24 has the capacity for variable output, linear output and short pulse-width. In other instances, the electrode 24 can comprise a coil configured to deliver magnetic stimulation. The electrode 24 may be mono-polar, bipolar or multi-polar. To minimize the risk of an immune response triggered by the subject against certain components of the neuromuscular stimulator 16, and also to minimize damage thereto (e.g., corrosion from other biological fluids, etc.), the electrode 24 (and any wires and optional housing materials) can be made of inert materials, such as silicon, metal, plastic and the like. In other instances, the electrode 24 can be a multi-vector electrode capable of directing current to different muscles of anterior lingual musculature 12. In further instances, the system 10 can include more than one electrode 24, such as an array of electrodes to stimulate a field of aborizing hypoglossal branches associated with a particular target muscle (or group of muscles).

In another aspect, the system 10 can be configured as an open-loop or closed-loop system. In an open-loop system, for example, a physician or the subject may, at any time, manually by the use of a remote controller adjust treatment parameters of the system 10. Alternatively, in a closed-loop system (discussed below), treatment parameters (e.g., electrical signals) may be automatically adjusted in response to a sensed physiological parameter or a related symptom indicative of the extent of OSA. In a closed-loop feedback system, a sensor that senses a physiological parameter associated with OSA (e.g., muscle and/or nerve electrical activity, tongue position, oropharyngeal airfow, etc.) can be utilized. More detailed descriptions of sensors that may be employed in a closed-loop system, as well as other examples of sensors and feedback control techniques that may be employed as part of the present disclosure are disclosed in U.S. Pat. No. 5,716,377.

Closed-Loop System

In another aspect, the present disclosure can include a closed-loop system 50 (FIG. 3) for treating OSA in a subject. The system 50 can comprise a power source 14, a neuromuscular stimulator 16, and a controller 26. The power source 14 and the neuromuscular stimulator 16 can be in direct and/or indirect electrical communication with one another. In some instances, the power source 14 and the neuromuscular stimulator 16 can be in direct electrical communication with one another via one or more wires (not shown). In other instances, the power source 14 and the neuromuscular stimulator 16 can be in indirect electrical communication with one another (e.g., via a wireless link). One or more components of the system 50 can be implantable in a subject suffering from OSA for a desired period of time (e.g., acute, semi-chronic, chronic). The system 50 can also be portable and adapted to be borne by a subject suffering from OSA for a desired period of time. In some instances, the system 50 can be borne by a subject for an acute period of time (e.g., during an emergency situation), for a semi-chronic period of time (e.g., less than about a week to about 6 weeks), or for a chronic period of time (e.g., greater than about 6 weeks). For example, the neuromuscular stimulator 16 can be temporarily or permanently implanted within, on, or otherwise associated with a subject suffering from OSA.

In another aspect, the power source 14 can be configured to deliver a therapy signal having certain power and stimulation parameters to the neuromuscular stimulator 16. Examples of such power and stimulation parameters can include the pulse waveform, the signal pulse width, the signal pulse frequency, the signal pulse phase, the signal pulse polarity, the signal pulse amplitude, the signal pulse intensity, and the signal pulse duration of the therapy signal. The power source 14 can be capable of conveying a variety of currents and voltages to the neuromuscular stimulator 16. In some instances, the power source 14 can communicate stimulating energy, such as electrical current pulses to the neuromuscular stimulator. The power source 14 can optionally include circuitry and/or other implantable components for outputting electrical pulses to the neuromuscular stimulator 16. Signals from the power source 14 can additionally or optionally be communicative in nature, for example, communicating stimulation program information, subject information, and other types of information. In some instances, the power source 14 is located external to the subject and in electrical communication with the neuromuscular stimulator 16 via inductive coupling. For example, the power source 14 can be configured as part of a wearable device, such as a chin strap (not shown), which may be worn at bedtime. In such instances, the power source 14 is not physically “wired” to the neuromuscular stimulator 16.

In another aspect, the neuromuscular stimulator 16 can include any active implantable medical device configured for implantation for a relatively short or long period of time. As discussed in more detail below, all or only a portion of the neuromuscular stimulator 16 can be configured for implantation on or in the mandible of a subject. For example, all or only a portion of the neuromuscular stimulator 16 can be configured for implantation on, in, or through a mandible 28 (e.g., the mentum 29) of the subject.

