US20100241191A1 - Method and apparatus for assisting deglutition - Google Patents

Abstract

Methods and systems for artificially stimulating user deglutition without substantial aspiration are provided. Methods and systems include artificially stimulating user deglutition according to various specialized programs, including passive user secretion maintenance programs, active feeding programs, proprioceptive feedback programs, and others.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• This application is a continuation application of U.S. Non-Provisional patent application Ser. No. 11/611,367, filed on Dec. 15, 2006, issuing as U.S. Pat. No. 7,734,351 on Jun. 8, 2010, the contents of which are hereby incorporated by reference.
BACKGROUND
• The present invention relates to systems and methods for assisting deglutition, and more particularly to systems and methods for stimulating deglutition musculature in order to reduce effects of dysphagia.
• The condition of having an inability to swallow is generally described as “dysphagia.” Dysphagia is commonly associated with ailments such as strokes, neurodegenerative diseases, brain tumors, respiratory disorders, and others. In some forms, dysphagia results in aspiration during “deglutition,” the act of swallowing. Aspiration during deglutition is of great concern as it increases the risk of aspiration pneumonia. In particular, there is evidence that aspiration pneumonia inflicts about a 20% death rate in the first year after a stroke and about a 10% to 15% death rate each year thereafter. Traditional treatments for dysphagia have employed either temporary feeding through a nasogastric tube or enteric feeding through a stoma to the stomach in chronic cases.
• Techniques of electrical stimulation of electrically excitable tissue within the body of a living subject have been developed utilizing stimulating electrodes and a signal generator to supply electrical charges in a controlled or predetermined manner. PCT App. Pub. WO 2004/028433 (“Ludlow”) (entitled “Methods and Devices for Intramuscular Stimulation of Upper Airways and Swallowing Muscle Groups;” published Apr. 8, 2004) describes stimulation of muscles within a neck region of a human subject for the purpose of causing muscles to react as a swallowing effect. More specifically, Ludlow describes inducement of swallowing in a subject's body by implanting electrodes in two or more muscles of the upper airway musculature and connecting the electrodes with a signal generator that provides coordinated control signals. Other techniques and methods of artificial stimulation using transcutaneous, non-implanted systems are disclosed in U.S. Pat. Nos. 5,725,564; 5,891,185; 5,987,359; 6,104,958; and 6,198,970, all to Freed et al.
SUMMARY
• Some aspects relate to a method of stimulating user deglutition without substantial aspiration, including use of a passive user secretion maintenance program. The method includes providing a portable system born by a user for controlling a component of a complete swallowing act, the system including a controller, a signal generator, and an electrode array including at least one electrode. The signal generator is in communication with the electrode array. The electrode array is subcutaneously positioned in stimulating communication with deglutition musculature. User deglutition is artificially stimulated via the signal generator and electrode array according to a passive user secretion maintenance program adapted to automatically, periodically stimulate deglutition of user secretions without substantial aspiration of the user secretions.
• Other aspects relate to a method of stimulating user deglutition without substantial aspiration including use of a plurality of specialized deglutition programs. The method includes providing a portable system born by a user for controlling a component of deglutition, the system including a controller, at least one stimulating electrode, and a signal generator. The at least one stimulating electrode is subcutaneously positioned in stimulating communication with deglutition musculature. A desired deglutition program is selected from a plurality of specialized programs maintained by the controller based upon a characteristic of a bolus to be consumed by the user. The system is operated according to the selected deglutition program.
• Yet other aspects relate to a method of stimulating user deglutition without substantial aspiration. The method includes providing a portable system born by a user for controlling at least a component of deglutition, the system including a controller, an electrode array, and a signal generator in communication with the electrode array. A first portion of the electrode array is subcutaneously positioned in stimulating communication with deglutition musculature, whereas a second portion of the electrode array is subcutaneously positioned in stimulating communication with sensory mucosa of at least one of a mouth and a throat of the user. The sensory mucosa is stimulated with the electrode array to provide the user with tactile, sensory feedback. The deglutition musculature is stimulated with the electrode array to cause user deglutition without substantial aspiration.
• Yet other aspects relate to a method of stimulating user deglutition without substantial aspiration. The method includes providing a portable system born by a user for controlling at least a component of deglutition, the system including a controller, a signal generator, and an electrode array including at least one electrode. The electrode array is subcutaneously positioned in stimulating communication with deglutition musculature. The deglutition musculature is stimulated via the electrode array with a subthreshold, baseline signal prior to user deglutition. The deglutition musculature is stimulated via the electrode array with a stimulating signal following stimulation with the subthreshold, baseline signal. In particular, the stimulating signal causes a component of user deglutition to be artificially stimulated.
• Yet other aspects relate to a system for assisting user deglutition without substantial aspiration. The system includes an electrode array adapted to be subcutaneously positioned in stimulating communication with deglutition musculature. The system also includes a sensor array adapted to be subcutaneously positioned for providing deglutition information. A signal generator is electronically connected to the electrode array for providing a stimulating signal to the electrode array. A controller is also provided and is electronically connected to the sensor array and the signal generator, such that the controller receives the deglutition information and prompts operation of the signal generator to cause a component of deglutition to occur. In particular, the controller is adapted to actively modify the stimulating signal delivered by the signal generator based upon the received deglutition information.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a schematic view of a system for assisting deglutition according to some embodiments.
• FIG. 2 shows an epimysial electrode according to some embodiments.
• FIG. 3 shows a nerve cuff electrode according to some embodiments.
• FIG. 4 is a schematic view of the system ofFIG. 1 including a self-contained electrode according to some embodiments.
• FIG. 5A is a schematic view of bodily components associated with deglutition.
• FIG. 5B is a schematic view of a hylayrngeal complex and associated bodily components associated with deglutition.
• FIG. 6 is a schematic view of an implantable system for assisting deglutition according to some embodiments.
• FIG. 7 illustrates several muscle activation patterns according to some embodiments.
• FIG. 8 shows an electrode array of the system ofFIG. 1 in stimulating communication with deglutition musculature via a plurality of nerves according to some embodiments.
DETAILED DESCRIPTION
• In order to provide a better understanding of various embodiments, the following description has been formatted with several headings. However, it is to be understood that such headings are not intended as limiting, and that description is intended to be read as a whole, as a cumulative narrative of various embodiments with interrelating features where appropriate. With that in mind, descriptions of the following, general topics are provided: Deglutition Assistance Systems Overview; Overview of Deglutition; Artificial Deglutition Muscle Stimulation via Nerves; Muscle Activation Patterns and Associated Stimulation Patterns; Single Muscle Stimulation and Select Muscle Group Stimulation; Stimulation Program Initiation and Selection; and System Feedback.
Deglutition Assistance Systems Overview
• FIG. 1 is a schematic view of asystem20 for assisting deglutition. Thesystem20 includes acontroller22, asignal generator24, anelectrode array26 including at least one electrode, asensor array28 including at least one sensor, and apower source30. In some embodiments, various components of thesystem20 are maintained in an implantable housing32 (FIG. 6), which is optionally substantially similar to a pacemaker “can,” with an external switch or sensor (FIG. 6) optionally included for activating thesystem20. As indicated generally by dotted lines, the various aspects of thesystem20 communicate with one another, such communication being accomplished via a variety of mechanisms. For example, the components are optionally in direct, electrical communication; radio frequency communication; magnetic communication; optical communication; sonic communication; combinations thereof; and others.
• Thesystem20 is generally adapted to control deglutition musculature. In some embodiments, thesystem20 is portable and adapted to be born by a user, for example a chronic dysphagia sufferer, for extended periods of time. Thecontroller22, thesignal generator24, theelectrode array26, thesensor array28, and/or thepower source30, or portions thereof, are provided as separate, distinct components; as partially integrated components; or as fully integrated components as desired. For example, some embodiments include one or more integrated electrodes having processing, signal generating, external communicating, and/or sensing capabilities, one or more of which are fully or partially integrated into the integrated electrode(s).
• In some embodiments, thecontroller22 includes a microprocessor, a hardwired circuit, or other appropriate means for controlling various aspects of thesystem20. In particular, thecontroller22 operates thesignal generator24 and/or receives information from various sources, such as thesensor array28. In some embodiments, thecontroller22 is adapted to store a stimulation program or programs and operate thesignal generator24 according to the stimulation program(s). Stimulation programs include predetermined, set programs, for example hardwired into thecontroller22, but can also include adaptive, dynamic programs, for example software that adapts artificial deglutition stimulation according to various inputs, such as input from thesensor array28.
• It follows that, in some embodiments, thecontroller22 selects between various programs and/or actively modifies a stimulation program according to various inputs, such as information received from a user, information received from thesensor array28, information received from thesignal generator24, information received from theelectrode array26, information received from a remote processor (not shown), and/or information received from a technician or surgeon, for example.
