Method and system for sensing breath of a subject and use of the method and system in treating obstructive sleep apnea - Patent Application 20070123333

Abstract

The invention described herein refers, for example, to a method for measuring the degree of airway patency based on acoustic signals and / or muscle displacement, a system for implementing the method, and the use of the method and system in obstructive sleep apnea therapy. A method for sensing a subject's breath includes measuring an acoustic signal and / or a movement signal caused by the subject's breath during an electrical neurostimulation session, and assigning a value indicative of a match rate and / or an inspiratory airflow to the measured acoustic signal and / or to the measured movement signal.

Description

[Technical field]

[0001] The invention described herein refers to a method for sensing breath of a subject, a system for implementing the method, and the use of the method and system in obstructive sleep apnea therapy. [Background technology]

[0002] Neuromodulation, i.e., electrical stimulation of nerves, is well known in the prior art as a reliable and effective type of medical treatment. It presents an opportunity to address many physiological conditions and disorders by interacting with the body's own natural nerve processes. Neuromodulation involves the inhibition (e.g., blocking), stimulation, modification, regulation, or therapeutic alteration of electrical or chemical activity within the central, peripheral, or autonomic nervous system. By modulating the activity of the nervous system, several different goals can be achieved. For example, motor neurons can be stimulated at the appropriate time to cause muscle contraction. Furthermore, sensory neurons can be blocked to relieve pain or stimulated to provide a signal to a subject (i.e., a human suffering from sleep apnea). In yet other examples, modulation of the autonomic nervous system may be used to regulate various involuntary physiological parameters such as heart rate and blood pressure. Neuromodulation may provide an opportunity to treat several diseases or physiological conditions. Various devices and techniques are used in an attempt to provide optimal stimulation of the tissue of interest.

[0003] In the context of this disclosure, the expressions "neurostimulation", "neural stimulation", "neuromodulation" and "neuromodulation" are used synonymously unless otherwise clear from the particular context. In general, the above expressions refer to the process of generating an electric field in the vicinity of a nerve or group of nerves to cause contraction of one or more muscles associated with the nerve. Similarly, the expressions "subject" and "patient" are used synonymously unless otherwise clear from the particular context. Both terms refer to a human potentially suffering from OSA.

[0004] One of the conditions to which neural modulation can be applied is obstructive sleep apnea (OSA), a breathing disorder characterized by recurrent episodes of partial or complete obstruction of the upper airway during sleep. One of the main causes of OSA is the inability of the tongue muscle to resist the negative inspiratory pressure in the pharynx due to sleep-related loss of muscle tone. As the tongue is drawn backward, this obstructs the upper airway, reducing ventilation and lowering lung and blood oxygen levels. Stimulation of the hypoglossal nerve ("hypoglossal nerve stimulation", or HGNS) contracts the tongue muscle, thereby maintaining an open, unobstructed airway. When a person who does not suffer from OSA sleeps, the pharyngeal muscles, the group of muscles that form the pharynx, relax and progressively collapse and narrow the airway. The narrowing of the airway, in turn, limits the effectiveness of the sleeper's breath and causes an increase in CO2 levels in the sleeper's blood. The increase in CO2 causes the pharyngeal muscles to contract, opening the airway and restoring proper breathing. The larger of the pharyngeal muscles involved in upper airway expansion is the genioglossus, which is one of several different muscles in the tongue.

[0005] The genioglossus muscle is involved in the forward movement of the tongue and the stiffening of the anterior pharyngeal wall. In patients with OSA, the neuromuscular activity of the genioglossus muscle is reduced compared to normal individuals, causing insufficient response and contraction to open the airway compared to normal individuals. This lack of response contributes to partial or complete airway obstruction, which significantly limits the sleeper's ability to breathe. In OSA patients, several airway obstruction events often occur during the night. Due to the obstruction, a gradual decrease in O2 levels in the blood (hypoxemia) occurs. Hypoxemia leads to night-time awakenings, which can be detected by EEG and indicate that the brain is awakened from any stage of sleep to a short awakening. During the awakening, conscious gasping or wheezing occurs, which resolves the airway obstruction. An increase in the rate of sympathetic tone activity through the release of hormones such as epinephrine and noradrenaline also often occurs as a response to hypoxemia. Increased sympathetic tone causes the heart to enlarge in an attempt to pump more blood, increasing blood pressure and heart rate, further arousing the patient after resolution of the apneic event, and as the patient returns to sleep, the airway collapses again, leading to further arousals.