The controller 26 can be configured to receive the power and stimulation parameters associated with a therapy signal from the power source 14. In some instances, the controller 26 can include a microprocessor (not shown), a hardwired circuit (not shown), or other appropriate means for controlling various aspects of the system 50. For example, the controller 26 can operate the power source 14, convey therapy signals to at least one electrode 24, and/or receive information from various sources, such as the electrode or a sensing component 52. The controller 26 can be configured to store a stimulation program (or programs) and operate the power source 14 according to the stimulation program(s). Stimulation programs can include predetermined, set programs (e.g., hardwired into the controller) and adaptive, dynamic programs (e.g., software that adapts an artificial stimulation pattern according to various inputs). The controller 26 can select between various programs and/or actively modify a stimulation program according to various inputs, such as information received from a subject, information received from the sensing component 52, information received from the power source 14, information received from the at least one electrode 24, and/or information received from a health care provider.

In another aspect, the neuromuscular stimulator 16 can include one or more leads 22 (FIG. 4), each of which has at least one electrode 24 in electrical communication with the controller 26. The at least one electrode 24 can be configured to deliver a therapy signal to a target tissue associated with direct or indirect control of a posterior base of the tongue of a subject. In further describing representative electrodes 24, which are described in the singular, it will be apparent that more than one electrode may be used as part of the system 50. Accordingly, the description of a representative electrode 24 suitable for use in the system 50 of the present disclosure is applicable to other electrodes that may be employed.

The electrode 24 can include one or more of the following types and/or categories of electrodes: epimysial electrodes; intramuscular electrodes, such as Peterson electrodes; nerve cuff electrodes; self-contained electrodes; monopolar electrodes; bipolar electrodes; multi-contact electrodes; and/or other known electrode types/categories and combinations thereof. It will be appreciated that the electrode 18 can include one or more associated flexible, extensible electrical leads 22. The lead 22 and/or the electrode 24 can be highly flexible so as to not hinder regular tongue movement. In some instances, all or only a portion of the lead 22 can include one or more deployable anchoring elements (not shown) (e.g., barbs, hooks, etc.). The anchoring element(s) can be selectively retractable and extendable. The anchoring element(s) facilitate secure placement of the lead 22 (and thus the electrode 24) in or about a target tissue, such as a muscle, which is under constant flexion and relaxation.

The electrode 24 can be controllable to provide therapy signals that may be varied in voltage, frequency, pulse-width, current and/or intensity. For example, the electrode 24 can also provide both positive and negative current flow from the electrode and/or be capable of stopping current flow from the electrode and/or changing the direction of current flow from the electrode. In some instances, the electrode 24 has the capacity for variable output, linear output and short pulse-width. In other instances, the electrode 24 can comprise a coil configured to deliver magnetic stimulation. The electrode 24 may be mono-polar, bipolar or multi-polar. To minimize the risk of an immune response triggered by the subject against certain components of the neuromuscular stimulator 16, and also to minimize damage thereto (e.g., corrosion from other biological fluids, etc.), the electrode 24 (and any wires and optional housing materials) can be made of inert materials, such as silicon, metal, plastic and the like. In other instances, the electrode 24 can be a multi-vector electrode capable of directing current to different muscles of anterior lingual musculature. In further instances, the system 50 can include more than one electrode 24, such as an array of electrodes to stimulate a field of arborizing hypoglossal branches associated with a particular target muscle (or group of muscles including bilateral stimulation of arborizing branches).

In another aspect, the system 50 also includes one or more sensing components 52 configured to detect at least one physiological parameter or a related symptom of OSA. The presence of the sensing component 52 enables closed-loop operation of the system 50 to treat OSA, meaning that treatment parameters (e.g., therapy signals) may be automatically adjusted in response to the sensed or detected physiological parameter or a related symptom of OSA. In some instances, the sensing component 52 and the electrode 24 can be the same structure or element. Advantageously, use of a single structure or element as the sensing component 52 and the electrode 24 reduces the invasive nature of the surgical procedure associated with implanting the system 50, while also reducing the number of foreign bodies introduced into a subject.