• Thesignal generator24 is in communication with theelectrode array26 and is adapted to provide one or more stimulating signals to theelectrode array26. In some embodiments, the simulating signals communicate stimulating energy, such as electrical current pulses, to theelectrode array26 in order to activate deglutition musculature. As described in greater detail below, thesignal generator24 optionally includes circuitry and/or other implantable components for outputting electrical pulses through electrical leads to theelectrode array26. For example, the stimulating signals are optionally a series of overlapping, electrical current pulse trains communicated to theelectrode array26 and ultimately to deglutition musculature. It is also contemplated that thesignal generator24 optionally communicates power to theelectrode array26 via other mechanisms than electrical connection, for example radiofrequency power transmission and/or magnetic power transmission.
• Additionally, or alternatively, signals from thesignal generator24 can be otherwise communicative in nature, for example, communicating stimulation program information, patient information, and other types of information. In some embodiments, thesignal generator24 includes a radio frequency transmitter communicating with a self-contained electrode acting as a receiver, i.e., an electrode that is not physically “wired” to a separate signal generator via electrical leads or other means. In particular, the self-contained electrode receives the radio frequency transmission as a source of power and/or as a control signal for timing delivery of stimulating energy to deglutition musculature. It should also be noted that in some embodiments, the self-contained electrodes include an associated signal generator for providing stimulating signals to the particular self-contained electrode. For reference, embodiments of self-contained electrodes and various examples of stimulation signal patterns and stimulation programs are subsequently described in association with methods of artificially stimulating deglutition.
• As previously alluded to, unless specified otherwise, thecontroller22 and the signal generator24 (as well as other components of the system20) are configured as separate, distinct components; partially integrated components; or fully integrated components as desired. As one example, a combinedcontroller22 andsignal generator24 include a shared processor or processors providing a stimulating signal to theelectrode array26 in the form of an electrical current output or other appropriate output from the processor. Thus, in the absence of limiting language, such as “wherein thesignal generator24 and thecontroller22 are separate, distinct components,” “thesignal generator24 being apart from thecontroller22,” or alternatively “wherein thesignal generator24 and thecontroller22 are fully integrated,” for example, it is contemplated that thecontroller22 andsignal generator24 are not so limited.
• Theelectrode array26 includes one or more electrodes, such as afirst electrode26a, asecond electrode26b, and athird electrode26c. Theelectrode array26 is adapted be in stimulating communication with deglutition musculature, for example via subcutaneous, intramuscular placement; subcutaneous, exterior placement on a muscle surface; and/or subcutaneous implantation and association with one or more nerves controlling deglutition musculature. Alternatively, one or more electrodes of theelectrode array26 are adapted for percutaneous application or application external to skin, for example.
• In some embodiments, theelectrode array26 includes 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. As described in greater detail below, in some embodiments, theelectrode array26 includes one or more associated flexible, extensible electrical leads suited for use in deglutition stimulation applications, such as those described in co-pending U.S. application Ser. Nos. 11/413,316 (entitled “Implantable Medical Leads And Lead Assemblies With Improved Flexibility And Extensibility To Facilitate Body Movements”); 11/413,435 (entitled “Methods For Customizing Implantable Medical Lead Assemblies With Improved Flexibility And Extensibility”); 11/413,437 (entitled “Implantable Medical Assemblies With Improved Flexibility, Extensibility, And Positionability With Branched Structures”); and 11/413,440 (entitled “Implantable Medical Leads And Lead Assemblies With Improved Flexibility And Extensibility And Having A Substantially Two-Dimensional Nature”); all filed on Apr. 28, 2006 and the contents of each of which are incorporated herein by reference (cumulatively referred to herein as “the Extensible Lead Applications”).
• For general reference purposes,FIG. 3 shows anepimysial electrode33 useful as, or as part of, the electrode array26 (FIG. 1) in accordance with some embodiments. Theepimysial electrode33 includes aninsulated housing34 and one ormore contacts36 maintained by theinsulated housing34. Anelectrical lead38 is connected to theepimysial electrode33 to provide an electrical conduit to eachcontact36 on an individual or ganged basis as desired. In some embodiments, theepimysial electrode33 includes asingle contact36 and is monopolar to reduce overall size and/or provide increased overall structural flexibility.
• Theepimysial electrode33 is adapted to be secured to a muscle surface, for example by sewing or other appropriate means. In some embodiments, theepimysial electrode33 helps avoid problems associated with intramuscular electrodes, such as plunging intramuscular electrodes into tissue located behind a target muscle. For example, theepimysial electrode33 can exhibit less tissue reaction than intramuscular electrodes and is well-suited for use with what can be considered relatively thin deglutition muscles according to some embodiments. Examples of epimysial electrodes can be found in U.S. Pat. No. 5,843,147, issued Dec. 1, 1998, to Testerman et al., and entitled “Implantable Eyelid Electrode and Method of Implanting the Same,” the contents of which are incorporated herein by reference.
• FIG. 3 is a simplified view of anerve cuff electrode40 useful as, or as part of, the electrode array26 (FIG. 1). Thenerve cuff electrode40 includes a plurality of radially disposedcontacts42 maintained by a tubular,insulated housing44. Thenerve cuff electrode40 is connected to anelectrical lead46 providing an electrical conduit to each of the plurality ofcontacts42, for activation either individually or on a ganged basis as appropriate. In general terms, thenerve cuff electrode40 is adapted to be disposed about, and in stimulating communication with nerves to deliver stimulating energy to the nerves. In some embodiments, thenerve cuff electrode40 is substantially U-shaped, for example as described in U.S. Pat. No. 5,344,438, issued Sep. 6, 1994 to Testerman et al., and entitled “Cuff Electrode,” the contents of which are incorporated herein by reference. Other examples of suitable nerve cuff electrodes include the self-sizing electrode cuffs described in U.S. Pat. No. 4,603,624, issued Jul. 29, 1986, to Naples et al., and entitled “Cuff, Method of Manufacture, and Method of Installation.” As described in greater detail below, thenerve cuff electrode40 is adapted to selectively stimulate muscles controlled by nerves in some embodiments. For example, thenerve cuff electrode40 is optionally adapted to allow individual energizing of the radially disposedcontacts42 using a multi-channel signal generator, such as the signal generator24 (FIG. 1), in order to effectuate current steering techniques, or is otherwise adapted to selectively stimulate nerve fascicles of a nerve as desired.
• Returning toFIG. 1, as used herein, “self-contained electrodes” refer to electrodes that are not “hardwired” to thesignal generator24 and/or include their own signal generator, such as those described in the Schulman patents subsequently referenced herein. For example, thesignal generator24 optionally communicates and/or supplies power to theelectrode array26 via radiofrequency transmission and/or magnetic transmission mechanisms. Still further, in some embodiments, self-contained electrodes, or alternately “hardwired” electrodes if desired, are optionally integrated with various control/operation components, such as a signal generator and/or processor for controlling electrode activation, a power source for providing power to activate the electrode, and one or more contacts for receiving/conveying stimulating energy.
• FIG. 4 is a schematic view of an embodiment where thesystem20 includes at least one self-containedelectrode48 useful as, or as a part of, theelectrode array26. The self-containedelectrode48 is shown receiving a signal S, for example a radiofrequency and/or magnetic signal, from a transmitter (not shown) provided with thesystem20. In some embodiments, the self-containedelectrode48 is an implantable microstimulator, such as those described in U.S. Pat. No. 5,193,539, issued Mar. 16, 1993, to Schulman et al., and entitled “Implantable Microstimulator;” U.S. Pat. No. 5,193,540, issued Mar. 16, 1993, to Schulman et al., and entitled, “Structure and Method of Manufacture of an Implantable Microstimulator;” and U.S. Pat. No. 5,324,316, issued Jun. 28, 1994 to Schulman et al., and entitled “Implantable Microstimulator” (collectively referred to herein as “the Schulman patents”), the contents of all of which are incorporated herein by reference. For example, thecontroller22 and/or thesignal generator24 optionally include an electrical coil (not shown) and are provided externally to a dysphagia sufferer, with the self-containedelectrode48 being subcutaneously implanted. In some embodiments, thesystem20 is configured such that the self-containedelectrode48 receives power and/or stimulation commands through the signal S, for example with the signal S being an AC magnetic link established between thesignal generator24 and the self-containedelectrode48 using the external electrical coil.
• Returning toFIG. 1, thesensor array28 includes one or more sensors, such as afirst sensor28a, asecond sensor28b, and athird sensor28c. Thesensor array28 is adapted to provide information relating to deglutition and/or thesystem20. Thesensor array28 includes sensors adapted for subcutaneous use; exterior placement, for example on skin or hair; and/or percutaneous placement as appropriate. In some embodiments, thesensor array28 includes one or more force, movement, pressure, and/or position sensors, such as accelerometers; force gauges, for example strain gauges; EMG sensors; displacement sensors, for example sensors using piezo crystals to provide ultrasonic generating/sensing transducers; pressure sensors; and others.
• Operating requirements of the various sensors, for example thesensors28a-28c, are better understood with reference to various embodiment methods of artificially stimulating deglutition using thesystem20 that follow. Examples of suitable sensors and/or sensors which are suitably adapted for use with thesystem20 can be found, for example, in U.S. Pat. No. 7,037,266, issued May 2, 2006 to inventors Ferek-Petric et al. and entitled “Ultrasound Methods and Implantable Medical Devices Using Same,” the contents of which are incorporated herein by reference.
• As previously referenced, thepower source30 is a single component or multiple components, and is provided separately and distinct from other components of thesystem20 or as an integrated part of other components of thesystem20. Thepower source30 is optionally a chemical battery, a capacitor, or other appropriate means for powering thesystem20. In some embodiments, thepower source30 is adapted to be safely implanted into a living creature, for example a person suffering from dysphagia.
Overview of Deglutition
