system can select a target ECAP feature value based on the detected patient posture state.

[0005] In one example, a system includes: a sensing circuit system configured to sense an evoked compound action potential (ECAP) signal induced by a control stimulus pulse from a plurality of control stimulus pulses; and a processing circuit system configured to: control the delivery of a first notification stimulus pulse defined at least by a first value of a notification stimulus parameter, the notification stimulus pulse being one of a plurality of notification stimulus pulses; control the delivery of the control stimulus pulse to a patient, the control stimulus pulse being defined at least by the first value of the control stimulus parameter; determine a characteristic value of the ECAP signal induced by the control stimulus pulse; receive a posture state signal representing the patient's posture state from a sensor; adjust the first value of the notification stimulus parameter to a second value of the notification stimulus parameter based on the characteristic value of the ECAP signal and the posture state signal; and control the delivery of a second notification stimulus pulse from the plurality of notification stimulus pulses defined at least by the second value of the notification stimulus parameter.

[0006] In another example, a method includes: controlling the delivery of a first notification stimulus pulse defined at least by a first value of a notification stimulus parameter, the notification stimulus pulse being one of a plurality of notification stimulus pulses, by a processing circuitry system; controlling the delivery of a control stimulus pulse, one of a plurality of control stimulus pulses, to a patient by the processing circuitry system, the control stimulus pulse being defined at least by the first value of the control stimulus parameter; sensing an evoked compound action potential (ECAP) signal induced by the control stimulus pulse by a sensing circuitry system; determining a characteristic value of the ECAP signal induced by the control stimulus pulse by the processing circuitry system; receiving a posture state signal representing the patient's posture state by the processing circuitry system and from a sensor; adjusting the first value of the notification stimulus parameter to a second value of the notification stimulus parameter by the processing circuitry system based on the characteristic value of the ECAP signal and the posture state signal; and controlling the delivery of a second notification stimulus pulse, one of the plurality of notification stimulus pulses, defined at least by the second value of the notification stimulus parameter, by the processing circuitry system.

[0007] In another example, a computer-readable storage medium includes instructions that, when executed by a processing circuitry system, cause the processing circuitry system to control the delivery of a first notification stimulus pulse defined at least by a first value of a notification stimulus parameter, the notification stimulus pulse being one of a plurality of notification stimulus pulses; control the delivery of a control stimulus pulse of a plurality of control stimulus pulses to a patient, the control stimulus pulse being defined at least by the first value of the control stimulus parameter; control a sensing circuitry system to sense an evoked compound action potential (ECAP) signal induced by the control stimulus pulse; determine a characteristic value of the ECAP signal induced by the control stimulus pulse; receive a posture state signal representing the patient's posture state from a sensor; adjust the first value of the notification stimulus parameter to a second value of the notification stimulus parameter based on the characteristic value of the ECAP signal and the posture state signal; and control the delivery of a second notification stimulus pulse of the plurality of notification stimulus pulses defined at least by the second value of the notification stimulus parameter.

[0008] The summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive interpretation of the systems, apparatus, and methods described in detail in the accompanying drawings and the following detailed description. Further details of one or more examples of this disclosure are set forth in the accompanying drawings and the following detailed description. Other features, objectives, and advantages of these techniques will be apparent from the specification, drawings, and claims. Attached Figure Description

[0009] Figure 1This is a conceptual diagram illustrating an exemplary system including a medical device programmer and an IMD according to the technology of this disclosure.

[0010] Figure 2 yes Figure 1 A block diagram of an exemplary IMD.

[0011] Figure 3 yes Figure 1 A block diagram of an exemplary external programmer.

[0012] Figure 4 This is a graph of an exemplary ECAP signal sensed from a stimulus pulse.

[0013] Figure 5A , Figure 5B , Figure 5C and Figure 5D This is a timing diagram illustrating exemplary electrical stimulation pulses and corresponding sensed ECAPs according to one or more techniques of this disclosure.

[0014] Figure 6 This is a graph of an exemplary growth curve derived from the sensed ECAP during the corresponding posture state.

[0015] Figure 7 This is a flowchart illustrating exemplary operations for delivering control stimulus pulses and notifying stimulus pulses according to one or more techniques of this disclosure.

[0016] Figure 8 This is a diagram illustrating an exemplary technique for adjusting electrical stimulation therapy.

[0017] Figure 9 It is shown as follows Figure 8 A flowchart illustrating an exemplary operation for controlling stimulation therapy.

[0018] Figure 10 It is a graph showing the relationship between the ECAP voltage amplitude sensed according to one or more techniques of this disclosure and the stimulation current amplitude.

[0019] Figure 11 It is shown as follows Figure 10 A flowchart illustrating an exemplary operation for controlling stimulation therapy.

[0020] Throughout the specification and drawings, similar reference numerals represent similar elements. Detailed Implementation

[0021] This disclosure describes examples of medical devices, systems, and techniques for adjusting electrical stimulation delivered to a patient based on one or more characteristics of the patient's postural state and ECAP signals. Electrical stimulation therapy is typically delivered to a target tissue (e.g., a nerve in the spinal cord or muscles) via two or more electrodes. Parameters of the electrical stimulation therapy (e.g., electrode combination, voltage or current amplitude, pulse width, pulse frequency, etc.) are selected by the clinician and / or patient to provide relief for various symptoms (such as pain, neurological disorders, muscle disorders, etc.). However, the distance between the electrodes and the target tissue changes when the patient moves. Since neural recruitment at the nerve is a function of stimulation intensity (e.g., amplitude and / or pulse frequency) and the distance between the target tissue and the electrode, moving the electrode closer to the target tissue can lead to increased neural recruitment (e.g., possible pain sensation or impaired motor function), while moving the electrode further away from the target tissue can lead to decreased therapeutic efficacy for the patient. Certain patient postures (which may or may not include patient movement) can represent a corresponding distance (or change in distance) between the electrode and the nerve, and are therefore informational feedback variables used to modulate stimulation therapy.

[0022] In some cases, patients may experience discomfort or pain caused by transient patient states, referred to herein as transient hyperstimulation. For a variety of reasons, including coughing, sneezing, laughing, valsalva maneuvers, leg raises, neck movements, deep breathing, or other transient patient movements, electrodes can move closer to the target tissue. If the system delivers stimulation during these movements, the patient may perceive the stimulation as stronger (and potentially uncomfortable) because the distance between the electrode and the target tissue decreases for a short period. Although patients may anticipate such movements and preemptively reduce the intensity of the stimulation in an attempt to avoid these uncomfortable sensations, these patient movements can interfere with normal activity and may not be sufficient to consistently avoid the uncomfortable stimulation.

[0023] ECAP is a measure of neural recruitment because each ECAP signal represents a superposition of potentials generated by the firing of a population of axons in response to electrical stimulation (e.g., a stimulation pulse). Changes in the characteristics of the ECAP signal (e.g., the amplitude of a portion of the signal or the area under the curve of the signal) occur as a function of the number of axons that have been activated by the delivered stimulation pulse. For a given set of parameter values ​​defining the stimulation pulse and a given distance between the electrode and the target nerve, the detected ECAP signal may have specific characteristic values ​​(e.g., amplitude or area under the curve). Therefore, the system can determine whether the distance between the electrode and the nerve has increased or decreased in response to determining whether the measured ECAP characteristic value has increased or decreased. For example, if the set of parameter values ​​remains the same and the ECAP characteristic value of the amplitude increases, the system can determine that the distance between the electrode and the nerve has decreased.

[0024] In some examples, effective stimulation therapy may rely on a certain level of neural recruitment at the target nerve. Such effective stimulation therapy can alleviate one or more symptoms (e.g., pain perceived by the patient) without unacceptable levels of side effects (e.g., overwhelming stimulation perception). However, if the patient changes posture or otherwise engages in physical activity, the distance between the electrode and the nerve also changes. If the parameters defining the stimulation are not adjusted to compensate for this distance variation, it may lead to a loss of effective therapy and / or side effects. Furthermore, different distances between the electrode and the target nerve (e.g., caused by a shift from one postural state to another) may also result in different sensitivities to stimulation intensity (e.g., a smaller distance may lead to greater sensitivity to changes in stimulation intensity). If the system does not adjust its control strategies for these changes, adjustments to the stimulation parameter values ​​may be insufficient to maintain effective therapy or may provide too strong a stimulus in that postural state. Therefore, it may be beneficial to maintain effective therapy by adjusting how the stimulation intensity changes within a given postural state and / or by changing the target ECAP characteristic values ​​when the patient's postural state has changed.

[0025] As described herein, systems, devices, and techniques provide solutions to one or more of the aforementioned problems by adjusting the electrical stimulation therapy delivered to the patient based on one or more characteristics of the patient's postural state and ECAP signals. As mentioned above, the distance between the implanted electrodes and the target nerve changes when the patient moves. For example, when the subject is in a supine position, the electrodes implanted along the spine move closer to the spinal cord than when the subject is in a standing position, the electrodes are moved closer to the spinal cord. Because postural state affects the distance between the electrodes and the target nerve, the system can detect or otherwise acquire the patient's current postural state and adjust one or more aspects of the control strategy employed by the system to modulate the stimulation therapy in response to the detected ECAP signal. Postural state can refer to patient posture, activity level, or a combination of patient posture and activity level. In some examples, the system can select a treatment procedure or set of stimulation parameter values ​​based on the detected patient postural state.

[0026] The system may store or otherwise acquire gain values, growth curves, target ECAP characteristics, or other factors that influence the modulation of stimulation associated with the corresponding postural state. Electrical stimulation may be delivered to the patient by a medical device in the form of a series of stimulation pulses, and parameters defining the stimulation pulses may include pulse amplitude (current and / or voltage), pulse frequency, pulse width, pulse shape, and / or electrode combination. The system may modify, adjust, change, or otherwise regulate one or more parameters of the stimulation pulses over time to maintain a desired level of stimulation efficacy for the patient.

[0027] After the delivered stimulation pulse initially depolarizes the nerve, the nerve pulse, detectable as an ECAP signal, travels rapidly along the nerve fiber. If the stimulation pulse delivering the first electrode that induces the ECAP signal has an excessively long pulse width, different electrodes configured to sense the ECAP will sense the stimulation pulse itself as an artifact that blurs the lower-amplitude ECAP signal. Although the sensing electrodes can be positioned further away from the delivery stimulation pulse to avoid this artifact, the ECAP signal loses fidelity as the potential propagates from the electrical stimulation because different nerve fibers propagate the potential at different speeds. Therefore, sensing the ECAP at a location far from the stimulation electrode can avoid artifacts caused by stimulation pulses with long pulse widths, but the ECAP signal may lose the fidelity required to detect changes in the ECAP signal that occur as the distance from the electrode to the target tissue changes. In other words, the system may not be able to identify ECAP induced by certain stimulation pulses with relatively long pulse widths (e.g., stimulation pulses configured to provide a therapeutic effect to the patient) at any distance from the stimulation electrode that would interfere with the detection of the ECAP signal.

[0028] To avoid this ECAP detection problem with some stimulation pulses, in some examples, the medical device can be configured to deliver multiple control pulses and multiple notification pulses. The notification pulses can be configured to contribute to the patient's treatment outcome, but they may have stimulation parameters, such as pulse width, that overlap with the ECAP signal and prevent the system from detecting the ECAP signal or otherwise using the ECAP signal for feedback to adjust the parameter values ​​of the notification pulse. On the other hand, multiple control pulses can be configured to elicit a detectable ECAP signal. For example, the control pulses may have sufficiently short pulse widths to avoid interfering with ECAP signal detection. The control pulses may or may not contribute to the patient's treatment outcome. In this way, the system can be configured to adjust one or more parameters defining the notification pulses based on the detectable ECAP signal elicited by one or more control pulses.

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

[0030] The system can monitor one or more characteristic values ​​representing the detected ECAP signal and adjust stimulation parameter values ​​to attempt to achieve a target ECAP characteristic value. The system can adjust notification parameters that at least partially define subsequent notification pulses and control parameters that at least partially define subsequent control pulses. When adjusting notification and / or control parameter values ​​in response to determining that a characteristic value of the sensed ECAP signal is below or above the target ECAP characteristic value, the system can employ a gain value representing the amplitude or rate of change applied to the stimulation parameters to achieve the target ECAP characteristic value. The gain values ​​can be the same or different for the notification and control pulses. In some examples, the system can apply a scaling factor or otherwise adjust the gain value to suit notification and control pulses that may have different amplitudes or other parameters. For example, if the control pulse has a higher amplitude value than the notification pulse, the system can effectively reduce the gain value, or reduce the effect of the gain value on changes in the amplitude of the notification pulse, because the lower amplitude value of the notification pulse may not require as much change as the amplitude of the control pulse. Therefore, the system can increase or decrease the stimulation parameters based on the gain value to maintain the target ECAP characteristic value.

[0031] In some examples, the gain value can be a multiplier applied to the difference between the target ECAP feature value and the detected ECAP feature value. If the gain value is constant, the result is a linearly varying stimulus parameter value. For example, the system can choose a gain value for any detected ECAP feature value less than the target ECAP feature value, and the system can choose a different gain value for any detected ECAP feature value greater than the target ECAP feature value. In other examples, the gain value can be calculated using a function that can be linear or non-linear. In other words, for a given input or a set of inputs (e.g., the detected ECAP feature value and / or postural state can be inputs that affect the calculated gain value), the system can calculate different gain values ​​for increasing and / or decreasing the stimulus intensity.

[0032] In one example, the system may determine a gain value that changes for different sensed ECAP feature values ​​or different differences between a sensed ECAP feature value and a target ECAP feature value. Changing the gain value (via a linear or nonlinear function) will produce a nonlinear function that determines the adjusted stimulus parameter (e.g., the output of a nonlinear function). For example, the system may adjust the stimulus parameter value exponentially or logarithmically based on the difference between the sensed ECAP feature value and a threshold ECAP amplitude. In one example, the gain value is calculated by multiplying the difference between the sensed ECAP feature value and the threshold ECAP amplitude by a multiplier (e.g., a linear function) such that the gain value changes according to that difference between the sensed ECAP feature value and the threshold ECAP amplitude. In some examples, the gain value may represent a value selected from a table storing gain values ​​for the corresponding differences between sensed ECAP feature values ​​and threshold ECAP amplitudes. This table may produce a linear or nonlinear function for determining the next stimulus parameter value.

[0033] For example, a larger gain value will cause the system to make a larger adjustment to the stimulation parameters (e.g., notification parameters or control parameters) of the same stimulus pulse than would result from a smaller gain value. For nonlinear functions, this comparison of the gain value can be made relative to the same value of the difference between the sensed ECAP characteristic value and the threshold ECAP amplitude (e.g., the difference in the value representing the input value of the gain function). Therefore, for a given input value (or set of input values) of the gain function, the corresponding gain value (or set of gain values) changes. For ease of discussion, various examples have been discussed regarding the change of gain value relative to linear functions. It should be understood that nonlinear functions can also be used in such implementations, where the relative change of the gain value is therefore relative to the same value of the difference between the sensed ECAP characteristic value and the threshold ECAP amplitude.

[0034] Without varying gain values ​​for different postural states, the system may respond too slowly or too quickly due to adjustments in stimulation parameter values. If the gain value is too large for a postural state, the system may overcorrect the stimulation parameter values ​​(e.g., causing discomfort or reducing therapeutic efficacy). If the gain value is too small for a postural state, the system may need to iterate through the stimulation parameters multiple times before providing the appropriate stimulation intensity (e.g., also causing prolonged discomfort or prolonged ineffective treatment periods). Generally, postural states associated with a greater distance between the electrode and the target nerve tend to have larger gain values ​​than those associated with a closer distance. In this way, smaller gain values ​​can be associated with smaller distances between the electrode and the target nerve (e.g., postural states more sensitive to changes in stimulation intensity, such as the supine position). Conversely, larger gain values ​​can be associated with larger distances between the electrode and the target nerve (e.g., postural states less sensitive to changes in stimulation intensity, such as the prone position). The gain value can be inversely proportional to the growth curve of a specific posture state, where the growth curve can be a best-fit curve or line of ECAP characteristic values ​​(e.g., voltage amplitude) for a given stimulus parameter value (e.g., the current amplitude of the corresponding pulse that elicits the corresponding ECAP signal). In some examples, the target ECAP characteristic value can be the same for some or all posture states, but in other examples, the target ECAP characteristic value can be different between posture states. In this way, the system can select the target ECAP characteristic value associated with the detected posture state.

[0035] In another type of control strategy (e.g., a closed-loop feedback scheme), the system may employ a threshold ECAP feature value instead of a target ECAP feature value. The system may monitor the feature value of the sensed ECAP signal and decrease one or more stimulus parameter values ​​(e.g., notification parameter values ​​and / or control parameter values) from predetermined values ​​only in response to the feature value exceeding the threshold ECAP feature value. In other words, the system may be configured to attempt to keep the feature value of the sensed ECAP signal below the threshold ECAP feature value and increase the stimulus parameters back to predetermined values ​​only in response to the feature value falling back below the threshold ECAP feature value. In some examples, the system may select the gain value for adjusting the stimulus parameters based on the patient's current postural state. Alternatively, the system may select the threshold ECAP feature value based on the detected patient postural state.

[0036] In some examples, stimulation parameter values ​​can be predetermined and / or automatically adjusted by the system based on ECAP signal characteristics, postural state, and other types of feedback. An external programmer for the IMD can provide various features to support the association of stimulation parameter values ​​and / or ECAP signal characteristics with different postural states. As an example, the programmer can receive user input indicating the postural state the patient is currently occupying, along with the associated ECAP signal and / or corresponding characteristics. As another example, when the patient is in or transitioning to a defined postural state, the patient can indicate a previously undefined stimulation parameter value for that postural state. The indicated value can be defined for that postural state. As yet another example, the user can link multiple postural states and select a set of stimulation parameter values ​​for each of the linked postural states to deliver treatment. In this way, it may not be necessary to specify a separate set of stimulation parameter values ​​for each individual postural state.

[0037] In some examples, the medical device delivering electrical stimulation (e.g., an implantable medical device (IMD)) may also employ a posture state detector (e.g., one or more sensors) to detect the patient's postural state. In other examples, the IMD may receive data from one or more separate devices that sense the patient's postural state. The IMD may then adjust one or more stimulation parameters in response to different postural states, such as those indicated by the posture state detector.

[0038] Users can define stimulus parameter values ​​(e.g., notification parameter values ​​for notification pulses and / or control parameter values ​​for control pulses) used to deliver treatment to a patient, and, for example, simultaneously associate stimulus parameter values ​​with multiple postural states based on user input. As another example, when storing a set of pre-established postural state definitions for delivering postural state-responsive treatment, the device can allow the patient to submit a request to update that set of pre-established postural state definitions via a patient programmer. For example, the programmer can be configured to receive user input that changes the definitions of one or more postural states. Additionally, postural state definitions can be modified based on user treatment adjustments and / or postural state information. In some cases, postural states can be expanded and split. In other cases, the size of a postural state can be reduced based on postural state information. Therefore, using one or more features described in this disclosure, stimulus parameter values ​​can be flexibly, conveniently, and efficiently specified for various postural states, including predetermined postural states and patient-created postural states.

