Patent Publication Number: US-2022218988-A1

Title: Systems and methods for improving sleep disordered breathing

Description:
TECHNICAL FIELD 
     An electrical stimulation system for improving sleep disordered breathing is provided. 
     BACKGROUND 
     Obstructive sleep apnea (OSA) is the most common type of sleep apnea and is characterized by repeated episodes of complete or partial obstructions of the upper airway during sleep, despite the effort to breathe, and is usually associated with a reduction in blood oxygen saturation. Individuals with OSA are rarely aware of difficulty breathing, even upon awakening. It is often recognized as a problem by others who observe the individual during episodes or is suspected because of its effects on the body. OSA is commonly accompanied with snoring. OSA can be associated with symptoms during the daytime (e.g. excessive daytime sleepiness, decreased cognitive functions). Symptoms may be present for years or even decades without identification, during which time the individual may become conditioned to the daytime sleepiness and fatigue associated with significant levels of sleep disturbance. Individuals who generally sleep alone are often unaware of the condition, without a regular bed-partner to notice and make them aware of the signs. 
     The most widely used current therapeutic intervention for treating OSA is positive airway pressure whereby a breathing machine pumps a controlled stream of air through a mask worn over the nose, mouth, or both. The additional pressure holds open the relaxed muscles. There are several mechanisms for treating OSA with positive airway pressure therapy. The most common treatment involves the use of continuous positive airway pressure (CPAP) machines. CPAP machines are worn by the OSA patient at nighttime during sleep, with the patient wearing a mask connected by hose to an air pump that maintains positive airway pressure. 
     Neurostimulation therapy can be an alternative for patients who cannot use a continuous positive airway pressure device. One neurostimulation system senses respiration and deliver mild electrical stimulation to the hypoglossal nerve (HGN) in order to increase muscle tone at the back of the tongue so it will not collapse over the airway. The HGN innervates the tongue musculature. It provides motor control for the muscles of the tongue and helps with important voluntary and involuntary functions like swallowing, speaking, and mastication. Stimulating the HGN can restore the tone to key tongue muscles that, when relaxed, can lead to obstructive sleep apnea. 
     Conventional HGN neurostimulation systems utilize stimulation leads implanted in the patient&#39;s neck/throat, with electrodes touching, e.g., a cuff electrode that surrounds the HGN or in close proximity to the HGN. The leads are connected via wire to a pulse generator implanted under the skin in the patient&#39;s chest. From time-to-time, the pulse generator is surgically accessed for battery changes. The system includes a handheld patient controller to allow it to be switched on before sleep. 
     While HGN neurostimulation therapy has proven to be an effective treatment for OSA, the bulk of the conventional systems and the degree of invasiveness in implanting, using, and maintaining the system is undesirable. 
     SUMMARY 
     A neuromodulation system is provided herein. In an aspect, a neuromodulation system comprises a nerve cuff electrode comprising a cuff body having at least one stimulating electrical contact disposed thereon configured to deliver a stimulation signal to a target site. The system also includes a sensor configured to be implantable adjacent to an anterior lingual muscle and configured to record physiological data. The system further includes an antenna configured to produce an induced current in response to being disposed in an electromagnetic field and comprising an upper and a lower coil electrically connected to each other in parallel. The system further includes an electronics package comprising electrical components to control the application of a stimulation signal via the at least one stimulating electrical contact of the nerve cuff electrode. An external controller is provided which comprises a control unit and a power mat that supports one or more power transmission coils that are excitable to produce an electromagnetic field for inducing electrical current in the antenna to power the electronics package. The system also includes a computing device comprising a non-transitory memory storing instructions and a processor to access the non-transitory memory and execute the instructions. Such instructions include monitoring the physiological data recorded by the sensor, identifying a trigger within the physiological data, wherein the trigger is identified as a biomarker for a physiological condition related to sleep, and applying a rule-based classification to the trigger to determine whether one or more parameters of the stimulation signal should be altered based on the biomarker and altering the one or more parameters of the stimulation signal in response to the biomarker. In certain aspects, the sensors can comprise a plurality of sensors disposed on the lead body of a neuromodulation lead. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating an example configuration of a neuromodulation system according to an aspect of the present disclosure. 
         FIG. 2  is a schematic illustration of an implantable neuromodulation device of an implantable stimulation system according to an aspect of the present disclosure. 
         FIG. 3  is a schematic illustration of a neuromodulation device according to an aspect of the present disclosure. 
         FIG. 4 . is a schematic illustration of a portion of a neuromodulation device according to an aspect of the present disclosure. 
         FIG. 5  is a section view taken generally along line  3 - 3  of  FIG. 3 , illustrating an antenna portion of the implantable neuromodulation device. 
         FIG. 6  is a schematic illustration depicting an exemplary configuration of a sensing lead or stimulation lead of a neuromodulation device according to an aspect of the present disclosure. 
         FIG. 7  is a schematic illustration depicting an exemplary configuration of a sensing lead or stimulation lead of aneuromodulation device according to an aspect of the present disclosure. 
         FIGS. 8A-8B  are schematic illustrations depicting an exemplary configuration of an antenna portion of a neuromodulation device according to an aspect of the present disclosure. 
         FIGS. 9A-9C  are schematic illustrations depicting exemplary configurations of a power mat portion of a neuromodulation system according to an aspect of the present disclosure. 
         FIG. 10  is a block diagram of an example system that can provide neural stimulation according to a closed loop algorithm to treat sleep disordered breathing (SDB), which can be part of the system of  FIG. 1 . 
         FIG. 11  is a block diagram of an example of the computing device shown in  FIG. 11 . 
         FIG. 12  is a process flow diagram of an example method for providing neural stimulation according to a closed loop algorithm to treat SDB, including OSA, according to an aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein with respect to a described element, the terms “a,” “an,” and “the” include at least one or more of the described element including combinations thereof unless otherwise indicated. Further, the terms “or” and “and” refer to “and/or” and combinations thereof unless otherwise indicated. By “substantially” is meant that the shape or configuration of the described element need not have the mathematically exact described shape or configuration of the described element but can have a shape or configuration that is recognizable by one skilled in the art as generally or approximately having the described shape or configuration of the described element. As used herein, “stimulate” or “modulate” in the context of neuromodulation includes stimulating or inhibiting neural activity. A “patient” as described herein includes a mammal, such as a human being. By “improving,” the patient&#39;s medical disorder is better after therapy than before therapy. As used herein, the terms, “inferior,” “superior,” “cranial,” and caudal refer to anatomical planes and directions when the patient is in a standard anatomical position. Similarly, the terms “left” and “right” refer to the position of elements that correspond to the left and right side of a patient&#39;s body in a standard anatomical position. By “integral” or “integrated” is meant that the described components are fabricated as one piece or multiple pieces affixed during manufacturing or the described components are otherwise not separable using a normal amount of force without damaging the integrity (i.e. tearing) of either of the components. As used herein, a “neuromodulation device” is a device that is not implanted in the oral cavity of a patient. 
     The present disclosure relates to an implantable electrical stimulation or neuromodulation system, which can be used to provide a variety of electrical therapies, including neuromodulation therapies such as nerve and/or muscle stimulation. Stimulation can induce excitatory or inhibitory neural or muscular activity. Such therapies can be used at various suitable sites within a patient&#39;s anatomy. In one example implementation, the system can be used to treat sleep disordered breathing (SDB) including obstructive sleep apnea (OSA) via neuromodulation of the hypoglossal nerve (HGN) and/or other nerves that innervate anterior lingual muscles such as protruser muscles; other muscles of the tongue; and/or pharyngeal muscles, such as the posterior pharyngeal walls. 
     Referring to  FIG. 1 , in an embodiment, a neuromodulation system  11  is provided that include a stimulator  13 , a sensor  15 , an antenna  17 , an electronics assembly  19 , an external controller  21 , and an internal computing device  27 . 
     As described in more detail below, stimulator  13  can have a stimulating electrical contact disposed thereon configured to deliver a stimulation signal to a stimulation site. The neuromodulation system can include a plurality of stimulators and a plurality of stimulating electrical contacts disposed on each stimulator. Sensor  15  can have a sensing contact disposed thereon configured to be implantable adjacent to a sensing site and configured to record physiological signals. The neuromodulation system can comprise a plurality of sensors and a plurality of sensing contacts on each sensor. For example, the neuromodulation system can comprise a first cuff lead having a cuff body comprising a plurality of stimulating electrical contacts disposed thereon and a second cuff lead having a cuff body comprising a plurality of stimulating electrical contacts disposed thereon. The sensor can comprise a sensing lead having a lead body comprising a plurality of sensing contacts disposed thereon. The first cuff lead can have a cuff body sized and configured to at least partially wrap around a first nerve branch site comprising a hypoglossal nerve branch distal to the hypoglossal nerve trunk. The second cuff lead can have a cuff body sized and configured to at least partially wrap around a second nerve branch site proximal to the first nerve branch site. In certain aspects, the stimulator is a stimulating lead and the sensor is a sensing lead. Both leads can be operably coupled to the electronics assembly and the electronics assembly can be operably coupled to the antenna. The antenna can be configured to supply electrical current to the electronics assembly to power the electronics assembly. The stimulating lead, the sensing lead, the electronics assembly, and the antenna can be parts of a single neuromodulation device. The antenna can be located at a proximal end of the neuromodulation device, the electronics assembly can be operably coupled to the antenna, and the stimulating lead and sensing lead can extend distally from the electronics assembly. In certain aspects, the sensor can be a sensing lead comprising a lead body with a right portion, a left portion, and an intermediate portion defining an apex of the lead body. A left set of sensors can be disposed on the left portion of the lead body and a right set of sensors can be disposed on the right portion of the lead body. The lead body can be biased towards an omega shape when the neuromodulation lead is fully deployed and the intermediate portion of the lead body can be biased towards an inferior position relative to the left and right sensor sets when the neuromodulation lead is fully deployed. 