• With the understanding provided by the foregoing, it is useful to give some background on various aspects of deglutition, the act of swallowing, as well as various body parts associated with deglutition prior to describing additional specifics of thesystem20 and methods of use thereof.FIG. 5A is a generalized, schematic view ofbodily components50 associated with deglutition. In turn,FIG. 5B is a second, generalized schematic view of some of thebodily components50 ofFIG. 5A presented for additional understanding. Generally speaking, thebodily components50 are described with reference to human anatomy. However, it is contemplated that, though human anatomy may not be identical to that of other organisms, similar concepts to those described herein are applicable to other living organisms, such as monkeys, cats, dogs, horses, reptiles, or other animals, for example. Regardless, in general terms thebodily components50 generally include one ormore nerves52, one ormore deglutition muscles54, and one ormore deglutition structures56. As described in greater detail, thenerves52 perform motor functionality by directly stimulating thedeglutition muscles54 and/or providing sensory activation of thedeglutition muscles54, including via sensory mucosa or muscular sensory endings. In turn, thedeglutition muscles54 move thedeglutition structures56 to complete deglutition, or otherwise effectuate a complete swallowing act.
• By way of background, a complete act of swallowing can be broken down into several, basic stages—an oral stage, a pharyngeal stage, and an esophageal stage. Each stage includes a series of movements for effectuating deglutition of a bolus. As used herein, “bolus” refers to any substance to be swallowed, including liquids and solids, unless indicated otherwise. In cases of dysphagia, there is insufficient muscle activity (e.g., timing, type, or amount of activity) during one or more stages of deglutition, such that deglutition is defective. Often times, defective deglutition results in aspiration of the bolus or a portion thereof. At times, a particular case of dysphagia affects swallowing in different manners and/or to different extents according to the individual, including the particular swallowing structures/muscles affected, and/or according to a type/size/consistency of the bolus being swallowed.
• Generally, the oral stage entails voluntary control of oral structures, for example controlling the anterior position of the soft palate. During the oral stage, the bolus is typically pushed back in the oral cavity with the tongue. An end portion of the oral stage is generally indicated by the bolus passing the anterior faucial arches of a throat. Typically, the pharyngeal phase commences as an involuntary reflex initiated by the end portion of the oral stage. It should be noted that portions of the three stages often overlap. In some cases of dysphagia, insufficient movement during the oral stage results in a delay of initiation of a beginning portion of the pharyngeal phase, which, in turn, can lead to aspiration during swallowing.
• The beginning portion of the pharyngeal stage typically includes using muscles of the hyolaryngeal complex that control hyoid movement and laryngeal elevation to raise or lift the hyolaryngeal complex and move it forward in an anterior direction. Normally, as a part of the pharyngeal stage, thyroarytenoid and ventricular cords are closed to form a velopharyngeal seal. The epiglottis is tilted and an upper esophageal sphincter (UES) is relaxed, opening the esophagus. The UES is located in a cricopharyngeal region and includes a cricopharyngeus muscle which is attached to cricoid cartilage. In some cases of dysphagia there is insufficient lifting/forward movement of the hyolaryngeal complex, insufficient tilting of the epiglottis, and/or insufficient relaxation/opening of the UES, all of which can contribute to aspiration and/or other defects in a complete swallowing act.
• A beginning portion of the esophageal stage is typically initiated as the upper esophageal sphincter (UES) opens. The bolus is transferred down the esophagus by a series of peristaltic wave contractions which are typically initiated during the pharyngeal stage. The bolus eventually works its way to the inferior esophageal sphincter and enters the stomach. In some cases of dysphagia, the cricopharyngeal opening remains lax following the pharyngeal stage, and does not sufficiently constrict. This can also result in some material remaining in the pharynx, raising the risk of subsequently aspirating the remaining material.
• With the above overview in mind, thebodily components50 and relative interactions between thebodily components50 are described in greater detail, beginning with thenerves52. Thenerves52 include a plurality of nerves, such as afirst nerve52a, asecond nerve52b, and athird nerve52c. In general terms, thenerves52 stimulate activation of thedeglutition muscles54 and/or provide sensory feed back relating to deglutition, with each of thenerves52a,52b,52cbeing formed of a plurality of nerve fibers, such nerve fibers being grouped into nerve fascicles. For example, thefirst nerve52aincludes a first plurality ofnerve fascicles60, such as afirst nerve fascicle60a, asecond nerve fascicle60b, athird fascicle60c, and afourth fascicle60d. Thesecond nerve52balso includes a second plurality ofnerve fascicles62, such as afifth nerve fascicle62aand asixth nerve fascicle62b. As described in greater detail below, when associated with muscular motor response, the nerve fascicles are “tied” to one or more of thedeglutition muscles54, such that a particular nerve fascicle or group of nerve fascicles stimulates or otherwise causes activation of a particular muscle or group of muscles. Some embodiments include selectively stimulating one or more nerve fascicles of a particular nerve to selectively stimulate deglutition muscles associated with the particular nerve.
• Thefirst nerve52ais a hypoglossal nerve with thenerve fascicles60 activating the geniohyoid, hyoglossus, thyrohyoid, omohyoid, sternothyroid, sternohyoid, genioglossus, and/or styloglossus muscles, for example. In turn, thesecond nerve52bis a mylohyoid nerve (from an inferior alveolar nerve) activating the mylohyoid muscle and/or a digastric muscle, for example. Thethird nerve52cis a cervicalis nerve activating one or more associateddeglutition muscles54. Although specific examples for the first, second, andthird nerves52a-52chave been provided, it should be understood that thenerves52 are any of the nerves (including nerve branches, nerve roots, nerve rootlets, etc.) that stimulate musculature associated with deglutition (motor function) and/or carry sensory signals (sensory function). For example, thenerves52 are selected from one or more of a vagus, hypoglossal, mylohyoid, glossopharyngeus, laryngeal, superior laryngeal, recurrent laryngeal, facial, C1 trigeminal, mandibular, inferior alveolar, and cervical nerves, including the ansa cervicalis, and other nerves.
• With reference betweenFIG. 5A,FIG. 5B, andFIG. 8, and as previously referenced, thedeglutition muscles54 cause movements corresponding to various stages of deglutition. For referenceFIG. 5B represents several of thedeglutition muscles54 according to associated directions they move thehyolaryngeal complex64. Thedeglutition muscles54 are generally any of the plurality of muscles causing movements associated with components of deglutition, including muscles associated with any one or more of the oral, pharyngeal, and esophageal stages of deglutition. For illustrative purposes, afirst muscle54a, asecond muscle54b, athird muscle54c, afourth muscle54d, afifth muscle54e, asixth muscle54f, aseventh muscle54ganeighth muscle54h, and aninth muscle54iare described. In particular, themuscles54a-54iare mylohyoid, geniohyoid, thyrohyoid, anterior belly of a digastric, hyoglossus, stylohyoid, genioglossus, sternohyoid, and sternothyroid, respectively.
• Though specific ones of thedeglutition muscles54 are listed above, it should be understood that thedeglutition muscles54 also include any one or more of the muscles or muscle groupings selected from the following, non-exclusive list: muscles supporting the larynx and hyoid bone; intrinsic laryngeal muscles, extrinsic laryngeal muscles, posterior intrinsic muscles of the tongue, hyoglossus, genioglossus, thyrohyoid, constrictor pharyngis superior, constrictor pharyngis medius, constrictor pharyngis inferior, cricopharyngeus (UES), digastricus, cricoarytenoid lateralis, geniohyoid, levator veli palatini, mylohyoid, omohyoid, palatoglossus, palatopharyngeus, sternohyoid, sternothyroid, styloglossus, stylohyoid, stylopharyngeus, tensor veli palatine, thyroarytenoid inferior, thyroarytenoid superior, and others. For reference, where a bilateral pair of muscles is implicated, the term “a single deglutition muscle,” for example, is indicative of a unilateral one of such a bilateral muscle pair.
• Thedeglutition structures56 are formed of bone, cartilaginous matter, tissue, muscles (including one or more of the deglutition muscles54), and/or other materials. In general terms, thedeglutition structures56 include the UES, the epiglottis, the hyoid, and other components of the larynx and/or the pharynx, for example, as well as other deglutition structures.
• With reference to the schematic view ofFIG. 5A, thedeglutition structures56 include a hyolaryngeal complex64, components of which are also presented inFIG. 5B. As used herein, the term “hyolaryngeal complex” refers to a deglutition structure of the neck including the larynx, the hyoid, and associated deglutition muscles. With reference toFIG. 5A, the hyolaryngeal complex64 includes a hyoid70, anepiglottis72, aUES76, and lowerlaryngeal cartilages78 defining a vestibule80. The hyolaryngeal complex64 defines a rostrocaudal axis H_RCand an anterior-posterior axis H_AP. For reference, and in general terms, the pharynx P (designated generally in the indicated direction) extends to the hyolaryngeal complex64, where respiratory and digestive pathways diverge. This divergence is characterized by the pharynx P communicating with an esophagus E (designated generally in the indicated direction) posteriorly, where theUES76 closes off the esophagus E from the pharynx P during breathing. Typically, the esophagus E conducts food and fluids to the stomach as previously described. In turn, air entering from the pharynx P proceeds anteriorly through thelaryngeal vestibule80 to a trachea T (designated generally in the indicated direction) during breathing.
• With reference betweenFIG. 5A andFIG. 5B, during swallowing, thelaryngeal vestibule80 is closed off while material is transported posteriorly into the esophagus E. In particular, during a normal swallow, the hyolaryngeal complex64 is lifted forward and upward. Theepiglottis72 folds down to close off thelaryngeal vestibule80. This movement helps trigger relaxation of theUES76 such that food or liquid can pass into the esophagus E.
• In a properly functioning swallow, the various movements are involuntarily coordinated to avoid substantial aspiration of a bolus of liquid or solid matter. However, in cases of dysphagia, such deglutition movement is improperly timed and/or insufficient. For example, the hyolaryngeal complex64 moves an insufficient amount upward and forward, theepiglottis72 does not fold down sufficiently, and/or theUES76 does not sufficiently relax in some cases of dysphagia, such that aspiration during deglutition results. As described below, the system20 (FIG. 1) is usable to assist deglutition and, in particular, reduce or substantially eliminate aspiration during swallowing in dysphagia sufferers.
• In view of the above overview of deglutition and dysphagia, various embodiments of the following are described: implantation of thesystem20; various stimulation programs carried out by thesystem20 and their features; stimulation of a single deglutition muscle and select muscle groups to artificially stimulate deglutition with thesystem20; muscle activation patterns and corresponding stimulation patterns for stimulating deglutition muscles; provision of user feedback in order to facilitate timing of user initiated deglutition movement, for example; stimulation of deglutition musculature with thesystem20 via associated nerves; and system feedback for controlling artificial deglutition stimulation with thesystem20, for example by modifying a stimulation program or programs.
Implantation of Deglutition Assistance Systems