[0006] To quantify the effectiveness of neuromodulation as a therapeutically effective method (especially HGNS), as well as for analytical purposes, it is important that the therapeutic response is closely monitored. This is usually accomplished through monitoring the subject's thoracic movement and nasal and / or oral airflow, for example with the use of PSG (sleep study, i.e., polysomnography) or CPAP (continuous positive airway pressure) masks.

[0007] The above methods have several drawbacks. Solutions involving airflow are not suitable for seamless implementation for neurostimulation in existing systems. Furthermore, using masks and the like can be perceived as cumbersome by the subject. With regard to self-assessment or visualization of airway patency or tongue protrusion, these methods can be highly subjective and therefore subject to variable results or errors. Furthermore, even objective visual assessments only provide qualitative results, not quantitative ones.

[0008] Other concepts for monitoring the therapeutic effectiveness of neurostimulation focus on breath detection, where implanted intercostal breath sensing leads are used to monitor the patient's breathing patterns. However, this method is invasive because implanting an electronic system that is not located within the area of ​​the stimulation implant requires longer or even additional surgical procedures.

[0009] The objective technical problem of the present disclosure is to eliminate the shortcomings of the prior art, and to provide a method for sensing the subject's inhalation to facilitate the quantification of the effectiveness of neuromodulation therapy, and to determine the degree of therapy coverage for a desired time period of treatment.Furthermore, the method should improve electrical neurostimulation in patients associated with OSA. Summary of the Invention [Means for solving the problem]

[0010] SUMMARY OF THEINVENTION The main features of the method according to the present disclosure are defined by claim 1. Special embodiments or advantageous variants of the method are depicted in claims 2-9. A system for implementing the method is defined in claims 10-11. Furthermore, a use of the method is defined by claim 12.

[0011] According to a first aspect of the present disclosure, an objective technical problem is solved by a method for sensing breath of a subject in response to electrical neural stimulation, the method comprising: - measuring acoustic and / or motor signals evoked by the subject's breathing during an electrical neurostimulation session; - assigning values ​​to the measured acoustic signals and / or to the measured movement signals indicative of match rate and / or inspiratory airflow (i.e., inhalation and / or occlusion events); A method comprising:

[0012] The match rate and / or inspiratory airflow values ​​allow for determining breathing patterns and synchronization of stimulation to desired periods of the subject's inhalation and / or obstruction events.

[0013] Preferably, the acoustic signal is measured using at least one acoustic sensing unit, which may in particular comprise at least one microphone. The acoustic sensing unit or microphone may for example be located outside the subject's body. According to a preferred embodiment, the at least one sensing unit may be arranged directly under the subject's chin.

[0014] The acoustic signal may include any noise emitted by the subject. However, the acoustic signal may preferably be the breathing or snoring sounds of the subject. The acoustic sensing unit or microphone may be configured to capture even some breathing sounds of the subject while sleeping. Furthermore, dedicated signal processing algorithms may be implemented with which the subject's inhalation and exhalation phases over time may be detected.

[0015] The motion signal may include any motion caused by subject movement and sensed by the motion sensing unit. However, the motion signal may preferably be airway muscle or jaw displacement caused by subject breathing. The motion sensing unit may comprise an inertial measurement unit (IMU) and / or a gyroscope and may be configured to capture even minor breathing movements of the subject while sleeping. Furthermore, dedicated signal processing algorithms may be implemented with which the subject's inhalation and exhalation phases over time may be detected.

[0016] Using the above method, it is possible to reliably measure and / or monitor the breathing pattern of a subject and, based thereon, to quantify the level of stimulation synchronization with the inhalation phase of the subject (so-called coincidence rate quantification), and further, to optimize the timing of the initiation of the stimulation train within the breathing cycle of the subject.