     Antenna  17  can be configured to produce an induced current in response to being disposed in an electromagnetic field. The antenna can comprise an upper and a lower coil electrically connected to each other in parallel. 
     Electronics assembly  19  can comprise electrical components to control the application of the stimulation signal via the stimulating electrical contact of the stimulator and sensing of the physiological signal by the sensor. External controller  21  can comprise control unit  23  and power transducer  25  that supports a power transmission coil that is excitable to produce an electromagnetic field for inducing electrical current in the antenna to power the electronics assembly. The power transducer can be a mat as described in more detail below. 
     Internal computing device  27  can comprise a non-transitory memory storing instructions and a processor to access the non-transitory memory. The processor can execute the instructions to at least monitor the physiological signals recorded by the sensor and identify a trigger within the physiological signals, where the trigger is identified as a biomarker for a condition related to sleep. In certain aspects, the trigger indicates a change in phasic and/or tonic genioglossus muscle activity during respiration. The processor can further execute instructions to apply a rule-based classification to the trigger to determine whether one or more parameters of the stimulation signal should be altered based on the biomarker and to alter the one or more parameters of the stimulation signal in response to the biomarker. In certain aspects, the rule-based classification is adaptive. The initial rules of an algorithm used by the rule-based classification can be determined based on historical values for a population, historical values for a patient, and/or patient derived values. 
     In certain aspects, a method of improving sleep disordered breathing in a patient suffering therefrom is provided. Such a method can comprise obtaining a neuromodulation system as described above and herein. The method can further include placing the stimulator on a stimulation target site comprising a trigeminal nerve or a branch thereof, a facial nerve or a branch thereof, a glossopharyngeal nerve or a branch thereof, a vagus nerve or a branch thereof, a hypoglossal nerve trunk, a lateral branch of the hypoglossal nerve, a medial branch of the hypoglossal nerve, or suitable combinations thereof. A sensor can be placed on a sensing target site comprising a trigeminal nerve or a branch thereof, a facial nerve or a branch thereof, a glossopharyngeal nerve or a branch thereof, a vagus nerve or a branch thereof, a hypoglossal nerve trunk, a lateral branch of the hypoglossal nerve, a medial branch of the hypoglossal nerve, a tongue muscle, an upper airway muscle, a pharyngeal muscle, a cricopharyngeus muscle, or suitable combinations thereof. The method can further include activating the sensor to sense physiological signals from the sensing target site and activating the stimulator to stimulate the stimulation target site based on the sensed physiological signals to improve the patient&#39;s sleep disordered breathing. 
     Electrical Neuromodulation Device System 
     Referring to  FIG. 1 , the system  10  can include an implantable neuromodulation device  20  and external controller  100 . Controller  100  can power neuromodulation device  20  through electromagnetic induction. Neuromodulation device  20  can include power receiver  30  with antenna  32 . Electrical current can be induced in antenna  32  when it is positioned above power mat  112  of controller  100 , in an electric field produced by power transmit antenna  112 . Antennas  112  and  32  can also facilitate communication between controller  100  and neuromodulation device  20 , respectively. This power/communication link between neuromodulation device  20  and controller  100  is shown generally by the arrow  70  in  FIG. 1 . 
     System  10  can also include a user interface  200  in the form of a computer platform  202  running a custom application that enables communication with controller  100  wirelessly, as indicated generally by arrow  204 . This can be done, for example, using Bluetooth or WiFi radio communication. In the example configuration of  FIG. 1 , computer platform  202  is a smartphone. The type of computer platform  202  could, however, vary. For example, the computer platform  202  can be a physician or patient platform. Each platform  202  can have an application or “app” installed thereon that is user specific, i.e., a patient app or a physician app. The physician platform would have the physician app installed, and the patient platform would have the patient app installed. The patient app can allow the patient to execute certain commands necessary for controlling operation of neurostimulation device  20 , such as, for example, start/stop therapy, increase/decrease stimulation power or intensity, and select a stimulation program. In addition to the controls afforded the patient, the physician app can also allow the physician to modify stimulation settings, such as pulse settings (patterns, duration, waveforms, etc.), stimulation frequency, amplitude settings, and electrode configurations, closed-loop and open loop control settings and tuning parameters for the embedded software that controls therapy delivery during use. 
     As indicated generally by arrow  206 , computer platform  202  can be connected (e.g., WiFi and/or LTE) to internet/cloud  208 , which facilitates communication  214  with remote or cloud-based server  216 . This can allow for the transfer of data between server  216  and computer platform  202  via internet  208 . Additionally, controller  100  itself can also be internet connected (e.g., WiFi), as shown at  210 . This can also allow for the transfer of data between controller  100  and server  216  via internet  208 . 
     System Communication 
     As shown in  FIG. 1  and described above, system  10  can be configured to provide various communication paths between the system components. For example, computer platform  202  being connected to controller  100  (see  204 ) and to internet  208  (see  206 ) can facilitate a communication path from remote server  216  (see  214 ) to neuromodulation device  20  itself (see  70 ). A communication path between server  216  and neuromodulation device  20  can also be established via WiFi link  210  of controller  100 . 
     Additionally, recognizing that the physician may be remote from the patient, a physician communication path can be established via the internet connection  206  of the remotely located physician platform  202 . Through this connection, remote physician platform  202  can communicate with server  216  through internet connection  206 . Remote physician platform  202  can also communicate with controller  100 , either via internet connection  210  (when enabled) or through patient controller  202 . 
     In addition to facilitating local control of system  10 , e,g, controller  100  and neuromodulation device  20 , the various communication paths described above can also enable:
         Distributing from server  216  software/firmware updates for the computer platform  202 , controller  100 , and/or neuromodulation device  20 .   Downloading from server  216  therapy settings/parameters to be implemented by computer platform  202 , controller  100 , and/or neuromodulation device  20 .   Facilitating therapy setting/parameter adjustments/algorithm adjustments by a remotely located physician.   Uploading data recorded during therapy sessions.   Maintaining coherency in the settings/parameters by distributing changes and adjustments throughout the system components.       

     System Operation Overview 
     The therapeutic approach implemented with system  10  can involve implanting only neuromodulation device  20 , leaving controller  100  as an external component to be used only during the application of therapy. To facilitate this, neuromodulation device  20  can be configured to be powered by controller  100  through electromagnetic induction. In operation, power mat  110 , operated by control unit  120 , can be positioned external to the patient in the vicinity of neuromodulation device  20  to position transmitting antenna  112  of the controller, located in the mat, close to receiving antenna  32  of the neuromodulation device. In the implementation where the system  10  is used to treat OSA, the power mat  110  can be positioned on or sufficiently near the sleeping surface while the patient sleeps to maintain the position of the receiving antenna  32  within the target volume of the electromagnetic field generated by the power antenna  112 . 
     Through this approach, system  10  can deliver therapy to improve SDB such as OSA, for example, by stimulating the HGN, for example, through a shorter, less invasive procedure. The elimination of an on-board, implanted power source in favor of an inductive power scheme can eliminate the need for batteries and the associated battery changes over the patient&#39;s life. 
     Additionally, neuromodulation device  20  can implement electromyography (EMG) electrodes for sensing neuromuscular responses to physiological needs of the patient during sleep. Such sensing electrodes can continuously monitor physiological intrinsic EMG signals from the anterior lingual musculature. For instance, EMG sensing electrodes can be configured to detect neuromuscular responses from the genioglossus muscle, which is innervated by the HGN or to detect neuromuscular responses from other anterior lingual muscles and other muscles of the tongue. 
     Controller  100  can use transmitting antenna  112  for multiple purposes, for example: 1) to provide power to neuromodulation device  20  during therapy sessions, and 2) to communicate with the neuromodulation device. This communication can, for example, include programming, e.g., uploading software/firmware revisions to neuromodulation device  20 , changing/adjusting stimulation settings and/or parameters, and adjusting parameters of control algorithms. Controller  100  can receive the programming, software/firmware, and settings/parameters through any of the communication paths described above, e.g., from user interface  200  or through direct WiFi internet connection, when available. The communication paths can also be used to download data from neuromodulation device  20 , such as measured data regarding completed stimulation therapy sessions, to the controller  100 . The controller  100  can transmit the downloaded data to the user interface  200 , which can send/upload the data to server  216  via internet  208 . 
     In operation, sensed EMG responses from the genioglossus muscle, for example, can allow closed-loop operation of the neuromodulation device  20  while eliminating the need for a chest lead. Operating in closed-loop, the neuromodulation device  20  can maintain stimulation synchronized with respiration, for example, while preserving the ability to detect and account for momentary obstruction. The neuromodulation device  20  can also detect and respond to snoring, for example. 