• With reference betweenFIG. 1,FIG. 5A,FIG. 5B, andFIG. 6, various embodiment methods of implanting thesystem20 are described. For additional reference, various ancillary procedures, for example, suturing incisions, irrigating surgical sites, applying prophylactic antibiotics, or checking bodily homeostasis, are clearly contemplated, but left from further discussion. In terms of use and configuration, thesystem20 is optionally adapted to be portable and subcutaneously implanted and/or otherwise born by auser90 of thesystem20 for sustained periods of time in some embodiments.
• With that in mind, and with particular reference toFIG. 6, implantation of thesystem20 generally includes disposing thecontroller22, thesignal generator24, and thepower source30 in theimplantable housing32 as a single unit. One or more external devices, such as ahand switch116, are optionally connected to thecontroller22 or are otherwise in communication therewith for user-controlled deglutition stimulation, as will be described in greater detail below. A first incision is made to define asubcutaneous pocket92 in theupper chest94 and beneath theclavicle96 of theuser90 of thesystem20. Thesubcutaneous pocket92 is sized, shaped, and otherwise formed to maintain theimplantable housing32. Theimplantable housing32 is then disposed in thesubcutaneous pocket92. Alternatively, in some embodiments, thecontroller22,signal generator24, and/orpower source30 are optionally left external to theuser90, for example where theelectrode array26 includes self-contained electrodes, for example similar to embodiments of the self-containedelectrode48 previously described.
• A second incision, for example a modified apron incision with standard superior and inferior subplatysmal flaps, is formed in aneck98 of theuser90 at about a thyrohyoid-membrane level100 of theneck98. The first and second incisions are connected by forming a first tunnel between the two incisions. The tunnel generally courses under the skin between the first and second incisions over themanubrium102 of theuser90.
• In some embodiments, theelectrode array26 includes a firstelectrical lead104aand a secondelectrical lead104b, each lead104a,104badapted to form an electrical connection between theelectrode array26 and thesignal generator24. For example, where bilateral muscle stimulation is desired, the secondelectrical lead104bis optionally subcutaneously disposed on an opposite side of theneck98 to the firstelectrical lead104a, with corresponding electrodes of theelectrode array26 also subcutaneously positioned in an opposing manner in theneck98. As referenced above, theelectrical leads104a,104bare optionally substantially similar to those provided for in the Extensible Lead Applications.
• Regardless, theelectrical leads104a,104beach definefirst end regions106a,106bandsecond end regions108a,108b, respectively. Thefirst end region106aof the firstelectrical lead104ais fed through the first tunnel to thesubcutaneous pocket92. In some embodiments, a third incision substantially similar to the second incision is formed on an opposite side of the neck. A second tunnel is optionally subcutaneously formed from the third incision to the first tunnel, or directly from the third incision to thesubcutaneous pocket92 formed via the first incision, though a variety of manners of subcutaneously positioning theelectrical leads104a,104bare contemplated. Regardless, thefirst end region106bof the secondelectrical lead104bis optionally fed through the second tunnel to thesubcutaneous pocket92.
• In some embodiments, theelectrical leads104a,104beach branch out proximate thesecond end regions108a,108b(branching of the secondelectrical lead108bis hidden in the view ofFIG. 6), such as branching point BP of the firstelectrical lead104a. One or more of the points where each of thesecond end regions108a,108bbranch out are optionally placed anterior to the sternocleidomastoid muscles of theuser90, although other positions are also contemplated.
• Although, as referenced above,FIG. 6 is indicative of bilateral implantation of theelectrode array26 in theneck98 of theuser90, unilateral implantation is also contemplated, for example using only the firstelectrical lead104a. In general terms, bilateral implantation is used to facilitate stimulation of bilateral deglutition musculature although other scenarios are contemplated for bilateral implantation. One or more of thedeglutition muscles54 are identified, such as the thyrohyoid, the hyoglossus, the mylohyoid, and the geniohyoid, and/or anyother deglutition muscles54. Additionally, or alternatively, one or more of thenerves52 controlling the deglutition muscles54 (motor function) and/ornerves54 providing sensory functionality are identified. For example, in some embodiments, visual confirmation and/or neurostimulation is used to identify the deglutition muscle(s)54 and/or nerve(s)52 of interest.
• Following identification of the nerve(s)52 and/or deglutition muscle(s)54, one or more electrodes of theelectrode array26, for example theelectrodes26a-26c, are placed in stimulating communication with the selected deglutition muscle(s)54, either directly or via the nerve(s)52 related to or otherwise controlling the selected muscle(s)54. Theelectrode array26 is optionally secured in place using a suture, surgical clamp, or other means as appropriate. In some embodiments, placing theelectrode array26 in stimulating communication with deglutition muscle(s)54 includes: fixing one or more electrodes of theelectrode array26 to a surface of a one or more of thedeglutition muscles54; inserting one or more electrodes into one ormore deglutition muscles54; and/or placing one or more electrodes in stimulating communication with one or more of thenerves52 causing activation of one or more of the selected deglutition muscle(s)54.
• At some point, the second ends108a,108bof theelectrical leads104a,104bare secured to theimplantable housing32 and placed in communication with thesignal generator24. In turn, the first ends106a,106bof theelectrical leads104a,104bare connected to electrodes of theelectrode array26. It should be noted that in some embodiments, electrodes of theelectrode array26 can also serve sensing functionality, for example serving as a sensor in thesensor array28. Also of note, thesensor array28 is optionally implanted with substantially similar techniques to those used in association with theelectrode array26. To provide additional understanding, some embodiment methods of implanting thesensor array28 are described below in association with thesensors28a-28c.
• In particular, a fourth incision is optionally made at a chin bone, and more specifically themental protuberance110 of the mandible of theuser90. Thefirst sensor28ais subcutaneously affixed to themental protuberance110, for example with an adhesive, suture, bone anchor, or other means. Thefirst sensor28ais optionally connected to one of the first and secondelectrical leads104a,104b. In other embodiments, thefirst sensor28ais connected to a thirdelectrical lead112, such as a flexible, extensible electrical lead, coursing over themanubrium102 in a substantially similar manner to the first and secondelectrical leads104a,104b.
• With reference betweenFIG. 5A,FIG. 5B, andFIG. 6, thesecond sensor28bis optionally inserted through the second or third incision for example, or a fifth incision is optionally made in theneck98 of theuser90 with thesensor28bsubcutaneously positioned through the fifth incision. Thesecond sensor28bis optionally secured to adeglutition structure56, such as the hyolaryngeal complex64, for example. In some embodiments, thesecond sensor28bis secured relative to thehyoid bone70, theepiglottis72, or any laryngeal cartilages, including a thyroid cartilage, a cricoid cartilage, an arytenoid cartilage, a cuneiform cartilage, and/or a corniculate cartilage, for example. Additionally, or alternatively, thesecond sensor28bis optionally secured relative to theUES76.
• In some embodiments, thesecond sensor28bis oriented substantially parallel to the rostro-caudal axis H_RCand anterior-posterior axis H_APof the hyolaryngeal complex64 or a particular component thereof. Where applicable, thesecond sensor28bis connected to an electrical lead, for example thesecond sensor28bis optionally connected to firstelectrical lead104a. From this, it should be understood that theelectrical leads104a,104boptionally serve multiple purposes, including, for example, conveying stimulating energy to theelectrode array26 along with conveying power to and/or conveying sensor information from thesensor array28.
• With particular reference toFIG. 6, in some embodiments, thethird sensor28cis secured relative to theimplantable housing32 of thesystem20. For example thethird sensor28cis optionally implanted prior to, concurrently with, or following, implantation of thehousing32. In some embodiments thethird sensor28cis secured on theimplantable housing32 or otherwise secured such that thethird sensor28cis at a substantially set distance from theimplantable housing32 and in communication with thecontroller22 and/or thesignal generator24.
• Following implantation of thesystem20, various testing and/or optimization of thesystem20 is performed as desired. In some embodiments, thesystem20 performs a self-configuration operation by stimulating user deglutition using theelectrode array26 and receiving information from thesensor array28 to optimize deglutition stimulation as described in greater detail below. Following evaluation of the sensor array information, thesystem20 modifies a system configuration, for example by changing a stimulation program, to better control user deglutition. In other embodiments, thesystem20 is manually configured by a technician or other appropriate personnel. Implantation information regarding implantation of thesystem20 is also optionally recorded. For example information relating to electrode type/placement, sensor type/placement, system testing results, and/or other pertinent information is optionally stored remotely or directly in memory associated with thesystem20.
Stimulation Program Initiation and Selection
• With reference toFIG. 1, following implantation, thesystem20 is used to stimulate a component of user deglutition, according to one or more stimulation programs. In particular, thesystem20 is adapted for stimulating multiple deglutition responses in the user90 (FIG. 6) in order to assist one or more components of user deglutition without substantial aspiration. As referenced above, thesystem20 optionally stimulates one or more components of user deglutition as part of a method of configuring thesystem20, as part of a therapeutic method for teaching theuser90 how to swallow, and/or as part of a method of sustained assistance over an extended period of time, for example.
• Thesystem20 generally activates one or more of thedeglutition muscles54 according to one or more stimulation programs. For example, thecontroller22 optionally stores one or more stimulation programs and operates thesignal generator24 according to the desired deglutition program to send stimulating energy to theelectrode array26 for activating the one ormore deglutition muscles54. In some embodiments, the stimulation programs include an active feeding program for stimulating deglutition of at least one of food and drink without substantial aspiration and a passive user secretion maintenance program for stimulating deglutition of user secretions without substantial aspiration. The active feeding program is optionally further divided into specific bolus deglutition program categories according to a bolus characteristic, for example a specialized liquid deglutition program and a specialized solid deglutition program, specialized deglutition programs optimized according to bolus volume or consistency, as well as others, as desired.