The sensing component 52 can be in direct and/or indirect electrical communication with the controller 26 and/or the power source 14 (e.g., via one or more leads 22 or a wireless link). In one example, the sensing component 52 can comprise a sensor (e.g., an electrode 24 as described above) that senses a physiological parameter or related symptom associated with OSA (e.g., muscle and/or nerve electrical activity, tongue position, oropharyngeal airflow, etc.). Examples of sensors that may be employed in a closed-loop system 50, as well as other examples of sensors and feedback control techniques that may be employed as part of the present disclosure are disclosed in U.S. Pat. No. 5,716,377.

The system 50 can be configured for highly selective stimulation and modulation of the anterior lingual musculature. In some instances, the system 50 can comprise multiple leads 22, each of which includes at least one electrode 24 and at least one sensing component 52. For example, the system 50 can have an “octopus-like” configuration whereby the tentacles correspond to the multiple leads 22 and the body corresponds to the neuromuscular stimulator 16. A distal end of each of the leads 22 can be configured for embedding into a pre-determined portion of a muscle comprising the anterior lingual musculature. The muscle(s) in which the distal ends of the leads 22 is/are embedded can be the same or different. Thus, in some instances, the distal ends of the leads 22 can be embedded in a single muscle but at different spatial locations. In such instances, the system 50 can be operated to activate (stimulate) a first portion of the muscle associated with a first lead (not shown), while simultaneously or sequentially inhibiting muscle function in a second different portion of the muscle associated with a second lead (not shown). Advantageously, a system 50 having a multiple-lead configuration provides highly selective control over targeted muscles of the anterior lingual musculature and, thus, the ability to therapeutically modulate the laryngeal introitus.

One example of a system 50 for treating OSA is illustrated in FIGS. 4-6B. The system 50 can comprise a chin implant 54 for a human mandible 28 (FIGS. 6A-B). The chin implant 54 (FIG. 4) has a generally crescent-shaped configuration and, when implanted, gives the appearance of a natural chin contour. All or only a portion of the chin implant 54 can be made of one or more materials that is/are biologically inert and non-reactive to avoid infection in a subject's body (e.g., silicone and/or or plastic). By virtue of its construction, the chin implant 54 can be pliant, flexible and compressible.

As shown in FIGS. 4-5, the chin implant 54 can comprise an implant body 56, a controller 26, at least one electrode 24, a sensing component 52, and a power source 14. The implant body 56 can have a front face 58 and a back face 60. The back face 60 can have a surface 62 for placement adjacent the mental protuberance 64 of the mandible 28 (FIG. 6A). The front face 58 can have a curved projection surface 66 for protruding from the chin to create a natural chin profile after implantation (FIG. 6B). Each of the controller 26, the at least one electrode 24, the sensing component 52, and the power source 14 can be directly or indirectly associated with the implant body 56. As shown in FIG. 4, for example, the controller 26 and the power source 14 can be housed within a portion of the implant body 56, while the at least one electrode 24 and the sensing component 52 are located external to the implant body and directly connected to the controller (e.g., by leads 22). Although the power source 14 is shown as being disposed within the implant body 56, it will be appreciated that the power source may also be located external to the implant body (e.g., via a wireless link).

Methods

Another aspect of the present disclosure can include a method 30 (FIG. 7) for treating OSA in a subject. The method 30 can generally include the steps of providing a system 10 (Step 32), implanting a neuromuscular stimulator 16 of the system into a subject suffering from OSA (Step 34), and activating the system to treat the OSA (Step 36). The system 10 provided at Step 32 can be identically or similarly constructed as the system shown in FIG. 1 and described above. For the purpose of illustration only, the method 30 will be described below using the system 10 shown in FIG. 1.

At Step 34, the neuromuscular stimulator 16 can be implanted in the subject. In some instances, a trans-mandibular surgical approach can be used to implant the neuromuscular stimulator 16. A variety of trans-mandibular surgical approach options may be used, such as a submental approach or an intraoral bucca-gingival sulcus approach. Generally speaking, a submental approach allows for other adjunctive procedures including, but not limited to, cervical liposuction (e.g., for effacement of platysmal banding), elevation of hyoid positioning, and mandibular distal bone advancement for aesthetic purposes and/or functionally repositioning the anterior lingual musculature 12. Unlike the submental approach, an intraoral approach does not produce a facial scar. A trans-mandibular surgical approach can be performed under local anesthetic or in an outpatient setting; however, it will be appreciated that general anesthetic may alternatively be used as patients may be more comfortable and the patient's airway is better protected.