[0039] Notification pulses and control pulses are generally described herein as different stimulation pulses reflecting different types of electrical stimulation. However, different types of electrical stimulation and their corresponding pulses can be described with different properties. For example, a first type of electrical stimulation may include a first pulse (such as a notification pulse) configured to primarily contribute to the treatment of the patient. This first pulse of the first type of electrical stimulation may also have one or more features (e.g., pulse width) that prevent or reduce the system's ability to detect an ECAP signal induced by the first pulse of the first type of electrical stimulation, because artifacts representing the first pulse itself overlap with and obscure at least a portion of the corresponding induced ECAP signal. A second type of electrical stimulation may include a second pulse (such as a control pulse) defined by one or more parameter values ​​selected to induce an ECAP signal that is sensed and detectable by the system. Because the second pulse is configured to induce a detectable ECAP signal, it may be referred to as a "sensing pulse" or a "test pulse." For example, the second pulse of the second type of electrical stimulation may improve the detectability of the ECAP signal, such as by not generating artifacts that obscure the ECAP signal, or by not otherwise preventing or reducing the system's ability to detect the ECAP signal from each second pulse. Furthermore, the second pulse can be defined by parameter values ​​selected to elicit an ECAP signal that modifies at least one or more parameter values ​​of the first pulse of the first type of electrical stimulation. Therefore, the first and second pulses can differ in at least one parameter (e.g., current and / or voltage amplitude, pulse width and / or frequency). The first pulse can be at least partially interleaved with at least some of the second pulses. For example, the system can deliver one first pulse and one second pulse alternately. In another example, the number of first pulses can differ from the number of second pulses by a certain ratio or percentage. When the first and second pulses are completely interleaved, this ratio can be 1:1. In examples where the second pulse is delivered at a lower frequency than the first pulse, the ratio of the first pulse to the second pulse can be 10:1. In other examples, when the second pulse and the corresponding sensed ECAP signal occur more frequently than the first pulse, the ratio of the first pulse to the second pulse can be 1:4. The second pulse may or may not contribute to the treatment and / or the sensation perceived by the patient, but the primary purpose of the second pulse is to elicit a corresponding ECAP signal that can be detected by the system and is separate from any sensed artifacts representing the second pulse itself.

[0040] Although electrical stimulation is typically described herein as an electrical stimulation pulse, it can be delivered in a non-pulsed form in other examples. For instance, electrical stimulation can be delivered as a signal with various waveform shapes, frequencies, and amplitudes. Thus, electrical stimulation in the form of a non-pulsed signal can be a continuous signal that may have a sinusoidal waveform or other continuous waveforms.

[0041] Figure 1 This is a conceptual diagram illustrating an exemplary system 100, which includes an implantable medical device (IMD) 110 for delivering electrical stimulation therapy to a patient 102. While the techniques described in this disclosure are generally applicable to a variety of medical devices, including external devices and IMDs, for illustrative purposes, the application of such techniques to IMDs, and more specifically, to implantable electrical stimulators (e.g., neurostimulators), will be described. More specifically, for illustrative purposes, this disclosure relates to implantable SCS systems, but is not limited thereto, and also to other types of medical devices or other therapeutic applications of medical devices.

[0042] like Figure 1 As shown, system 100 includes an IMD 110, leads 108A and 108B, and an external programmer 104, illustrated in conjunction with a patient 102 (typically a human patient). Figure 1 In one example, IMD 110 is an implantable electrical stimulator configured to generate and deliver electrical stimulation therapy to patient 102 via one or more electrodes of leads 108A and / or 108B (collectively, “leads 108”), for example, to relieve chronic pain or other symptoms. In other examples, IMD 110 may be coupled to a single lead carrying multiple electrodes, or more than two leads each carrying multiple electrodes. In some examples, a stimulation signal or pulse (e.g., a control pulse) may be configured to trigger a detectable ECAP signal that IMD 110 can use to determine the postural state occupied by patient 102 and / or to determine how to adjust one or more parameters defining the stimulation therapy. IMD 110 may be a chronic electrical stimulator implanted in patient 102 for weeks, months, or even years. In other examples, IMD 110 may be a temporary or experimental stimulator used to screen or evaluate the efficacy of electrical stimulation for long-term treatment. In one example, the IMD 110 is implanted in patient 102, while in another example, the IMD 110 is an external device coupled to a percutaneously implanted lead. In some examples, the IMD 110 uses one or more leads, while in other examples, the IMD 110 is leadless.

[0043] IMD 110 may be made of components sufficient to mount IMD 110 (e.g., Figure 2The component shown may be constructed from any polymer, metal, or composite material housed within the patient 102. In this example, the IMD 110 may be constructed with a biocompatible shell such as titanium or stainless steel, or a polymeric material such as silicone, polyurethane, or liquid crystal polymer, and surgically implanted into a site near the pelvis, abdomen, or buttocks of the patient 102. In other examples, the IMD 110 may be implanted in other suitable sites within the patient 102, depending on, for example, the target site within the patient 102 for delivering electrical stimulation therapy. The outer shell of the IMD 110 may be constructed to provide a hermetically sealed component, such as a rechargeable or non-rechargeable power source. Furthermore, in some examples, the outer shell of the IMD 110 is selected from materials that facilitate the reception of energy to charge a rechargeable power source.

[0044] Electrical stimulation energy (which may be, for example, pulses based on constant current or constant voltage) is delivered from the IMD 110 to one or more target tissue sites in the patient 102 via one or more electrodes (not shown) of the implanted lead 108. Figure 1 In one example, lead 108 carries electrodes placed adjacent to the target tissue of spinal cord 106. One or more of these electrodes may be positioned at the distal end of lead 108 and / or at other locations along the midpoint of the lead. Lead 108 may be implanted and coupled to IMD 110. The electrodes may deliver electrical stimulation generated by an electrical stimulation generator in IMD 110 to the tissue of patient 102. Although each lead 108 may be a single lead, lead 108 may include lead extensions or other segments that may facilitate implantation or positioning of lead 108. In some other examples, IMD 110 may be a leadless stimulator having one or more electrode arrays disposed on the housing of the stimulator, rather than leads extending from the housing. Furthermore, in some other examples, system 100 may include one or more leads, each coupled to IMD 110 and pointing to similar or different target tissue sites.

[0045] The electrodes of lead 108 may be electrode pads on a paddle-shaped lead, circular (e.g., annular) electrodes surrounding the lead body, conformal electrodes, cuff electrodes, segmented electrodes (e.g., electrodes disposed at different circumferential positions around the lead, rather than continuous annular electrodes), any combination thereof (e.g., annular electrodes and segmented electrodes), or any other type of electrode capable of forming a combination of monopolar, bipolar, or multipolar electrodes for treatment. For illustrative purposes, annular electrodes disposed at different axial positions at the distal end of lead 108 will be described.

[0046] The deployment of electrodes via lead 108 has been described for illustrative purposes, but the electrode array can be deployed in different ways. For example, a housing associated with a leadless stimulator can hold the electrode array, such as rows and / or columns (or other patterns), to which displacement operations can be applied. Such electrodes can be arranged as surface electrodes, ring electrodes, or protrusions. 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 examples, the electrode array includes electrode segments arranged at corresponding locations around the periphery of the leads, for example, arranged as one or more segmented rings around the circumference of a cylindrical lead. In other examples, one or more leads in lead 108 are linear leads having eight ring electrodes along the axial length of the lead. In yet another example, the electrodes are segmented rings arranged linearly along the axial length of the lead around the periphery of the lead.

[0047] The set of stimulation parameters defining the stimulation pulses for electrical stimulation therapy performed by the electrodes of the IMD 110 via the leads 108 may include information identifying which electrodes have been selected to deliver stimulation according to the stimulation program, the polarity of the selected electrodes (i.e., the electrode combination used in the program), and the voltage or current amplitude, pulse frequency, pulse width, and pulse shape of the stimulation delivered by the electrodes. These stimulation parameter values ​​constituting the set of stimulation parameters defining the pulses may be predetermined parameter values ​​defined by the user and / or automatically determined by the system 100 based on one or more factors or user input. Notification pulses may be defined by a set of notification stimulation parameter values, and control pulses may be defined by a set of control stimulation parameter values.

[0048] although Figure 1 Involving SCS therapy, such as for pain treatment, but in other examples, system 100 can be configured to treat any other condition that can benefit from electrical stimulation therapy. For example, system 100 can be used to treat tremor, Parkinson's disease, epilepsy, pelvic floor abnormalities (e.g., urinary incontinence or other bladder dysfunction, fecal incontinence, pelvic pain, bowel dysfunction, or sexual dysfunction), obesity, gastroparesis, or mental disorders (e.g., depression, mania, obsessive-compulsive disorder, anxiety, etc.). In this way, system 100 can be configured to provide therapy in the form of deep brain stimulation (DBS), peripheral nerve stimulation (PNS), peripheral nerve field stimulation (PNFS), cortical stimulation (CS), pelvic floor stimulation, gastrointestinal stimulation, or any other form of stimulation therapy capable of treating the condition of patient 102.

[0049] In some examples, lead 108 includes one or more sensors configured to allow IMD 110 to monitor one or more parameters of patient 102, such as patient activity, pressure, temperature, or other characteristics. One or more sensors may be provided to supplement or replace treatment delivery performed by lead 108.

[0050] The IMD 110 is typically configured to deliver electrical stimulation therapy (e.g., notification pulses and / or control pulses) to a patient 102, either alone or in combination with electrodes carried or defined by the outer housing of the IMD 110, via selected combinations of electrodes carried by one or two leads of leads 108. The target tissue for the electrical stimulation therapy can be any tissue affected by electrical stimulation, which can be in the form of electrical stimulation pulses or continuous waveforms. In some examples, the target tissue includes nerves, smooth muscle, or skeletal muscle. Figure 1 In the examples shown, the target tissue is tissue close to the spinal cord 106 (such as within the intrathecal space or epidural space of the spinal cord 106), or in some examples, it is an adjacent nerve branching from the spinal cord 106. The lead 108 can be introduced into the spinal cord 106 via any suitable area (such as the thoracic, cervical, or lumbar region). For example, stimulation of the spinal cord 106 can prevent pain signals from traveling through the spinal cord 106 and reaching the brain of the patient 102. The patient 102 can perceive the interruption of the pain signal as pain relief, and thus as an effective therapeutic outcome. In other examples, stimulation of the spinal cord 106 can produce sensory abnormalities, which can reduce the patient 102's perception of pain, thus providing an effective therapeutic outcome.

[0051] The IMD 110 is configured to generate electrical stimulation therapy according to one or more therapeutic stimulation programs and deliver it to a target stimulation site within the patient 102 via electrodes connected to a lead 108 leading to the patient 102. The therapeutic stimulation program typically defines notification pulses, but may also define control pulses (if the control pulses also contribute to the therapeutic effect). The therapeutic stimulation program defines the values ​​of one or more parameters (e.g., a set of parameters) that define one aspect of the therapy delivered by the IMD 110 according to the program. For example, a therapeutic stimulation program that controls the IMD 110 to deliver stimulation in pulsed form may define the values ​​of voltage or current pulse amplitude, pulse width and pulse rate (e.g., pulse frequency), electrode combination, pulse shape, etc., of the stimulation pulses delivered by the IMD 110 according to the program.

[0052] Users (such as clinicians or patients 102) can interact with the user interface of external programmer 104 to program the IMD 110. Programming the IMD 110 typically refers to the generation and transfer of commands, programs, or other information to control the operation of the IMD 110. In this way, the IMD 110 can receive transmitted commands and programs from external programmer 104 to control stimulation, such as stimulation pulses to provide electrical stimulation therapy. For example, external programmer 104 can transmit therapeutic stimulation programs, stimulation parameter adjustments, therapeutic stimulation program selections, postural states, user input, or other information to control the operation of the IMD 110, for example, via wireless telemetry or a wired connection.

[0053] In some cases, if the external programmer 104 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 104 is primarily intended for use by a patient, it may be characterized as a patient programmer. The patient programmer is typically accessible to the patient 102 and, in many cases, may be a portable device that accompanies the patient 102 throughout their daily life. For example, the patient programmer may receive input from the patient 102 when the patient wishes to terminate or change electrical stimulation therapy, or when the patient perceives the stimulation being delivered. Generally, a physician or clinician programmer may support the selection and generation of programs by a clinician for use by the IMD 110, while a patient programmer may support the adjustment and selection of such programs by the patient during regular use. In other examples, the external programmer 104 may include or be part of an external charging device for recharging the power source of the IMD 110. In this way, a user can use one or more devices to program and charge the IMD 110.

[0054] As described herein, information can be transmitted between the external programmer 104 and the IMD 110. Therefore, the IMD 110 and the external programmer 104 can communicate wirelessly using any technology known in the art. Examples of communication technologies may include, for example, radio frequency (RF) telemetry and inductive coupling, but other technologies are also contemplated. In some examples, the external programmer 104 includes a communication head that can be placed near the implantation site of the IMD 110 close to the patient's body to improve the quality or safety of communication between the IMD 110 and the external programmer 104. Communication between the external programmer 104 and the IMD 110 may occur during power transmission or separately from power transmission.

[0055] In some examples, the IMD 110, in response to commands from an external programmer 104, delivers electrical stimulation therapy (e.g., notification pulses and / or control pulses) to the target tissue site of the spinal cord 106 of the patient 102 via electrodes (not shown) on lead 108 according to multiple therapeutic stimulation programs. In some examples, the IMD 110 modifies the therapeutic stimulation programs as the patient 102's treatment needs evolve over time. For example, modification of the therapeutic stimulation programs may cause adjustment of at least one parameter of multiple stimulation pulses. The efficacy of the treatment may decrease when the patient 102 receives the same treatment for an extended period. In some cases, the parameters of multiple stimulation pulses may be updated automatically.

[0056] As described herein, the IMD 110 can be configured to detect ECAP signals representing the number of nerve fibers activated by a delivered stimulus signal (e.g., a control pulse). Since the distance between the electrode and the target nerve varies for different postural states (e.g., static posture and / or active component), the characteristic values ​​of one or more ECAP signals can indicate the currently occupied postural state when the IMD 110 detects one or more ECAP signals. In one example, the IMD 110 can deliver multiple control pulses defined by different parameter values ​​and detect the corresponding ECAP signal triggered by each pulse. The IMD 110 can determine a relationship between the characteristic values ​​from each ECAP signal and the different parameter values ​​of the control pulses, and this relationship may be different for each different postural state. In one example, this relationship can be a curve of the characteristic values ​​of the ECAP (e.g., the amplitude of the ECAP signal) versus the values ​​of the stimulus parameters (e.g., the current amplitude of the corresponding control pulse) that trigger each ECAP signal from which the characteristic values ​​are derived. Each postural state may have a corresponding curve with changes in slope and / or intercept. In some examples, the gain value can be determined from the slope of the growth curve, where the gain value can be inversely proportional to the slope.

[0057] In this disclosure, the efficacy of electrical stimulation therapy can be indicated by one or more characteristics of the action potentials induced by control pulses delivered by the IMD 110 (e.g., the amplitude of one or more peaks or the amplitude between one or more peaks, or the area under the curve of one or more peaks) (i.e., characteristics of the ECAP signal). Electrical stimulation therapy delivered by the leads 108 of the IMD 110 can induce compound action potentials in neurons within the target tissue, which travel up and down along the target tissue and eventually reach the sensing electrodes of the IMD 110. Furthermore, stimulation can also elicit at least one ECAP signal, and the ECAP in response to stimulation can also be a substitute for therapeutic effect. The amount of induced action potentials (e.g., the number of action potential signals propagating in neurons) can be based on various parameters of the electrical stimulation pulses, such as amplitude, pulse width, frequency, pulse shape (e.g., the switching rate at the start and / or end of the pulse), etc. The switching rate can be defined as the rate of change of the voltage and / or current amplitude of the control pulse at the start and / or end of each phase within each control pulse. For example, a very high slew rate indicates a steep pulse or even near-vertical edges, while a low slew rate indicates a longer rise (or fall) in the amplitude of the control pulse. In some examples, these parameters contribute to the intensity of the electrical stimulation. Additionally, the characteristics of the ECAP signal (e.g., amplitude) can vary based on the distance between the stimulating electrode and the nerve affected by the electric field generated by the delivered control pulse.

[0058] Some example techniques for adjusting stimulation parameter values ​​for stimulation pulses (e.g., notification pulses and / or control pulses that may or may not contribute to the treatment of the patient) are based on comparing characteristic values ​​of a measured ECAP signal with target ECAP characteristic values. In response to the delivery of a control pulse defined by a set of stimulation parameter values, the IMD 110 senses the potential of tissue of the spinal cord 106 of the patient 102 via two or more electrodes inserted on leads 108 to measure the electrical activity of the tissue. The IMD 110, for example, utilizes electrodes on one or more leads 108 and associated sensing circuitry to sense the ECAP from the target tissue of the patient 102. In some examples, the IMD 110 receives signals indicative of the ECAP from one or more sensors (e.g., one or more electrodes and circuitry) inside or outside the patient 102. Such exemplary signals may include signals indicative of the ECAP of the tissue of the patient 102. Examples of the one or more sensors include one or more sensors configured to measure the compound action potential of the patient 102 or indicative of the physiological effects of the compound action potential. For example, to measure the physiological effects of a compound action potential, one or more sensors may be an accelerometer, a pressure sensor, a flexure sensor, a sensor configured to detect the posture of patient 102, or a sensor configured to detect the respiratory function of patient 102. However, in other examples, external programmer 104 receives a signal indicating a compound action potential in target tissue of patient 102 and sends a notification to IMD 110.

[0059] exist Figure 1 In the example, IMD 110 is described as performing a variety of processing and computational functions. However, external programmer 104 may alternatively perform one, several, or all of these functions. In this alternative example, IMD 110 is used to relay sensed signals to external programmer 104 for analysis, and external programmer 104 sends instructions to IMD 110 to adjust one or more parameters defining electrical stimulation therapy based on the analysis of the sensed signals. For example, IMD 110 may relay sensed signals indicating ECAP to external programmer 104. External programmer 104 may compare the parameter values ​​of ECAP with target ECAP characteristic values, and in response to the comparison, external programmer 104 may instruct IMD 110 to adjust one or more stimulation parameters that define the electrical stimulation notification pulses delivered to patient 102, and in some examples, define control pulses delivered to the patient.

[0060] In some examples, the system may vary the target ECAP characteristic value and / or growth rate over a period of time based on changes in a stimulus threshold (e.g., a patient-specific perception threshold or detection threshold). The system can be programmed to alter the target ECAP characteristic to adjust the intensity of the notification pulse, thereby providing the patient with a sensory experience of variation (e.g., an increase or decrease in neural activation volume). Although the system can alter the target ECAP characteristic value, it can still use the received ECAP signal to adjust one or more parameter values ​​of the notification pulse and / or control pulse to satisfy the target ECAP characteristic value.

[0061] One or more devices within system 100 (such as IMD 110 and / or external programmer 104) may perform various functions as described herein. For example, IMD 110 may include a stimulation circuitry configured to deliver electrical stimulation, a sensing circuitry configured to sense a plurality of ECAP signals, and a processing circuitry. The processing circuitry may be configured to control the stimulation circuitry to deliver a plurality of electrical stimulation pulses (e.g., control pulses) with different amplitude values, and to control the sensing circuitry to detect a corresponding ECAP signal among the plurality of ECAP signals after each of the plurality of electrical stimulation pulses has been delivered. The processing circuitry of IMD 110 may then determine the patient’s postural state based on the plurality of ECAP signals.

[0062] As described herein, the IMD 110 can adjust or modify one or more stimulation parameters that at least partially define the electrical stimulation based on the detected postural state of the patient 102. The IMD 110 can use the detected postural state to determine how to use the ECAP signal in a closed-loop feedback system to adjust the stimulation parameters defining the notification pulse and / or control pulse. In one example, the IMD 110 includes a stimulation generation circuitry configured to generate and deliver electrical stimulation to the patient 102 based on one or more sets of stimulation parameters (e.g., notification parameters and / or control parameters) of the corresponding notification pulse and / or control pulse that at least partially defines the electrical stimulation. Each set of stimulation parameters may include at least one of amplitude, pulse width, pulse frequency, or pulse shape.