• Initiation of the active feeding program is optionally under “user control.” In particular, the active feeding program, including any specialized deglutition programs, is optionally initiated in response to a user feeding request prompt, for example via an external hand-held switch sensor, such as ahand switch116 as shown generally inFIG. 6, or via voice command, motion sensor, or one or more of the sensors of thesensor array28, either “wired” or otherwise in communication withsystem20 as described above, for example via radio frequency communication. Thus, in some embodiments, the user is able to provide thesystem20 with a feeding request prompt in order to initiate the active feed program.
• In some embodiments, theuser90 is able to initiate the active feeding program and sustain deglutition muscle stimulation with thesystem20 for a desired period or duration, for example by holding down thehand switch116 for the desired duration of stimulation. Additionally, stimulation intensity is optionally the subject of user control, for example according to a degree of depression of thehand switch116 or other sensor. It is also contemplated that a safety override be provided, wherein after a preset time period of substantially continuous deglutition stimulation, for example twenty seconds, or after a certain amount of stimulating energy has been delivered, for example as measured in joules, thesystem20 automatically interrupts further stimulation. Although some embodiments include user-controlled initiation of the active feeding program, it should also be understood that thesystem20 optionally automatically senses when a user is eating or desires to swallow, for example using one or more sensors of thesensor array28. Also, in some embodiments, theuser90 provides user input, for example using a hand switch, as to what type of bolus and/or corresponding deglutition program should be run by thesystem20.
• As alluded to above, the active feeding program is optionally optimized for liquid or solid bolus consumption, consumption of boluses having different bolus volumes, or consumption of boluses having different bolus consistencies, for example, via provision of specialized programs. As will be described, stimulation according to such specialized programs is optionally modeled to exhibit a deglutition response characteristic of “normal” liquid-like or solid-like deglutition according to such conditions, e.g., deglutition of a liquid by a person not suffering from dysphagia.
• In some embodiments, the user secretion maintenance program operates passively, or as a background program. In particular, the user secretion maintenance program is adapted to automatically, periodically stimulate deglutition of user secretions, such as saliva or mucous. There is evidence that an average adult produces between about 500 ml and about 1500 ml of saliva each day. Providing an automatic maintenance program facilitates disposing such user secretions without theuser90 substantially aspirating those secretions. Periodicity, i.e., the timing between deglutition sequences initiated according to the user secretion maintenance program, is optionally determined via observation of a particular individual, for example an average time that a human or other animal exhibits between secretion deglutition, or periodically stimulates deglutition as otherwise selected. The user secretion maintenance program can also be operated as part of a “night mode” operation setting of thesystem20. For example, the user secretion maintenance program optionally starts and ends during a particular period, such as from 10 p.m. to 6 a.m., when theuser90 is in a substantially reclined position or state, or according to other criteria, for example. The user secretion maintenance program optionally operates continuously in the background until the active feeding program is initiated. As previously alluded to, the user secretion maintenance program includes stimulation patterns optimized for muscle activation associated with secretion deglutition in some embodiments.
Single Muscle Stimulation and Select Muscle Group Stimulation
• With reference toFIG. 1,FIG. 5A, andFIG. 5B, while various embodiments include using a plurality of thedeglutition muscles54 to stimulate user deglutition, in some embodiments, thesystem20 is adapted to stimulate one or more components of user deglutition using only a single one of thedeglutition muscles54 throughout a complete swallowing act. In particular, theelectrode array26 is placed in stimulating communication with a single one of thedeglutition muscles54. The single deglutition muscle is activated by placing one or more electrodes in contact with the single muscle, for example, although the single deglutition muscle can also be directly stimulated via one or more nerves controlling the single muscle, with one or more electrodes placed in stimulating communication with the single deglutition muscle via one or more of thenerves52 to stimulate that single muscle.
• Thus, in some embodiments a single deglutition muscle is artificially stimulated with thesystem20 according to a stimulation program to cause a desired component of a complete deglutition act to occur. Although the single deglutition muscle is the only one of thedeglutition muscles54 directly targeted from stimulation via theelectrode array26 during the complete deglutition act, it is contemplated that some stimulating energy might inadvertently or otherwise indirectly delivered to other ones of thedeglutition muscles54, for example by current bleed or current being transmitted through the single deglutition muscle.
• With reference toFIG. 5B in particular, and as alluded to above, some types of dysphagia aspiration arise as a result of an inability to activate lifting of the hyolaryngeal complex64 to a sufficient degree and/or with appropriate timing, as well as an inability to sufficiently relax the UES76 (FIG. 5A). Indeed, there is evidence that a substantial portion of dysphagia-related aspiration arises as a result of such defects in deglutition. In some embodiments, the hyolaryngeal complex64 is sufficiently lifted by directly stimulating a single one of thehyoglossus54e, the posterior belly of the digastric54d, or the stylohyoid54f, each of those muscles being generally represented inFIG. 5B according to a direction of movement therespective deglutition muscle54 exerts hyolaryngeal complex64. Thus, with reference toFIG. 5B and the foregoing, associated description, the method of stimulating a single muscle is particularly advantageous in some embodiments where theuser90 is characterized as being capable of autonomously stretching the UES76 a sufficient amount in combination with the lifting and/or forward motion of the hyolaryngeal complex64 provided by single deglutition muscle stimulation using the system20 (FIG. 1). In some embodiments, a presence of sufficient, autonomous UES stretching, movement, and/or opening force is determined using the sensor array28 (FIG. 1), as subsequently described.
• With reference toFIGS. 5A and 5B, in some other embodiments, the system20 (FIG. 1) is adapted to stimulate one or more components of user deglutition using a plurality of thedeglutition muscles54, such as one or more of those specifically described. Thesystem20 can operate to engender synergistic muscle movement or otherwise produce synergistic laryngeal elevation and opening of the upper esophageal sphincter using the plurality ofdeglutition muscles54. The PCT App. Pub. WO 2004/028433 to inventors Ludlow et al. and entitled “Methods and Devices for Intramuscular Stimulation of Upper Airway and Swallowing Muscle Groups” (published Apr. 8, 2004) describes some systems and methods for producing synergistic laryngeal elevation and opening of the UES, the contents of which are incorporated herein by reference.
• In some embodiments, thesystem20 is further adapted to stimulate a targeted group of thedeglutition muscles54 including the mylohyoid, the geniohyoid, and the thyrohyoid in addition to at least one of the anterior belly of the digastric and the hyoglossus of theuser90. By stimulating the mylohyoid, the geniohyoid, and the thyrohyoid in addition to one or both of the anterior belly of digastric and the hyoglossus, it is believed thesystem20 can artificially induce completed deglutition with the targeted group without any other artificial intervention.
Muscle Activation Patterns and Stimulation Patterns
• With reference toFIG. 7 several muscle activation patterns are shown. In particular, according to some EMG studies of muscle activation during deglutition, natural muscle activation occurs over a series of sequential, overlapping patterns.FIG. 7 is illustrative of EMG measurements of muscle activation patterns in areas of a mouth, pharynx, and larynx in each of monkey, cat, and dog during deglutition as described in R. W. Doty & J. F. Bosma,An electromyographic analysis of reflex deglutition,19 J. NEUROPHYSIOLOGY44-60 (1956), the contents of which are incorporated herein by reference.
• A “leading complex” of muscle activation patterns includesmylohyoid activation pattern150,geniohyoid activation pattern152, posterior intrinsic tonguemuscles activation pattern154,palatopharyngeus activation pattern156, and superiorconstrictor activation pattern158. Also included are activation patterns of the palatoglossus, styloglossus, and stylohyoid (not shown) as part of the “leading complex.” The leading complex activation patterns initiate deglutition, showing concurrent elevated muscle activity for between about 250 milliseconds and about 500 milliseconds.
• Other delayed muscle activation patterns show inhibited onset of elevated muscle activity, including thyrohyoidmuscle activation pattern160,thyroarytenoid activation pattern162, middleconstrictor activation pattern164,cricothyroid activation pattern166, inferiorconstrictor activation pattern168, anddiaphragm activation pattern170. In fact, the inferiorconstrictor activation pattern168 shows deferred muscle activation until elevated muscle activity of the leading complex is nearly over. Several of the leading complex and delayed activation patterns exhibit features such as baseline activation, decreased transient activation, increasing activation ramping, and/or decreasing activation ramping. For example, themylohyoid activation pattern150 showsbaseline activation segments180a,180b, decreasedtransient activation segments182a,182b, an increasingramp segment184, a decreasingactivation ramp186, and anelevated activation segment188.
• In some embodiments a stimulation program or programs are determined or set according to activation patterns, such as those described above, including activation of a leading muscle complex and delayed activation patterns for other deglutition muscles as desired. In order to obtain one or more activation patterns for the deglutition muscle(s)54, averaged natural deglutition muscle stimulation patterns are optionally determined from a test group such as a group of healthy, dysphagia-free test subjects. The stimulation program then sets or drives deglutition muscle stimulation to imitate the averaged natural deglutition muscle activation patterns. In some embodiments, individual natural deglutition muscle stimulation patterns for a particular individual are measured or calculated to determine a customized activation pattern. In some embodiments, the stimulation program then sets or drives deglutition muscle stimulation to the customized pattern. In other embodiments, theoretical natural deglutition muscle stimulation patterns are derived from empirical data, qualitative observation, user feedback, measurement of actual bolus deglutition with various applied stimulation patterns, and/or via other means. Such theoretical and/or iterative evaluation techniques may be particularly advantageous where theuser90 is a sufferer of dysphagia and appropriate natural deglutition stimulation patterns are not directly measurable from theuser90.
• Furthermore, particular categories of deglutition are optionally measured or modeled, for example liquid deglutition, solid deglutition, and/or user secretion deglutition. In at least this manner, specialized feeding programs, such as a specialized liquid or solid deglutition programs, user secretion maintenance programs, or even changes in deglutition according to body position or environment, for example when theuser90 is in a reclined position, is at high altitude, is under water, and others, are optionally identified by measuring or modeling deglutition muscle activation when theuser90 or test group is swallowing such boluses and/or is in the states described.