Whether a submental or intraoral bucca-gingival sulcus approach is used, the dissection can be carried out to the level of the periosteum overlying the mentum 29 of the mandible 28 (FIG. 8). Surgical awareness is highlighted at this time in an effort to preserve and not traumatize the mental nerves (not shown). The mental nerves exit at the mid-vertical level of the mandible 28, between the region of the first and second pre-molars bilaterally. Like many surgeries in the head and neck, preservation of a nerve (or nerves) along with strict attention to hemostasis are key features of a successful operation. In making the gingivo-labial sulcus incision, for example, it can be important to leave an adequate cuff of mucosa along with a sufficient portion of the mentalis muscle (not shown) for later resuspension. Doing so can avoid lower-lip ptosis.

FIGS. 8-10 illustrate a submental approach for implanting the neuromuscular stimulator 16 in a subject. First, an external submental crease incision (not shown) can be made. A subperiosteal dissection can then be made to elevate the periosteum and protect the mental nerves. At this point, a surgical mark can be made at the midline of the bony mentum 29. One or more drill holes (65a and 65b illustrated in FIG. 6C) can be made above the inferior edge of the mentum 29, and on either side of the midline. For example, multiple drill holes can be made about 1 cm above the inferior edge of the mentum 29, and about 1.5 cm on either side of the midline. The diameter of each drill hole should be sufficient to pass the lead(s) (22a and 22b illustrated in FIG. 6D) of the neuromuscular stimulator 16 through both cortices of the mandible 28 into electrical communication with one or more of the sublingual muscles that control the anterior positioning of the tongue base when contraction occurs.

In another example, an intraoral bucca-gingival sulcus approach can alternatively be used to implant the neuromuscular stimulator 16. Subperiosteal dissection can be carried out laterally to identify the mental nerves. The foramina (not shown) of the mental nerves are generally found between the first and second premolar teeth at the level of the origin of the mentalis muscle, or 2-4 mm below the level of the bicuspid premolar teeth apices. The foramina are situated deep to the midportion of the depressor anguli oris. Dissection can occur inferolaterally to allow for a longer osteotomy and thereby prevent unsightly mandibular notching. During dissection, the periosteum at the inferior rim of the mentum 29 can be left intact. Next, the skeletal midline can be aligned with the overlying soft tissue corollary. A sagittal saw with a 30-degree bend can then be used to facilitate an even cut while minimizing soft tissue trauma. Lateral cuts can be made about 4-5 mm below the foramina to compensate for the path of the inferior alveolar nerve.

In another variation of the method 30, the neuromuscular stimulator 16 can be configured to also serve as a chin implant. This may be desirable in instances where a subject desires an aesthetic change to their anterior mandibular profile. Alternatively, if a subject does not desire a change in their anterior mandibular profile, a relatively small or low-profile neuromuscular stimulator 16 that does not cause any profile changes can be used. For example, a neuromuscular stimulator 16 can be sized and dimensioned for placement within a drilled sulcus (31 illustrated in FIG. 9B) such that attachment of the neuromuscular stimulator therein does not interfere with the anterior mandibular profile of the subject.

Regardless of the trans-mandibular surgical approach used, the neuromuscular stimulator 16 can be implanted so that the electrode 24 is in electrical communication with a target tissue associated with control of a posterior base of the tongue of the subject (e.g., the electrode can be placed directly on and/or within the target tissue). In some instances, the electrode 24 can be placed into electrical communication with one or more muscles of the anterior lingual musculature 12. In other instances, two or more electrodes 24 can be placed bilaterally into electrical communication with one or more muscles of the anterior lingual musculature 12. In one example, the electrode 24 can be placed into electrical communication with a genioglossus muscle (not shown). In another example, the electrode 24 can be placed into electrical communication with an anterior belly digastric muscle 38 (FIG. 9). In another example, the electrode 24 can be placed into electrical communication with a hyoglossus muscle (not shown). In another example, the electrode 24 can be placed into electrical communication with a mylohyoid muscle (not shown).