     To facilitate real-time, closed-loop control, a control algorithm can be implemented locally on neuromodulation device  20 . This can be achieved, for example, by programming a control algorithm on an application-specific integrated circuit (ASIC) component of neuromodulation device  20  (see below for the description of the neuromodulation device electronics). 
     Operating in real-time, neuromodulation device  20  can record data related to the stimulation session including, for example, stimulation settings, EMG responses, respiration, sleep state including different stages of REM and non-REM sleep, etc. For example, changes in phasic and tonic EMG activity of genioglossus muscle during inspiration can serve as a trigger for stimulation or changes in stimulation can be made based on changes in phasic and tonic EMG activity of the genioglossus muscle during inspiration or during different sleep stages. After the sleep session, this recorded data can be uploaded to user interface  200  and to server  216 . Also, the patient can be queried to use the interface  200  to log data regarding their perceived quality of sleep, which can also be uploaded to the server  216 . Offline, the server  216  can execute a software application to evaluate the recorded data to determine whether settings and control parameters can be adjusted to further optimize the stimulation therapy. The software application can, for example, include artificial intelligence (AI) models that, learn from recorded therapy sessions, how certain adjustments affect the therapeutic outcome for the patient. In this manner, through AI learning, the model can provide patient-specific optimized therapy. 
     With reference to  FIG. 9 , system  300  can be implemented within the system  10  and/or the neuromodulation device  20  to provide stimulation to improve SDB according to open-loop control or closed-loop control. The system can include one or more sensors  302  (which can be implanted and/or external), a computing device  304  (which can be implanted and/or external, and may be part of another device like the controller), and one or more electrodes  306  (which can be implanted and/or external). The one or more sensors can be configured to record/detect physiological data (e.g. data originating from the patient&#39;s body) over time including changes therein. Exemplary physiological data can include phasic contraction of anterior lingual musculature, such as phasic genioglossus muscle contraction, underlying tonic activity of anterior lingual musculature, such as tonic activity of the genioglossus muscle, and combinations thereof. Phasic contraction of the genioglossus muscle can be indicative of inspiration, particularly the phasic activity that is layered within the underlying tonic tone of the genioglossus muscle. Changes in physiological data include changes in phasic contraction of anterior lingual musculature, such as phasic genioglossus muscle contraction, changes in underlying tonic activity of anterior lingual musculature, such as changes in tonic activity of the genioglossus muscle, and combinations thereof. For example, EMG signal changes can include changes in the frequency, amplitude, spike rate, or other features within the EMG signal. In particular, changes in phasic contraction of the genioglossus muscle can indicate a respiration or inspiration change and can be used to as a trigger for stimulation. Such physiological data and changes therein can be identified in recorded EMG signals, such as during different phases of respiration including inspiration. As such, one or more sensors  302  can include EMG sensors. The one or more sensors  302  can also include, for example, wireless or tethered sensors that measure, body temperature, movement, breath sounds (e.g. audio sensors), heart rate, pulse oximetry, eye motion, etc. 
     The computing device  304  can be configured to provide open-loop control and/or closed-loop stimulation to configure parameters for a stimulation. In other words, with respect to closed-loop stimulation, the computing device can be configured to track the patient&#39;s respiration (such as each breath of the patient) and stimulation can be applied during inspiration, for example. However, with respect to open-loop stimulation, stimulation can be applying without tracking specific physiological data, such as respiration or inspiration. However, even under such an “open loop” scenario, the computing device can still adjust stimulation and record data, to act on such information. For example, one way the computing device can act upon such information is that the computing device can configure parameters for stimulation to apply stimulation in an open loop fashion but can monitor the patient&#39;s respiration to know when to revert to applying stimulation on a breath to breath, close-loop fashion such that the system is always working in a close looped algorithm to assess data. Accordingly, adjustments to stimulation may be based on an input to the computing device  304 , which may be based on one or more trends in physiological data recorded by the one or more sensors  302  over time. Treatment parameters of the system may be automatically adjusted in response to the physiological data. The physiological data can be stored over time and examined to change the treatment parameters; for example, the treatment data can be examined in real time to make a real time change to the treatment parameters. 
     An example of the computing device  304  programmed to implement the closed-loop scenario is shown in  FIG. 10 . The computing device  304  can include a memory  422  (e.g., a non-transitory memory), a processor  424  (e.g., an integrated circuit, such as an application specific integrated circuit (ASIC)), or an ASIC comprising both a memory and a processor. For example, the memory  422  can be a computer-usable or computer-readable medium that can contain or store the machine-readable instructions (which are, for example, a program) for use by or in connection with the instruction or execution of a system, apparatus or device (like the computing device  304 ) by the processor  424 . The computer-usable or computer-readable medium can be, for example but not limited to, random access memory (RAM) including static or dynamic RAM, read-only memory (ROM), flash memory, an Erasable Programmable Read Only Memory (EPROM), floating point memory, or combination thereof including combinations thereof on the same ASIC. The processor  424 , for example, can include one or more processing cores, processing units, or the like. The memory  422  can store machine readable instructions, while the processor  424  can access the memory  422  and execute the machine readable instructions (e.g., which can include one or more programs) and cause the computing device  304  to perform operations of a monitoring component  426 , an identification component  427 , and/or a classification component  428 . The processor  424  can interpret the physiological information coming from the sensors, including decoding data, analyzing data, recognizing patterns, etc. 
     The monitoring component  426  can monitor the physiological data recorded by the sensor(s)  302 . The identification component  427  can identify a trigger within the physiological data (e.g., related to respiration). For example, the monitoring component can monitor EMG waveform characteristics like spike rate, amplitude, and frequency, as well as phasic activity and tonic activity (again monitoring for changes in amplitude, frequency or other parameters of the EMG). The identification component can identify the trigger during such monitoring (e.g. a characteristic change in the EMG waveform). In one example, the trigger can be an associated change in the EMG, such as short term contraction of the genioglossus muscle indicating phasic genioglossus muscle activity or longer term changes in genioglossus muscle activity indicating a change in underlying tonic tone of the genioglossus muscle seen over one or more parts or repetitions of the physiological data. The trigger can be identified as a biomarker for a condition related to sleep, such as a change in at least one parameter physiological data. In some instances, the biomarker can be inspiration. In other instances, the biomarker can be a body position. In other instances, the biomarker can be a stage in a sleep cycle (e.g., awake, non-REM sleep—stage 1 light sleep, stage 2 light sleep, stage 3 deep sleep, REM sleep, etc.). In some instances, motion detection and/or other biomarkers can be used to automatically turn the therapy on only once the patient has fallen asleep and to determine the parameters of stimulation to optimally maintain airway patency throughout the night (including adapting stimulation based on sleep stage and body position) without causing unnecessary discomfort or leading to arousal events to increase patient comfort and adherence to therapy. Stimulation can be ramped up as the patient moves from light to deep sleep or ramped during each stimulation phase such that the first pulse in a pulse train has less amplitude and/or pulse width than the last pulse in the pulse train. In some instances, stimulation will automatically shut off if the patient wakes up and re-initiate as they fall back to sleep. 
     The awake stage of the sleep cycle refers to a relaxation stage when the subject is first lying in bed or lying in bed trying to fall asleep again. Non-REM sleep has three stages and is a stage of sleep without rapid eye movement. The REM stage includes REM sleep, where eyes move rapidly from side to side behind closed eyelids, breathing becomes faster and irregular, heart rate and blood pressure increase to near waking levels, and arm and leg muscles become temporarily paralyzed. 
     Non-REM stage 1 refers to the changeover from wakefulness to sleep (lasting several minutes). During non-REM stage 1, a subject&#39;s heartbeat, breathing, and eye movements slow and muscles relax with occasional twitches. Non-REM stage 2, the longest of all the stages, is a period of light sleep before entering deeper sleep, where heartbeat and breathing slow, muscles relax even further, body temperature drops and eye movement stops. Non-REM stage 3 refers to the period of deep sleep needed to feel refreshed in the morning, where heartbeat and breathing slow to their lowest levels during sleep, muscles are relaxed, and it may be difficult to awaken. 
     The sleep state can be determined, for example, based on information in the physiological data (e.g., tonic genioglossus muscle activity as indicated on an EMG). Once the sleep state is recognized, the goal is to apply therapy in such a way to minimize patient discomfort and to also minimize potential stimulation related arousal events. This may include, reducing the amplitude of stimulation during stage 1 and stage 2 sleep, and increase amplitude during stage 3 and REM. This may also include ramping therapy over a longer period of time, meaning from zero to programmed output over a longer time period, during stage 1 and 2 sleep vs. stage 3 and REM sleep or ramping therapy within each pulse train, when applied during inspiration for example. 
     For example, if certain EMG activity is detected, like phasic changes in EMG activity that is indicative of inspiration during any phase of sleep, the system may deliver stimulation during the respiratory period of inspiration. The system can apply stimulation to the hypoglossal nerve, for example, using a particular set of electrodes, waveform, pulse width, frequency, intra-pulse interval and pulse ramp rate that provide therapeutic airway patency during inspiration. The system can stop stimulation during the exhalation period and can continue to monitor the physiological EMG, from the genioglossus muscle for example, throughout the inspiratory and exhalation periods of each breath. The system can adjust the stimulation parameters and/or the electrodes selected for stimulation as necessary to optimize the stimulation to provide the optimal airway patency, based on additional biomarkers including, sleep state, body position, or the like. The closed loop algorithms embedded within the neuromodulation device or neuromodulation lead can continuously monitor and adjust therapy based on the physiological data and triggers and use rule based classification to determine when, how and for what period of time, to apply and adjust stimulation to provide optimal airway patency during sleep. 