• With reference betweenFIGS. 1 and 7, in some embodiments, thesystem20 uses one or more of the stimulation programs to stimulate a plurality of thedeglutition muscles54 to imitate natural deglutition muscle activation patterns. For example, some embodiments include using thesignal generator24 to cause theelectrode array26 to stimulate thedeglutition muscles54 with a group of sequential and overlapping electrical pulse trains in order to activate thedeglutition muscles54 similarly to sequential, overlapping patterns of muscle activation, such as those illustrated inFIG. 7. In some embodiments, the group of sequential and overlapping electrical pulse trains includes at least one asymmetric, biphasic waveform.
• Thus, in some embodiments, the stimulating electrical pulse trains themselves imitate the muscle activation patterns, or have somewhat similar amplitude and timing to the muscle activation patterns. In other embodiments, regardless of whether electrical pulses delivered by thesystem20 are delivered to the deglutition muscles54 (FIG. 5A) as sequential and overlapping pulses, the stimulating energy pattern delivered by theelectrode array26 is configured such that resultant activation patterns of the plurality ofdeglutition muscles54 imitate or are similar to a desired set of activation patterns. Furthermore, analogously to the muscle activation patterns described above, thesystem20 optionally delivers one or more electrical pulses defining one or more stimulation pattern features, such as baseline segments, decreased transient segments, increasing ramps, decreasing ramps and/or others, such features imitating corresponding muscle activation pattern features, or others.
• In some embodiments, baseline segments are included in the stimulation patterns or baseline activation segments are otherwise simulated to adjust muscle tension before triggering a component of deglutition associated with aparticular deglutition muscle54. In some embodiments, baseline segments in a stimulation program optionally serve to place deglutition musculature of theuser90 in a state of partial activation prior to at least one of activation of the partially activated deglutition musculature via autonomous user stimulation and artificial activation of the partially activated musculature via thesystem20. As evidenced byFIG. 7, many of thedeglutition muscles54 exhibit baseline activity prior to full muscle activation. Incorporating a baseline stimulation segment in the stimulation program pattern for a deglutition muscle can serve various roles, including, for example, adjusting muscle slack and hyolaryngeal position in preparation for deglutition and/or providing proprioceptive and tactile user feedback to a central nervous system of theuser90.
• FIG. 7 also evidences that many of the deglutition muscles54 (FIG. 5A) exhibit decreased transient activity before and/or after full muscle activation. In some embodiments, decreased transient segments are also present in stimulation program patterns or decreased transient activation is otherwise simulated. In some embodiments, decreased transient activation serves to inhibit baseline activation activity as described above, with such inhibition occurring just prior to and/or following full activation of one or more of thedeglutition muscles54.
• User Feedback and Deglutition Timing with Artificial Deglutition Stimulation
• With reference toFIGS. 1 and 5, in some embodiments, user feedback helps theuser90 time autonomous deglutition efforts with the artificial stimulation provided by thesystem20. In particular, some embodiments include theuser90 autonomously providing some of the movement required for deglutition in response to the user feedback, with thesystem20 also providing stimulation for remaining deglutition movement to help prevent aspiration as desired. For example, theuser90 is optionally provided with a subthreshold, baseline signal prior to user deglutition, such as the baseline signals described above, which provides proprioceptive user feedback. In turn, artificial stimulation of deglutition musculature with thesystem20 is coordinated with the user feedback, for example at a desired timing or delay between initiation of the baseline signal and initiation of a stimulating signal by thesystem20. Additionally, or alternatively, the user feedback optionally can also serve to help “retrain” theuser90 how to swallow, such that the user feedback is part of a therapeutic program.
• In some embodiments user feedback is additionally or alternatively provided by stimulating sensory mucosa (not shown) of at least one of the mouth and throat of theuser90, such as sensory mucosa associated with the hyolaryngeal complex64 and/or pharynx P to provide tactile, sensory feedback to theuser90. In particular, one or more electrodes of theelectrode array26 are placed in stimulating communication with sensory mucosa of the hyolaryngeal complex64 or the pharynx P, for example. During artificial deglutition stimulation, thesystem20 stimulates the sensory mucosa to provide tactile user feedback as desired. It should be understood that it is contemplated that any sensory mucosa of thedeglutition components50 could be stimulated to provide user feedback. Also, as described above, other embodiments alternatively or additionally include using subthreshold, baseline or other low-level muscle stimulation signal with theelectrode array26 to provide proprioceptive feedback. In some embodiments, sensory feedback is provided by placing one or more electrodes in direct stimulating communication with one or more of thenerves52.
Artificial Deglutition Muscle Stimulation Via Nerves
• As referenced above, while thesystem20 is optionally adapted to deliver stimulating energy to one or more of thedeglutition muscles54 by placing contacts of theelectrode array26 in or on deglutition musculature, some embodiments also include stimulating one ormore deglutition muscles54 via thenerves52 as will be described with reference betweenFIG. 1,FIG. 5A, andFIG. 8. For example, the various stimulation programs and/or muscle activation patterns described above are optionally delivered via stimulation of deglutition musculature by stimulating thenerves52 with theelectrode array26 or by stimulating thedeglutition muscles54 using electrodes implanted on (epimysial electrodes) or in (intramuscular electrodes) thedeglutition muscles54, for example. With that in mind, some embodiments including artificial deglutition muscle stimulation via thenerves52 are described in greater below.
• With particular reference toFIG. 8, a schematic illustration of theelectrode array26 placed in stimulating communication with the first andsecond nerves52a,52bis shown. For reference,FIG. 8 illustratesvarious deglutition components50 previously described, and also presents a schematic view of atooth200 and atongue210 of theuser90. In some embodiments thefirst electrode26aof theelectrode array26 is adapted for stimulating nerves, for example being substantially similar to embodiments of the nerve cuff electrode40 (FIG. 3) previously described. Thesecond electrode26bis similarly configured, also optionally being a nerve cuff electrode substantially similar to embodiments of thenerve cuff electrode40. For reference, one or both of the first andsecond nerves52a,52boptionally provide sensory and/or motor functionality, with deglutition muscle response occurring as a result of sensory stimulation or motor function stimulation.
• With additional reference toFIGS. 1 and 5, in some embodiments, thesystem20 is adapted for selectively stimulating nerve fascicles of thenerves52 in order to activate one or more of thedeglutition muscles54 to assist with any one or more of the stages of deglutition. For a discussion of selective muscle stimulation and acceptable electrode types see, for example, M. D. Tarler & J. T. Mortimer,Elective and independent activation of four motor fascicles using a four contact nerve-cuff electrode,12(2) IEEE TRANSACTIONS ONNEURALSYS. REHAB. ENG'G251-257 (2004); W. M. Grill & J. T. Mortimer,Inversion of the current-distance relationship by transient depolarization, IEEE TRANSACTIONS ONBIOMEDICALENG'G1-9 (1997); U.S. Pat. No. 5,344,438 (issued Sep. 6, 1994) (inventors Testerman et al.) (entitled, “Cuff Electrode”); and U.S. Pat. No. 6,907,293 (issued Jun. 14, 2005) (inventors Grill et al.) (entitled, “Systems and Methods for Selectively Stimulating Components in, on, or near the Pudendal Nerve or Its Branches to Achieve Selective Physiologic Responses”), the contents of each of which are incorporated herein by reference. In general terms, selective stimulation can be advantageous where non-selective stimulation of one or more of thenerves52 would result in improper timing or interfere with other stages of swallowing. For example, stimulation of the hypoglossal nerve without selective fascicle stimulation could result in early activation of the styloglossus and the intrinsic muscles of the tongue, which would otherwise interfere with the oral stage of swallowing.
• Regardless, in some embodiments, each of the first andsecond electrodes26a,26bis adapted to allow selective stimulation of nerves and is placed in stimulating communication with one of thenerves52, and thus one or more of thedeglutition muscles54. In some embodiments, thefirst electrode26ais disposed about thefirst nerve52a, which is the hypoglossal nerve, for example. In turn, thesecond electrode26bis disposed about thesecond nerve52b, which is the mylohyoid nerve, for example. In particular, thefirst electrode26ais located on thefirst nerve52ato deliver stimulating energy to thenerve fascicles60 offirst nerve52afor stimulating or otherwise causing activation of one or more of the geniohyoid, hyoglossus, thyrohyoid, omohyoid, sternothyroid, sternohyoid, genioglossus, and styloglossus muscles. In turn, thesecond electrode26bis located on thesecond nerve52bto deliver stimulating energy to thenerve fascicles62 of thesecond nerve52bfor stimulating or otherwise causing activation of one or more of the mylohyoid and a digastric muscle, for example. In particular, some embodiments include selectively stimulating activation of one or more of the hyoglossus, geniohyoid, and thyrohyoid muscles by selectively stimulating fascicles of thefirst nerve52aand selectively stimulating activation of one or more of the mylohyoid and anterior belly of the digastric muscles by selectively stimulating fascicles of thesecond nerve52b.
• In some embodiments where bilateral stimulation desired, the third andfourth electrodes26c,26dare placed on an opposite side of theuser90 in communication with second hypoglossal and mylohyoid nerves opposite the first andsecond nerves52a,52b, for example. The third andfourth electrodes26c,26dare optionally substantially similar in form and operation to the first andsecond electrodes26a,26b, and thus are left from further discussion.
• Regardless, where selective stimulation is appropriate, thecontroller22 is adapted to operate thesignal generator24 to selectively stimulate one or more fascicles of thenerves52 with theelectrode array26, such as thefascicles60 of thefirst nerve52aand/or thefascicles62 of thesecond nerve52b. Some embodiments include selectively stimulating thefirst fascicle60aof thefirst nerve52a, selectively stimulating thesecond fascicle60bof thefirst nerve52a, and selectively stimulating thethird fascicle60cof thefirst nerve52a, where each of the first, second, andthird fascicles60a-60ccontrol activation of a different deglutition muscle than the others. Similarly, embodiments include selectively stimulating thefirst fascicle62aof thesecond nerve52band selectively stimulating thesecond fascicle62bof thesecond nerve52b, thefirst fascicle62acontrolling activation of a different deglutition muscle than thesecond fascicle62b, and so forth.