[0017] According to an advantageous embodiment, the method may further comprise generating a modulated signal, the modulated signal comprising an electrical stimulation pattern, applying the modulated signal to at least a pair of electrodes associated with an implant unit implanted inside the subject's body, and adjusting at least one parameter of the electrical stimulation pattern in response to a value indicative of the match rate and / or the inspiratory airflow, i.e. in response to the measured acoustic / motion signal. In this way, monitoring of the effectiveness of a stimulation session can be optimized even further, since two separate effects of the stimulation are independently monitored, allowing a clearer picture.

[0018] Using the method described above, the effectiveness of neurostimulation during the treatment of a patient suffering from OSA, particularly the effectiveness of stimulation of the hypoglossal nerve or cervical nerve trap, can be monitored in an easy and accurate manner. It should be understood that the hypoglossal nerve innervates the genioglossus muscle, and the cervical nerve trap innervates the subhyoid cingulum muscle, which are involved in stiffening or collapsing the subject's upper airway. The subhyoid muscles include the sternohyoid, sternothyroid, omohyoid, and thyrohyoid muscles. Furthermore, if required, the system allows for continuous monitoring over a desired period of time, providing important information regarding the long-term effectiveness of neurostimulation therapy.

[0019] Muscle contraction in the sense of the present disclosure may refer to muscle displacement, and these terms are used synonymously unless otherwise indicated. Muscle contraction may particularly (but not exclusively) refer to displacement of the tongue of a subject or other muscles associated with the airway of a subject.

[0020] The movement of one or more muscles associated with the subject's airway may also include the movement of the subject's jaw, in the sense of the present disclosure, since the displacement of one or more of the muscles involved in the patient's airway during breathing will also result in the jaw being moved. Thus, for example, monitoring of the patient's breathing based on acoustic signals and / or muscle displacements may also be determined by measuring the subject's jaw movement and the subject's breathing sounds within the jaw area.

[0021] The modulated signal comprising the electrical stimulation pattern is preferably generated by an external device, which may be configured for placement beneath the subject's chin. In particular, the modulated signal may be generated by a control unit and / or by a processor, both of which may be part of the external unit. The modulated signal may further be transmitted to the implanted unit using a transmission element, which may comprise an antenna or coil associated with the control unit.

[0022] According to another embodiment, the control unit may be part of an implanted unit that is implanted directly under the skin of the subject, either instead of or in addition to the control unit of an external device. Thus, the control unit may be located directly on the muscle to be monitored, for example on the genioglossus muscle, or on one or more of the infrahyoid muscles, in particular on the sternohyoid or sternothyroid muscles. In other words, the location of the control unit is not essential to the method underlying the present disclosure. In any case, the control unit may preferably be in electrical communication with at least one motion sensing unit.

[0023] The step of applying the modulated signal to at least a pair of electrodes may preferably be implemented by an implant unit. The implant unit may be implantable near or adjacent to any muscle associated with the subject's airway, for example, the genioglossus muscle, which is innervated by the hypoglossal nerve. The implant unit may comprise an electrical circuit that receives the electrical stimulation pattern through electrical communication between an external device and the implant unit, and thus generates an electric field via the at least a pair of electrodes associated with the implant unit.

[0024] The step of determining the movement of one or more muscles associated with the subject's tongue in response to the modulated signal may preferably be implemented by a motion sensing unit. The method may further be characterized in that at least one motion sensing unit comprises at least one inertial measurement unit (IMU) and / or at least one strain gauge. According to an exemplary embodiment, the movement of one or more muscles associated with the subject's tongue may also be determined by detecting the movement of the subject's jaw, since the movement of the subject's tongue will also result in the movement of the subject's jaw.

[0025] Using the presented method, the physiological effect to be achieved through stimulation therapy, i.e., increasing a subject's inspiratory airflow, can be monitored with greater accuracy than known methods.