Alternatively or additionally, the electrode 24 can be placed into electrical communication with a nerve (or nerves) that innervates one or muscles associated with control of a posterior base of the tongue of the subject, such as the hypoglossal nerve 40 and/or its distal arborizing branches at or near its neuromuscular junction. In some instances, the electrode 24 can be implanted directly in or on the target tissue. In other instances, the electrode can be implanted so that the electrode 24 is not in direct physical contact with the target tissue, but located in sufficient proximity to the target tissue such that delivery of a therapy signal to the electrode can modulate target tissue activity.

Proper positioning of the lead 22 can be confirmed by delivering test signals to the electrode 24 and then noting if the test signals result in anterior displacement of the posterior base of the tongue. Once the lead 22 is properly positioned, the housing 20 can be securely affixed to the subject. For example, the housing 20 can be securely affixed (e.g., with bone screws) into the external cortex of the mandible 28, or simply placed in a tight surgical subperiosteal pocket. Once the neuromuscular stimulator 16 is secured to the subject, the soft tissue can be closed in layers while paying special attention to the reattachment of the mentalis muscle to avoid ptotic lower lip. The soft tissue can then be re-draped with tape and the procedure completed (FIG. 10). Overall, the surgical implant procedure can take about 15 minutes to complete.

At Step 34, the power source 14 can be associated with the subject (if it has not been done so already) so that the power source is in electrical communication with the neuromuscular stimulator 16. As shown in FIG. 2 and discussed above, for example, the power source 14 can be configured as a chin strap 18 and placed around the head of the subject.

With the neuromuscular stimulator 16 implanted in the subject, the power source 14 can be activated at Step 36. Activation of the power source 14 causes one or more therapy signals, having desired power and stimulation parameters, to be delivered to the neuromuscular stimulator 16. In some instances, the therapy signal(s) (e.g., an electrical signal) may be constant, varying and/or modulated with respect to the current, voltage, pulse-width, cycle, frequency, amplitude, and so forth. For example, a current may range from about 0.001 to about 1000 microampere (mA) and, more specifically, from about 0.1 to about 100 mA. Similarly, the voltage may range from about 0.1 millivolt to about 25 volts, or about 0.5 to about 4000 Hz, with a pulse-width of about 10 to about 1000 microseconds. The type of stimulation may vary and involve different waveforms known to the skilled artisan.

Depending upon the desired treatment regimen, the therapy signal(s) is/are relayed to the electrode 24. The therapy signal(s) can be relayed to the electrode 24 for a time and in an amount sufficient to displace the posterior base of the tongue in an anterior direction, which opens the oropharyngeal airway to the laryngeal introitus. Delivery of the therapy signal(s) to the target tissue can be done, for example, while the subject is sleeping. In patients with OSA, the posterior base of the tongue can fall backwards and obstruct breathing, especially when individuals lay flat on their backs. Therapy signal(s) from the neuromuscular stimulator 16 can be delivered to the target tissue on a continuous, periodic, or an as-needed basis to displace the posterior base of the tongue in an anterior direction (and/or change the surface morphology of the posterior tongue base to allow and increase oropharyngeal airway volume) while the subject is sleeping. This prevents obstruction of the airway during sleep by ensuring that airflow through the airway of the subject is properly maintained. Additionally or optionally, the therapy signal(s) can be relayed to the electrode 24 to achieve selective muscle activation; that is, targeted activation of less than all of the muscles comprising the anterior lingual musculature 12. Advantageously, selective stimulation of the anterior lingual musculature 12 can prevent or mitigate dysarthria.

Another aspect of the present disclosure can include a method 70 (FIG. 11) for treating OSA in a subject. The method 70 can generally include the steps of: providing a closed-loop system 50 (Step 72); implanting the system into a subject suffering from OSA (Step 74); generating a sensor signal based on a detected at least one physiological parameter or related symptom associated with OSA (Step 76); and delivering a therapy signal, by the system, to a target tissue to treat the OSA (Step 78). Steps 76-78 can be repeated for a desired period of time to treat the OSA (Step 80). The closed-loop system 50 provided at Step 72 can be identically or similarly constructed as the system shown in FIG. 3 and described above. For example, the system 50 shown in FIG. 3 can be configured to include multiple electrodes 24 and sensing components 52, which may limit total extrinsic and intrinsic tongue contraction and assist in anterior-superior elevation of the suprahyoid muscles (and thus the hyoid bone) to open the laryngeal introitus. At Step 74, the system 50 can be implanted in the subject.