     For example, if certain EMG activity, like tonic and phasic EMG activity drops or ceases during REM, the system may deliver a stimulation periodically based on predetermined physician programmed parameters, the system may rely on previous known patient specific parameters to apply stimulation, or the system may use a default periodic stimulation that is applied throughout REM sleep. The system can also monitor EMG through the REM period to determine when to stop using the periodic stimulation and when to re-initiate applying stimulation during each inspiratory event. 
     In some instances, the system may not turn on stimulation immediately when the neuromodulation device is within the field from the transmit coil. In this case, the system can turn on and monitor an EMG signal, e.g., detecting tonic and phasic muscle activity, to understand the sleep stage. Once the system has determined the patient is sleeping, entering stage 1 of sleep or stage 2 of sleep, the system  10  can start to provide therapy in a physiological manner, e.g., starting to apply small amount of stimulation using a stimulus ramp during each stimulation period, such that unnecessary arousal events or discomfort is not caused during initial phases of sleep. In this configuration, the EMG may be monitored for several minutes or several hours to determine the state before the system initiates therapy. Many individuals with OSA also suffer from insomnia, in which the individual has trouble falling asleep, and in this case, a negative feedback loop can cause the patient additional anxiety, such that they are fearful that the therapy will turn on prior to when they fall asleep and as such are not relaxed enough to fall asleep. This can cause the individual to turn off therapy, or over time discontinue use of the therapy. A “smart” system that is able to recognize when patients are asleep and apply therapy such that it is physiological will increase therapy adherence and efficacy. Once the system recognizes non-REM stage 1, for example, the system can start to recognize non-REM stage 2, non-REM stage 3, REM sleep, or the like. 
     For example, the ASIC (an example of processor  424 ) can be configured to control a custom algorithm, which can control the therapy application. For example, the ASIC can be configured to run embedded digital logic that uses information gathered by an EMG sensor to decide when, for how long, and at what stimulation parameters to stimulate to provide the optimal therapy to the subject to control the volume of air capable of flowing through the upper airway, also known as airway patency. The embedded digital logic can sense EMG activity, which can be known to the algorithm to correspond with respiration, more specifically to inspiration and exhalation. The algorithm can decode the EMG activity to trigger stimulation of the anterior musculature and/or the hypoglossal nerve (including distal branches thereof) bilaterally, for example, to open the airway, such that the therapy is linked to each respiration, each inspiration and each exhalation, for example. Therapy can thus be provided during each breath, specifically during inspiration, for example, all by using embedded correlative knowledge of the EMG features that correspond to respiration. The embedded logic can include knowledge of EMG features that are specific to body position, chin position, sleep state (e.g. REM, non-REM), movement, and other physiological parameters that can elucidate and optimize therapy. The algorithm can use adaptive learning to learn individual subject specific EMG features that correlate to the above physiological states during sleep to provide additional optimization that is subject specific. The adaptive learning can be done manually with physician input or may be done completely within the algorithm based on pre-determined limits and knowledge or can be done with the cloud database and the additional adaptive learning that the cloud software can use to analyze the data from each patient and each sleep session. The algorithm, while still based on respiratory information sensed through the EMG sensor, can also have different modes. In one mode, the algorithm can be running and can provide therapy breath to breath, specifically during inspiration; in another mode, the algorithm can be learning, looking for inputs from the EMG and also from the user (e.g. patient, physician, etc.); in another mode, the algorithm can provide more continuous control of the airway, providing periodic stimulation that can be sustained for periods of time. In another mode, the algorithm can be sensing EMG information, but not providing therapy breath to breath, instead waiting until a forthcoming collapse of the airway has been identified and reacting by providing therapy that prevents the collapse from occurring. The EMG information can include, the amplitude of the EMG, the frequency components of the EMG, spike sensing, envelope sensing, and other features that can be taken directly from the EMG signal to control the algorithm and provide biomarkers for respiration and for collapse of the airway. It is understood, that the algorithm may use any or all of these features throughout the sleep period and can switch between modes based on the EMG activity as sensed by the EMG sensor or the system may be hard programmed to only run one algorithm. 
     The system can apply therapy in a manner that is not causing discomfort and/or arousal events in the patient. As the patient moves through the stages over the course of the entire night, the system can continuously adapt to the sleep stage (and/or patient need). For example, the largest need for stimulation can be during deep sleep (non-REM stage 3) and REM, where discomfort and arousal are unlikely, so the system can apply more stimulation, since arousal and discomfort are unlikely during these stages. The amount of time the patient is spending in each stage of sleep can also be tracked, which is very useful for tracking outcomes, as most OSA patient do not enter into deep sleep often due to arousals. 
     The classification component  428  can apply a rule-based classification to the trigger to determine whether one or more stimulation parameters applied by one or more of the stimulating electrodes should be altered based on a biomarker related to sleep. As stated above, biomarkers include respiration phase (such as inspiration including periods within inspiration), sleep stage during one or more sleep cycles, and/or body position during sleep as indicated by an EMG or other sensor or sensed activity. Stimulation parameters, as stated above, include, for example, pulse width, amplitude, frequency, waveform shape, electrode position/configuration, or the like). Initial rules of the rule-based classification used by the algorithm can be set for the patient and/or set based on historical values for a population, historical values for a patient, and/or patient derived values. Subsequent rules of the algorithm can be learned and/or updated and/or personalized based on an artificial intelligence learning process. 
     Feedback related to the stimulation (e.g., after it is delivered) can be given to the computing device  304 . The computing device  304  can receive the feedback and may change one or more stimulation parameters. 
     An example closed-loop control scenario involves the one or more sensors  302  (implanted adjacent to an anterior lingual muscle, such as the genioglossus muscle) that can detect/record physiological data over time. The physiological data can include EMG data from the musculature of the anterior airway, which can include characteristic signals that correlate to respiration, but also can correlate to sleep position, sleep state, and/or other physiological characteristics important for the treatment of SDB. The computing device  304  can monitor the physiological data recorded by the one or more sensors  302  to identify a trigger within the physiological data. The trigger can be identified as a biomarker for a condition related to sleep (e.g., inspiration). A rule-based classification can be applied to the trigger to determine whether one or more parameters of the stimulation (e.g., delivered by one or more electrodes  306  or electrode contacts to the hypoglossal nerves or other nerves) should be altered based on the biomarker. 
     Changes in voltages on the transmit receptor can be sensed, as well as on the power receiver and resulting changes in impedances to determine the position and movement of the power receptor within the magnetic field. In this aspect, the changes in voltage and impedance between the two coils of the power antenna can provide additional information to the system to inform the close loop algorithm and to inform additional refinement to the therapy. This type of position sensor may have additional usages beyond therapy optimization as it may provide additional data about sleep quality over time, as well as health related information. In addition, the impedance data between the coils can be correlated with activity, which can be used to also track wake vs. sleep cycles. These data along with EMG data, e.g. tonic EMG activity from the genioglossus muscle, can be used together to understand and learn wake vs. sleep throughout the period spent attempting to sleep (e.g., when the power receive coil is within the inductive field volume of the transmit coil). 
     Several wired or wireless input applications, including smart phone or tablet applications can also be used, wireless remote controls for example. These additional input applications can provide additional inputs to the system to adjust the therapy, adjust the closed loop algorithm, adjust stimulation outputs, adjust optimization or to adjust the algorithm mode as necessary. The input application can display electromyogram data for the user, allows the user to adjust the parameters that control the EMG collection, such as the input filters, trigger amplitudes, frequency ranges, etc. 
     An input application can also allow for automated therapy titration. In this mode, the application can run custom software that provides stimulation to a target site of the subject, such as a target nerve or target muscle and monitors the resulting evoked EMG activity of a muscle, such as an anterior lingual muscle, including the genioglossus muscle. The resulting EMG activity can correlate to the amount of airway opening desired (as inputted into the application) and thus can allow for automated therapeutic stimulation parameter settings and eliminate time consuming parameter adjustments during sleep Non-limiting example of stimulation parameter settings include stimulation pulse width, amplitude, frequency, electrode position/configuration and the like. In this aspect, the system can determine the therapeutic stimulation outputs and allows the subject/physician to fine tune as necessary. The subject or physician can rerun the automated parameter adjustment application at any time, and through the applications can be monitored remotely so that titration, programming can be done from the comfort of the subject&#39;s home. 
     The resultant evoked EMG signal can be continuously monitored and stimulation parameters needed to produce the required tongue motion for effective treatment can be determined, even if the response to a given set of stimulation parameters changes over time, effectively reducing the amount of testing required for initial programming as well as the need for ongoing follow-up testing. Also, issues with the therapy (e.g., stimulation according to certain stimulation parameter settings is not providing the tongue movement necessary to open the airway) can be identified and alerts can be generated for the patient and/or physician (this allows for quicker response and proactive management of the system). 
     Another aspect of the present disclosure can include a method  700  ( FIG. 11 ) for providing neural and/or muscular stimulation according to a closed loop algorithm to treat SDB. The method  700  can be executed by components of the systems as described and shown in the figures, for example. Portions of the method  700  can be stored at least in part on a non-transitory memory and executed by a processor. 