[0063] IMD 110 may also include a sensing circuitry configured to sense an ECAP signal triggered by delivered electrical stimulation (such as a control pulse). IMD 110 may also include a processing circuitry configured to control the delivery of a notification pulse to patient 102 based on a first value of a notification stimulation parameter, and to determine a characteristic value of the ECAP signal detected from the control pulse. IMD 110 may also receive a posture state signal from a sensor representing the patient's posture state. In some examples, IMD 110 may then determine a gain value of the stimulation parameter based on the posture state signal, and adjust the first value of the notification stimulation parameter to a second value based on the characteristic value and gain value of the ECAP signal. In other examples, IMD 110 may additionally or alternatively adjust a target ECAP characteristic value or a threshold ECAP characteristic value based on the posture state signal. IMD 110 may then control the subsequent delivery of one or more notification stimulation pulses based on the second value of the notification stimulation parameter. In this way, the ECAP signal "notification" triggered by the control pulse defines the notification parameter value of the next notification pulse.

[0064] In some examples, the processing circuitry of the IMD 110 can be configured to adjust a first value of a notification parameter to a second value of a notification parameter by increasing or decreasing one of the notification parameters of the notification pulse based on a growth curve associated with the patient's postural state. Additionally, the processing circuitry can be configured to adjust the control parameter values ​​of subsequent control pulses based on the growth curve. As discussed herein, the growth curve can represent the relationship between one or more parameters of the delivered control pulse and a characteristic of the ECAP signal. For example, this characteristic can be the amplitude of the ECAP signal (e.g., the amplitude between the N1 peak and P2 peak of the ECAP signal), one or more areas under the peaks of the ECAP signal, or some other measure indicating neural activation that generates the ECAP signal. In some examples, the gain value can be inversely proportional to the slope of the growth curve.

[0065] When the IMD 110 is configured to modulate stimulation pulses to maintain consistent neural activation (such as increasing and decreasing stimulation parameters to maintain target ECAP characteristic values), the IMD 110 can perform exemplary procedures. For example, the IMD 110 can monitor the amplitude as a characteristic value of the detected ECAP signal. The IMD 110 can adjust a first value of the stimulation parameters to a second value by subtracting the amplitude from the patient's target ECAP amplitude value to generate a differential amplitude. The differential amplitude is the difference between the amplitude detected from the ECAP signal and the target ECAP amplitude value. The IMD 110 can then multiply the differential amplitude by a gain value that at least partially defines the control pulse to generate the differential value. The gain value can be a multiplier or fraction selected based on the detected postural state. A larger gain value can be associated with postural states where the distance between the electrode and the target nerve is greater, as this distance results in reduced sensitivity to changes in stimulation pulse intensity. IMD 110 can then add the differential value to the previous amplitude value (e.g., the amplitude value of the last control pulse delivered and triggering the ECAP signal) to generate a second value that at least partially defines the next control pulse to be delivered to patient 102. IMD 110 can then multiply the differential value by a scaling factor to generate a notification differential value that indicates how much the amplitude of the notification pulse needs to be changed. The scaling factor can be greater than one when the notification pulse amplitude is greater than the control pulse amplitude, and conversely, the scaling factor can be less than one when the notification pulse amplitude is less than the control pulse amplitude. IMD 110 can then add the notification differential value to the previous amplitude value of the notification pulse to generate a second value for the notification pulse to be subsequently delivered to the patient.

[0066] In other examples, the IMD 110 may not attempt to maintain consistent neural activation by adjusting the stimulation pulse to achieve a target ECAP eigenvalue. Instead, the IMD 110 monitors the eigenvalue of the ECAP signal and takes action only when the eigenvalue exceeds a threshold ECAP eigenvalue. An eigenvalue exceeding the threshold ECAP eigenvalue indicates increased stimulus perception, which may be higher than the patient's discomfort or pain threshold. Therefore, reducing the intensity of the stimulation pulse when the eigenvalue exceeds this stimulation level reduces the likelihood that the patient 102 will experience any discomfort that may arise due to changes in postural state or any momentary movement. For example, the IMD 110 may be configured to compare the eigenvalue of the ECAP signal with a threshold ECAP eigenvalue and determine that the eigenvalue of the ECAP signal is greater than the threshold ECAP eigenvalue. In response to determining that the eigenvalue of the ECAP signal is greater than the threshold ECAP eigenvalue, the IMD 110 may be configured to decrease a first value of the notification stimulation parameter to a second value of the notification stimulation parameter to deliver a subsequent notification pulse. Similarly, the IMD 110 may be configured to decrease the value of a control stimulation parameter that defines the subsequent control pulse to be delivered.

[0067] As long as the ECAP characteristic value continues to exceed the threshold ECAP characteristic value, the IMD 110 may continue to decrease the notification stimulus parameter value and / or control stimulus parameter value. Once the notification and control stimulus parameters have been decreased, the IMD 110 may attempt to increase the notification and control stimulus parameter values ​​back to a predetermined first value for the notification stimulus pulse and / or control stimulus pulse. The IMD 110 may be configured to determine other characteristic values ​​of subsequent ECAP signals triggered by a control stimulus pulse delivered after the first ECAP signal is sensed. In response to determining that another characteristic value of the subsequent ECAP signal has decreased below the threshold ECAP characteristic value, the IMD 110 may then increase the value of the notification and / or control stimulus parameter back to a value that is restricted to being less than or equal to the first value (e.g., increasing back to a predetermined value for the notification and / or control stimulus pulse that may be determined by a set of stimulus parameters or treatment procedures). In some examples, the IMD 110 may iteratively increase the notification and / or control stimulus parameter value until the first value or the original value is reached again after the characteristic value of the ECAP signal has remained below the threshold ECAP characteristic value. The IMD 110 can increase the notification and / or control stimulus parameter values ​​at a slower rate than decreasing them, but in other examples, the IMD 110 can increase and decrease the notification and / or control stimulus parameters at the same rate.

[0068] The detected postural state can be one of multiple postural states. In some examples, each postural state may be associated with a corresponding growth curve representing the relationship between the ECAP value and the control stimulus parameter value when the patient occupies that particular postural state. In some examples, the IMD 110 may select a gain value from multiple gain values ​​associated with the corresponding postural state based on the postural state signal. The gain value may represent at least one of the increment rate (e.g., how quickly the IMD 110 should increase the stimulus parameter value) or decrement rate (e.g., how slowly the IMD 110 should decrease the stimulus parameter value) of the control stimulus parameter (or, in some examples, the notification stimulus parameter) that at least partially defines the control stimulus pulse. In other examples, the gain value may represent a specific amplitude by which the IMD 110 should increment or decrement the previous parameter value of the control pulse and / or notification pulse each time the IMD 110 increases or decreases the parameter value. This specific amplitude can effectively generate the rate of change of the stimulus parameter value that the IMD 110 can adjust. Alternatively, the IMD 110 may select a target ECAP feature or a threshold ECAP feature based on the detected postural state. Patients may or may not benefit from postural state-specific target or threshold ECAP features.

[0069] The IMD 110 can sense the postural state of the patient 102 at predetermined intervals or within predetermined time periods. In some examples, the IMD 110 can sense the postural state in response to triggering events, such as changes requested by the patient during stimulation therapy, sensing events indicating the patient's condition such as pain, or any other trigger. In some examples, the IMD 110 can adjust the postural state sensing frequency based on whether a change in postural state is detected. For example, the IMD 110 can determine, at least from signals indicating the patient's postural state, that the patient's postural state has changed. In response to determining that the postural state has changed, the IMD 110 can change at least one of the ECAP sensing frequencies. The IMD 110 can increase the postural state sensing frequency when more postural state changes are expected, and decrease the postural state sensing frequency when fewer postural state changes are expected. The sensing frequency can refer to the sensor sampling frequency and / or the frequency at which the processing circuitry analyzes data obtained from one or more sensors. In this way, the IMD 110 can adjust the sensing frequency to save power consumption or otherwise reduce processing tasks.

[0070] As discussed herein, some exemplary techniques for adjusting the notifying stimulation parameter values ​​and / or controlling stimulation parameter values ​​of an electrical stimulation signal are based on comparing characteristic values ​​of a measured ECAP signal with target ECAP characteristic values, or using control parameter values ​​at a determined target ECAP characteristic to notify adjustments to one or more control parameter values ​​and / or notifying parameter values ​​to maintain the target ECAP based on known relationships between the parameters. For example, during the delivery of an electrical stimulation signal, the IMD 110 senses the potentials of tissue 106 of the spinal cord 102 of the patient 102 via two or more electrodes inserted on lead 108 to measure the electrical activity of the tissue. The IMD 110, for example, utilizes electrodes on one or more leads 108 and associated sensing circuitry to sense the ECAP from the target tissue of the patient 102. In some examples, the IMD 110 receives signals indicative of the ECAP from one or more sensors (e.g., one or more electrodes and circuitry) inside or outside the patient 102. Such exemplary signals may include signals indicative of the ECAP of the tissue of the patient 102. Examples of one or more sensors include one or more sensors capable of measuring the compound action potential of the patient 102 or indicative of the physiological effects of the compound action potential. For example, to measure the physiological effects of a compound action potential, one or more sensors may be an accelerometer, a pressure sensor, a flexure sensor, a sensor that can detect the posture of patient 102, or a sensor that can detect the respiratory function of patient 102. However, in other examples, external programmer 104 receives a signal indicating a compound action potential in target tissue of patient 102 and sends a notification to IMD 110.

[0071] exist Figure 1In this example, IMD 110 is described as performing various processing and computational functions. However, external programmer 104 may alternatively perform one, several, or all of these functions. In this alternative example, IMD 110 is used to relay sensed signals to external programmer 104 for analysis, and external programmer 104 sends instructions to IMD 110 to adjust one or more parameters defining the electrical stimulation signal based on the analysis of the sensed signals. For example, IMD 110 may relay sensed signals indicating ECAP to external programmer 104. External programmer 104 may compare the parameter values ​​of ECAP with target ECAP characteristic values, and in response to this comparison, external programmer 104 may instruct IMD 110 to adjust one or more stimulation parameters defining the electrical stimulation signal.

[0072] In the exemplary technology described herein, notification stimulation parameter values, control stimulation parameter values, growth curves, postural states, and target ECAP characteristics (e.g., ECAP values ​​indicating target stimulus intensity) may be initially set in the clinic but may be set and / or adjusted by the patient 102 at home. Once the target ECAP characteristics are set, the exemplary technology allows for automatic adjustment of the notification and / or control stimulation parameters to maintain consistent neural activation volume and consistent treatment perception for the patient as the distance from the electrode to the neuron changes. The ability to change the stimulation parameter values ​​also allows for long-term therapeutic efficacy and enables consistency of stimulus intensity (e.g., as indicated by the ECAP) by comparing the measured ECAP values ​​to the target ECAP characteristics. IMD 110 can perform these changes without intervention from the physician or patient 102.

[0073] In some examples, the system may change the target ECAP feature value over a period of time (e.g., based on sensed changes in posture or patient condition). The system may be programmed to change the target ECAP feature to adjust the intensity of notification and / or control impulses, thereby providing the patient with a sensation of change (e.g., increasing or decreasing neural activation volume). In one example, the system may be programmed to cause the target ECAP feature value to oscillate between a maximum and a minimum target ECAP feature value at a predetermined frequency to provide the patient with a sensation that can be perceived as a wave or other sensation that can provide therapeutic relief. The maximum target ECAP feature value, the minimum target ECAP feature value, and the predetermined frequency may be stored in the memory of IMD 110 and may be updated in response to signals from external programmer 104 (e.g., user requests to change the values ​​stored in the memory of IMD 110). In other examples, the target ECAP feature value may be programmed to steadily increase or steadily decrease to a baseline target ECAP feature value over a period of time. In other examples, the external programmer 104 can program the target ECAP characteristic value to change automatically over time according to other predetermined functions or modes. In other words, the target ECAP characteristic value can be programmed to change incrementally by a predetermined amount or percentage, selected based on a predetermined function (e.g., a sine function, ramp function, exponential function, logarithmic function, etc.). The increment of the target ECAP characteristic value change can be varied for each specific number of pulses or a specific unit of time. Although the system can change the target ECAP characteristic value, the system can still use the received ECAP signal to adjust one or more notification and / or control parameter values ​​of the electrical stimulation signal to meet the target ECAP characteristic value.

[0074] Although in one example the IMD 110 takes the form of an SCS device, in other examples the IMD 110 takes the form of any combination of the following devices: such as a deep brain stimulation (DBS) device, an implantable cardioverter defibrillator (ICD), a pacemaker, a cardiac resynchronization therapy device (CRT-D), a left ventricular assist device (LVAD), an implantable sensor, an orthopedic device, or a drug pump.

[0075] Figure 2 This is a block diagram of IMD 200. IMD 200 can be... Figure 1 An example of IMD 110. In Figure 2In the example shown, IMD 200 includes a switching circuit system 202, a stimulus generation circuit system 204, a sensing circuit system 206, a processing circuit system 208, a sensor 210, a telemetry circuit system 212, a power source 214, and a memory 216. Each of these circuits may be or includes a programmable or fixed-function circuit system capable of performing the functions attributed to the respective circuit system. For example, processing circuit system 208 may include a fixed-function or programmable circuit system, stimulus generation circuit system 204 may include circuitry capable of generating electrical stimulation signals (such as pulses or continuous waveforms) on one or more channels, sensing circuit system 206 may include sensing circuitry for sensing signals, and telemetry circuit system 212 may include telemetry circuitry for transmitting and receiving signals. Memory 216 may store computer-readable instructions that, when executed by processing circuit system 208, cause IMD 200 to perform the various functions described herein. Memory 216 may be a storage device or other non-transitory medium.

[0076] exist Figure 2 In the example shown, memory 216 stores patient posture state data 218, which may include one or more patient postures, activity levels, or combinations of patient postures and activity levels. A pre-established set of patient posture state definitions may be stored in the patient posture state data 218. Posture state definitions may be modified based on user treatment adjustments and / or posture state information. In some cases, posture states may be expanded and split, or alternatively, the size of a posture state may be reduced based on posture state information. Posture state definitions may be updated automatically or by the patient, including creating new posture states. Posture states may include, for example, supine positions, prone positions, left lateral and / or right lateral positions, sitting positions, reclining positions, standing positions, and / or activities such as running or riding in a car.

[0077] The memory 216 may store the stimulation parameter settings 220 within the memory 216 or in a separate area within the memory 216. Each stored stimulation parameter setting 220 defines values ​​for one or more sets of electrical stimulation parameters (e.g., notification stimulation parameter sets and control stimulation parameter sets), such as pulse amplitude, pulse width, pulse frequency, electrode combination, pulse burst rate, pulse burst duration, and / or waveform shape. The stimulation parameter settings 220 may also include additional information, such as instructions regarding the delivery of electrical stimulation signals based on stimulation parameter relationship data, which may include relationships between two or more stimulation parameters based on data from electrical stimulation signals delivered to the patient 102 or data transmitted from an external programmer 104. The stimulation parameter relationship data may include measurable aspects associated with the stimulation, such as ECAP characteristic values. Another portion of the stimulation parameter settings 220 or the memory 216 may include instructions regarding how the processing circuitry system 208 may adjust the notification stimulation parameters and / or control stimulation parameters based on at least one of the detected postural state and / or target ECAP characteristic values ​​or threshold ECAP characteristic values, as described herein.

[0078] Memory 216 also stores patient ECAP characteristics 222, which may include target ECAP characteristics and / or threshold ECAP characteristic values ​​determined for the patient and / or a history of ECAP characteristic values ​​measured for the patient. Memory 216 may also store growth curve data 224 in a region separate from or as part of the patient stimulation parameter settings. Instead of or in addition to growth curve data 224, memory 216 may include processing circuitry 208 available for adjusting the gain value of notification and / or control stimulation pulses as described herein. In other examples, growth curve data 224 may include information about the relationship between ECAP characteristics of one or more postural states and control stimulation parameters.

[0079] Therefore, in some examples, the stimulation generation circuit system 204 generates electrical stimulation signals (e.g., notification pulses and control pulses) according to the described electrical stimulation parameters. Other ranges of stimulation parameter values ​​may also be useful and may depend on the target stimulation site within the patient 102. Although stimulation pulses are described, the stimulation signal can be of any form, such as a continuous-time signal (e.g., a sine wave). The switching circuit system 202 may include one or more switch arrays, one or more multiplexers, one or more switches (e.g., a switch matrix or other set of switches), or other circuit systems configured to direct stimulation signals from the stimulation generation circuit system 204 to one or more of the electrodes 232, 234 or to direct sensed signals from one or more of the electrodes 232, 234 to the sensing circuit system 206. In other examples, the stimulation generation circuit system 204 and / or the sensing circuit system 206 may include sensing circuit systems to direct signals to one or more of the electrodes 232, 234 and / or to one or more of the electrodes 232, 234, which may or may not include the switching circuit system 202.

[0080] The sensing circuitry 206 can be configured to monitor signals from any combination of electrodes 232, 234. In some examples, the sensing circuitry 206 includes one or more amplifiers, filters, and analog-to-digital converters. The sensing circuitry 206 can be used to sense physiological signals, such as ECAP. In some examples, the sensing circuitry 206 detects ECAP from a specific combination of electrodes 232, 234. In some cases, the specific combination of electrodes used to sense ECAP includes electrodes different from a set of electrodes 232, 234 used to deliver control and / or notification stimulation pulses. Alternatively, in other cases, the specific combination of electrodes used to sense ECAP includes at least one electrode from the same set of electrodes used to deliver notification and / or control stimulation pulses to patient 102. The sensing circuitry 206 can provide signals to the analog-to-digital converter for conversion into digital signals for processing, analysis, storage, or output by the processing circuitry 208.

[0081] The processing circuitry system 208 may include one or more of the following: a microprocessor, a controller, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a discrete logic circuitry system, or any other processing circuitry system that can provide functionality attributable to the processing circuitry system 208, which may be embodied herein as firmware, hardware, software, or any combination thereof. The processing circuitry system 208 controls the stimulus generation circuitry system 204 to generate electrical stimulation signals according to the stimulus parameter settings 220 stored in the memory 216, applying stimulus parameter values ​​such as the pulse amplitude, pulse width, pulse frequency, and waveform shape of each electrical stimulation signal.

[0082] exist Figure 2 In the example shown, the set of electrodes 232 includes electrodes 232A, 232B, 232C, and 232D, and the set of electrodes 234 includes electrodes 234A, 234B, 234C, and 234D. In other examples, a single lead may include all eight electrodes 232 and 234 along a single axial length of the lead. The processing circuitry 208 also controls the stimulation generation circuitry 204 to generate electrical stimulation signals and apply these signals to a selected combination of electrodes 232, 234. In some examples, the stimulation generation circuitry 204 includes a switching circuit (instead of or as a supplement to the switching circuitry 202) that couples the stimulation signals to selected conductors within the lead 230, which in turn delivers the stimulation signals through the selected electrodes 232, 234. Such a switching circuit can be a switch array, a switch matrix, a multiplexer, or can selectively couple stimulation energy to selected electrodes 232, 234 and use the selected electrodes 232, 234 to selectively sense the patient ( Figure 2 (Not shown in the image) Any other type of switching circuit system for bioelectric nerve signals of the spinal cord.

[0083] However, in other examples, the stimulus generation circuit system 204 does not include a switching circuit, and the switching circuit system 202 is not connected between the stimulus generation circuit system 204 and the electrodes 232, 234. In these examples, the stimulus generation circuit system 204 includes multiple pairs of voltage sources, current sources, voltage absorbers, or current absorbers connected to each of the electrodes 232, 234, such that each pair of electrodes has a unique signal circuit. In other words, in these examples, each of the electrodes 232, 234 is independently controlled via its own signal circuit (e.g., via a combination of a regulated voltage source and absorber or a regulated current source and absorber), which is the opposite of the switching signal between the electrodes 232, 234.