At Step 76, a sensor signal can be generated by the sensing component 52 in response to at least one physiological parameter or a related symptom associated with OSA detected by the sensing component. Where the sensing component 52 is an EMG electrode, for example, the activity of one or more muscles of the anterior lingual musculature (e.g., a genioglossus muscle or a suprahyoid muscle) can be detected. A detected decrease in muscle activity (relative to a control or baseline level) may cause the sensing component 52 to generate a corresponding sensor signal, which is then relayed to the controller 26 and/or the power source 14.

In response to the generated sensor signal, the system 50 can cause a therapy signal (or signals) to be delivered to the electrode 24 (Step 78). The controller 26 can then control operation of the neuromuscular stimulator to adjust application of the therapy signal(s) to the first target tissue in response to the sensor signal. For example, the therapy signal(s) can be relayed to the electrode 24 for a time and in an amount sufficient to displace the posterior base of the tongue in an anterior direction, which opens the oropharyngeal airway to the laryngeal introitus. Delivery of the therapy signal(s) to the target tissue can be done, for example, while the subject is sleeping. In patients with OSA, the posterior base of the tongue can fall backwards and obstruct breathing, especially when individuals lay flat on their backs. Therapy signal(s) from the neuromuscular stimulator 16 can be delivered to the first target tissue on a continuous, periodic, or an as-needed basis to displace the posterior base of the tongue in an anterior direction (and/or change the surface morphology of the posterior tongue base to allow and increase oropharyngeal airway volume) while the subject is sleeping. This prevents obstruction of the airway during sleep by ensuring that airflow through the airway of the subject is properly maintained. Additionally or optionally, the therapy signal(s) can be relayed to the electrode 24 to achieve selective muscle activation; that is, targeted activation of less than all of the muscles comprising the anterior lingual musculature. Advantageously, selective stimulation of the anterior lingual musculature can prevent or mitigate dysarthria. It will be appreciated that although the method 70 is described in terms of unilateral stimulation, the method can also be performed using bilateral stimulation (e.g., stimulating two muscles simultaneously or in sequence).

As shown in FIG. 11, Steps 76-78 can be repeated for a period of time to treat the OSA. Advantageously, the method 70 provides a minimally invasive, automatic, and aesthetically acceptable treatment modality for OSA that is continually titrated to optimize its efficacy based on continuous physiological feedback, thereby enabling a high degree of patient-specific customization.

Another aspect of the present disclosure includes a method for treating sleep disordered breathing (SBD) in a subject by using an electromyogram (EMG) signal to initiate stimulation of a muscle that controls the upper airway and/or the tongue of the subject (also referred to herein as an “upper airway muscle”), such as the genioglossus muscle. In certain embodiments, the EMG activity of an upper airway muscle can be used as a biomarker for respiration and electrical stimulation of the upper airway muscle can be triggered or predicted from an EMG signal of the upper airway muscle during certain periods of the subject's respiratory cycle. Preferably, a single neurostimulator is used to record an EMG signal from the upper airway muscle and to initiate stimulation to neuromuscular tissue of the upper airway muscle based on the recorded EMG signal to decrease the subject's airway resistance to treat the subject's SBD. Non-limiting examples of SBDs are increased upper airway resistance including snoring; upper airway resistance syndrome (UARS); and sleep apnea. Sleep apnea can include OSA, central sleep apnea (CSA), and mixed sleep apnea.