     For purposes of simplicity, the method  700  is shown and described as being executed serially; however, it is to be understood and appreciated that the present disclosure is not limited by the illustrated order as some steps could occur in different orders and/or concurrently with other steps shown and described herein. Moreover, not all illustrated aspects may be required to implement the method  700  and/or more than the illustrated aspects may be required to implement the method  700 . Additionally, one or more aspects of the method  700  can be stored in one or more non-transitory memory devices and executed by one or more hardware processors. 
     At  752 , physiological data (e.g., related to inspiration, sleep stage and/or body position as indicated by an EMG, for example) recorded by one or more sensors can be monitored. The one or more sensors can be implanted adjacent to the anterior lingual muscle, such as the genioglossus muscle, or in the plane between the genioglossus muscle and geniohyoid muscle, for example. At  754 , a trigger can be identified within the physiological data. The trigger be a change in at least one parameter of the physiological data (e.g., indicative of inspiration during respiration, body position, and/or a stage in the sleep cycle as indicated by an EMG, for example). 
     At  756 , a rule-based classification can be applied to the trigger to determine whether one or more parameters of the stimulation should be altered based on a biomarker represented by the trigger. A signal comprising configuration/setting information for the parameters can be sent to one or more electrodes located adjacent to the hypoglossal nerve, for example. The stimulation parameter(s) can be titrated and adapted based on the trigger to optimize airway muscle tone. 
     Neuromodulation Device Configuration 
     The neuromodulation device can have a variety of configurations, which can be tailored to the specific therapy being applied and/or to the anatomy at the site at which the stimulation therapy is applied. An example configuration of a neuromodulation device  20  is illustrated in  FIG. 2 . Neuromodulation device  20  can include a first stimulation lead  21 A and a second stimulation lead  21 B, each comprising a lead body  23  having a nerve cuff electrode  25  located thereon. The nerve cuff electrode  25  (enlarged in both  FIGS. 1 and 2  for clarity) can comprise a cuff body  27  comprising a stimulating electrical contact  29  disposed thereon configured to deliver a stimulation signal to a target site. Although neuromodulation device  20  is illustrated as including two stimulation leads for stimulation of the left and the right hypoglossal nerve, for example, the neuromodulation device can include only one stimulation lead or more than two stimulation leads. Stimulating lead  21  can be generally elongated and include a plurality of electrodes  29  spaced along its length. The lead body can have different shapes. For example, the lead body can be cylindrical, flat or have an oval cross-sectional shape. The lead body can also have enlarged segments to allow for disposition of larger electrode pads or contacts thereon along the length of the lead body. 
     The stimulation leads as well as the nerve cuff electrodes can be configured to stimulate nerves bilaterally or unilaterally. The stimulation leads and nerve cuff electrodes can be configured to stimulate various combinations of nerves and nerve branches. Such nerves and nerve branches include the HGN (including a HGN nerve trunk, a medial branch of the HGN, a lateral branch of the HGN (as described in more detail below)); a glossopharyngeal nerve or other nerves that innervate a pharyngeal muscle; a lingual nerve; other nerves that innervate anterior lingual muscles; and/or other nerves that innervate the tongue. 
     The tongue receives afferent (sensory) innervation from branches emanating from four cranial nerves: a) trigeminal nerve, mainly the mandibular and lingual nerves, b) facial nerve, mainly the chorda tympani nerve, c) glossopharyngeal nerve and d) vagus nerve, mainly the superior laryngeal nerve. The efferent (motor) innervation of the tongue emanates from the hypoglossal nerve with small contribution form the cervical vagus nerve. The upper esophageal sphincter (otherwise called the cricopharyngeus muscle) has motor control through the glossopharyngeal nerve as well. Finally, innervation to the larynx originates from branches of the vagus nerve, the superior laryngeal nerve and recurrent laryngeal nerve. 
     The stimulation lead, which can be configured in many shapes, orientation and include one or more electrodes as needed to provide improved therapy, can be configured to stimulate any of these nerves and/or muscles bilaterally or unilaterally. The sensing lead can be configured to sense from different lingual muscles as to adopt a close loop control for therapy. 
     Further, although the second stimulating lead  21 B is illustrated as having three stimulating electrical contacts  29   b  and first stimulating lead  21 A is illustrated as having four stimulating electrical contacts  29   a , the stimulating leads can have more or less stimulating electrical contacts. Each electrode  29  can be configured and utilized independently of the other electrodes. Because of this, all or some of electrodes  29 , whichever is determined to be most effective for a particular implementation, can be utilized during the application of stimulation therapy. 
     Further, although  FIG. 2  illustrates only one nerve cuff electrode located on the stimulating leads, the lead(s) can comprise more than one nerve cuff electrode. Referring to  FIG. 3 , a stimulating lead  53  can comprise a plurality of nerve cuff electrodes. For example,  FIG. 3  (which mainly illustrates the nerve cuff electrodes of the lead) depicts stimulating lead  53  having a proximal cuff electrode  33  comprising a cuff body  51  having a stimulating electrical contact  37  disposed thereon. Proximal nerve cuff electrode  33  is sized and dimensioned to at least partially wrap around the circumference of a hypoglossal nerve trunk at or proximal to a branch point between a medial branch and a lateral branch of a hypoglossal nerve that innervates the genioglossus muscle. Stimulation lead  53  also includes a medial cuff electrode  39  comprising a cuff body  41  comprising a stimulating electrical contact  43  disposed thereon. Medial cuff electrode  39  is sized and dimensioned to at least partially wrap around the circumference of a medial branch of the hypoglossal nerve at or proximate to the branch point between the medial branch and the lateral branch of the hypoglossal nerve that innervates the genioglossus muscle. Stimulation lead  53  further includes a lateral cuff electrode  45  comprising a cuff body  47  comprising a stimulating electrode contact  49  disposed thereon. Lateral cuff electrode  45  is sized and dimensioned to at least partially wrap around the circumference of a lateral branch of the hypoglossal nerve at or proximate to the branch point between the medial branch and the lateral branch of the hypoglossal nerve that innervates the genioglossus muscle. The branch point referred to above is distal to the branch of the hypoglossal nerve that innervates the styloglossus and hyoglossus muscle and proximal to the distal most fibers of the hypoglossal nerve. The medial cuff electrode and the lateral cuff electrode can be sized and dimensioned to at least partially wrap around the circumference of the medial branch and the lateral branch of the hypoglossal nerve respectively at a location distal to the proximal cuff electrode. Although the proximal, medial and lateral nerve cuff electrodes are illustrates as being separate cuff electrodes, they can be an integral one-piece nerve cuff electrode. The nerve cuff electrode can collectively have a Y-shape. Each of the nerve cuff electrodes can comprise one to two stimulating electrical contacts, although they can also include more than two stimulating electrical contacts. In certain aspects, one or more of the nerve cuff electrodes comprises a plurality of electrodes arranged circumferentially about the respective cuff body spaced approximately 90 degrees apart. The stimulating electrical contacts can have various configurations such as a half-moon configuration arranged circumferentially about the respective cuff body. Again, as mentioned above, the nerve cuff electrodes can be configured to stimulate the hypoglossal nerve trunk, the lateral branch of the hypoglossal nerve, and/or the medial branch of the hypoglossal nerve either individually or in various combinations including in combination with stimulation of the glossopharyngeal nerve and/or lingual nerve. 
     It is well known in the art that one limitation of using cuff electrodes is the ability to selectively stimulation specific nerve fibers that produce the neurological function of interest when using a nerve cuff electrode on the main nerve trunk. This limitation can limit therapy and outcomes due to unwanted stimulation that causes side effects and discomfort. Therefore, applying stimulation via a nerve cuff on the main trunk of a nerve causes limitation in the therapy, however, using nerve cuff electrodes have advantages when placed on the right nerve or nerve branch to produce the stimulation of interest while minimizing side effects. Nerve cuff electrodes can reduce electrical current spread to structures outsides the nerve cuff, hence reducing side effects. Placing one or more nerve cuffs at specific nerve branches can provide direct stimulation to the nerve fibers of interest and allow for tailoring of the therapy by stimulating one or more nerve branches to produce improved stimulation for therapeutic outcomes that are meaningful to patients. The stimulation can be tailored by using specific levels of current at each of the one or more cuff electrodes on the nerve branches to cause the right outcomes for each patient. The nerve branching patterns can and are different patient to patient and hence the need to provide one or more cuff electrodes placed on specific branches and the system flexibility to provide specific amount of current to each cuff is advantageous to cause specific actions without unwanted side effects. Each of the one or more cuff electrodes, can have one or more electrodes that are sized, shaped and orientated to address the specific fibers within the nerve branch of interest and to stimulate those specific fibers for therapeutic outcomes. The electrodes within each cuff may not all be the same and can have different shapes and sizes to provide specific stimulation to each nerve branch. The size of the nerve branch and the types of fibers within the nerve branch can be important to the understanding of the stimulation and electrode configurations. 