[0084] The electrodes 232, 234 on the corresponding leads 230 can be constructed using a variety of different designs. For example, one or two leads of the leads 230 may include one or more electrodes at each longitudinal location along the length of the lead, such as including one electrode at different peripheral locations around the periphery of the lead at each of locations A, B, C, and D. In one example, the electrodes may be electrically coupled to the stimulation generation circuit system 204, for example, via the switching circuit system 202 and / or the stimulation generation circuit system 204, via corresponding wires of a straight or coiled connector within the lead housing extending to the proximal end of the lead. In another example, each electrode of the leads may be an electrode deposited on a thin film. The thin film may include conductive traces for each electrode extending along the length of the film to the proximal end connector. The thin film may then be wrapped (e.g., spirally wrapped) around an internal component to form the lead 230. These and other configurations can be used to form leads with complex electrode geometries.

[0085] Although the sensing circuit system 206 is in Figure 2 The stimulation generation circuitry system 204 and the processing circuitry system 208 are integrated into a common housing, but in other examples, the sensing circuitry system 206 may be located in a separate housing from the IMD 200 and may communicate with the processing circuitry system 208 via wired or wireless communication technologies.

[0086] In some examples, one or more of electrodes 232 and 234 may be used to sense the ECAP. For example, electrodes 232 and 234 may sense a portion of the voltage amplitude of the ECAP signal, wherein the sensed voltage amplitude is characteristic of the ECAP signal.

[0087] Memory 216 may be configured to store information within IMD 200 during operation. Memory 216 may include a computer-readable storage medium or a computer-readable storage device. In some examples, memory 216 includes one or more of short-term memory or long-term memory. Memory 216 may include, for example, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), magnetic disk, optical disk, flash memory, or electrically programmable memory (EPROM) or electrically erasable programmable memory (EEPROM). In some examples, memory 216 is used to store data indicating instructions to be executed by processing circuitry system 208. As discussed herein, memory 216 may store patient posture state data 218, stimulation parameter settings 220, patient ECAP characteristics 222, and growth curve data 224.

[0088] Sensor 210 may include one or more sensing elements that sense values ​​of corresponding patient parameters. As described above, electrodes 232 and 234 may be electrodes that sense values ​​of the ECAP via sensing circuitry 206, the ECAP values ​​indicating the target stimulation intensity caused at least in part by a set of control stimulation parameter values. Sensor 210 may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other type of sensor. Sensor 210 may output patient parameter values ​​that can be used as feedback to control the delivery of electrical stimulation signals. IMD 200 may include additional sensors coupled within the housing of IMD 200 and / or via one of the leads in lead 108 or other leads. Additionally, for example, IMD 200 may wirelessly receive sensor signals from remote sensors via telemetry circuitry 212. In some examples, one or more of these remote sensors may be located outside the patient's body (e.g., carried on an outer surface of the skin, attached to clothing, or otherwise positioned outside the patient's body). In some examples, signals from sensor 210 may indicate a postural state (e.g., sleep, wakefulness, sitting, standing, etc.), and processing circuitry 208 may select target and / or threshold ECAP feature values ​​based on the indicated postural state. In this way, processing circuitry 208 may be configured to determine the postural state currently occupied by patient 102.

[0089] Under the control of the processing circuit system 208, the telemetry circuit system 212 supports the IMD 200 and an external programmer ( Figure 2 Wireless communication between the IMD 200 (not shown) or another computing device. As updates to the program, the processing circuitry 208 of the IMD 200 can receive (e.g., notification and / or control pulses) values ​​of various stimulation parameters (such as amplitude and electrode combinations) from an external programmer via the telemetry circuitry 212. Updates to the stimulation parameter settings 220 and the input efficacy threshold settings 226 can be stored in memory 216. The telemetry circuitry 212 in the IMD 200, as well as the telemetry circuitry in other devices and systems described herein (such as external programmers), can communicate via radio frequency (RF) communication technology. Furthermore, the telemetry circuitry 212 can interact with the external medical device programmer (IMD 200) via proximal sensing interaction with the external programmer. Figure 2 (Not shown in the image) communicates. An external programmer can be... Figure 1 An example of an external programmer 104. Thus, the telemetry circuit system 212 can continuously, periodically, or upon request from the IMD 110 or the external programmer, send information to the external programmer.

[0090] Power source 214 delivers operating power to various components of IMD 200. Power source 214 may include a rechargeable or non-rechargeable battery and power generation circuitry to generate operating power. Recharging can be achieved via proximal inductive interaction between an external charger and an inductive charging coil within IMD 200. In other examples, a conventional primary battery may be used. In some examples, processing circuitry 208 may monitor the remaining charge (e.g., voltage) of power source 214 and select stimulation parameter values ​​that can deliver similarly effective therapy at lower power consumption levels when an extended operating time of power source 214 is required. For example, power source 214 may switch to a lower pulse frequency based on a relationship of parameters that provide similar ECAP characteristic values.

[0091] According to the technology disclosed herein, the stimulation generation circuitry system 204 of the IMD 200 receives instructions via telemetry circuitry system 212 to deliver electrical stimulation to a target tissue site in the patient's spinal cord via a plurality of electrode combinations of electrodes 232, 234 via leads 230 and / or the housing of the IMD 200, according to stimulation parameter settings 220. Each electrical stimulation signal can trigger an ECAP sensed by sensing circuitry system 206 via electrodes 232 and 234. Processing circuitry system 208 can receive information indicating the ECAP signal generated in response to the electrical stimulation signal (e.g., a numerical value indicating the characteristics of the ECAP expressed in electrical units such as voltage or power) via the electrical signals sensed by sensing circuitry system 206. Stimulation parameter settings 220 can be updated according to the ECAP recorded at sensing circuitry system 206.

[0092] Typically, the pulse width of the notification pulse is greater than the pulse width of the control pulse. This difference in pulse width allows the system to detect ECAPs induced from the control pulse, provided that the longer pulse width of the notification pulse prevents the induced ECAP or at least some portion of the induced ECAP from being detectable. In some examples, multiple notification stimulus pulses are defined by notification pulse widths greater than about 300 microseconds and less than about 1000 microseconds, while multiple control stimulus pulses are defined by control pulse widths less than about 300 microseconds. In one example, multiple notification pulses each have a pulse width greater than about 300 μs and less than about 2000 μs (e.g., 2 milliseconds). In some examples, the notification pulse width is greater than about 300 μs and less than about 900 μs. In another example, the notification pulse width is greater than about 300 μs and less than about 500 μs. In one example, the notification pulse has a pulse width of about 450 μs and a pulse frequency of about 60 Hz. The amplitude of the pulse (current and / or voltage) can be between approximately 0.5 mA (or volts) and approximately 10 mA (or volts), but in other examples the amplitude can be lower or higher.

[0093] In one example, the predetermined pulse frequency of the multiple notification pulses may be less than approximately 400 Hz. In some examples, the predetermined pulse frequency of the multiple pulses may be between approximately 50 Hz and 70 Hz. In one example, the predetermined pulse frequency of the multiple pulses may be approximately 60 Hz. However, in other examples, the notification pulses may have a frequency greater than 400 Hz or less than 50 Hz. Additionally, the notification pulses may be delivered in the form of a pulse train, wherein the inter-train frequency of the notification pulses is low enough that the sensing ECAP triggered by the control pulse can still be matched within a window between consecutive pulses delivered within the pulse train. In any example, the processing circuitry system 208 may be configured to detect the ECAP triggered from the corresponding control stimulus pulse.

[0094] The pulse width of the control pulse can be shorter than that of the notification pulse to reduce or prevent sensed electrical artifacts from the control pulse from obscuring the ECAP signal (in other words, the pulse width of the notification pulse can be longer than that of the control pulse). For example, the control pulse can be less than approximately 300 microseconds (μs). In one example, the control pulse can be a biphasic pulse with approximately 100 μs of positive phase and approximately 100 μs of negative phase separated by an interphase interval of approximately 30 μs. In this way, the stimulation electrode at one end of the lead can deliver the control pulse, and the electrode at the other end of the same lead can sense the ECAP signal with minimal or no interference from the control pulse itself. Generally, the term "pulse width" herein refers to the total duration of each phase of a single pulse, and the interphase interval where appropriate. In some examples, a single pulse may include a single phase (i.e., a monophasic pulse), or in other examples, it may include two or more phases (e.g., a biphasic or triphasic pulse). The pulse width defines the time period that begins at the start time of the first phase of the pulse and ends at the end time of the last phase of the pulse (e.g., a biphasic pulse having a positive phase lasting 100 μs, a negative phase lasting 100 μs, and a phase interval lasting 30 μs defines a pulse width of 230 μs).

[0095] The processing circuitry system 208 may be configured to compare one or more features of the ECAP sensed by the sensing circuitry system 206 with target ECAP features (e.g., patient ECAP feature 222) stored in the memory 216. For example, the processing circuitry system 208 may determine the amplitude of each ECAP signal received at the sensing circuitry system 206, and may determine a representative amplitude of at least one corresponding ECAP signal, and compare the representative amplitudes of a series of ECAP signals with the target ECAP feature value.

[0096] In other examples, the processing circuitry 208 may use a representative amplitude of at least one corresponding ECAP to modify other parameters of the stimulation pulse to be delivered (e.g., notification pulse and / or control pulse), such as pulse width, pulse frequency, and pulse shape. All of these parameters can contribute to the intensity of the stimulation pulse, and changing one or more of these parameter values ​​can effectively adjust the intensity of the stimulation pulse to compensate for the altered distance between the stimulation electrode and the nerve indicated by the characteristics of the ECAP signal (e.g., representative amplitude).

[0097] In some examples, lead 230 may be a linear 8-electrode lead (not shown); a different set of electrodes can be used to perform sensing and stimulation delivery. In a linear 8-electrode lead, each electrode can be numbered consecutively from 0 to 7. For example, electrode 1 can be used as a cathode and electrodes 0 and 2 as anodes (e.g., protected cathodes) to generate pulses, and electrodes 6 and 7, located at opposite ends of the electrode array, can be used to sense the corresponding ECAP signal. This strategy minimizes interference of the stimulation pulse on the sensing of the corresponding ECAP. Other electrode combinations can be implemented, and the electrode combinations can be changed via telemetry circuitry system 212 using a patient programmer. For example, the stimulating electrode and sensing electrode can be positioned closer together. Shorter pulse widths for non-therapeutic pulses allow the sensing electrode to be closer to the stimulating electrode.

[0098] In one example, sensor 210 can detect the patient's postural state, including changes in activity or posture. Processing circuitry 208 can receive indications of changes in the patient's activity level or posture from sensor 210, and can initiate or modify the delivery of multiple pulses based on stimulation parameter settings 220. For example, processing circuitry 208 can increase the frequency of pulse delivery and the corresponding ECAP sensing in response to receiving an indication that the patient's activity has increased (which could indicate a possible change in the distance between the electrode and the nerve). Alternatively, processing circuitry 208 can decrease the frequency of pulse delivery and the corresponding ECAP sensing in response to receiving an indication that the patient's activity has decreased. In some examples, one or more treatment parameters (e.g., frequency, amplitude, slew rate, pulse width, etc.) can be adjusted (e.g., increased or decreased) in response to receiving an indication that the patient's postural state has changed. Processing circuitry 208 can update patient postural state data 218 and growth curve data 224 based on signals received from sensor 210.

[0099] Figure 3 This is a block diagram of an exemplary external programmer 300. The external programmer 300 can be... Figure 1An example of an external programmer 104. Although programmer 300 is generally described as a handheld device, external programmer 300 can be a larger portable device or a more fixed device. Additionally, in some examples, external programmer 300 may be included as part of an external charging device or include the functionality of an external charging device. Figure 3 As shown, the external programmer 300 may include a processing circuitry 302, a memory 304, a user interface 306, a telemetry circuitry 308, and a power source 310. The memory 304 may store instructions that, when executed by the processing circuitry 302, cause the processing circuitry 302 and the external programmer 300 to provide the functions attributed to the external programmer 300 throughout this disclosure. Each of these components, circuitry, or modules may include circuitry capable of performing some or all of the functions described herein. For example, the processing circuitry 302 may include processing circuitry that performs the processes discussed with respect to the processing circuitry 302.

[0100] Generally, programmer 300 includes any suitable hardware arrangement, individually or in combination with software and / or firmware, to perform techniques belonging to programmer 300 and its processing circuitry 302, user interface 306, and telemetry circuitry 308. In various examples, programmer 300 may include one or more processors, such as one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry system, and any combination of such components. In various examples, programmer 300 may also include memory 304 (such as RAM, ROM, PROM, EPROM, EEPROM, flash memory, hard disk, CD-ROM) containing executable instructions for causing one or more processors to perform actions belonging to them. Furthermore, although processing circuitry 302 and telemetry circuitry 308 are described as separate, in some examples, processing circuitry 302 and telemetry circuitry 308 are functionally integrated. In some examples, processing circuitry 302 and telemetry circuitry 308 correspond to individual hardware units, such as ASICs, DSPs, FPGAs, or other hardware units.

[0101] Memory 304 (e.g., a storage device) may store instructions that, when executed by processing circuitry 302, enable processing circuitry 302 and programmer 300 to provide the functions attributed to programmer 300 throughout this disclosure. For example, memory 304 may include instructions that enable processing circuitry 302 to retrieve stimulation parameter settings from memory, select a spatial electrode motion mode, or receive user input and send a corresponding command to programmer 300, or instructions for any other function. Additionally, memory 304 may include multiple stimulation parameter settings, each including a set of parameters defining the electrical stimulation. Memory 304 may also store data received from a medical device (e.g., IMD 110). For example, memory 304 may store ECAP-related data recorded at the sensing circuitry of the medical device, and memory 304 may also store data from one or more sensors of the medical device.

[0102] User interface 306 may include buttons or a keypad, lights, a speaker for voice commands, and a display such as a liquid crystal display (LCD), a light-emitting diode (LED), or an organic light-emitting diode (OLED). In some examples, the display may be a touchscreen. User interface 306 may display any information related to the delivery of electrical stimulation, identified patient behavior, sensed patient parameter values, patient behavior criteria, or any other such information. External programmer 300 may receive user input (e.g., an indication of when the patient changes their postural state) via user interface 306. Input may be in the form of, for example, pressing a button on a keypad or selecting an icon from a touchscreen. Input may request to start or stop electrical stimulation, may request a new spatial electrode movement pattern or a change to an existing spatial electrode movement pattern, or may request other changes to the delivery of electrical stimulation. In other examples, user interface 306 may receive input from the patient and / or clinician regarding treatment efficacy, such as binary feedback, numerical ratings, text input, etc. In some examples, processing circuitry system 302 may interpret a patient's request to change treatment as negative feedback regarding the current parameter values ​​used to define the treatment.

[0103] Under the control of the processing circuitry 302, the telemetry circuitry 308 can support wireless communication between the medical device and the programmer 300. The telemetry circuitry 308 can communicate with another computing device via wireless communication technology or directly via a wired connection. In some examples, the telemetry circuitry 308 provides wireless communication via RF or a near-side sensing medium. In some examples, the telemetry circuitry 308 includes an antenna, which can take various forms, such as an internal antenna or an external antenna.

[0104] Examples of local wireless communication technologies that can be used to facilitate communication between the programmer 300 and the IMD 110 include RF communication according to the 902.11 or Bluetooth specification set or other standards or proprietary telemetry protocols. In this way, other external devices may be able to communicate with the programmer 300 without establishing a secure wireless connection. As described herein, the telemetry circuitry system 308 can transmit spatial electrode movement patterns or other stimulation parameter values ​​to the IMD 110 to deliver electrical stimulation.

[0105] In some examples, selections of stimulus parameter settings (e.g., notification parameter settings and / or control parameter settings) may be transmitted to a medical device for delivery to the patient. In other examples, stimulus parameter settings may include medication, activity, or other instructions that the patient must perform themselves or that a caregiver must perform for the patient 102. In some examples, the external programmer 300 may provide visual, auditory, and / or tactile notifications indicating the presence of a new instruction. In some examples, the external programmer 300 may need to receive user input confirming that the instruction has been completed.

[0106] According to the technology disclosed herein, the user interface 306 of the external programmer 300 receives from a clinician an instruction to update one or more patient posture settings, gain values, growth curve settings, or stimulation parameter settings. Updating posture settings, gain values, and growth curve settings may also update stimulation parameter settings, including changing one or more parameter values ​​of the notification stimulation pulse delivered by the medical device, such as pulse amplitude, pulse width, pulse frequency, electrode combination, and / or waveform shape, according to the settings. In some examples, gain values ​​and / or growth curve settings may be based on sensed ECAP signals, posture data, and stimulation parameter data. The user interface 306 may also receive instructions from the clinician to command any electrical stimulation.

[0107] Power source 310 can deliver operating power to various components of programmer 300. Power source 310 may be the same as or substantially similar to power source 214. Power source 310 may include a battery and power generation circuitry for generating operating power. In some examples, the battery is rechargeable to allow for long-term operation. Recharging can be achieved by electrically coupling power source 310 to a bracket or plug connected to an alternating current (AC) outlet. Alternatively, recharging can be achieved through near-side inductive interaction between an external charger and an inductive charging coil within external programmer 300. In other examples, conventional batteries (e.g., nickel-cadmium or lithium-ion batteries) may be used. Furthermore, external programmer 300 may be directly coupled to an AC outlet for operation.

[0108] Figure 3 The architecture of the external programmer 300 shown is illustrated as an example. The techniques described in this disclosure can be used in... Figure 3This includes the exemplary external programmer 300 and other types of systems not specifically described herein. Nothing in this disclosure should be construed as limiting the technology of this disclosure to... Figure 3 The exemplary architecture shown.

[0109] Figure 4 This is a graph 400 of an exemplary ECAP signal sensed in response to a corresponding stimulus pulse (e.g., a control pulse). Figure 3 As shown, graph 400 illustrates exemplary ECAP signals 402 (dashed line) and 404 (solid line). Each of ECAP signals 402 and 404 can be sensed from a control pulse delivered from a protected cathode and a biphasic pulse including an interphase interval between each positive and negative phase of the pulse. The protected cathode in the stimulating electrode is located at one end of an 8-electrode lead, while the two sensing electrodes are located at the other end of the 8-electrode lead. ECAP signal 402 shows the voltage amplitude sensed as a result of a subthreshold stimulating pulse. A peak 406 is detected in ECAP signal 402, representing an artifact of the delivered pulse. However, no propagating signal is detected after the artifact in ECAP signal 404 because the pulse is subthreshold.

[0110] Compared to ECAP signal 402, ECAP signal 404 represents the voltage amplitude detected from the overthreshold stimulation pulse. A peak 406 is detected in ECAP signal 404, representing an artifact of the delivered pulse. Following peak 406, ECAP signal 404 also includes peaks P1, N1, and P2, which are three peaks representing the propagating action potential from ECAP. The exemplary duration of the artifact along with peaks P1, N1, and P2 is approximately 1 millisecond (ms). When the ECAP of ECAP signal 404 is detected, different characteristics can be identified. For example, a characteristic of ECAP could be an amplitude between N1 and P2. This N1-P2 amplitude can be detected even if the artifact is projected onto a relatively large signal P1, and the N1-P2 amplitude is minimally affected by electronic drift in the signal. In other examples, the characteristic of ECAP used to control the pulse could be the amplitude of P1, N1, or P2 relative to a neutral voltage or zero voltage. In some examples, the ECAP characteristic used to control the pulse may be the sum of two or more of the peaks P1, N1, or P2. In other examples, the ECAP signal 404 may be the area under one or more of the peaks P1, N1, and / or P2. In other examples, the ECAP characteristic may be the ratio of one of the peaks P1, N1, or P2 to another of these peaks. In some examples, the ECAP characteristic may be the slope between two points in the ECAP signal, such as the slope between N1 and P2. In other examples, the ECAP characteristic may be the time between two points in the ECAP, such as the time between N1 and P2. The time between two points in the ECAP signal may be referred to as the ECAP delay and may indicate the type of fiber captured by the pulse. An ECAP signal with a lower delay (i.e., a smaller delay value) indicates a higher percentage of nerve fibers with faster signal propagation, while an ECAP signal with a higher delay (i.e., a larger delay value) indicates a higher percentage of nerve fibers with slower signal propagation. In other examples, other characteristics of the ECAP signal may be used.