• In order to accomplish selective fascicle stimulation, some embodiments include using thesignal generator24 to deliver subthreshold, rectangular current pulses, or current ramps to partially depolarize nerve fibers of the first and/orsecond nerves52a,52busing the first and/orsecond electrodes26a,26b. As used herein, the term “subthreshold” is indicative of an insufficient amount of stimulation to result in full muscle activation. Additionally, for reference, and in brief, stimulation of thenerves52 is generally characterized by a strength-to-distance relationship, where fascicles closer to a source of stimulating energy, for example an electrical current pulse delivered from theelectrode array26, are stimulated first and/or to a greater extent. By using subthreshold, rectangular current pulses or ramps, the strength-to-distance relationship is optionally inverted, such that fascicles can be selectively stimulated by partially depolarizing a corresponding nerve. In other words, thesystem20 can be configured to selectively stimulate a fascicle or group of fascicles more distant from the stimulating electrode than a closer group of fascicles, and prior to the closer group of fascicles, by depolarizing the nerve.
• Additionally or alternatively, the strength-to-distance relationship described above is taken advantage of in some embodiments by placing electrode contacts at various positions on or around one or more of thenerves52. By delivering a standard current pulse, for example a 100-μs rectangular current pulse, to a particular location on the one ormore nerves52, nerve fascicles closest to a particular contact are stimulated first or to a sufficient degree to result in muscle activation of one or more of thedeglutition muscles54. Thus, selectivity is also optionally accomplished by placing contacts at various locations about a nerve more proximate a fascicle group that is to be stimulated.
• As yet another, non-exclusive means for accomplishing selective fascicle stimulation, current steering techniques are optionally employed. In some embodiments, the first andsecond electrodes26a,26bare substantially similar to embodiments of the nerve cuff electrode40 (FIG. 3) previously described, with each of the first andsecond electrodes26a,26bincluding a plurality of radially positioned monopolar contacts, for example four monopolar contacts per electrode, although bipolar contacts are contemplated in some embodiments. Thesignal generator24 is configured to operate over multiple channels to deliver varying amounts of stimulating energy to each of the radially positioned contacts. In particular, subthreshold steering currents are applied about the nerve, for example thefirst nerve52a, at different amplitudes in order to shape an electrical field applied to the nerve as desired. The subthreshold steering currents do not necessarily result in nerve stimulation. In particular, in some embodiments, the steering currents are applied about one of thenerves52, for example thefirst nerve52a, to direct another, stimulus pulse or series of pulses generated with thefirst electrode26aor another electrode to a desired region of nerve activation. In other words, the steering currents are used to direct an additional stimulating current pulse or pulses to a selected fascicle or group of fascicles.
• Additionally, stimulation pattern waveforms are optionally selected to improve an ability to selectively stimulate nerve fascicles of thenerves52. For example, short duration current pulses have been identified as increasing stimulation threshold differences between nerve fibers of different diameters. While several mechanisms for accomplishing selective fascicle excitation/stimulation have been described above, it should be understood that other mechanisms are also contemplated, including electrical blocking of nerves/nerve fascicles.
• In some other embodiments, the first andsecond electrodes26a,26bare located along thenerves52 at a location where selective stimulation of nerve fascicles in order to activate desired deglutition musculature is not required.
• In particular, the first andsecond electrodes26a,26bare optionally located along a nerve branch rather than a nerve trunk, for example a peripheral branch of the hypoglossal nerve, sufficiently proximate one or more of thedeglutition muscles54, such that a desired timing of activation of a desired set of thedeglutition muscles54 is accomplished without selectively stimulating nerve fascicles. Thus, theelectrode array26 additionally or alternatively includes a plurality of electrodes disposed along, and in stimulating communication with, a plurality of nerves in order to effectuate deglutition musculature stimulation without selective fascicle stimulation.
System Feedback
• With reference toFIGS. 1 and 6 and turning back to thesensor array28, in some embodiments, thesensor array28 provides thesystem20 means for operating with system feedback. For example, the stimulation programs described above are optionally initiated, modified, or otherwise adapted according to sensor input information received by thecontroller22. Various sensors and their use are described below. For example, in some embodiments, thesensor array28 includes sensors configured and placed, for example subcutaneously and/or intramuscularly, to provide EMG feedback to thesystem20. Such EMG feedback is optionally used to drive a stimulation program to a predetermined, optimal muscle activation pattern as measured via the EMG feedback.
• In some embodiments, thesensor array28 includes one or more force sensors, such as strain gauges, providing force information to thecontroller22. According to some applications, one or more of the strain gauges are attached to one ormore deglutition muscles54 to provide force information during various states of muscle activation. For example, in some embodiments, thefirst sensor28ais a strain gauge and is attached to theUES76 to provide information relating to an opening force applied to theUES76. Such force information is optionally used by thesystem20, and in particular thecontroller22, to optimize a stimulation program or otherwise provide system feedback information for modifying deglutition muscle stimulation.
• In still other embodiments, thesensor array28 includes one or more positional sensors, such as accelerometers providing such information as acceleration, velocity, or position. In some embodiments thefirst sensor28ais a three-axis accelerometer providing head position information and is optionally secured relative to the chin, for example themental protuberance110. With additional reference toFIG. 5A, thesecond sensor28b, in turn, is a three-axis accelerometer secured relative to one ormore deglutition components50, such as a portion of thehyolaryngeal complex64 of theuser90. For example, thesecond sensor28bis optionally secured relative to the hyoid70 or other laryngeal cartilage, such as the thyroid cartilage. In some embodiments, thesecond sensor28bis optionally oriented parallel to the anterior-posterior and rostro-caudal axes H_AP, H_ARof the laryngeal complex64 or components thereof. Still yet, thethird sensor28cis optionally a three-axis accelerometer secured relative to theimplantable housing32.
• In some embodiments, overall body position information of theuser90 is provided by thesensor array28, and in particular thethird sensor28c. Movement of the hyolaryngeal complex64 or components thereof relative to a torso of theuser90 is provided using combined positional information from the second andthird sensors28b,28c. This information relating to relative positions of the torso and hyolaryngeal complex64 can then be used to optimize deglutition stimulation with thesystem20 for a desired relative movement of thedeglutition structures54, such as the hyolaryngeal complex64 or portions thereof. In turn, neck flexion information is optionally provided using combined positional information from thesensor28asecured relative to the chin and thesecond sensor28bsecured relative to the laryngeal complex64 or portions thereof. In this manner, thesystem20 compensates for neck flexion during deglutition stimulation. Additionally or alternatively, in some embodiments, thesensor array28 provides information related to whether theuser90 is in a reclined state, for example in order to determine whether to select the user secretion maintenance program or to optimize swallowing for a reclined position.
• Although combined utilization of positional information is contemplated as referenced above, non-combined positional information from a single position sensor, such as a three-axis accelerometer is also optionally used to optimize or otherwise modify deglutition stimulation with thesystem20. In some embodiments, information relating to whether the hyolaryngeal complex64 is being adequately lifted and moved forward is obtained where a standard orientation of the body of theuser90 is assumed and an accelerometer, for example one of the three-axis accelerometers as previously referenced, is oriented parallel to the anterior-posterior and rostro-caudal axes H_AP, H_ARof the hyolaryngeal complex64 or components thereof, for example.
• In still other embodiments, thesensor array28 includes one or more pressure sensors, for example sensors for measuring intrapharyngeal pressure. For example, intrapharyngeal pressure is optionally measured as an indicator of effective deglutition stimulation and/or artificial response.
• With reference betweenFIG. 1,FIG. 5A, andFIG. 6, in some embodiments, thesensor array28 alternatively or additionally includes one or more displacement sensors providing displacement information, such as sonomicrometers (not shown) including ultrasonic sensing and generating crystals to measure distance between crystals. One or more of the first, second, andthird sensors28a-28care optionally sonomicrometers attached to one or more components of the hyolaryngeal complex64. In some embodiments, thesensors28a-28care used to provide displacement information relating to lengths of one or more of thedeglutition muscles54. In particular, displacement ofvarious deglutition structures56 can be derived, or otherwise estimated, using such overall muscle length information. Additionally or alternatively, such displacement sensors are used in a substantially similar manner to the positional sensors as described above in order to optimize or otherwise modify stimulation programs. For example, relative positions of the hyolaryngeal complex64, including the hyoid70, the chin, and/or the thyroid cartilage, are optionally provided by thesensor array28 to adjust deglutition stimulation. In some embodiments, a thyroid-hyoid gap is determined using the displacement sensors with stimulation of the thyrohyoid muscle applied proportionally to the thyroid-hyoid gap.
• In sum, and in accordance with the understanding provided by the textual descriptions, figures, and the accompanying claims, systems for assisting deglutition and methods for constructing and using systems for assisting deglutition have been disclosed, taught, and suggested, with such systems and methods serving a variety of purposes, such as helping provide deglutition with reduced aspiration. Such systems and methods of assisting deglutition have applicability for use with at least humans or other animals and are useful as either partially or entirely external or non-implanted systems, as well as entirely implanted or internal systems. Although the present invention has been described with reference to various embodiments, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the present invention. For example, although systems and methods associated with deglutition have been described herein, it should also be understood that principles of the present invention are applicable to other areas of muscle stimulation, for example speech, breathing, or other types of bodily movement.