[0026] Using the methods described herein, physiological conditions that are directly affected by the underlying neurostimulation therapy, i.e., muscle contraction and, consequently, tongue protrusion of the subject, can be monitored in addition to monitoring the subject's breathing patterns. In this way, it is possible to obtain accurate information regarding therapy efficacy. Based on the determined degree of airway opening in response to stimulation with a defined set of stimulation parameters, it is further possible to adjust those parameters to improve therapy efficacy. For example, if a set of stimulation parameters is not sufficient to cause tongue protrusion and open the airway, the underlying stimulation parameters may be adjusted accordingly, e.g., by increasing the stimulation intensity, or if a set of stimulation parameters is not sufficient to cause a desired match rate, the underlying stimulation parameters may be adjusted accordingly, e.g., by adjusting the length and distribution of the stimulation cycle.

[0027] According to a further embodiment of the method, time periods indicative of the subject's inhalation phase and occlusion events are detected and then the level of stimulation synchronization with these periods is quantified, e.g., based on acoustic signals and / or muscle displacements.

[0028] According to one embodiment disclosed herein, the method may further include adjusting at least one parameter of the electrical stimulation pattern in response to the match rate and / or inhalation airflow, and / or in response to determined time periods indicative of the subject's inhalation phase and upper airway obstruction events. In this way, a feedback-based or closed-loop stimulation method is provided, where the effectiveness of an ongoing stimulation session is determined by measuring the displacement of airway muscles during the subject's aspiratory sounds or inhalation (i.e., detection of the inhalation phase and upper airway obstruction events), and then the stimulation parameters are adjusted in response to the measured degree of synchronization of the stimulation with these events (i.e., the estimated match rate). Detection of such an aspiratory event can be determined, for example, by measuring the acoustic signal alone, or by detecting the movement of muscles associated with inhalation in the airway, or by detecting the subject's jaw movement, in addition to measuring the acoustic signal. The adjustment of the at least one stimulation parameter can occur automatically, or manually (e.g., through a physician or through the subject himself), or both. In the case of automatic adjustment, at least one stimulation parameter can be changed after a set time delay or nearly immediately (i.e., in real time). This process may be automatically repeated in an iterative manner until one of the automatic adjustments of the stimulation parameters results in a determination of a value indicative of a desired degree of synchronization of the stimulation with the subject's inhalation and / or upper airway obstruction events.

[0029] To achieve a feedback-based or closed-loop stimulation session, the control unit may be configured to perform logical operations such as comparing a determined match rate based on data corresponding to the subject's aspiration sounds determined by the acoustic sensing unit, or additionally based on data corresponding to the movement of one or more muscles associated with the subject's inhalation determined by the motion sensing unit, to a predefined value and adjusting one or more of the stimulation parameters accordingly. For example, if a match rate is determined based on the measured acoustic signal that is below a predetermined value, the control unit may be configured to adjust the stimulation train length and interval.

[0030] Advantageously, the movement of the muscles associated with the subject's airway may comprise muscle contraction, a change in tongue position, and / or a change in the spatial orientation of the tongue in the subject, and / or a movement of the subject's jaw. In particular, but not exclusively, the muscle contraction may refer to the contraction of the genioglossus muscle, in particular when innervated by the hypoglossal nerve. It is also possible that the movement of one or more muscles associated with the subject's tongue is determined using at least one motion sensing unit. The method may further be characterized in that the at least one motion sensing unit comprises at least one inertial measurement unit and / or at least one strain gauge. According to another embodiment, the inertial measurement unit may comprise at least one accelerometer and / or at least one gyroscope and / or at least one magnetometer. Preferably, at least one accelerometer may be implemented, which may comprise a single-axis accelerometer or a multi-axis accelerometer. In this manner, the degree of airway patency, and therefore therapy effectiveness, can be determined with even greater accuracy since two separate and independent stimulation effects (breathing and muscle contraction) can be monitored using the preferred method.

[0031] The at least one parameter may comprise pulse train amplitude, pulse train length, single pulse frequency, single pulse duration, hold duration, pulse train interval, duty cycle, delay time, rise duration, step down amplitude, rise at train start duration, and / or confirmation pulse / train amplitude. The stimulation parameters may be adjusted automatically based on values ​​assigned to the measured match rate and degree of airway patency, or the parameters can be adjusted by a physician or by the patient themselves in response to receiving information that the current stimulation parameters are not sufficient.