[0111] As long as the pulse amplitude 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. When it is determined that the pulse delivers effective treatment to the patient, the target ECAP characteristic (e.g., target ECAP amplitude) can be determined based on the ECAP signal detected from the pulse. Therefore, the ECAP signal represents the distance between the stimulating electrode and the nerve that is suitable for the stimulation parameter values ​​of the pulse delivered at that time. Therefore, the IMD 110 can attempt to change the stimulation pulse parameter values ​​by attempting to detect changes in the measured ECAP characteristic values ​​and maintain the target ECAP characteristic value during the delivery of the stimulation pulse (e.g., notification pulse and / or control pulse). Alternatively, the IMD 110 can attempt to prevent undesirable stimulation intensity by reducing the stimulation pulse intensity in response to the ECAP characteristic value exceeding a threshold ECAP characteristic value.

[0112] Figure 5A This is a timing diagram 500A illustrating an example of an electrical stimulation pulse (e.g., a control pulse) and the corresponding sensed ECAP according to one or more techniques of this disclosure. For convenience, refer to... Figure 2 IMD 200 pairs Figure 5A The following description is provided. As shown in the figure, timing diagram 500A includes a first channel 502, multiple control pulses 504A–504N (collectively referred to as "control pulses 504"), a second channel 506, multiple corresponding ECAPs 508A–508N (collectively referred to as "ECAP 508"), and multiple stimulus interference signals 509A–509N (collectively referred to as "stimulus interference signals 509"). Figure 5A In the example, control pulse 504 may or may not contribute to the treatment of the patient. In either case, control pulse 504 may trigger a corresponding ECAP 508 to determine the relative neural recruitment induced by control pulse 504, which can be reflected as a growth curve of the sensed ECAP 508 specific to the patient's postural state.

[0113] The first channel 502 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In one example, the stimulating electrode of the first channel 502 may be located on the side of the lead opposite to the sensing electrode of the second channel 506. The control pulse 504 may be an electrical pulse delivered to the patient's spinal cord through at least one of the electrodes 232, 234, and the control pulse 504 may be a balanced biphasic square pulse with phase intervals. In other words, each control pulse in the control pulse 504 is shown to have a negative phase and a positive phase separated by phase intervals. For example, the control pulse 504 may have a negative voltage, the same amount of time and amplitude as when it has a positive voltage. Note that the negative voltage phase may precede or follow the positive voltage phase. The control pulse 504 may be delivered according to instructions stored in the storage device 212 of the IMD 200.

[0114] In some examples, each stimulation pulse in control pulse 504 may be part of a pulse scan configured to determine the relationship between the stimulation parameter values ​​of the pulses and the resulting characteristic values ​​of the corresponding ECAP 508. For example, this relationship may be a growth curve of the ECAP voltage amplitude versus the pulse current amplitude. In this way, each stimulation pulse in control pulse 504 may differ from each other by parameter values, such as iteratively increasing current amplitudes. This scan may be performed for each of multiple posture states to determine the growth curve, gain value, or some characteristic associated with the ECAP for that posture state. In one example, control pulse 504 may have a pulse width of less than approximately 300 microseconds (e.g., the total time of the positive phase, negative phase, and phase interval is less than 300 microseconds). In another example, for each phase of a biphasic pulse, control pulse 504 may have a pulse width of approximately 100 microseconds. In some examples, the pulse width of control pulse 504 may be longer than 300 microseconds, as long as the pulse width does not interfere with the detection of one or more desired characteristics of the induced ECAP 508. Figure 5A As shown, control pulse 504 can be delivered via channel 502. The delivery of control pulse 504 can be delivered via lead 230 in the protected cathode electrode assembly. For example, if lead 230 is a linear 8-electrode lead, the protected cathode assembly consists of a center cathode electrode and an anode electrode immediately adjacent to that cathode electrode.

[0115] The second channel 506 is a time / voltage (and / or current) graph indicating the voltage (or current) at at least one of the electrodes 232, 234. In one example, the electrode of the second channel 506 may be located on the side of the lead opposite to the electrode of the first channel 502. In response to a control pulse 504, an ECAP 508 can be sensed from the patient's spinal cord at electrodes 232, 234. The ECAP 508 is an electrical signal that can propagate along the nerve away from the origin of the control pulse 504. In one example, the ECAP 508 is sensed by an electrode different from the electrode used to deliver the control pulse 504. Figure 5A As shown, ECAP 508 can be recorded on the second channel 506. In some examples, ECAP 508 may not be sensed after each control pulse 504.

[0116] Stimulus interference signals 509A, 509B, and 509N (e.g., artifacts of the control pulse) can be sensed by lead 230 and can be sensed within the same time period as the delivery of control pulse 504. Because these interference signals can have a larger amplitude and intensity than ECAP 508, any ECAP arriving at IMD 200 during the occurrence of stimulus interference signal 509 may not be adequately sensed by the sensing circuitry 206 of IMD 200. However, ECAP 508 can be adequately sensed by the sensing circuitry 206 because at least a portion of each ECAP 508, or an ECAP 508 including one or more desired features for detecting posture state and / or as feedback to control pulse 504, decreases after each control pulse 504 completes. Figure 5A As shown, the stimulation interference signals 509 and ECAP 508 can be recorded on channel 506.

[0117] In some examples, for instance, the IMD 200 can continuously deliver the entire control pulse group 504 (e.g., scan) without any additional intervention pulses to detect the ECAP 508 from which corresponding characteristic values ​​are determined. The IMD 200 can then determine the relationship between the characteristic values ​​from the ECAP 508 and the different parameter values ​​of the control pulse 504. In one example, the scan of pulse 504 can be delivered by the IMD 200 during interruptions in the delivery of other types of control pulses.

[0118] Figure 5B This is a timing diagram 500B illustrating another example of an electrical stimulation pulse according to one or more techniques of this disclosure and the corresponding sensed ECAP. For convenience, refer to... Figure 2 IMD 200 pairs Figure 5BThe following description is provided. As shown in the figure, the timing diagram 500B includes a first channel 510, multiple control pulses 512A–512N (collectively referred to as “control pulses 512”), a second channel 520, multiple notification pulses 524A–524N (collectively referred to as “notification pulses 524”) including passive recharge phases 526A–526N (collectively referred to as “passive recharge phases 526”), a third channel 530, multiple corresponding ECAPs 536A–536N (collectively referred to as “ECAP 536”), and multiple stimulus interference signals 538A–538N (collectively referred to as “stimulus interference signals 538”).

[0119] The first channel 510 is a time / voltage (and / or current) graph indicating the voltage (or current) of at least one of the electrodes 232, 234. In one example, the stimulation electrode of the first channel 510 may be located on the side of the lead opposite to the sensing electrode of the third channel 530. The control pulse 512 may be an electrical pulse delivered to the patient's spinal cord through at least one of the electrodes 232, 234, and the control pulse 512 may be a balanced biphasic square pulse with phase intervals. In other words, each of the control pulses 512 is shown to have a negative phase and a positive phase separated by phase intervals. For example, the control pulse 512 may have a negative voltage, the same amount of time and amplitude as when it has a positive voltage. Note that the negative voltage phase may precede or follow the positive voltage phase. The control pulse 512 may be delivered according to control stimulation parameters stored in the memory 216 of the IMD 200, and these control stimulation parameters may be updated according to user input via an external programmer and / or according to signals from the sensor 210. In one example, the control pulse 512 may have a pulse width of less than approximately 300 microseconds (e.g., the total time for the positive phase, negative phase, and phase-to-phase interval is less than 300 microseconds). In another example, for each phase of the biphase pulse, the control pulse 512 may have a pulse width of approximately 100 microseconds. Figure 5B As shown, control pulse 512 can be delivered via channel 510. The delivery of control pulse 512 can be achieved via lead 230 in the protected cathode electrode assembly. For example, if lead 230 is a linear 8-electrode lead, the protected cathode assembly consists of a center cathode electrode and an anode electrode immediately adjacent to that cathode electrode.

[0120] The second channel 520 is a time / voltage (and / or current) graph indicating the voltage (or current) at at least one of the electrodes 232, 234 for the notification pulse. In one example, the electrodes of the second channel 520 may partially or completely share a common electrode with the electrodes of the first channel 510 and the third channel 530. The notification pulse 524 may also be delivered by the same lead 230 configured to deliver the control pulse 512. The notification pulse 524 may be interleaved with the control pulse 512 such that neither type of pulse is delivered during the overlapping time period. However, the notification pulse 524 may be delivered by, or may not be delivered by, the exact same electrode as the electrode delivering the control pulse 512. The notification pulse 524 may be a single-phase pulse with a pulse width greater than approximately 300 microseconds and less than approximately 1000 microseconds. In practice, the notification pulse 524 may be configured to have a longer pulse width than the control pulse 512. Figure 6 As shown in B, notification pulse 524 can be delivered on channel 520.

[0121] Notification pulse 524 can be configured for passive recharging. For example, each notification pulse 524 can be followed by a passive recharging phase 526 to equalize the charge on the stimulating electrodes. Unlike pulses configured for active recharging (where residual charge on the tissue is immediately removed from the tissue by an opposite applied charge after the stimulating pulse), passive recharging allows the tissue to discharge naturally to a reference voltage (e.g., ground or line voltage) after the notification pulse 524 terminates. In some examples, the electrodes of the medical device may be grounded at the body of the medical device. In this case, after the notification pulse 524 terminates, the charge on the tissue surrounding the electrodes can dissipate to the medical device, resulting in a rapid decay of residual charge at the tissue after the pulse terminates. This rapid decay is illustrated in the passive recharging phase 526. The passive recharging phase 526 may have a duration in addition to the pulse width of the preceding notification pulse 524. In other examples ( Figure 5B In (not shown), the notification pulse 524 can be a biphase pulse having a positive phase and a negative phase (and, in some examples, the phase interval between the phases), which can be referred to as a pulse that includes active recharging. The notification pulse 524, as a biphase pulse, may or may not have a subsequent passive recharging phase.

[0122] The third channel 530 is a time / voltage (and / or current) graph indicating the voltage (or current) at at least one of the electrodes 232, 234. In one example, the electrode of the third channel 530 may be located on the side of the lead opposite to the electrode of the first channel 510. In response to the control pulse 512, an ECAP 536 can be sensed from the patient's spinal cord at electrodes 232, 234. The ECAP 536 is an electrical signal that can propagate along the nerve away from the origin of the control pulse 512. In one example, the ECAP 536 is sensed by an electrode different from the electrode used to deliver the control pulse 512. Figure 5B As shown, ECAP 536 can be recorded on the third channel 530.

[0123] Stimulus interference signals 538A, 538B, and 538N (e.g., artifacts of the stimulation pulse) can be sensed by lead 230 and can be sensed during the same time period as the delivery of control pulse 512 and notification pulse 524. Because the amplitude and intensity of these interference signals may be greater than ECAP 536, any ECAP arriving at IMD 200 during the occurrence of stimulation interference signal 538 may not be sufficiently sensed by the sensing circuitry system 206 of IMD 200. However, ECAP 536 can be sufficiently sensed by the sensing circuitry system 206 because each ECAP 536 decreases after the end of each control pulse 512 and before the delivery of the next notification pulse 524. Figure 5B As shown, the stimulus interference signals 538 and ECAP 536 can be recorded on channel 530.

[0124] Two or more control pulses 512 may be delivered during each of multiple time events (e.g., windows), and each time event represents the time between two consecutive notification pulses 524. For example, during each time event, a first control pulse may be directly followed by a first corresponding ECAP, and a second control pulse may be directly followed by a second corresponding ECAP after the first corresponding ECAP ends. The notification pulse may begin after the second corresponding ECAP.

[0125] Continuous notification pulses 524 can be delivered without interfering with control pulse 512. For example, control pulse 512 may not be delivered during each of a plurality of time events (or windows), where each time event represents the time between two consecutive notification pulses 524. In any case, notification pulse 524 may be delivered at a predetermined frequency, and control pulse 512 may be delivered at any time between notification pulses.

[0126] Figure 5CThis is a timing diagram 500C illustrating another example of an electrical stimulation pulse and a corresponding ECAP according to the technology of this disclosure. For convenience, refer to... Figure 2 A's IMD 200 pairs Figure 5C The timing diagram 500C is described as follows: A first channel 540 includes multiple control pulses 542A–542N (collectively referred to as “control pulses 542”), a second channel 550 includes multiple notification pulses 554A–554N (collectively referred to as “notification pulses 554”) including passive recharge phases 556A–556N (collectively referred to as “passive recharge phases 556”), a third channel 560 includes multiple corresponding ECAPs 564A–564N (collectively referred to as “ECAP 564”) and multiple stimulus interference signals 562A–562N (collectively referred to as “stimulus interference signals 562”). Figure 5C It can be basically similar to Figure 5B Except for the differences detailed below.

[0127] Two or more control pulses 542 may be delivered during each of multiple time events (e.g., a window), and each time event represents the time between two consecutive notification pulses 554. For example, during each time event, a first control pulse in control pulse 542A may directly follow a first corresponding ECAP in ECAP 564A, and after the end of the first corresponding ECAP, a second control pulse in control pulse 542A may directly follow a second corresponding ECAP in ECAP 564A. Notification pulse 554 may begin after the second corresponding ECAP. In other examples not shown here, three or more control pulses 542 may be delivered during each of multiple time events, and corresponding ECAP signals may be sensed.

[0128] Figure 5D This is a timing diagram 500D illustrating another example of an electrical stimulation pulse and a corresponding ECAP according to the technology of this disclosure. For convenience, refer to... Figure 2 A's IMD 200 pairs Figure 5D The following description is provided. As shown in the figure, the timing diagram 500D includes a first channel 570, multiple control pulses 572A–572N (collectively referred to as "control pulses 572"), a second channel 580, multiple notification pulses 582A–582N (collectively referred to as "notification pulses 582") including passive recharge phases 584A–584N (collectively referred to as "passive recharge phases 584"), a third channel 590, multiple corresponding ECAPs 594A–594N (collectively referred to as "ECAP 594"), and multiple stimulus interference signals 592A–592N (collectively referred to as "stimulus interference signals 592"). Figure 6 It can be basically similar to Figure 5B and Figure 5C Except for the differences detailed below.

[0129] exist Figure 5B and Figure 5C In the previous example shown, at least one control pulse is delivered and interleaved between each pair of consecutive notification pulses. However, in some examples, control pulse 572 is not delivered during each time event (or window) of multiple time events, where each time event represents the time between two consecutive notification pulses 582. Figure 5D As shown in the example, the control pulse 572 is not delivered after the notification pulse 582A and before the notification pulse 582B. In other words, consecutive notification pulses 582A and 582B can be delivered without intervention from the control pulse. In any case, the notification pulses are delivered according to a predetermined frequency, and the control pulse can be delivered at any time between the notification pulses. In some examples, the parameter values ​​of both notification pulses 582A and 582B may be the same because they are defined by the same stimulation procedure. In other examples, notification pulses 582A and 582B may have at least one different stimulation parameter, such as different amplitudes, pulse widths, pulse frequencies, or electrode combinations. In this way, notification pulse 582A may be part of a first stimulation procedure, while notification pulse 582B may be part of a second stimulation procedure different from the first stimulation procedure. Therefore, the processing circuitry 214 can deliver notification pulses from two or more different stimulation programs, wherein the processing circuitry 214 uses a detected ECAP signal from the same control pulse (e.g., control pulse 572A) to “notify” or otherwise adjust one or more parameter values ​​of the notification pulses (e.g., both of notification pulses 582A and 582B) in multiple stimulation programs. This concept of multiple stimulation programs can be applied to any notification pulse described herein.

[0130] Control pulse 572 can be managed according to control stimulus parameters stored in memory 216. Processing circuitry 214 can be configured to update control pulse delivery instructions based on user input via telemetry circuitry 213 and also via signals from sensor 216. For example, a clinician can operate a patient programmer and send signals to telemetry circuitry 213, including instructions for updating control pulse parameters. The clinician can set the control stimulus to... Figures 5A to 5D Any of the examples shown, and clinicians can also customize the control stimulus to... Figures 5A to 5D The configuration is not shown in the diagram. Clinicians can choose to stop or start the controlled stimulation at any time. In some examples, the controlled stimulation will be initiated when a change in the patient's posture or activity level is detected.

[0131] Figure 6Graph 600 shows exemplary growth curves 602, 604, and 606 of the sensed ECAP from the corresponding stimulus pulse amplitude. Graph 600 illustrates exemplary ECAPs for which different current amplitudes for the stimulus pulse are shown as points (growth curve 602), squares (growth curve 604), and triangles (growth curve 606). The stimulation pulse amplitude is controlled until a threshold is reached. Figure 6 In the example, ECAP sometimes occurs at a current of approximately 4.5 mA. Then, as the current amplitude increases, the ECAP amplitude also increases approximately linearly. This linear relationship is illustrated by growth curves 602, 604, and 606. In addition to growth curves based on changes in the patient's postural state, the slope can also vary for each patient based on the type of implanted electrode, the location of the implanted electrode, the sensitivity of the patient's neurons to stimulation, neurological dysfunction, or other factors.

[0132] When a patient is in a given postural state, the sensed ECAP can be detected for controlled stimulation pulses with different current amplitudes. For example, each growth curve 602, 604, and 606 can be for a single postural state, such as supine, prone, sitting, standing, or lying on the right or left side. If the patient changes postural state, the growth curves can also change. When the patient changes postural state, such as from supine to standing and from standing to running, the corresponding growth curves can also change. For example, growth curve 602 can be associated with the supine postural state, growth curve 604 can be associated with the sitting postural state, and growth curve 606 can be associated with the prone postural state. In some examples, the patient can change postural state, but the same growth curve or gain value can be applied to different postural states.

[0133] The slopes of the linearly increasing growth curves 602, 604, and 606 indicate the relationship between the sensed ECAP amplitude and the control pulse amplitude. In some examples, the gain value used to increase or decrease the control stimulation parameter value and / or the notification stimulation pulse value can be inversely proportional to the slope of the growth curve for the characteristic value (e.g., amplitude, such as the N1-P2 amplitude or the amplitude of any peak of the ECAP signal) of the corresponding control stimulation pulse delivered to the patient and defined at least in part by different values ​​of the control stimulation parameter (e.g., current amplitude, voltage amplitude, or pulse width). For example, the patient's gain value can be used to dynamically adjust the pulse amplitude based on the sensed ECAP amplitude. In some examples, the patient's gain can be estimated based on historical data from similar patients. In other examples, the system can generate patient-specific customized growth curves and gains before treatment with the system begins.

[0134] Figure 7 This is a flowchart illustrating an exemplary operation 700 for notification delivery according to the technology of this disclosure. For convenience, relative to... Figure 2 The processing circuitry system 208 of the IMD 200 Figure 7 To describe. However, Figure 7 The technology can be performed by different components of the IMD200 or, in some examples, by additional or alternative medical devices.