     A neuromodulation lead can also include a sensing lead  81  comprising a lead body  83  having a sensor disposed thereon. The sensor is configured to record physiological data and can be, for example, an EMG electrode.  FIG. 5  illustrates one 3-D shape to which a sensing lead  81  (as well as a stimulation lead) can be formed. The example configuration of  FIG. 5  shows the sensing lead formed three-dimensionally in a generally omega-shape, as shown in the plan view of  FIG. 5 . This particular 3-D configuration can be implemented to position the sensing electrical contacts at different positions along the HGN and genioglossus muscle, where the neuromodulation device is configured to treat SDB, such as OSA, for example. More specifically, the configuration of the sensing lead in  FIG. 5  can allow for the right and left electrical contacts (as viewed in  FIG. 5 ) to be placed in very close proximity to the HGN branches and to provide slight cranial pressure to place the electrodes onto the surface of the genioglossus muscle, the largest of the tongue protrusion muscles. The right and left electrical contacts in an implanted configuration can extend along the posterior-anterior course of the HGN, placing the electrical contacts at or near the location of the branch points, such as distal branch points from the main trunk. Electromyography recording of the genioglossus muscle have shown that that the activity is more pronounced as the recordings progress to a more anterior positions on the genioglossus. By using this specific shape, the EMG recording using one or more electrodes can be modified as needed and moved to a more anterior location as needed to produce the best electrical signal characteristics. In addition, the electrodes configuration used for recording can be modified to capture unilateral EMG (one from both sides of the patient) which can be used to sense differences between the right and left side (or vice versa) during therapy or to naturally occurring differences that occur during different sleeping positions, which could be used by the system to direct therapy. Using this specific shape, that tracks the nerve branching patterns bilaterally and by applying an slight upward bias to each of the sections that house the electrodes allows for reduced signal to noise ratio in the recordings, reducing movement during use, and provides for stable recording over the duration of the implant. 
     In more detail, the sensing lead can be inserted and positioned in the plane between the geniohyoid muscle and the genioglossus muscle. The sensing lead can be configured to position sensing electrical contacts along the nerve distribution of the hypoglossal nerve and its branches bilaterally and configured to sense electrical information from the genioglossus muscle by applying a slight upward pressure against the dorsal surface of the genioglossus muscle with the 3D bias of the sensing lead when the electrode are placed. As depicted in  FIG. 5 , in an aspect, sensing lead  81  can comprise a lead body  83  having a left portion  55  comprising a left set of electrical contacts  57 , a right portion  59  comprising a right set of electrical contacts  61 , and an intermediate portion  63  therebetween defining an apex  65  of lead body  53 . As described in more detail below, the sensing electrical contacts can be used to sense electrical activity, such as intrinsic or evoked electrical signals.  FIG. 5  depicts two electrical contacts per side but the sensing lead can comprise more or less sensing electrical contacts. For example, the left and right portion of the lead body can each have one electrical contact and a common reference electrical contact can be located in the intermediate portion of the lead body for example. 
     Lead body  83  can be biased towards a substantially omega shape, more generally speaking a shape that allows for the two sections to extend from a center section, when fully deployed as shown in  FIG. 5 . In other words, lead body can be configured to transition from a substantially linear shape, in a non-deployed state, such as during insertion, to a substantially omega shape, as shown in  FIG. 5 , when fully deployed. When the sensing lead is in a non-deployed state, sensing electrodes  57  and  61  can be arranged in two groups of two electrical contacts spaced along the distal portion of lead body  83 . One group of electrical contacts  61   a  and  61   b  can be positioned distally near an end of lead body  53  and one group  57   a  and  57   b  can be positioned proximally, between the distal group and electronics package (not shown in  FIG. 5  but illustrated in  FIG. 2 ). The configuration of electrical contacts  57  and  61  can, however, vary. The sensing lead can include a different number of electrical contacts, and/or the electrical contacts can be grouped, spaced, or otherwise arranged in different configurations along the length of the lead. 
     The sensing lead is fully deployed when the neuromodulation lead is implanted in the patient&#39;s body and the electrical contacts are positioned at the desired locations in the patient&#39;s body. The omega shape of the sensing lead can be created at the time of manufacturing such that the final form of the lead body is biased to have the omega shape, such bias being overcome if needed during insertion of the lead. The bias can be created, for example, by heat shaping or material shaping or other methods of manufacturing a biased lead. 
     The sensing electrical contacts can be ring electrical contacts extending substantially 360° about the lead body, for example, and can have substantially the same size as the target stimulation site(s). The sensing electrical contacts can also be directional electrodes and not extend 360° about the lead body. Further, the electrical contacts can have coatings to reduce the signal to noise ratio and/or allow for better long-term recording characteristics. 
     Intermediate portion  63  of lead body  83  can define an apex  65  and an ultrasound marker  67  can be disposed at apex  65 . As such, the sensing lead can be inserted via ultrasound and ultrasound marker  67  can allow the user to identify when the apex of the sensing lead is positioned at midline, allowing the electrical contact sets  57  and  61  to be positioned along the distribution of the hypoglossal nerve and its branches bilaterally. Ultrasound can also be used to track motion or potential dislodgment of the lead over time. One or more anchors can be disposed on the lead body to secure the sensing lead in place. Such anchors can be hard or soft anchors, for example, including tines, barbs, prefabricated sutures, deployable anchors including time dependent deployable anchors (e.g. anchors that are polymer coated and deploy or release once the polymer dissolves), or combinations thereof. 
     In certain aspects and with respect to  FIG. 6 , when sensing lead  69  (as well as a stimulation lead) is fully deployed, intermediate portion  71  of lead body  73  defining apex  75  can be located inferior/caudal/lower to the left and right electrode sets  77  and  79  respectively. This can be seen in the inferior bend or bias of lead body  73  that leads into intermediate portion  71 . Such a bend or bias can allow the lead to exert upward/superior/cranial pressure to press the sensing electrodes against the genioglossal muscle and/or the hypoglossal nerve to allow for better contact between the electrode sets and the hypoglossal nerve and/or genioglossus muscle. In particular, this pressure is created by the intermediate portion, including the apex, being more caudal in the body and allowing the left and right portion of the lead body to be pushed more cranially into the genioglossus muscle. This bias allows for better contact with the genioglossus muscle, more lead stability and hence better long-term performance of the lead and allowing for a better signal to noise ratio for recording purposes. 
     In particular, such a bias can reduce motion of the lead after encapsulation/scar tissue grows around the lead and thus allow for better contact between sensing electrodes and the muscle(s) from which electrical activity is sensed. The inferior bias can also reduce the amount of encapsulating tissue around the lead as well. This can improve the recording of electromyography (EMG) signals from muscles innervated by the hypoglossal nerve since the more encapsulating tissue around the sensing electrodes, the harder it can be to detect an EMG signal long term. As such, reduced motion of the lead and less encapsulation of tissue around the lead can result in better EMG recording. 
     Referring back to  FIG. 2 , neuromodulation device  20  can include power receiver  30  and electronics package  50 . Power receiver  30  can include a coiled receiver antenna  32  that is packaged in a protective biocompatible material and is operatively connected to the electronics package  50  and electronic components  52  mounted therein. The stimulating and sensing leads  21  and  31  can be operatively connected to the electronics package  50 , which controls the operation of the stimulating electrical contacts  29  and sensing electrical contacts  35 . Electrical contacts  29  and  35  can be electrically connected to electronics package  50  by conductors, such as wires. As stated above, electrical contacts  29  can be utilized as stimulating electrodes to apply stimulation to a target anatomical structure, such as, for example, a nerve or muscle. Sensing electrodes  35  can be used to detect and measure an EMG response, for example, from a neuromuscular structure associated with the target nerve. For a SDB treatment implementation illustrated in this description, the target nerve can be the HGN and the associated muscle can be the genioglossus muscle. The neuromodulation device can, however, be used to target other nerves and to measure physiological electrical signals from other anatomical structures, such as EMG responses, from other neuromuscular structures. 
     Electronic components  52  are preferably implemented in an application-specific integrated circuit (ASIC). The electronic components  52  can, however, include one or more ASICs, discrete electronic components, and electrical connectors for connecting the electronic components to power receiver  30  and/or leads  21  and  31 . The electronic components, whether embodied in a single ASIC or one or more components, can, for example, include processing and memory components, e.g., microcomputers or computers-on-a-chip, charge storage devices (e.g., capacitors) for accumulating a charge and supplying stimulation power, and solid state switching devices for selecting the identities of the electrodes (e.g., anode, cathode, recording electrode) and modulating power supplied to the electrodes (e.g., pulse-width modulation (PWM) switches). 
     To provide comfort to the patient and ease of insertion for physicians, the neuromodulation device  20  can have a generally soft/flexible construction. This soft/flexible construction can apply to leads  21  and  31 , power receiver  30 , or both the leads and the power receiver. In one example configuration, the neuromodulation device components—power receiver  30 , electronics package  50 , and leads  21  and  31 —can be coated or otherwise encased simultaneously in a single operation, such as an insert molding with a biocompatible material, such as silicone, epoxy, and various suitable polymers. 
     The power receiver and the leads can have a flexible configuration that allows either or both structures to bend or flex, which facilitates implantation compatibility with a variety of anatomical structures. The power receiver can be generally flat and planar in configuration and the stimulation and sensing leads can be generally elongated in configuration in a non-deployed configuration and can extend axially from the electronics package. To facilitate the flexible configuration of the leads, the stimulating and sensing electrical contacts and the conductors that connect the sensing and stimulating electrical contacts to the electronics package can be encased and supported in a covering. The covering can be formed of a biocompatible material, such as silicone and various suitable polymers, and can be configured to leave exposed the stimulating and sensing electrical contacts or portions thereof. The covering can be formed, for example, in the aforementioned insert molded covering of the neuromodulation device. 