[0032] According to another aspect of the present invention, a system for measuring a match rate and / or a degree of inspiratory airflow based on, for example, an acoustic signal and / or muscle displacement of a subject is provided, the system comprising: an implantation unit configured for implantation near or in proximity to any muscle associated with the subject's airway, for example the genioglossus muscle, the implantation unit comprising at least a pair of electrodes; an external device configured for communication with the embedded unit; at least one acoustic sensing unit for sensing an acoustic signal of the subject caused by the subject's breathing, and / or at least one motion sensing unit for sensing a movement associated with the subject's breathing; Equipped with. The system may preferably be configured to implement the methods described herein.

[0033] According to a preferred embodiment, the motion sensing unit is a microphone that is part of an external device, such that the external device is placed externally on the subject in close proximity to the implant unit, i.e., directly under the subject's chin, such that an acoustic sensing unit that is part of the external device is automatically placed in a favorable location for detecting acoustic signals, e.g., breath sounds of the subject.

[0034] In addition to the above, the system may comprise a motion sensing unit for determining movement of one or more muscles associated with the subject's airway in response to a modulated signal applied to at least a pair of electrodes.

[0035] The system may further comprise a control unit. The control unit may be part of an external device. In that case, the control unit may transmit modulation or stimulation input signals, e.g., stimulation parameters and power, to the implanted unit. The control unit may further receive determined data corresponding to the subject's aspiratory sounds determined by the acoustic sensing unit, or in addition, data corresponding to the movement of one or more muscles associated with the subject's airway determined by the motion sensing unit, and assign a value to the assigned degree of airway opening. According to a preferred embodiment, the control unit may also adjust at least one of the stimulation parameters in response to a value indicative of the match rate and / or the inhaled airflow.

[0036] The control unit may thus comprise one or more processors, which may include any electrical circuitry configured to perform a logical operation on at least one input variable. The at least one processor of the control unit may thus include one or more integrated circuits, microchips, microcontrollers, and microprocessors, which may be all or part of a central processing unit (CPU), digital signal processor (DSP), field programmable gate array (FPGA), or any other circuitry known to those skilled in the art that may be suitable for executing instructions or performing logical operations.

[0037] The implant unit may be configured for implantation in a location that allows for modulation of a nerve (e.g., the hypoglossal nerve). The implant unit may be located in the subject such that intervening tissue is between the implant unit and the nerve to be modulated. The intervening tissue may include muscle tissue, connective tissue, organ tissue, or any other type of biological tissue. Thus, the location of the implant unit does not require immediate contact with the nerve for effective neuromodulation. The implant unit may also be located directly adjacent to the nerve such that there is no intervening tissue.

[0038] When treating OSA, the implant unit may be located over the genioglossus muscle of the patient or subject. Such a location is suitable for modulation of the hypoglossal nerve, whose branches extend medially to and innervate the genioglossus muscle. However, the implant unit may also be configured for placement in other locations.

[0039] The external device may be configured for placement on the outside of the patient, either in direct contact with or near the patient's skin. The external device may further be configured to be affixed to the patient, for example, by adhering to the patient's skin or through a band or other device configured to hold the external device in place. Adherence of the external unit to the skin may occur such that it is near or adjacent to the location of the implanted unit. Preferably, the external device comprises at least one acoustic sensing unit (e.g., a microphone).

[0040] The external device may be configured for fixation to the patient. For example, the external device may be configured for placement beneath the subject's chin and / or on the front of the patient's neck. The suitability of the placement location may be determined by communication between the external device and the implant unit. The external device may comprise a housing, which may be any suitable container configured to hold electrical components. In addition, the housing may be of any suitable size and / or shape and may be rigid or flexible. Examples of housings for the external device may include one or more of patches, buttons, or other receptacles having various shapes and dimensions and constructed of any suitable material. The external device may be configured to adhere to a desired location. Thus, in some embodiments, at least one side of the housing may include an adhesive material. The adhesive material may include a biocompatible material and may allow the patient to adhere the external unit to a desired location and remove the external device upon completion of use. The adhesive may be configured for single or multiple use of the external unit. Suitable adhesive materials may include, but are not limited to, biocompatible adhesive glues, starches, elastomers, thermoplastics, and emulsions.