[0135] exist Figure 7 In one example, IMD 200 delivers electrical stimulation therapy to patient 102, which includes multiple notification pulses delivered at a predetermined pulse frequency over a period of time (702). Additionally, IMD 200 delivers multiple control pulses (704) interleaved with at least some of the notification pulses during this time period. For example, one or more control pulses may be delivered between consecutive notification pulses. As another example, one or more notification pulses may be delivered between consecutive control pulses. IMD 200 may sense a corresponding ECAP after each control pulse and before the next notification pulse in the multiple notification pulses (706). After sensing, IMD 200 may adjust one or more notification parameter values ​​of the multiple notification pulses that at least partially define the electrical stimulation therapy based on at least one corresponding ECAP and a selected growth curve (708). IMD 200 may also determine the patient's current postural state and select a growth curve associated with the determined postural state. IMD 200 may compare the characteristic value of the sensed ECAP with a target ECAP characteristic value and adjust the notification pulses (in some examples, control pulses) to maintain the target ECAP characteristic value. As discussed herein, the IMD 200 can update the growth curve continuously or discontinuously to adjust for different postural states of the patient 102. The IMD 200 then delivers electrical stimulation therapy to the spinal cord 106 (710) of the patient 102 via electrode 108 based on one or more adjusted notification parameter values.

[0136] Figure 8 This is a diagram illustrating an example technique 800 for adjusting stimulation therapy. (See diagram for example.) Figure 8As illustrated in the example, a system (such as IMD 200 or any other device or system described herein) can dynamically adjust the pulse amplitude (or other parameters) based on a gain value representing the patient's sensitivity to stimulation. The processing circuitry system 208 of IMD 200 can control the stimulation generator 204 to deliver stimulation pulses, such as notification pulses and control pulses, to the patient. The processing circuitry system 208 can then control the sensing circuitry system 206 to sense the ECAP signal triggered by the control pulse and then identify characteristics of the ECAP signal (e.g., the amplitude of the ECAP signal). The processing circuitry system 208 can then determine parameter values ​​(e.g., amplitude, pulse width value, pulse frequency value, and / or slew rate value) that at least partially define the stimulation pulses (such as control and notification pulses) based on the characteristics of the ECAP signal and the gain value associated with the growth curve. The processing circuitry system 208 can then control the stimulation generator 204 to deliver notification and control pulses according to the determined stimulation parameters.

[0137] like Figure 8 As shown, a control pulse 812 is delivered to the patient via electrode assembly 814 (shown as the protected cathode of three electrodes). The resulting ECAP is sensed by two electrodes at opposite ends of the leads of electrode assembly 816 fed to differential amplifier 818. For each sensed ECAP, processing circuitry 208 can measure the amplitude of a portion of the ECAP signal, such as the N1-P2 voltage amplitude from that portion of the ECAP signal. Processing circuitry 208 can calculate the average of the most recently measured ECAP amplitudes, such as calculating the average of the most recent and consecutive 2, 3, 4, 5, 6 or more ECAP amplitudes. In some examples, the average can be the mean or median. In some examples, one or more ECAP amplitudes can be ignored from the calculation if the amplitude value is determined to be erroneous. The measured amplitude (or average measured amplitude) is then subtracted from the selected target ECAP amplitude 802 to generate the differential amplitude. The selected target ECAP amplitude 802 can be determined based on the ECAP sensed when the physician or patient initially detects effective treatment from the notification pulse and / or control pulse. This target ECAP amplitude 802 can essentially represent a reference distance between the stimulating electrode and the target neuron (e.g., the spinal cord in the case of SCS).

[0138] The differential amplitude is then multiplied by the patient's gain value to generate a differential value 808. The processing circuitry 208 may detect the patient's postural state 804 at varying intervals (including, for example, periodic time intervals) at certain steps of the technique 800 in response to a trigger event or continuously. For example, the processing circuitry 208 may continuously detect the patient's postural state 804 to select a growth curve 806 associated with the detected postural state. Once the growth curve 806 is selected, a gain value can be determined to generate the differential value 808. In other examples, the processing circuitry 208 may select the gain value directly from the detected postural state, rather than first selecting an associated growth curve. The processing circuitry 208 may add the differential value to the ECAP pulse amplitude to generate a new or adjusted control pulse amplitude 810 that at least partially defines the next pulse 812.

[0139] The following formula represents the function used to calculate the pulse amplitude of the next pulse 812. Equation 1 below represents the equation for calculating the new current amplitude using a linear function, where A... C D is the amplitude of the current pulse, which is the differential amplitude obtained by subtracting the measured amplitude from the target ECAP amplitude. G is the real number of the gain value, and A... N It's a new pulse amplitude:

[0140] A N =A C +(D×G) (1)

[0141] In this way, the gain value G may not change for a given input. Alternatively, the processing circuitry 208 may calculate the gain value G such that the gain value varies according to one or more inputs or factors (such as posture state). In this way, the processing circuitry 208 may change the gain value G for a given input or a set of inputs. The following Equation 2 represents an exemplary linear function used to calculate the gain value, where M is the multiplier, D is the differential amplitude obtained by subtracting the measured amplitude from the target ECAP, and G is the gain value:

[0142] G=M×D (2)

[0143] The processing circuit system 208 can use the gain value G calculated in Equation 2 in Equation 1. This makes Equation 1 a nonlinear function used to determine the new current amplitude. According to Equation 2 above, the gain value G may be large for larger differences between the measured amplitude and the target ECAP amplitude. Therefore, the gain value G will cause a nonlinear change in the current amplitude. In this way, the rate of change of the current amplitude will be high for larger differences between the measured amplitude and the target ECAP amplitude, and low for smaller differences between the measured amplitude and the target ECAP amplitude. In other examples, a nonlinear function can be used to calculate the gain value G.

[0144] To adjust the amplitude of the notification pulse, the difference value 808 is multiplied by a scaling factor 822 to generate a notification difference value. For example, the scaling factor could be the ratio of the amplitude of a previously delivered notification pulse to the amplitude of a previously delivered control pulse. The notification difference value is then added to the amplitude of the previously delivered notification pulse 824 to generate a new or adjusted notification pulse amplitude that at least partially defines the next notification pulse 826. The next notification pulse 826 is then delivered to the patient interleaved with the control pulse 812 via electrode assembly 815. In some examples, at least two control pulses may be delivered between consecutive notification pulses, and at least two corresponding ECAP signals may be sensed. This increased frequency of non-therapeutic pulses allows the system to rapidly adjust the amplitude of the notification pulse for any changes in the distance between the electrode and the neuron. Although electrode assembly 815 differs from electrode assemblies 814 and 816, electrode assembly 815 can be any electrode group on the leads required for treatment, as the notification pulse is delivered in a manner that does not overlap with the control pulse and the sensed ECAP signal.

[0145] The pulse width of the notification pulse may be less than approximately 300 μs and less than approximately 1000 μs. In other examples, the pulse width of the notification pulse may be less than approximately 300 μs or greater than 1000 μs. The stimulation pulse may be a monophasic pulse followed by a passive recharge phase. However, in other examples, the pulse may be a biphasic pulse including both positive and negative phases. In some examples, the pulse may be less than 300 μs, but the subsequent passive recharge phase (of the biphasic pulse) or even the active recharge phase may still obscure the detectable ECAP signal from that pulse.

[0146] In some examples, depending at least in part on the pulse width of the control pulse, the IMD 200 may not adequately detect the ECAP signal because the stimulation pulse is also detected as an artifact that obscures the ECAP signal. If the ECAP is not adequately recorded, the ECAP arriving at the IMD 200 cannot be used to determine the efficacy of the stimulation parameter settings, and the electrical stimulation signal cannot be altered according to the responsiveness of the ECAP. In some examples, the pulse width of the control pulse may be less than approximately 300 μs, which can increase the number of detected ECAP signals. Similarly, high pulse frequencies may interfere with the IMD 110's adequate detection of the ECAP signal. For example, at a pulse frequency value (e.g., greater than 1 kHz) at which the IMD 110 delivers another control pulse before the ECAP from the previous pulse can be detected, the IMD 110 may not be able to detect the ECAP.

[0147] Figure 9 This is a flowchart illustrating an exemplary operation 900 for adjusting stimulus parameters (such as notification parameters and control parameters). The IMD 200 and processing circuitry system 208 will... Figure 9 The example described herein may be used, but other IMDs such as IMD 110 or other devices or systems may perform or partially perform operation 900. Operation 900 may be similar to... Figure 8 Related diagrams and discussions.

[0148] exist Figure 9 In one example, the processing circuitry 208 determines the target ECAP amplitude (902). The target ECAP amplitude may be determined based on the sample stimulus initially delivered to the patient. The target ECAP amplitude may be the N1-P2 amplitude of the ECAP signal, but alternatively, other measures of amplitude may be used, such as the amplitude of one or more distinct peaks in the ECAP signal. Alternatively, the target ECAP amplitude may be a distinct feature of the ECAP signal, such as the area under one or more peaks of the ECAP signal. In some examples, the processing circuitry 208 is configured to automatically change the target ECAP amplitude over a period of time according to a predetermined function (e.g., a sine function) to alter the volume of neuronal activation, and in some examples, to alter the perceived sensation of the notification pulse.

[0149] The processing circuitry 208 receives a measured amplitude from a previously sensed ECAP signal. To use the ECAP signal as feedback to control notification pulses for electrical stimulation therapy on the patient, the processing circuitry 208 subtracts the measured amplitude from the target ECAP amplitude to generate a differential amplitude (904). In some examples, or when additional measured amplitudes are available from this process, the processing circuitry 208 may calculate the average of a number of recently measured amplitudes (e.g., two or more) to create a rolling average of the measured ECAP amplitudes and subtract the average measured amplitude from the target ECAP amplitude to eliminate variations between ECAP signals. Thus, the differential amplitude is a representation of how far the electrode has moved relative to the neuron and can be used to adjust the amplitude of notification and control pulses to maintain a consistent volume of neural activation of the neurons providing relief to the patient.

[0150] The processing circuitry system 208 can select a growth curve (906) based on the patient's posture state. Detection of the patient's posture state can be performed continuously at varying intervals (including, for example, periodic time intervals) at certain predetermined steps of method 800. For example, the processing circuitry system 208 can continuously detect the patient's posture state to select a growth curve for the patient's currently occupied posture state. Patient posture state data can be stored continuously or discontinuously (including at set time intervals) in memory 216. Once a growth curve is selected, the processing circuitry system 208 can use the relationship between sensed parameter values ​​and target parameter values ​​to select new parameter values. In some examples, the processing circuitry system 208 can determine a gain value from the growth curve. In other examples, the processing circuitry system 208 can select a gain value directly associated with the identified posture state without first identifying the growth curve.

[0151] The processing circuitry 208 then multiplies the differential amplitude from block 904 by a gain value representing the patient's postural state to generate a preliminary differential value (908). The gain value may represent the slope of the patient's growth curve. The processing circuitry 208 then uses the preliminary differential value to adjust the amplitude of both subsequent notification pulses and control pulses (e.g., ECAP test pulses). The processing circuitry 208 adds the preliminary differential value to the control pulse amplitude to generate a new control pulse amplitude (910). The processing circuitry 208 then controls the stimulation generation circuitry 208 to deliver subsequent control pulses defined by the new control pulse amplitude at a planned time, such as according to the frequency of the control pulse or according to the next available window between notification pulses (912). The processing circuitry 208 also controls the sensing circuitry 206 to measure the amplitude of the sensed ECAP triggered by the most recently delivered control pulse (914) to be used again as feedback in block 904.

[0152] In addition to adjusting the amplitude of the control pulse, the processing circuitry 208 also uses a preliminary amplitude to adjust the amplitude of the notification pulse. The processing circuitry 208 multiplies the differential value by a scaling factor to generate a new notification differential value (916). The scaling factor can be determined as the ratio between the amplitude of the most recently delivered notification pulse and the amplitude of the most recently delivered control pulse that triggered the ECAP signal used to generate the measured amplitude in block 904. The scaling factor can amplify or reduce the differential amplitude of the notification pulse, since the differential amplitude is generated based on the amplitude of the control pulse. The processing circuitry 208 then adds the therapeutic differential value to the most recently delivered notification pulse amplitude to generate a new notification pulse amplitude (918). The processing circuitry 208 then controls the stimulation generator 204 to deliver the next notification pulse with the newly adjusted notification pulse amplitude at a planned time according to a predetermined pulse frequency of the notification pulse (920).

[0153] Although operation 900 is described as adjusting the amplitude of the notification and control pulses, similar operations can be used to adjust other stimulation parameters in other examples. For example, parameters contributing to the intensity of the notification and control pulses can affect the volume of neural activation, such as pulse width, pulse frequency, or even pulse shape (e.g., the amount of charge per pulse). Therefore, the processing circuitry 208 can use the sensed ECAP signal triggered by the control pulse to adjust different parameters instead of amplitude, or adjust different parameters in addition to amplitude. For example, the processing circuitry 208 can increase the pulse width of the notification and control pulses in response to detecting a decrease in ECAP amplitude. Additionally, the processing circuitry 208 can adjust parameters based on changes in the patient's postural state and different selected growth curves.

[0154] Figure 10 A graph 1000 is shown illustrating the control pulse current amplitude 1002, notification pulse current amplitude 1004, threshold ECAP amplitude 1006, and ECAP voltage amplitude 1008 as a function of time according to one or more techniques of this disclosure. For convenience, relative to... Figure 2 IMD 200 pairs Figure 10 To describe. However, Figure 10 The technology can be performed by different components of the IMD 200 or by additional or alternative medical devices.

[0155] Graph 1000 illustrates the relationship between the sensed ECAP voltage amplitude 1008 and the stimulation current amplitude. For example, the control pulse current amplitude 1002 and the notification pulse current amplitude 1004 are plotted together with the ECAP voltage amplitude 1008 as a function of time, thus showing how the processing circuitry system 208 of the IMD 200 can change the stimulation current amplitude relative to the ECAP voltage amplitude 1008. In some examples, the IMD 200 delivers multiple control pulses and multiple notification pulses, respectively, with control pulse current amplitude 1002 and notification pulse current amplitude 1004. Initially, the IMD 200 may deliver a first set of control pulses, wherein the IMD 200 delivers the first set of control pulses with a current amplitude I2. Additionally, the IMD 200 may deliver a set of notification pulses, wherein the IMD 200 delivers the first set of notification pulses with a current amplitude I2. I1 and I2 may be referred to as predetermined values ​​for the amplitudes of the respective control pulses and notification pulses, respectively. The predetermined value can be a programmed value or a value otherwise selected by the stimulation procedure to at least partially define the stimulation pulses to the patient in the absence of transient conditions (e.g., when the ECAP amplitude is below a threshold ECAP value). The first set of control pulses and the first set of notification pulses can be delivered before time T1. In some examples, I1 is 8 mA and I2 is 4 mA. Although the control pulse current amplitude 1002 is shown to be greater than the notification pulse current amplitude 1004, in other examples, the control pulse current amplitude 1002 may be less than or equal to the notification pulse current amplitude 1004. In some examples, the current amplitudes I1 and I2 may be less than 25 mA and may be between about 2 mA and about 18 mA. However, the current amplitudes I1 and I2 can be any current amplitude that the IMD 200 can deliver to the patient and is suitable for inducing an ECAP signal and / or effective stimulation therapy to the patient.

[0156] During the delivery of the first set of control pulses and the first set of notification pulses, the IMD 200 can record the ECAP voltage amplitude 1008, a characteristic value derived from the ECAP signal triggered by the corresponding control pulse. During dynamic and transient conditions occurring in the patient 102 (such as coughing, sneezing, laughing, valsalva maneuvers, leg raising, neck movements, or deep breathing), if the control pulse current amplitude 1002 and the notification pulse current amplitude 1004 remain constant, the ECAP voltage amplitude 1008 may increase. This increase in the ECAP voltage amplitude 1008 can be caused by a decrease in the distance between the electrode and the nerve. For example, as... Figure 10As shown, the ECAP voltage amplitude 1008 can increase before time T1, while the stimulation current amplitude remains constant. The increased ECAP voltage amplitude 1008 can indicate that the patient 102 is at risk of experiencing transient overstimulation due to the control pulses and notification pulses delivered by the IMD 200. To prevent the patient 102 from experiencing transient overstimulation, the IMD 200 can decrease the control pulse current amplitude 1002 and the notification pulse current amplitude 1004 in response to the ECAP voltage amplitude 1008 exceeding the threshold ECAP amplitude 1006. For example, if the IMD 200 at time T1 as Figure 10 If an ECAP voltage amplitude 1008 that meets or exceeds a threshold ECAP amplitude 1006 is sensed, the IMD 200 can enter a decrement mode in which the pulse current amplitude 1002 is controlled and the pulse current amplitude 1004 is notified to decrease. In some examples, the threshold ECAP amplitude 1006 is selected from the range of approximately 10 microvolts (μV) to approximately 100 μV or from approximately 15 microvolts (μV) to approximately 40 μV. For example, the threshold ECAP amplitude 1006 is 30 μV. In other examples, the threshold ECAP amplitude 1006 is less than or equal to 10 μV or greater than or equal to 100 μV. The precise value of the threshold ECAP amplitude 1006 may depend on the patient's perception of the delivered stimulus, the spacing between the sensing / stimulating electrode and the nerve tissue, increasing or decreasing the stimulus intensity, or other factors.

[0157] The IMD 200 can respond relatively quickly when the ECAP voltage amplitude 1008 exceeds the threshold ECAP amplitude 1006. For example, the IMD can be configured to detect an ECAP amplitude exceeding the threshold within 20 milliseconds (ms). If the IMD 200 delivers a control pulse at a frequency of 50 Hz, the time interval for a single sample, including the delivery of the control pulse and the detection of the resulting ECAP signal, can be 20 ms or less. However, since the ECAP signal can occur within one or two ms of the delivery of the control pulse, the IMD 200 can be configured to detect an ECAP signal exceeding the threshold ECAP amplitude within less than 10 ms. For transient conditions (such as a patient coughing or sneezing), these sampling periods will be sufficient to identify an ECAP amplitude exceeding the threshold and a decrease in responsiveness of subsequent pulse amplitudes before the ECAP amplitude reaches a higher level that may cause discomfort to the patient.

[0158] In some cases, the decreasing pattern can be stored in the storage device 216 of the IMD 200. Figure 10In the example shown, the decreasing mode is executed by IMD 200 on a second set of control pulses and a second set of notification pulses occurring between time T1 and time T2. In some examples, to execute the decreasing mode, IMD 200 reduces the control pulse current amplitude 1002 of each control pulse in the second set of control pulses according to a first function relative to time. In other words, IMD 200 reduces each consecutive control pulse in the second set of control pulses proportionally to the amount of time elapsed since the previous control pulse. Additionally, during the decreasing mode, IMD 200 may reduce the notification pulse current amplitude 1004 of each notification pulse in the second set of notification pulses according to a second function relative to time. Although linear first and second functions are shown, in other examples, the first and / or second functions may be nonlinear, such as logarithmic functions (e.g., a rate of change decreasing with time), exponential functions (e.g., a rate of change increasing with time), parabolic functions, step functions, multiple different functions, etc. In some examples, the processing circuitry 208 may select a first or second function, defining the amplitude or rate of change of each step in the pulse amplitude variation, based on the detected patient posture. For example, the first or second function may represent a gain value or other function controlling the rate of change of the current amplitude. These functions selected based on posture can be used in the decrementing and / or increasing modes described herein. In some examples, the processing circuitry 208 may select a threshold ECAP amplitude 1006 based on the detected patient posture. During a time period when the IMD 200 operates in decrementing mode (e.g., time interval T2-T1), the ECAP voltage amplitude 1008 sensed by the IMD 200 may be greater than or equal to the threshold ECAP amplitude 1006.