Claims (27)

1. A method of stimulating user deglutition without substantial aspiration, the method comprising:

providing a portable system born by a user for controlling a component of a complete swallowing act, the system including a controller, a signal generator, and an electrode array including at least one electrode, the signal generator in communication with the electrode array;

subcutaneously positioning the electrode array in stimulating communication with deglutition musculature; and

artificially stimulating user deglutition via the signal generator and electrode array according to a passive user secretion maintenance program adapted to automatically, periodically stimulate deglutition of user secretions without substantial aspiration of the user secretions.

2. The method ofclaim 1, further comprising:

stimulating user deglutition according to an active feeding program adapted for stimulating deglutition of at least one of food and drink without substantial aspiration.

3. The method ofclaim 2, wherein the system further comprises a user input adapted to receive a feeding request prompt from a user, the method further comprising:

receiving a feeding request prompt at the user input; and

operating the signal generator according to the active feeding program in response to the feeding request information.

4. The method ofclaim 2, further comprising:

continuing to stimulate user deglutition according to the active feeding program for a duration selected by the user with the user input.

5. The method ofclaim 4, further comprising automatically interrupting continuous deglutition stimulation selected by the user after a predetermined period of time.

6. The method ofclaim 2, further comprising changing a stimulation intensity of the active feeding program to a user stimulation intensity desired by the user based upon information received from the user input.

7. The method ofclaim 1, further comprising:

automatically sensing that the user is in a substantially reclined position, wherein the portable system automatically operates according to the passive user secretion maintenance program in response to the user assuming the substantially reclined position.

8. A method of stimulating user deglutition without substantial aspiration, the method comprising:

providing a portable system born by a user for controlling a component of deglutition, the system including a controller, at least one stimulating electrode, and a signal generator;

subcutaneously positioning the at least one stimulating electrode in stimulating communication with deglutition musculature;

selecting a desired deglutition program from a plurality of specialized deglutition programs maintained by the controller based upon a characteristic of a bolus to be consumed by a user; and

operating the system according to the selected deglutition program.

9. The method ofclaim 8, wherein the bolus characteristic includes at least one of bolus volume and bolus consistency.

10. The method ofclaim 8, wherein the bolus characteristic includes whether the bolus is liquid-like or solid-like.

11. The method ofclaim 8, wherein one or more of the specialized deglutition programs include a group of pre-determined, sequential, and overlapping pulse trains.

12. The method ofclaim 11, wherein one or more of the group of pre-determined, sequential, and overlapping pulse trains includes a signal ramp at a beginning of the at least one pulse train.

13. The method ofclaim 11, wherein at least one of the group of pre-determined, sequential, and overlapping pulse trains includes at least one asymmetric, biphasic waveform.

14. A method of stimulating user deglutition without substantial aspiration, the method comprising:

providing a portable system born by a user for controlling at least a component of deglutition, the system including a controller, an electrode array, and a signal generator in communication with the electrode array;

subcutaneously positioning a first portion of the electrode array in stimulating communication with deglutition musculature;

subcutaneously positioning a second portion of the electrode array in stimulating communication with sensory mucosa of at least one of a mouth and a throat of the user;

stimulating the sensory mucosa with the electrode array to provide the user with tactile, sensory feedback; and

stimulating the deglutition musculature with the electrode array to cause user deglutition without substantial aspiration.

15. The method ofclaim 14, wherein the electrode array includes a first electrode and a second electrode, the first electrode being positioned in stimulating communication with the deglutition musculature and the second electrode being positioned in stimulating communication with sensory mucosa of the at least one of the mouth and the throat of the user.

16. A method of stimulating user deglutition without substantial aspiration, the method comprising:

providing a portable system born by a user for controlling at least a component of deglutition, the system including a controller, a signal generator, and an electrode array including at least one electrode;

subcutaneously positioning the electrode array in stimulating communication with deglutition musculature;

stimulating the deglutition musculature via the electrode array with a subthreshold, baseline signal prior to user deglutition; and

stimulating the deglutition musculature via the electrode array with a stimulating signal following stimulation with the subthreshold, baseline signal, the stimulating signal causing a component of user deglutition to be artificially stimulated.

17. The method ofclaim 16, wherein the subthreshold, baseline signal and the stimulating signal are coordinated according to a predetermined time delay between initiation of the baseline signal and initiation of the stimulating signal to assist the user in timing autonomous deglutition efforts with artificial stimulation of the component of user deglutition.

18. The method ofclaim 16, wherein the subthreshold, baseline signal places the deglutition musculature of the user in a state of partial activation prior to at least one of:

full activation of the partially activated deglutition musculature via autonomous user stimulation; and

full activation of the partially activated deglutition musculature via the stimulating signal.

19. A system for assisting user deglutition without substantial aspiration, the system comprising:

an electrode array adapted to be subcutaneously positioned in stimulating communication with deglutition musculature;

a sensor array adapted to be subcutaneously positioned for providing deglutition information;

a signal generator electronically connected to the electrode array for providing a stimulating signal to the electrode array; and

a controller electronically connected to the sensor array for receiving the deglutition information and electronically connected to the signal generator to prompt operation of the signal generator in delivering the stimulating signal to cause a component of deglutition to occur, wherein the controller is adapted to actively modify the stimulating signal delivered by the signal generator based upon the received deglutition information.

20. The system ofclaim 19, wherein the deglutition information is selected from the group consisting of: hyolaryngeal complex position information, overall user body position information, upper esophageal opening force information, upper esophageal displacement information, intrapharyngeal pressure information, larynx position information, system position information, user chin position information, user head position information, user torso position information, deglutition muscle length information, and combinations thereof.

21. The system ofclaim 19, wherein the sensor array includes at least one of an accelerometer, a force gauge, a strain gauges, an EMG sensor, a displacement sensor, a piezoelectric ultrasonic transducer, a pressure sensors, and combinations thereof.

22. The system ofclaim 19, wherein the controller is programmed to:

store a plurality of specialized deglutition programs; and

select a desired deglutition program from the plurality of specialized deglutition programs based upon a characteristic of a bolus to be consumed by a user.

23. The system ofclaim 22, wherein the bolus characteristic includes at least one of bolus volume and bolus consistency.

24. The system ofclaim 22, wherein the bolus characteristic includes whether the bolus is liquid-like or solid-like.

25. The system ofclaim 22, wherein at least one of the specialized deglutition programs includes a group of predetermined, sequential, and overlapping pulse trains.

26. The system ofclaim 25, wherein at least one of the group of predetermined, sequential, and overlapping pulse trains includes a signal ramp at a beginning of the at least one pulse train.

27. The system ofclaim 25, wherein at least one of the group of predetermined, sequential, and overlapping pulse trains includes at least one asymmetric, biphasic waveform.

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