Referring to FIG. 12, method 80 can include obtaining a neurostimulation system comprising a neurostimulator having a stimulating electrode and an EMG sensor located thereon (step 82). In certain embodiments, the EMG sensor is located on a separate device than the neurostimulator. The neurostimulator can be part of a closed loop system 50 as shown in FIG. 3 or a neurostimulation system as schematically depicted in FIG. 13 and described below. Method 80 can further include positioning the neurostimulator so that the stimulating electrode and the EMG sensor are in electrical communication with an upper airway muscle of the subject, such as the genioglossus muscle (step 84). The stimulating electrode can be positioned in direct electrical communication with the upper airway muscle such that the upper airway muscle is the target site as opposed to a proximal site that innervates the upper airway muscle or a muscle or nerve that is anatomically adjacent to the upper airway muscle. In such embodiments, the stimulating electrode is adjacent to the upper airway muscle to directly stimulate the upper airway muscle. Similarly, the EMG sensor can be positioned in direct electrical communication with the upper airway muscle such that the upper airway muscle is the target sensing site as opposed to a proximal site that innervates the upper airway muscle or a muscle or nerve that is anatomically adjacent to the the upper airway muscle. In such embodiments, the EMG sensor is adjacent to the upper airway muscle such that the EMG sensor is receiving input directly from the upper airway muscle as opposed to receiving input from a proximal site that innervates or is anatomically adjacent to the upper airway muscle. At step 86, method 80 can include monitoring the subject for an EMG signal indicative of a certain period of the subject's respiratory cycle by sensing EMG activity of the upper airway muscle. At step 88, method 80 can include activating the neurostimulator to provide electrical stimulation to the upper airway muscle in response to the EMG signal to decrease the subject's airway resistance and treat the SBD. Steps 86-88 can be repeated for a desired period of time to treat the SBD.

Referring to FIG. 13, neurostimulation system 90 can include neurostimulator 92 that is at least one lead 94 having stimulating electrode 96 and EEG sensor 98 located thereon. The neurostimulator is illustrated in other figures as being a lead but the neurostimulator could have other configurations.

Neurostimulator 92 can also include an interface circuit and an amplifier (not shown), and a controller 100. The interface circuit can receive EMG activity input from EMG sensor 98 and can send an EMG signal to the amplifier. The amplifier can supply an amplified and filtered EMG signal to controller 100. Controller 100 can process the amplified and filtered EMG signal to determine whether the EMG signal is indicative of a certain period of a subject's respiratory cycle such that the upper airway muscle should be stimulated. For example, the EMG signal can represent a spike or increase in EMG activity compared to a baseline level that may indicate the onset of inspiration; a gradual increase in EMG activity compared to a baseline level that may indicate an imminent onset of inspiration; or another detectable feature of EMG activity of the upper airway muscle indicative of a certain period of the subject's respiratory cycle, such as before, during or after the onset of the expiration phase. The EMG activity can represent a spike in upper airway muscle activity or an absence of upper airway muscle activity.

When controller 100 detects an EMG signal indicative of a certain period of a subject's respiratory cycle such that the upper airway muscle should be stimulated, it can output a trigger signal to the interface circuit. Once the interface circuit receives the trigger signal, it can output a stimulation signal to electrode 96 to stimulate to the upper airway muscle. Controller 100 can also be programmed to define a threshold level of EMG activity or a delta of a baseline level (e.g. an amplitude limit) of EMG activity. When this threshold level or delta value is reached, the controller can send a trigger signal to the interface circuit to output a stimulation signal to the stimulating electrode.

Neurostimulation system 90 can include a power supply 102 and an external processor 104. The power supply can be an internal power supply, as depicted in FIG. 13, such as a rechargeable battery that is rechargeable from outside the subject's body via inductive or radiofrequency coils. Alternatively, the power supply can be an external power supply. A two-way communication link can be associated with controller 100 for communication between controller 100 and external processor 104. External processor 104 can have the capability to receive data from controller 100 and transmit data to controller 100 via the communication link. In this manner, a clinician can evaluate physiological data and system data accumulated by neurostimulator 92. Such data can be stored on a memory device (not shown) of the neurostimulation system.

FIG. 14 is a graphic illustration of airflow (Resp) during an exemplary subject's respiratory cycle and the corresponding EMG activity measured at the upper airway muscle. In an embodiment, the EMG sensor can continuously monitor the EMG activity of an upper respiratory muscle of a given subject beginning at time to. For example, at the onset of the inspiration phase of respiration at time t2, the controller can detect EMG activity indicative of the onset of the inspiration phase of respiration from the signals supplied by the EMG sensor. For example, there can be a spike in EMG activity for a given subject upon the onset of the inspiration phase compared to a baseline level. At this point, the controller can send a control signal to a stimulating electrode to electrically stimulate the upper airway muscle to decrease airway resistance to open the subject's airway. There can also be a gradual increase in EMG activity compared to a baseline level for a given subject prior to the onset of the inspiration phase at t₁that the controller can detect from the signals supplied by the EMG sensor. At this point, the controller can send a control signal to the stimulating electrode to electrically stimulate the upper airway muscle. At time t