[0159] exist Figure 10In the example shown, IMD 200 can sense the ECAP at time T2, where the ECAP has an ECAP voltage amplitude 1008 that falls below a threshold ECAP amplitude 1006. In some cases, the ECAP sensed at time T2 can be the first ECAP sensed by IMD 200 with an amplitude below the threshold since IMD 200 began the decrementing mode at time T1. Based on the ECAP sensed at time T2, IMD 200 can deactivate the decrementing mode and activate the incrementing mode. In some cases, the incrementing mode can be stored in the storage device 216 of IMD 200. IMD 200 can execute the incrementing mode on a third set of control pulses and a third set of notification pulses occurring between time T2 and time T3. In some examples, to execute the incrementing mode, IMD 200 increases the control pulse current amplitude 1002 of each control pulse in the third set of control pulses according to a third function relative to time, which can be selected based on the detected patient posture state. In other words, IMD 200 increases each consecutive control pulse in the third set of control pulses proportionally to the amount of time elapsed since the previous control pulse. Additionally, during the increment mode, IMD 200 can increase the notification pulse current amplitude 1004 of each notification pulse in the third set of notification pulses according to a fourth function relative to time.

[0160] like Figure 10 As shown, IMD 200 is configured to decrease the amplitude at a faster rate than increasing the amplitude after the ECAP voltage amplitude 1008 drops below the threshold ECAP amplitude 1006. In other examples, the rate of change during the decreasing and increasing modes may be similar. In other examples, IMD 200 may be configured to increase the amplitude of the notification pulse and control pulse at a faster rate than when decreasing the amplitude. In other examples, the rate of change of the pulse amplitude may be relatively instantaneous (e.g., a very fast rate). As mentioned above, this rate may be correlated with the gain value of the detected posture state, such that for posture states with shallow growth curves or large distances between the electrodes and the target nerve, the rate of increase or decrease in amplitude is faster. In one example, in response to the ECAP voltage amplitude 1008 exceeding the threshold ECAP amplitude 1006, IMD 200 may immediately reduce the amplitude of one or both of the control pulse current amplitude 1002 or the notification pulse current amplitude 1004 to a predetermined or calculated value. Then, in response to the ECAP voltage amplitude 1008 decreasing back below the threshold ECAP amplitude 1006, the IMD 200 can enter the incrementing mode as described above.

[0161] When the control pulse current amplitude 1002 and the notification pulse current amplitude 1004 return to current amplitudes I2 and I1, respectively, the IMD 200 can deactivate the incremental mode and deliver stimulation pulses with a constant current amplitude. By reducing stimulation in response to the ECAP amplitude exceeding a threshold and subsequently increasing stimulation in response to the ECAP amplitude falling below a threshold, the IMD 200 can prevent the patient 105 from experiencing transient overstimulation or reduce the severity of transient overstimulation experienced by the patient 105, whether the reduction is in terms of duration, relative intensity, or both.

[0162] In other examples, the processing circuitry 208 may adjust the stimulation parameters only when the ECAP voltage amplitude 1008 is above an upper threshold or below a lower threshold. In this way, when the ECAP voltage amplitude 1008 is between the upper and lower ECAP amplitude thresholds, the processing circuitry 208 does not increase the stimulation amplitude value back to a predetermined value or decrease the stimulation amplitude value. This “buffer” can reduce the oscillation amplitude value when the ECAP amplitude is similar to the ECAP amplitude threshold. These oscillation amplitude values ​​may be perceived as uncomfortable or unwanted by the patient. However, once the ECAP amplitude drops below the lower ECAP amplitude threshold, the processing circuitry 210 can return the amplitude value to the predetermined amplitude value intended for therapeutic use.

[0163] While in some examples the IMD 200 can be increased and decreased by a linear function, in other examples the IMD 200 can employ a nonlinear function. For example, the gain value can represent a nonlinear function, where the increment or decrement changes exponentially or logarithmically based on the difference between the sensed ECAP characteristic value and the threshold ECAP amplitude 1006. Figure 10 This describes the scenario where the IMD 200 delivers both control pulses and notification pulses. However, the IMD 200 can... Figure 10 The technology is applied to situations where only control pulses are delivered to provide treatment to the patient. In this way, the IMD 200 will similarly enter a decreasing or increasing mode for controlling the pulse current amplitude 1002 based on the detected ECAP voltage amplitude 1008, without adjusting the amplitude or other parameters of any other type of stimulation pulse.

[0164] Figure 11 This is a flowchart illustrating exemplary operation for controlling stimuli based on one or more sensed ECAPs according to one or more techniques of this disclosure. For convenience, relative to... Figure 2 IMD 200 pairs Figure 11 To describe. However, Figure 11 The technology can be performed by different components of the IMD 200 or by additional or alternative medical devices. Figure 11 technology and Figure 10 The curve is associated with 1000.

[0165] The stimulation generation circuitry system 204 of the IMD 200 can deliver electrical stimulation therapy to a patient (e.g., patient 102). To control the electrical stimulation therapy, the processing circuitry system 208 can guide the delivery of at least some stimulation pulses, wherein the electrical stimulation therapy may include multiple control pulses and / or notification pulses. In some cases, the notification pulses can generate an ECAP detectable by the IMD 200. However, in other cases, the polarization of the notification pulses may interfere with the sensing of the ECAP in response to the notification pulses. In some examples, to induce an ECAP detectable by the IMD 200, the stimulation generation circuitry system 204 delivers multiple control pulses, which are interleaved with at least some of the notification pulses. The processing circuitry system 208 can control the delivery of the control pulses according to instructions stored in memory 216. Because the control pulses can be interleaved with the notification pulses, the sensing circuitry system 206 of the IMD 200 can detect multiple ECAPs, wherein the sensing circuitry system 206 is configured to detect each of the multiple ECAP signals after a control pulse in the multiple control pulses and before a subsequent notification pulse in the multiple notification pulses. In this way, the IMD 200 can induce multiple ECAPs in the target tissue by delivering control pulses without any notification pulses interfering with the IMD 200's sensing of ECAPs.

[0166] like Figure 11 As shown, the processing circuitry 208 guides the stimulation generation circuitry 204 to deliver a control pulse (1102). The stimulation generation circuitry 204 can deliver the control pulse to the target tissue of the patient 102 via any combination of electrodes 232, 234 of the lead 230. In some examples, the control pulse may include a balanced biphasic square pulse employing an active recharge phase. However, in other examples, the control pulse may include a monophasic pulse followed by a passive recharge phase. In other examples, the control pulse may include an unbalanced biphasic portion and a passive recharge portion. Although not required, the biphasic control pulse may include an interphase interval between positive and negative phases to facilitate the propagation of a nerve impulse in response to the first phase of the biphasic pulse. The control pulse may have a pulse width of less than about 300 μs, such as a biphasic pulse with each phase having a duration of about 100 μs.

[0167] After the delivery of the control pulse, the IMD 200 attempts to detect the ECAP (1104). For example, the sensing circuitry 206 may monitor signals from any combination of electrodes 232, 234 of the lead 230. In some examples, the sensing circuitry 206 detects the ECAP from a specific combination of electrodes 232, 234. In some cases, the specific combination of electrodes used to sense the ECAP includes electrodes different from the set of electrodes 232, 234 used to deliver the stimulation pulse. Alternatively, in other cases, the specific combination of electrodes used to sense the ECAP includes at least one electrode from the same set of electrodes used to deliver the stimulation pulse to the patient 102. In some examples, the specific electrode combination used to sense the ECAP may be located on the side of the lead 230 opposite to the specific electrode combination used to deliver the stimulation pulse. The IMD 200 may detect the ECAP in response to the control pulse. The IMD 200 may measure one or more characteristics of the responsive ECAP, such as ECAP amplitude, ECAP duration, interpeak duration, or any combination thereof. For example, to measure the amplitude of ECAP, the IMD 200 can determine the voltage difference between the peak value of N1 ECAP and the peak value of P2 ECAP.

[0168] At box 1106, processing circuitry 208 determines whether the ECAP amplitude of the responsive ECAP is greater than an ECAP amplitude threshold. If the ECAP amplitude is greater than the ECAP amplitude threshold (the "Yes" branch of box 1106), processing circuitry 208 activates / continues the decrement mode in IMD 200 (1108). For example, if the decrement mode is "on" in IMD 200 when processing circuitry determines that the ECAP amplitude is greater than the ECAP amplitude threshold, processing circuitry 208 maintains IMD 200 in decrement mode. If the decrement mode is "off" in IMD 200 when processing circuitry determines that the ECAP amplitude is greater than the ECAP amplitude threshold, processing circuitry 208 activates the decrement mode. In some examples, processing circuitry 208 may adjust the pulse amplitude based on a gain value or other factors selected based on, such as the patient's current postural state determined by processing circuitry 208. The decrement mode can be a set of instructions that cause IMD 200 to decrease one or more parameter values ​​of each successive notification pulse from corresponding predetermined values ​​(e.g., values ​​determined by the stimulation procedure and / or posture state), and to decrease one or more parameter values ​​of each successive control pulse from corresponding predetermined values ​​(e.g., values ​​determined by the stimulation procedure and / or posture state). In other words, the parameter values ​​can be reduced from values ​​that IMD 200 uses to limit the corresponding pulse in the absence of an ECAP amplitude exceeding a threshold ECAP amplitude. For example, when the decrement mode is activated, processing circuitry 208 can reduce the current amplitude of each successive notification pulse delivered by IMD 200 and reduce the current amplitude of each successive control pulse delivered by IMD 200. After processing circuitry 208 activates / continues the decrement mode, exemplary operation can return to block 1102, and IMD 200 can deliver another control pulse.

[0169] If the ECAP amplitude is not greater than the ECAP amplitude threshold (the "No" branch of box 1106), the processing circuitry 208 determines whether a decrement mode is activated in the IMD 200 (1110). If a decrement mode is activated in the IMD 200 (the "Yes" branch of box 1110), the processing circuitry 208 deactivates the decrement mode and activates an increment mode in the IMD 200 (1112). An increment mode can be a set of instructions that cause the IMD 200 to increase one or more parameter values ​​for each successive notification pulse and one or more parameter values ​​for each successive control pulse. For example, when an increment mode is activated, the processing circuitry 208 may increase the current amplitude of each successive notification pulse delivered by the IMD 200 and increase the current amplitude of each successive control pulse delivered by the IMD 200. In some examples, the processing circuitry 208 may adjust the pulse amplitude based on a gain value or other factors selected based on the patient's current postural state as determined by the processing circuitry 208. After the processing circuit system 208 deactivates the decrement mode and activates the increment mode, the exemplary operation can return to block 1102, and IMD 200 can deliver another control pulse.

[0170] when Figure 11 When the exemplary operation reaches box 1110 and the decrement mode is not activated in IMD 200 (the "No" branch of box 1110), the processing circuitry system 208 determines whether the increment mode is activated in IMD 200 (1114). If the increment mode is activated in IMD 200 (the "Yes" branch of box 1114), the processing circuitry system 208 may complete the increment mode in IMD 200 (1116). In some examples, to complete the increment mode, the processing circuitry system 208 may increase the current amplitude of each successive notification pulse delivered by IMD 200 and increase the current amplitude of each successive control pulse delivered by IMD 200 until the pulse amplitude of the stimulation pulse reaches the current amplitude of the stimulation pulse delivered by IMD 200 (e.g., a predetermined value that may be set by the stimulation program selected for treatment) before the decrement mode is activated. In this way, the process may not be referred to as a fully closed-loop system. In other words, IMD 200 can monitor the high end (ECAP amplitude threshold) used to adjust the stimulation pulse, rather than monitoring any low end of the sensed ECAP amplitude. For example, IMD 200 can continue to increase the current amplitude of the continuous notification pulses without any feedback from the sensed ECAP, unless the sensed ECAP value exceeds the ECAP amplitude threshold again. After the processing circuitry system 208 completes the incrementing mode, the exemplary operation can return to block 1102, and IMD 200 can deliver another control pulse. When Figure 11When the exemplary operation reaches box 1114 and the incremental mode is not activated in IMD 200 (the "No" branch of box 1114), the processing circuitry system 208 maintains the stimulus (1118) in IMD 200. Although Figure 11 The description covers both notification pulses and control pulses, but when the IMD 200 delivers only control pulses (e.g., no notification pulses) to the patient for treatment, Figure 11 The technology can also be applied.

[0171] This document describes the following embodiments. Embodiment 1: A system comprising: a sensing circuit system configured to sense an evoked compound action potential (ECAP) signal induced by a control stimulus pulse from a plurality of control stimulus pulses; and a processing circuit system configured to: control the delivery of a first notification stimulus pulse defined at least by a first value of a notification stimulus parameter, the notification stimulus pulse being one of a plurality of notification stimulus pulses; control the delivery of the control stimulus pulse to a patient, the control stimulus pulse being defined at least by the first value of the control stimulus parameter; determine a characteristic value of the ECAP signal induced by the control stimulus pulse; receive a posture state signal representing the posture state of the patient from a sensor; adjust the first value of the notification stimulus parameter to a second value of the notification stimulus parameter based on the characteristic value of the ECAP signal and the posture state signal; and control the delivery of a second notification stimulus pulse from the plurality of notification stimulus pulses defined at least by the second value of the notification stimulus parameter.

[0172] Example 2: The system according to Example 1 further includes a stimulus generation circuit system configured to deliver the plurality of control stimulus pulses and the plurality of notification stimulus pulses to the patient, and wherein the processing circuit system is configured to control the stimulus generation circuit system to deliver the plurality of control stimulus pulses and the plurality of notification stimulus pulses.

[0173] Example 3: The system according to any one of Example 1 or 2, wherein the notification stimulus parameter and the control stimulus parameter include at least one of amplitude, pulse width or pulse shape.

[0174] Example 4: The system according to any one of Examples 1 to 3, wherein the processing circuit system is configured to: determine a gain value of the posture state based on the posture state signal; and adjust the first value of the notification stimulation pulse to the second value of the notification stimulation pulse by increasing or decreasing one of the stimulation parameters of the electrical stimulation based on the gain value associated with the patient's posture state.

[0175] Example 5: The system according to Example 4, wherein the characteristic value is an amplitude of a portion of the ECAP signal, wherein the notification stimulation parameter includes a notification amplitude, wherein the control stimulation parameter includes a control amplitude, and wherein the processing circuitry is configured to adjust a first value of the notification stimulation pulse to a second value of the notification stimulation pulse by: subtracting the amplitude from the patient's target ECAP amplitude value to generate a differential amplitude; multiplying the differential amplitude by the gain value to generate a preliminary differential value; multiplying the preliminary differential value by a scaling factor to generate a notification differential value, wherein the scaling factor represents the ratio of the first value of the notification amplitude of the first notification stimulation pulse defined before the control stimulation pulse to the control amplitude defining the control stimulation pulse; adding the notification differential value to the first value of the notification amplitude to generate a second value of the notification amplitude that at least partially defines the electrical stimulation to be delivered to the patient; and adding the preliminary differential value to the first value of the control stimulation parameter to generate a second value of the control stimulation parameter for a subsequent control stimulation pulse among the plurality of control stimulation pulses.

[0176] Example 6: According to the system described in Example 5, the amplitude of the portion of the ECAP signal includes the voltage amplitude between the N1 peak value and the P2 peak value of the ECAP signal.

[0177] Example 7: The system according to any one of Examples 4 to 6, wherein the gain value is inversely proportional to the slope of a growth curve defining the relationship between the patient's ECAP value and the value of the control stimulation parameter.

[0178] Example 8: According to the system of Example 7, the posture state is one of a plurality of posture states, and each posture state includes a corresponding growth curve representing the relationship between the ECAP value and the value of the control parameter when the patient occupies the posture state.

[0179] Example 9: A system according to any one of Examples 1 to 8, wherein the processing circuitry is configured to adjust the first value of the notification stimulus parameter to the second value of the notification stimulus parameter by: comparing the feature value of the ECAP signal with a threshold ECAP feature value; determining that the feature value of the ECAP signal is greater than the threshold ECAP feature value; and in response to determining that the feature value of the ECAP signal is greater than the threshold ECAP feature value, reducing the first value of the notification stimulus parameter to the second value of the notification stimulus parameter.

[0180] Example 10: According to the system of Example 9, wherein the ECAP signal is a first ECAP signal and the feature value is a first feature value, wherein the control stimulus pulse is a first control stimulus pulse, and wherein the processing circuitry is configured to: determine a second feature value of a second ECAP signal triggered by a second stimulus pulse delivered after sensing the first ECAP signal; determine that the second feature value of the second ECAP signal subsequently decreases below the threshold ECAP feature value; and in response to determining that the second feature value of the second ECAP signal decreases below the threshold ECAP feature value, increase the second value of the notification stimulus parameter to a third value of the notification stimulus parameter, wherein the third value of the notification stimulus parameter is limited to be less than or equal to the first value.

[0181] Example 11: The system according to Example 10, wherein the processing circuitry is configured to increase the second value of the notification stimulus parameter at a slower rate than decreasing the first value of the notification stimulus parameter to the second value of the notification stimulus parameter.

[0182] Example 12: A system according to any one of Examples 1 to 11, wherein the processing circuitry is configured to select a gain value from a plurality of gain values ​​associated with a corresponding posture state based on the posture state signal, and wherein the gain value represents at least one of an increasing rate or a decreasing rate of at least one of the notification stimulus parameter or the control stimulus parameter.

[0183] Example 13: The system according to any one of Examples 1 to 12, wherein the processing circuit system is configured to: select a target ECAP feature value based on the posture state signal; compare the feature value of the ECAP signal with the threshold ECAP feature value; and adjust the first value of the notification stimulus parameter to the second value of the notification stimulus parameter based on the comparison of the feature value of the ECAP signal with the threshold ECAP feature value and the gain value.

[0184] Example 14: The system according to any one of Examples 1 to 13, wherein the processing circuitry is configured to: determine, at least from the posture state signal representing the posture state of the patient, that the patient's posture state has changed; and in response to determining that the posture state has changed, change the ECAP sensing frequency.

[0185] Example 15: The system according to any one of Examples 1 to 14 further includes an implantable medical device, the implantable medical device including the sensing circuit system and the processing circuit system.

[0186] Example 16: The system according to any one of Examples 1 to 15, wherein the plurality of notification stimulation pulses are defined by a notification pulse width greater than about 300 microseconds and less than about 1000 microseconds, and wherein the plurality of control stimulation pulses are defined by a control pulse width less than about 300 microseconds.

[0187] Example 17: A method comprising: controlling the delivery of a first notification stimulus pulse defined at least by a first value of a notification stimulus parameter, the notification stimulus pulse being one of a plurality of notification stimulus pulses, by a processing circuit system; controlling the delivery of a control stimulus pulse of a plurality of control stimulus pulses to a patient, the control stimulus pulse being defined at least by the first value of the control stimulus parameter, by the processing circuit system; sensing an evoked compound action potential (ECAP) signal induced by the control stimulus pulse by a sensing circuit system; determining a characteristic value of the ECAP signal induced by the control stimulus pulse by the processing circuit system; receiving, by the processing circuit system and from a sensor, a posture state signal representing the posture state of the patient; adjusting the first value of the notification stimulus parameter to a second value of the notification stimulus parameter by the processing circuit system based on the characteristic value of the ECAP signal and the posture state signal; and controlling the delivery of a second notification stimulus pulse of the plurality of notification stimulus pulses defined at least by the second value of the notification stimulus parameter by the processing circuit system.

[0188] Example 18: The method according to Example 17 further includes delivering the plurality of control stimulation pulses and the plurality of notification stimulation pulses to the patient by a stimulation generation circuit system.

[0189] Example 19: The method according to any one of Examples 17 and 18, wherein the notification stimulus parameter and the control stimulus parameter include at least one of amplitude, pulse width, or pulse shape.

[0190] Example 20: The method according to any one of Examples 17 to 19 further includes determining a gain value of the posture state based on the posture state signal, wherein adjusting the first value of the notification stimulation pulse to the second value of the notification stimulation pulse includes increasing or decreasing one of the stimulation parameters of the electrical stimulation based on the gain value associated with the patient's posture state.