[0041] According to an embodiment, at least one motion sensing unit may be part of the implanted unit and / or at least one motion sensing unit may be part of the external device. It is also possible that both the implanted unit and the external device comprise a motion sensing unit. If this is the case, the motion sensing units may be different from each other, i.e., the motion sensing unit of the internal unit may be a strain gauge and / or a gyroscope, and the motion sensing unit of the external device may be a gyroscope. For example, if the motion sensing unit is part of the external device, the motion sensing unit may be an IMU, preferably configured to detect jaw movement, since the external device is preferably located directly under the subject's jaw and since a stimulation event resulting in a contraction of one or more muscles related to airway or tongue movement will also result in a movement of the subject's jaw. If the motion sensing unit is part of the implanted unit, the motion sensing unit may preferably comprise a strain gauge, either as a stand-alone component or together with an IMU, since a strain gauge is suitable for detecting and measuring muscle contractions and an IMU is suitable for detecting some motion movements induced by respiratory phases and muscle collapse.

[0042] Thus, using the system described herein, it is possible to monitor at least one physiological effect of neural stimulation of one or more nerves involved in muscles controlling a subject's airway (i.e., the subject's aspiration sounds) via implementation of an acoustic sensing unit, and to determine the degree of airway patency based on the measured acoustic signals. Furthermore, the system may be configured to automatically adjust at least one or more stimulation parameters to improve the stimulation based on the degree of airway patency thus determined. For example, it is possible to quantify the level of stimulation synchronization with the subject's inhalation phase (match rate quantification) using the system described.

[0043] Advantageously, the degree of airway patency can be determined based on detected movement of one or more muscles associated with the subject's airway, in addition to being determined based on measured acoustic signals (e.g., the subject's breath sounds).

[0044] According to another aspect of the present disclosure, the use of the method disclosed herein for the treatment of obstructive sleep apnea is presented. The treatment of obstructive sleep apnea, for which the present method may be used, may, for example, comprise the following steps: - receiving a modulated signal at an implant unit that is implanted at an internal location on the underside of the subject's jaw (e.g., near the genioglossus muscle); - applying a modulated signal to at least a pair of electrodes associated with the implanted unit to generate an electric field; - Causing modulation of the subject's hypoglossal nerve, or of the cervical nerve fascicle, in response to an electric field generated by at least a pair of electrodes, where the modulation of the hypoglossal nerve may be localized to the medial branch of the hypoglossal nerve and may be initiated from a single modulation site along the medial branch; may include:

[0045] Thus, at least a pair of modulation electrodes may be configured for implantation through the dermis on the underside of a subject's jaw and for placement proximate to terminal fibers of the medial branch of the hypoglossal nerve of the subject. Additionally, the implantable unit and the electrodes may be configured to cooperate to generate an electric field adapted to modulate one or more of the terminal fibers of the medial branch of the hypoglossal nerve.

[0046] Any of the embodiments, examples, or features disclosed herein may be used in combination or separately and with any one of the aspects of the disclosed subject matter. [Brief description of the drawings]

[0047] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the disclosed subject matter.

[0048] [Figure 1] FIG. 1 shows a schematic diagram of the system disclosed herein according to a first embodiment.

[0049] [Diagram 2] FIG. 2 shows a schematic diagram of a system according to a second embodiment.

[0050] [Diagram 3] FIG. 3 shows a schematic diagram of a system according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Detailed Description of the Drawings FIG. 1 shows a schematic diagram of a system 100 for measuring a match rate and / or a degree of respiratory airflow based on, for example, an acoustic signal and / or muscle displacement caused by a breathing subject, for example, in response to electrical neurostimulation, where the acoustic signal may include the subject's breathing sounds and the muscle may include one or more movements of the tongue, the genioglossus, or the subhyoid cingulum. The flow diagram of FIG. 1 may serve as an example of an implementation of the method. According to FIG. 1, a neurostimulation system 100 configured for implementing the method comprises a control unit 500 and an acoustic sensing unit 400. Furthermore, the system 100 may comprise an implantation unit 200 (not shown), preferably configured for implantation proximate to any muscle associated with the subject's airway, for example, the genioglossus, and an external device 300 (not shown) configured for electrical communication with the implantation unit 200.