     To facilitate the flexible configuration of power receiver  30 , antenna  32  can be formed on a soft substrate so as to be flexible and conform to the anatomy at the site of implantation. For example, power receiver  30  can have a flexible printed circuit board (PCB) construction in which antenna  32  is etched from a thin layer of conductive metal laminated on a substrate  38  (see  FIG. 4 ) constructed of a flexible material, such as a polymer. In one particular flexible PCB construction, the substrate can be a polyimide material and the conductive metal can be copper. Other flexible PCB constructions can be implemented. Antenna  32  can be encased and supported in covering  48 . Covering  48  can be formed of a biocompatible material, such as silicone, epoxy and various suitable polymers. Covering  48  can be formed, for example, in the aforementioned insert molded covering of the entire neuromodulation device  20  structure. 
     The flexible PCB of power receiver  30  can extend into electronics package  50  and can be configured to mount the electronic components  52 . The PCB can also be configured to interface conductors of the leads, and/or to form portions of the lead itself. In this instance, power receiver  30 , electronics package  50 , and leads  21  and  31  (or portions thereof) can be encased in the biocompatible material (e.g., silicone, epoxy and various suitable polymers) simultaneously. 
     The power receiver is designed with the goal of delivering maximum power to the neuromodulation device from a given external magnetic field. With this goal in mind, for the HGN stimulation implementation of the example configuration disclosed herein, power receiver  30  and receiving antenna  32  have a unique configuration designed to adhere to several criteria for neuromodulation device  20 . The criteria depend, of course, on the intended therapeutic use of the system and the configuration resulting therefrom. The criteria set forth below are specific to an example configuration of system  10  for treating SDB including OSA via neuromodulation of the HGN:
         The neuromodulation device  20  operates within the guidelines for maximum permissible magnetic field exposure as recommended in IEEE Standard C95.1-2005 (Reference 3).   The receiving antenna  32  allows for near continuous power consumption (10-30 milliwatts (mW)) from the neuromodulation device  20 .   The receiving antenna operates at a frequency ranging from 100 kHz to 2.4 GHz ISM (industrial, scientific, medical band of the radiofrequency spectrum). In one particular implementation, frequencies of 6.78 MHz or 13.56 MHz were used.   The receiving antenna  32  has a diameter of 2-3 cm. and be as thin as possible to maintain flexibility.   The neuromodulation device  20  is small enough for minimally invasive subcutaneous implantation within the soft tissue of the sub-maxillary neck.   The neuromodulation device  20  maintains a soft, flexible design so that it can be manipulated to conform to the anatomy of the patient.
 
Other stimulation therapies or implementations of the implantable stimulation system  10  can cause some or all of these criteria to be changed or adjusted, and also for certain criteria to be added or removed.
       

     To meet these criteria, receiving antenna  32  can have a double-layer, flat, “pancake” configuration. Referring to  FIG. 4 , antenna  32  can have a flexible PCB construction in which first or upper/top antenna coil  34  is formed on a first or upper/top side of substrate  38  and second or lower/bottom antenna coil  36  is formed on a second or lower/bottom side of the substrate. Substrate  38  can be a thin (e.g., 1 to 3 mil) polyimide layer and coils  34 ,  36  can be etched from thin layers of copper or gold (e.g., 1 oz./ft 2 ≈1.4 mil) laminated onto substrate  38 . 
     PCB  38  can also support electronic components  52  in electronics package  50 . Using guidelines for maximum permissible magnetic field exposure, IEEE Standard C95.1-2005 (which is incorporated herein by reference in its entirety), the maximum achievable delivered power is approximately 10-30 mW at 6.78 MHz frequency. These power requirements were chosen based on the estimated requirements for components  52  of electronics package  50 , the estimated maximum stimulation parameters, and pre-clinical studies, while also including a safety factor to allow for capacitor charging and to provide transitional power. Transitional power can be provided via a variety of components, such as capacitors, supercapacitors, ultracapacitors, or even a rechargeable power source, such as a battery. Continuous power during patient movement, especially at the high end of power ratios and/or when coupling is not ideal. The transitional power source helps ensure complete, continuous operation of the neuromodulation device  20 , even during patient movement. 
     Those skilled in the art will appreciate that, in operation, an antenna can be susceptible to power losses due to substrate losses and parasitic capacitance between coils  34 ,  36  and between the individual coil turns. Substrate losses occur due to eddy currents in the substrate due to the non-zero resistance of the substrate material. Parasitic capacitance occurs when these adjacent components are at different voltages, creating an electric field that results in a stored charge. All circuit elements possess this internal capacitance, which can cause their behavior to depart from that of “ideal” circuit elements. 
     Advantageously, antenna  32  can implement a unique two-layer, pancake style coil configuration in which coils  34 ,  36  are configured in parallel. As a result, coils  34 ,  36  can generate an equal or substantially equal induced voltage potential when subjected to an electromagnetic field. This can help to equalize the voltage of coils  34 ,  36  during use, and has been shown to significantly reduce the parasitic capacitance of antenna  32 . In this parallel coil configuration of antenna  32 , top and bottom coils  34 ,  36  are shorted together within each turn. This design has been found to retain the benefit of lower series resistance in a two-layer design while, at the same time, greatly reducing the parasitic capacitance and producing a high maximum power output. 
     This improved, parallel configuration of antenna  32  is illustrated in  FIGS. 7A and 7B , which illustrate the top and bottom coils  34  and  36 , respectively, on PCB substrate  38 . Each coil  34 ,  36  can include a plurality of coil windings or turns  40  and can be characterized by the following properties: number of turns (N), outside diameter (OD), coil pitch (P), trace width (W), trace thickness (T), and coil spacing (S). These properties are measured as follows:
         The OD is the diameter of coil  34 ,  36  measured across the coil between outer edges of outermost turn  40 .   The coil pitch P is the spacing between turns  40  measured between any two adjacent turns.   The coil width W is the width of each coil turn  40 .   The trace thickness T is the thickness of turns  40 , which is determined by the thickness of the conductive (Cu) layers laminated onto substrate  38  in the PCB construction.   The coil spacing S is the distance between coils  34 ,  36 , which is determined by the thickness of substrate  38  in the PCB construction.       

     In one particular configuration of antenna  32 , PCB substrate  38  is a 2 mil polyimide layer and coils  34 ,  36  are etched from 1.4 mil copper laminated onto the substrate. The parallel coil configuration of the antenna  32  results from electrically connecting the turns  40  of the coils  34 ,  36  through substrate  38 . These connections can be in the form of electrically conductive connectors illustrated at  42  in  FIGS. 9A and 9B . Connectors  42  between the turns  40  can, for example, be formed by drilling or laser etching holes through the PCB structure, e.g., through substrate  38  and turns  40  of the upper and lower coils  34 ,  36 , and plating or filling the holes with a metal, such as plated copper/gold or melted and/or flowed tin-lead, for example, to electrically connect the turns on the opposite surfaces of the substrate. The connectors could also be formed mechanically, e.g., pins or rivets. 
     Coils  34 ,  36  of antenna  32  have a unique configuration that allows for their parallel interconnection. On each side of antenna  32 , turns  40  are semi-circular, each having a fixed diameter with closely spaced ends. This is opposed to a traditional coil configuration in which the diameter of the turns varies continuously in a spiral that decreases progressively from outside to inside. To create the coiled configuration of the antenna  32 , on one side of the antenna (upper coil  34  side in the example configuration of  FIG. 7A ), links  44  can extend diagonally between adjacent turns  40  of upper coil  34 . Links  44  can be formed as portions of the copper layer, for example, laminated onto substrate  38 , and therefore can be formed coextensively with turns  40  of upper coil  34  as one continuous conductive (Cu) strip. Upper coil  34  can therefore be configured as a continuous coil having decreasing diameter from outside to inside and can therefore function as a spirally configured coil. 
     On the lower coil  36  side of antenna  32 , turns  40  can also be semi-circular, each having a fixed diameter with closely spaced ends. There can be no links connecting adjacent turns  40  of lower coil  36 . Instead, on the lower coil  36  side of antenna  32 , terminals  46  can be formed—one connected to a terminal end of the innermost turn of the lower coil, and one connected to a terminal end of the outermost turn of the lower coil. Terminals  46  can be connected to innermost turn  40  and can extend in the space between the ends of the remaining turns. 
     Viewing  FIGS. 7A and 7B , turns  40  of upper and lower coils  34 ,  36  can be interconnected at each of connectors  42 . Through connectors  42 , the links  44  interconnecting the adjacent turns  40  of the upper coil  34  can also interconnect the adjacent turns of lower coil  36 . Thus, turns  40  of the lower coil  36  also can be arranged in a continuous coiled configuration through connectors  42  and links  44 . Lower coil  36  therefore can be configured as a continuous coil having decreasing diameter from outside to inside and can therefore function as a spirally configured coil. 