[0191] Example 21: According to the method of Example 20, wherein the characteristic value is an amplitude of a portion of the ECAP signal, wherein the notification stimulation parameter includes a notification amplitude, wherein the control stimulation parameter includes a control amplitude, and wherein adjusting the first value of the notification stimulation pulse to the second value of the notification stimulation pulse includes: subtracting the amplitude from the patient's target ECAP amplitude value to generate a differential amplitude; multiplying the differential amplitude by the gain value to generate a preliminary differential value; multiplying the preliminary differential value by a scaling factor to generate a notification differential value, wherein the scaling factor represents the ratio of the first value of the notification amplitude of the first notification stimulation pulse defined before the control stimulation pulse to the control amplitude defining the control stimulation pulse; adding the notification differential value to the first value of the notification amplitude to generate a second value of the notification amplitude that at least partially defines the electrical stimulation to be delivered to the patient; and adding the preliminary differential value to the first value of the control stimulation parameter to generate a second value of the control stimulation parameter for a subsequent control stimulation pulse among the plurality of control stimulation pulses.

[0192] Example 22: According to the method of Example 21, the amplitude of the portion of the ECAP signal includes the voltage amplitude between the N1 peak value and the P2 peak value of the ECAP signal.

[0193] Example 23: The method according to any one of Examples 20 to 22, wherein the gain value is inversely proportional to the slope of a growth curve defining the relationship between the patient's ECAP value and the value of the control stimulation parameter.

[0194] Example 24: According to the method of Example 23, the posture state is one of a plurality of posture states, and each posture state includes a corresponding growth curve representing the relationship between the ECAP value and the value of the control parameter when the patient occupies the posture state.

[0195] Example 25: The method according to any one of Examples 17 to 24, wherein adjusting the first value of the notification stimulus parameter to the second value of the notification stimulus parameter comprises: comparing the feature value of the ECAP signal with a threshold ECAP feature value; determining that the feature value of the ECAP signal is greater than the threshold ECAP feature value; and in response to determining that the feature value of the ECAP signal is greater than the threshold ECAP feature value, reducing the first value of the notification stimulus parameter to the second value of the notification stimulus parameter.

[0196] Example 26: According to the method of Example 25, wherein the ECAP signal is a first ECAP signal and the feature value is a first feature value, wherein the control stimulus pulse is a first control stimulus pulse, and wherein the method further comprises: determining a second feature value of a second ECAP signal triggered by a second stimulus pulse delivered after sensing the first ECAP signal; determining that the second feature value of the second ECAP signal subsequently decreases below the threshold ECAP feature value; and in response to determining that the second feature value of the second ECAP signal decreases below the threshold ECAP feature value, increasing the second value of the notification stimulus parameter to a third value of the notification stimulus parameter, wherein the third value of the notification stimulus parameter is restricted to be less than or equal to the first value.

[0197] Example 27: The method according to Example 26 further includes increasing the second value of the notification stimulus parameter at a slower rate than decreasing the first value of the notification stimulus parameter to the second value of the notification stimulus parameter.

[0198] Example 28: The method according to any one of Examples 17 to 27 further includes selecting the gain value from a plurality of gain values ​​associated with the corresponding posture state based on the posture state signal, wherein the gain value represents at least one of the increment rate or decrement rate of at least one of the notification stimulus parameter or the control stimulus parameter.

[0199] Example 29: The method according to any one of Examples 17 to 28 further includes: selecting a target ECAP feature value based on the posture state signal; comparing the feature value of the ECAP signal with the threshold ECAP feature value; and adjusting the first value of the notification stimulus parameter to the second value of the notification stimulus parameter based on the comparison of the feature value of the ECAP signal with the threshold ECAP feature value and the gain value.

[0200] Example 30: The method according to any one of Examples 17 to 29 further includes: determining, at least from the posture state signal representing the posture state of the patient, that the patient's posture state has changed; and changing the ECAP sensing frequency in response to determining that the posture state has changed.

[0201] Example 31: The method according to any one of Examples 17 to 30, wherein the implantable medical device includes the sensing circuit system and the processing circuit system.

[0202] Example 32: The method according to any one of Examples 17 to 31, wherein the plurality of notification stimulation pulses are defined by a notification pulse width greater than about 300 microseconds and less than about 1000 microseconds, and wherein the plurality of control stimulation pulses are defined by a control pulse width less than about 300 microseconds.

[0203] Example 33: A computer-readable storage medium comprising instructions that, when executed by a processing circuitry system, cause the processing circuitry system to: control the delivery of a first notification stimulus pulse defined at least by a first value of a notification stimulus parameter, the notification stimulus pulse being one of a plurality of notification stimulus pulses; control the delivery of a control stimulus pulse, one of a plurality of control stimulus pulses, to a patient, the control stimulus pulse being defined at least by the first value of the control stimulus parameter; control a sensing circuitry system to sense an evoked compound action potential (ECAP) signal induced by the control stimulus pulse; determine a characteristic value of the ECAP signal induced by the control stimulus pulse; receive a posture state signal from a sensor representing the patient's posture state; adjust the first value of the notification stimulus parameter to a second value of the notification stimulus parameter based on the characteristic value of the ECAP signal and the posture state signal; and control the delivery of a second notification stimulus pulse, one of the plurality of notification stimulus pulses, defined at least by the second value of the notification stimulus parameter.

[0204] The techniques described in this disclosure can be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, aspects of the techniques can be implemented within one or more processors or processing circuitry systems, including one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry system, and any combination of such components. The terms "processor" or "processing circuitry system" can generally refer to any of the aforementioned logic circuitry systems, alone or in combination with other logic circuitry systems, or any other equivalent circuitry system. A control unit, including hardware, can also perform one or more of the techniques disclosed herein.

[0205] Such hardware, software, and firmware may be implemented within the same device or in separate devices to support the various operations and functions described in this disclosure. Furthermore, any described unit, circuit, or component may be implemented together or individually as discrete but interoperable logic devices. Describing different features as circuits or units is intended to highlight different functional aspects and does not necessarily imply that such circuits or units must be implemented by separate hardware or software components. Rather, the functionality associated with one or more circuits or units may be performed by separate hardware or software components, or integrated within common or separate hardware or software components.

[0206] The techniques described in this disclosure can also be embodied or encoded in a computer-readable medium (such as a computer-readable storage medium) containing instructions, which can be described as a non-transitory medium. Instructions embedded or encoded in a computer-readable storage medium can cause a programmable processor or other processor to perform the method, for example, when executing those instructions. Computer-readable storage media may include random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, hard disk, CD-ROM, floppy disk, magnetic tape cassette, magnetic media, optical media, or other computer-readable media.

Claims

1. A system comprising: A sensing circuit system configured to sense an evoked compound action potential (ECAP) signal triggered by a control stimulus pulse among a plurality of control stimulus pulses; as well as Processing circuitry system, the processing circuitry system being configured to: The delivery of a first notification stimulus pulse, defined at least by a first value of a notification stimulus parameter, is controlled; the notification stimulus pulse is one of a plurality of notification stimulus pulses. The delivery of one of the plurality of control stimulation pulses to the patient is controlled, the control stimulation pulse being defined at least by a first value of a control stimulation parameter, wherein the control stimulation pulse differs from the first notification stimulation pulse in at least one parameter, and wherein the delivery of the plurality of control stimulation pulses is at least partially interleaved with the delivery of the plurality of notification stimulation pulses. Determine the characteristic values ​​of the ECAP signal triggered by the control stimulus pulse; Receive posture state signals from the sensor that represent the patient's posture state; Based on the feature value of the ECAP signal and the posture state signal, the first value of the notification stimulus parameter is adjusted to the second value of the notification stimulus parameter; as well as The delivery of a second notification stimulus pulse, which is at least defined by the second value of the notification stimulus parameter, is controlled among the plurality of notification stimulus pulses.

2. The system of claim 1, further comprising a stimulus generation circuit system configured to deliver the plurality of control stimulus pulses and the plurality of notification stimulus pulses to the patient, wherein the processing circuit system is configured to control the stimulus generation circuit system to deliver the plurality of control stimulus pulses and the plurality of notification stimulus pulses.

3. The system of claim 1, wherein the notification stimulus parameter and the control stimulus parameter include at least one of amplitude, pulse width, or pulse shape.

4. The system of claim 1, wherein the processing circuitry is configured as follows: The gain value of the posture state is determined based on the posture state signal; and The first value of the notification stimulus pulse is adjusted to the second value of the notification stimulus pulse by increasing or decreasing one of the stimulation parameters of the notification stimulus pulse based on the gain value associated with the patient's postural state.

5. The system of claim 4, wherein the characteristic value is an amplitude of a portion of the ECAP signal, wherein the notification stimulus parameter includes a notification amplitude, wherein the control stimulus parameter includes a control amplitude, and wherein the processing circuitry is configured to adjust the first value of the notification stimulus pulse to the second value of the notification stimulus pulse in such a way that: The amplitude is subtracted from the patient's target ECAP amplitude value to generate the differential amplitude; Multiply the differential amplitude by the gain value to generate an initial differential value; The preliminary difference value is multiplied by a scaling factor to generate a notification difference value, wherein the scaling factor represents the ratio of the first value of the notification amplitude of the first notification stimulus pulse delivered prior to the control stimulus pulse to the control amplitude of the control stimulus pulse. The notification differential value is added to the first value of the notification amplitude to generate a second value of the notification amplitude that at least partially defines the electrical stimulation to be delivered to the patient; as well as The preliminary difference value is added to the first value of the control stimulus parameter to generate a second value of the control stimulus parameter for subsequent control stimulus pulses among the plurality of control stimulus pulses.

6. The system of claim 5, wherein the amplitude of the portion of the ECAP signal includes the voltage amplitude between the N1 peak value and the P2 peak value of the ECAP signal.

7. The system of claim 4, wherein the gain value is inversely proportional to the slope of a growth curve defining the relationship between the patient's ECAP value and the value of the control stimulation parameter.

8. The system of claim 7, wherein the posture state is one of a plurality of posture states, and wherein each posture state includes a corresponding growth curve representing the relationship between the ECAP value and the value of the control stimulus parameter when the patient occupies the posture state.

9. The system of claim 1, wherein the processing circuitry is configured to adjust the first value of the notification stimulus parameter to the second value of the notification stimulus parameter in such a way as: The characteristic value of the ECAP signal is compared with the threshold ECAP characteristic value; Determine that the characteristic value of the ECAP signal is greater than the threshold ECAP characteristic value; and In response to determining that the feature value of the ECAP signal is greater than the threshold ECAP feature value, the first value of the notification stimulus parameter is reduced to the second value of the notification stimulus parameter.

10. The system of claim 9, wherein the ECAP signal is a first ECAP signal and the feature value is a first feature value, wherein the control stimulation pulse is a first control stimulation pulse, and wherein the processing circuit system is configured to: Determine a second characteristic value of the second ECAP signal triggered by a second stimulation pulse delivered after sensing the first ECAP signal; The second characteristic value of the second ECAP signal is determined to subsequently decrease below the threshold ECAP characteristic value; and In response to determining that the second feature value of the second ECAP signal decreases below the threshold ECAP feature value, the second value of the notification stimulus parameter is increased to a third value of the notification stimulus parameter, wherein the third value of the notification stimulus parameter is restricted to be less than or equal to the first value.

11. The system of claim 10, wherein the processing circuitry is configured to increase the second value of the notification stimulus parameter at a slower rate than decreasing the first value of the notification stimulus parameter to the second value of the notification stimulus parameter.

12. The system of claim 1, wherein the processing circuitry is configured to select a gain value from a plurality of gain values ​​associated with a corresponding posture state based on the posture state signal, and wherein the gain value represents at least one of an increasing rate or a decreasing rate of at least one of the notification stimulus parameter or the control stimulus parameter.

13. The system of claim 1, wherein the processing circuitry is configured to: The threshold ECAP feature value is selected based on the posture state signal; The feature value of the ECAP signal is compared with the threshold ECAP feature value; Based on the comparison of the feature value of the ECAP signal with the threshold ECAP feature value and the gain value, the first value of the notification stimulus parameter is adjusted to the second value of the notification stimulus parameter.

14. The system of claim 1, wherein the processing circuitry is configured to: It is determined at least from the posture state signal representing the patient's posture state that the patient's posture state has changed; and In response to determining that the posture state has changed, the ECAP sensing frequency is changed.

15. The system of claim 1 further includes an implantable medical device, the implantable medical device including the sensing circuit system and the processing circuit system.

16. The system of claim 1, wherein the plurality of notification stimulation pulses are defined by a notification pulse width of greater than 300 microseconds and less than 1000 microseconds, and wherein the plurality of control stimulation pulses are defined by a control pulse width of less than 300 microseconds.

17. An implantable medical device, the implantable medical device comprising: Processing circuit system; A memory storing computer-readable instructions that, when executed by the processing circuitry system, cause the implantable medical device to perform a method comprising: The delivery of a first notification stimulus pulse, defined by at least a first value of a notification stimulus parameter, is controlled by the processing circuit system; the notification stimulus pulse is one of a plurality of notification stimulus pulses. The processing circuit system controls the delivery of a control stimulation pulse from a plurality of control stimulation pulses to the patient, the control stimulation pulse being defined at least by a first value of a control stimulation parameter, wherein the control stimulation pulse differs from the first notification stimulation pulse in at least one parameter, and wherein the delivery of the plurality of control stimulation pulses is at least partially interleaved with the delivery of the plurality of notification stimulation pulses. The sensing circuit system senses the evoked compound action potential (ECAP) signal triggered by the control stimulus pulse; The processing circuit system determines the characteristic values ​​of the ECAP signal triggered by the control stimulus pulse; The processing circuit system receives posture state signals representing the patient's posture state from the sensors; The processing circuitry adjusts the first value of the notification stimulus parameter to a second value based on the characteristic value of the ECAP signal and the posture state signal; and The processing circuit system controls the delivery of a second notification stimulus pulse, which is at least defined by the second value of the notification stimulus parameter, among the plurality of notification stimulus pulses.

18. The implantable medical device of claim 17, wherein the method further comprises delivering the plurality of control stimulation pulses and the plurality of notification stimulation pulses to the patient by a stimulation generation circuit system.

19. The implantable medical device of claim 17, wherein the notification stimulation parameter and the control stimulation parameter include at least one of amplitude, pulse width, or pulse shape.

20. The implantable medical device of claim 17, wherein the method further comprises determining a gain value of the posture state based on the posture state signal, wherein adjusting the first value of the notification stimulus pulse to the second value of the notification stimulus pulse comprises increasing or decreasing one of the stimulation parameters of the notification stimulus pulse based on the gain value associated with the patient's posture state.

21. The implantable medical device of claim 20, wherein the characteristic value is an amplitude of a portion of the ECAP signal, wherein the notification stimulation parameter includes a notification amplitude, wherein the control stimulation parameter includes a control amplitude, and wherein adjusting the first value of the notification stimulation pulse to the second value of the notification stimulation pulse comprises: The amplitude is subtracted from the patient's target ECAP amplitude value to generate the differential amplitude; Multiply the differential amplitude by the gain value to generate an initial differential value; The preliminary difference value is multiplied by a scaling factor to generate a notification difference value, wherein the scaling factor represents the ratio of the first value of the notification amplitude of the first notification stimulus pulse delivered prior to the control stimulus pulse to the control amplitude of the control stimulus pulse. The notification difference value is added to the first value of the notification amplitude to generate a second value of the notification amplitude that at least partially defines the electrical stimulation to be delivered to the patient; as well as The preliminary difference value is added to the first value of the control stimulus parameter to generate a second value of the control stimulus parameter for subsequent control stimulus pulses among the plurality of control stimulus pulses.

22. The implantable medical device of claim 21, wherein the amplitude of the portion of the ECAP signal includes the voltage amplitude between the N1 peak and the P2 peak of the ECAP signal.

23. The implantable medical device of claim 20, wherein the gain value is inversely proportional to the slope of a growth curve defining the relationship between the patient's ECAP value and the value of the control stimulation parameter.

24. The implantable medical device of claim 23, wherein the posture state is one of a plurality of posture states, and wherein each posture state includes a corresponding growth curve representing the relationship between the ECAP value and the value of the control stimulation parameter when the patient occupies the posture state.

25. The implantable medical device of claim 17, wherein adjusting the first value of the notification stimulus parameter to the second value of the notification stimulus parameter comprises: The characteristic value of the ECAP signal is compared with the threshold ECAP characteristic value; Determine that the characteristic value of the ECAP signal is greater than the threshold ECAP characteristic value; as well as In response to determining that the feature value of the ECAP signal is greater than the threshold ECAP feature value, the first value of the notification stimulus parameter is reduced to the second value of the notification stimulus parameter.

26. The implantable medical device of claim 25, wherein the ECAP signal is a first ECAP signal and the characteristic value is a first characteristic value, wherein the control stimulation pulse is a first control stimulation pulse, and wherein the method further comprises: Determine a second characteristic value of the second ECAP signal triggered by a second stimulation pulse delivered after sensing the first ECAP signal; The second characteristic value of the second ECAP signal is then determined to decrease below the threshold ECAP characteristic value; as well as In response to determining that the second feature value of the second ECAP signal decreases below the threshold ECAP feature value, the second value of the notification stimulus parameter is increased to a third value of the notification stimulus parameter, wherein the third value of the notification stimulus parameter is restricted to be less than or equal to the first value.

27. The implantable medical device of claim 26, wherein the method further comprises increasing the second value of the notification stimulus parameter at a slower rate than decreasing the first value of the notification stimulus parameter to the second value of the notification stimulus parameter.

28. The implantable medical device of claim 17, wherein the method further comprises selecting the gain value from a plurality of gain values ​​associated with a corresponding posture state based on the posture state signal, and wherein the gain value represents at least one of an increasing rate or a decreasing rate of at least one of the notification stimulus parameter or the control stimulus parameter.

29. The implantable medical device of claim 17, wherein the method further comprises: The threshold ECAP feature value is selected based on the posture state signal; The feature value of the ECAP signal is compared with the threshold ECAP feature value; as well as Based on the comparison of the feature value of the ECAP signal with the threshold ECAP feature value and the gain value, the first value of the notification stimulus parameter is adjusted to the second value of the notification stimulus parameter.

30. The implantable medical device of claim 17, wherein the method further comprises: It is determined, at least from the posture state signal representing the patient's posture state, that the patient's posture state has changed; as well as In response to determining that the posture state has changed, the ECAP sensing frequency is changed.

31. The implantable medical device of claim 17, wherein the implantable medical device includes the sensing circuit system.

32. The implantable medical device of claim 17, wherein the plurality of notification stimulation pulses are defined by a notification pulse width of greater than 300 microseconds and less than 1000 microseconds, and wherein the plurality of control stimulation pulses are defined by a control pulse width of less than 300 microseconds.

33. A computer-readable storage medium comprising instructions that, when executed by a processing circuit system, cause the processing circuit system to: The delivery of a first notification stimulus pulse, defined at least by a first value of a notification stimulus parameter, is controlled; the notification stimulus pulse is one of a plurality of notification stimulus pulses. The delivery of a control stimulation pulse of a plurality of control stimulation pulses to a patient is controlled, the control stimulation pulse being defined at least by a first value of a control stimulation parameter, wherein the control stimulation pulse is different from the first notification stimulation pulse in at least one parameter, and wherein the delivery of the plurality of control stimulation pulses is at least partially interleaved with the delivery of the plurality of notification stimulation pulses. The control sensing circuit system senses the evoked compound action potential (ECAP) signal triggered by the control stimulus pulse; Determine the characteristic values ​​of the ECAP signal triggered by the control stimulus pulse; Receive posture state signals from the sensor that represent the patient's posture state; Based on the feature value of the ECAP signal and the posture state signal, the first value of the notification stimulus parameter is adjusted to the second value of the notification stimulus parameter; as well as The delivery of a second notification stimulus pulse, which is at least defined by the second value of the notification stimulus parameter, is controlled among the plurality of notification stimulus pulses.

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