[0052] The implant unit 200 of the system 100, with which the method may be performed, may be implanted near one of the genioglossus muscle, innervated by the hypoglossal nerve, or the infrahyoid muscle, innervated by the cervical nerve trap. The implant unit 200 may further include a transmission element, which may include a secondary antenna or coil, and an electrical circuit that receives an electrical stimulation pattern through electrical communication between the external device 300 and the implant unit 200. In response to receiving the electrical stimulation pattern, the electrical circuit may generate an electric field through at least a pair of electrodes associated with the implant unit 200. If the electric field is strong enough and / or close enough to the hypoglossal nerve, the nerve will be stimulated and innervate the genioglossus muscle, which will in turn contract. The specifications of the implant unit 200 are not limited to an embodiment, so long as the implant unit 200 is configured for use with the methods described herein.

[0053] The external device 300 of the system 100, with which the method may be performed, may be configured for placement on the outside of the patient, specifically beneath the subject's chin and / or on the front of the patient's neck. The external device 300 may thus be configured for attachment to the patient, for example, by adhering to the patient's skin or through a band or other device configured to hold the external device in place. The external device 300 may preferably comprise a housing, which may be any suitable container configured to hold electrical components. In addition, the housing may be of any suitable size and / or shape, and may be rigid or flexible. Examples of housings for the external device 300 may include one or more of a patch, button, or other receptacle having various shapes and dimensions and constructed of any suitable material. The specifications of the external device 300 are not limited to certain embodiments, so long as the implant unit 200 is configured for use with the methods described herein.

[0054] To measure the acoustic signals caused by the object (i.e., breath noise sounds emitted by the object), the system 100 comprises an acoustic sensing unit 400, which may be a microphone. To measure the motion signals caused by the object, the system 100 comprises a motion sensing unit 600, which may be an inertial measurement unit, an accelerometer, at least one gyroscope, and / or at least one magnetometer.

[0055] 1 may comprise a control unit 500, for example as part of the external device 300. The control unit 500 may transmit modulation or stimulation input signals, for example stimulation parameters and power, to the implanted unit 200.

[0056] According to the method depicted in FIG. 1, the control unit 500 may also receive data corresponding to the acoustic signal measured by the acoustic sensing unit 400 or the motion signal measured by the motion sensing unit, and assign it a value related to the match rate and / or the inhaled airflow. According to a preferred embodiment of the method, the control unit 500 may also adjust at least one of the stimulation parameters in response to the value indicative of the match rate and / or the inhaled airflow. Thus, the control unit 500 may comprise one or more processors, which may include any electrical circuit configured to perform a logical operation on at least one input variable. The at least one processor of the control unit 500 may include, for example, one or more integrated circuits, microchips, microcontrollers, and microprocessors, which may be all or part of a central processing unit (CPU), a digital signal processor (DSP), a field programmable gate array (FPGA), or any other circuit known to those skilled in the art that may be suitable for executing instructions or performing logical operations. Thus, a method for feedback-based or closed-loop neural stimulation is provided in which the effectiveness of an ongoing stimulation session is determined by measuring the degree of airway patency and then automatically adjusting stimulation parameters in response to the measured degree of airway patency.

[0057] According to FIG. 1 , the control unit 500 can be part of the external device 300 , of the implanted unit 200 , or of both the external device 300 and the implanted unit 200 .

[0058] 2 shows a schematic diagram of a system 100 according to a second embodiment for measuring match rate and / or inspiratory airflow based on acoustic and / or motion signals elicited by, for example, a subject's breath, for example in response to electrical neural stimulation. The system 100 of FIG. 2 shows that the acoustic sensing unit 400 and / or motion sensing unit 600 and the control unit 500 are both part of the external device 300. In this case, the acoustic sensing unit 400 may be a microphone, preferably enclosed within the housing of the external device.