     Terminals  46  can be electrically connected to both upper coil  34  and lower coil  36  through connectors  42 . The terminal ends from which terminals  46  extend can be radially opposite ends of inner and outer turns  40 . As shown, terminal  46  of innermost turn  40  is connected to a first end of the turn, on a first side of the space between the opposite ends of the turns; whereas the terminal of outermost turn  40  is connected to an opposite second end of the turn, on an opposite second side of the space between the opposite ends of the turns. 
     For the configuration illustrated in  FIGS. 7A and 7B , the performance of the antenna can depend on the properties listed above. Example configurations of the antenna, for which some of these properties were adjusted, were tested. These example configurations are illustrated in the following table: 
                                                 Example   Example   Example   Example       Property   1   2   3   4                                                                    Outer Diameter   30   mm   30   mm   30   mm   26   mm       (OD)                                                                 # Turns (N)   12   10   8   10                                                 Coil Pitch (P)   1.0   mm   1.0   mm   1.0   mm   1.0   mm       Trace Width (W)   0.5   mm   0.5   mm   0.5   mm   0.5   mm       Trace Thickness   1.4   mil   1.4   mil   1.4   mil   1.4    mil       (T)                                       Coil Spacing (S)   2   mil   2   mil   2   mil   2   mil       Max. Power   32.0   mW   39.4   mW   43.7   mW   23.3   mW       Delivery                    
As shown in the above table, the maximum power delivered provided by each example coil configuration met or exceeded the 10-30 mW power requirement, even with the reduced coil outside diameter of Example 4.
 
     The external controller  100  can have two components: power mat  110  and bedside control unit  120 . Control unit  120  can be connected to power mat  110  by wire, for example, and is designed to be placed bedside, e.g., on a nightstand. The control unit can include a user interface, e.g., buttons, knobs, touchscreen, etc., to allow the user to control operation of the system when using the system in bed. Power mat  110  can be designed to be placed on the sleeping surface, such as a bed mattress, and therefore can be configured to have the form of a pad, e.g., a thin, flat, soft, flexible and non-slip configuration. Power mat  110  supports one or more wireless power transmit coils  112  in or on a flexible or semi-flexible surface  114 . Power mat  110  can be positioned on the sleeping surface so that a lower edge  116  of the mat corresponds approximately to the position of the patient&#39;s shoulders while sleeping. The shape and size of the power mat  110  can correspond, for example, to that of a pillow, such as a queen size pillow. 
     Control unit  120  can excite power transmit coils  112  to generate an electromagnetic field. External controller  100  can utilize transmit coils  112  in power mat  110  to provide tethered wireless power transfer to neuromodulation device  20  by way of receiving antenna  32  through electromagnetic induction. When the patient is in the sleeping position on the sleeping surface, antenna  32  of neuromodulation device  20  can be positioned within the electromagnetic field produced by transmit coils  112  of power mat  110 . The shape of the field can be tailored through the configuration of the coils  112  to provide a field that is optimized for powering the neuromodulation device  20  through various sleeping positions. For example, the field can be configured extend horizontally (as viewed in  FIGS. 8A-C ) between the coils  112 , so that the neuromodulation device  20  can be powered any time it is positioned within the vertical bounds of the horizontally extending field. 
     Through induction, electric current can be induced in receiving antenna  32  and that current can be provided to neuromodulation device electronics package  50 . Components  52  in electronics package  50  control the operation of the electrical contacts. Through this operation, electrical contacts  29  can be utilized as stimulating electrodes for applying electrical stimulation to nerves or muscles, for example and electrical contacts  35  can be used as EMG sensing electrodes, for example, for detecting a neuromuscular response, to the application of electrical stimulation. 
     In addition to providing power to neuromodulation device  20 , external controller  100  can also provide a data link for facilitating two-way communication between the controller and the neuromodulation device. While powering the neuromodulation device, controller  100  can simultaneously provide a wireless data signal that is used to program the neuromodulation device with settings, such stimulation parameters, and also retrieve stored data from the neuromodulation device, such as triggered stimulation events, measured EMG responses or other electrical physiological signals, current values, electrode impedances, and data related to the wireless power transfer between controller  100  and neuromodulation device  20 . 
     Additionally, the neuromodulation device  20  can monitor the impedance and/or voltage of the neuromodulation device antenna  32  so that the power supplied to the neuromodulation device can be calculated. This can be provided as feedback to the controller  100  that allows the controller to adjust the current supplied to the power transmit coils  112 . The controller  100  can control the power delivered to the neuromodulation device so as to remain within the standards/requirements set forth above. At the same time, the feedback can also facilitate increasing the current supplied to the power transmit coils  112  so that adequate power transfer to the neuromodulation device  20  is maintained, again within the prescribed limits. In this manner, the controller  100  can implement closed-loop control to optimize the power supplied to the neuromodulation device  20 . 
     The operation of the controller  100  can be controlled through the user interface  200 , which allows the user, e.g., the patient, physician or other caretaker, to control aspects of the operation of the implantable stimulation system  10 . The control can be local, e.g., by the patient using a user interface of the control unit  120  or the patient user interface  200 , or remote, e.g., by the physician through internet/cloud  208 . The control unit  120  can have a small footprint and power mat  110  can be flexible in design so that external controller  100  is small, discreet, and portable for travel purposes. 
     Power Mat Configuration 
     To account for varying sleeping positions throughout the night, power mat  110  can have a large enough footprint to allow patient movement while still maintaining the ability to transmit power to neuromodulation device  20 . At the same time, external controller  100  does produce electromagnetic radiation at a level that falls outside the guidelines for maximum permissible magnetic field exposure as recommended in IEEE Standard C95.1-2005 (Reference 3). 
     Example transmit coil configurations that can be implemented in power mat  110  are illustrated in  FIGS. 8A-8C . These example transmit coil configurations can be implemented with a flex circuit design, i.e., the coils can be formed (e.g., etched) from a conductive metal (e.g., copper or gold) laminated on a flexible substrate (e.g., polyimide). The examples of  FIGS. 8A-8C  illustrate the overall shape of transmit coils  112  without showing the individual turns of the transmit coils. This is because the properties of the transmit coils  112 , e.g., the number of turns, coil pitch/spacing, trace width, etc. is not limited, as can be the case with coils  34 ,  36  of antenna  32 . Antenna coils  34 ,  36  can be tailored specifically for maximum induced power generation due to the small footprint limitations of antenna  32  of neuromodulation device  20 . Power mat  110  can be larger in comparison and transmit coils  112  can be free to be configured to produce a magnetic field that can be limited only by requiring a level that falls within the IEEE magnetic field exposure guidelines mentioned previously. 
     Accordingly, transmit coils  112  can be configured to maximize the space or volume that the magnetic field covers so as to allow for variations in the patient position during sleep. This can give the system the ability to continuously power the neuromodulation device through a variety of sleeping positions throughout the night.  FIG. 8A  shows a twelve coil example configuration of transmit coils  112 ;  FIG. 8B  shows a two coil example configuration of transmit coils; and  FIG. 8C  shows a four coil example configuration of transmit coils. For all of these example configurations, experimental testing showed that transmit coils  112  are capable of meeting the system power requirements, within the IEEE exposure guidelines, while allowing for consistent power transfer to the antenna  32  over an effective volume of approximately 32×76×25 cm (L×W×H), which was found to be sufficient to cover the patient during a normal sleep cycle. 
     The twelve coil configuration of transmit coils  112  in  FIG. 8A  can allow for dynamic control of the magnetic field produced by the power mat  110 . Through data coupling and communication between external controller  100  with neuromodulation device  20 , a determination can be made as to which coil(s) of the twelve coil configuration are effectuating the power coupling between the external controller and the neuromodulation device. Through this determination, the external controller  100  can power only those coils necessary to power neuromodulation device  20 , given the current position of the patient relative to power mat  110 . As the patient changes positions, the neuromodulation device can detect any decrease in power transmission, which can trigger a reassessment and the selection of different coil(s). This configuration can thus be self-tuning, on-the-fly to maximize the electromagnetic field produced by the power mat  110  in the area of the antenna  32 . 
     The two coil configuration of the transmit coils  112  in  FIG. 8B  can be static power coils that produce a continuous electromagnetic field around power mat  110 . This configuration can be tuned to maximize the electromagnetic field strength in the largest possible volume so that power transmission is maximized throughout a wide variety of patient positions. 
     In the example configurations of both  FIG. 8A  and  FIG. 8B , power mat  110  can have a flexible construction facilitated by a flexible circuit construction of transmit coils  112  housed within a flexible cover, such as, for example, soft plastic, rubber, fabric, etc. Transmit coils  112  can, for example, have a flexible PCB construction similar to antenna  32  of neuromodulation device  20 . For instance, transmit coils  112  can be constructed as a single layer flexible PCB, with conductive traces etched from copper, for example, laminated on a polyimide, for example, substrate. 
     Each of the disclosed aspects and embodiments of the present disclosure may be considered individually or in combination with other aspects, embodiments, and variations of the disclosure. Further, while certain features of embodiments and aspects of the present disclosure may be shown in only certain figures or otherwise described in the certain parts of the disclosure, such features can be incorporated into other embodiments and aspects shown in other figures or other parts of the disclosure. Along the same lines, certain features of embodiments and aspects of the present disclosure that are shown in certain figures or otherwise described in certain parts of the disclosure can be optional or deleted from such embodiments and aspects. Additionally, when describing a range, all points within that range are included in this disclosure. Furthermore, all references cited herein are incorporated by reference in their entirety.