[0059] 3 depicts a flow diagram of a third embodiment of a system 100 for measuring match rate and / or inspiratory airflow based on acoustic and / or motion signals elicited by, for example, a subject's breath, e.g., in response to electrical neural stimulation. The system 100 of FIG. 3 is further defined in that a motion sensing unit 600 for detecting muscle contractions is implemented in addition to the acoustic sensing unit 400.

[0060] For example, to determine the movement (i.e., contraction) of one or more muscles associated with the subject's breathing pattern in response to the electric field applied by the implant unit 200, the system 100 includes a motion sensing unit 600 that includes at least one inertial measurement unit and / or at least one strain gauge. The inertial measurement unit may include at least one accelerometer and / or at least one gyroscope and / or at least one magnetometer. For example, the degree of protrusion of the subject can be determined, for example, by detecting the movement of muscles associated with the tongue or by detecting the movement of the subject's jaw. The automatic adjustment may include the control unit 500 receiving a value indicative of the inspiratory airflow from either the motion sensing unit 600 and / or the acoustic sensing unit 400, and adjusting at least one stimulation parameter accordingly, either after a set time delay or nearly immediately (i.e., in real time).

[0061] The invention is not limited to one of the embodiments described herein but can be modified in many other ways.

[0062] All features disclosed in the claims, the specification and the drawings, as well as all advantages, including architectural details, spatial arrangements and methodological steps, may be essential to the invention, either by themselves or in various combinations with one another.

[0063] List of Reference Numbers 100 Systems 200 Embedded Units 300 External Devices 400 Acoustic Sensing Unit 401 Inertial Measurement Unit 402 Strain Gauge 500 Control Unit 600 Motion Sensing Unit

Claims

1. 1. A method of operating a system for sensing breath of a subject, the method comprising: - at least one acoustic sensing unit of the system measuring acoustic signals caused by the subject's breathing during the electrical nerve stimulation session, and / or at least one movement sensing unit of the system measuring movement signals caused by the subject's breathing during the electrical nerve stimulation session; a control unit of the system assigning to the measured acoustic signal and / or to the measured movement signal a value indicative of a match rate and / or an intake airflow; A method of operation comprising:

2. The method of operation further comprises: - the control unit generating a modulated signal, the modulated signal comprising an electrical stimulation pattern; an implant unit of the system, implanted inside the subject's body, applying the modulated signal to at least a pair of electrodes associated with the implant unit; - said control unit adjusting at least one parameter of said electrical stimulation pattern in response to said measured match rate and said value indicative of inspiratory airflow; 2. The method of claim 1, comprising:

3. 2. The method of claim 1, wherein the acoustic signal comprises aspiration sounds of the subject, and the movement signal comprises movement or contraction of one or more muscles associated with the subject's airway.

4. The operating method described in claim 1, characterized in that the at least one acoustic sensing unit comprises at least one microphone.

5. 3. The method of claim 2, wherein the movement or contraction of the muscles associated with the subject's airway comprises airway muscle contraction, a change in the position of the subject's tongue, and / or a change in the spatial orientation of the tongue within the subject.

6. The method of claim 2 , wherein the at least one motion sensing unit comprises at least one inertial measurement unit and / or at least one strain gauge.

7. 7. The method of claim 6, wherein the inertial measurement unit comprises at least one accelerometer and / or at least one gyroscope and / or at least one magnetometer.

8. 2. The method of claim 1, wherein the at least one parameter comprises pulse train amplitude, pulse train length, single pulse frequency, single pulse duration, hold duration, pulse train spacing, duty cycle, delay time, rise duration, step down amplitude, rise at train start duration, and / or confirmation pulse / train amplitude.

9. A system under the control of the method of operation according to any one of claims 1 to 8, wherein the system comprises: an implantation unit configured for implantation near any muscle associated with airway patency in said subject; an external device configured for communication with said implant unit; said at least one acoustic sensing unit and / or said at least one motion sensing unit; A system comprising:

10. The system of claim 9 , wherein the at least one acoustic sensing unit is part of the external device and the at least one motion sensing unit is part of the external device or of the implanted device.

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