US20110178569A1 - Stimulating cranial nerve to treat pulmonary disorder - Google Patents

Abstract

Systems and methods to treat a pulmonary disorder are provided. A particular method includes positioning an electrode in a patient's body at a location proximate a branch of a vagus nerve. The branch of the vagus nerve includes at least one of a bronchial branch of the vagus nerve and a pulmonary plexus. The method also includes activating the electrode such that energy is delivered from the electrode to the branch of the vagus nerve so as to block intrinsic neural activity in the branch of the vagus nerve to treat the pulmonary disorder.

Description

CLAIM OF PRIORITY
• This application is a divisional patent application of, and claims priority from, U.S. patent application Ser. No. 11/191,896, filed on Jul. 28, 2005 and entitled “Stimulating cranial nerve to treat pulmonary disorder,” which is incorporated hereby by reference in its entirety for all purposes.
FIELD OF THE DISCLOSURE
• This disclosure relates generally to implantable medical devices and, more particularly, to methods, apparatus, and systems for stimulating a cranial nerve of a patient to treat a medical condition, such as pulmonary disorders.
BACKGROUND
• The human nervous system (HNS) includes the brain and the spinal cord, collectively known as the central nervous system (CNS). The central nervous system includes nerve fibers. The network of nerves in the remaining portions of the human body forms the peripheral nervous system (PNS). Some peripheral nerves, known as cranial nerves, connect directly to the brain to control various brain functions, such as vision, eye movement, hearing, facial movement, and feeling. Another system of peripheral nerves, known as the autonomic nervous system (ANS), controls blood vessel diameter, intestinal movements, and actions of many internal organs. Autonomic functions include blood pressure, body temperature, heartbeat and essentially all the unconscious activities that occur without voluntary control.
• Like the rest of the human nervous system, nerve signals travel up and down the peripheral nerves, which link the brain to the rest of the human body. Nerve tracts or pathways in the brain and the peripheral nerves are sheathed in a covering called myelin. The myelin sheath insulates electrical pulses traveling along the nerves. A nerve bundle may include up to 100,000 or more individual nerve fibers of different types, including larger diameter A and B fibers which include a myelin sheath and C fibers which have a much smaller diameter and are unmyelinated. Different types of nerve fibers, among other things, include different sizes, conduction velocities, stimulation thresholds, and myelination status (i.e., myelinated or unmyelinated).
• Breathing functions are controlled by various cranial nerves that traverse portions of the human body. For example, the cranial nerve X (i.e., the vagus nerve) traverses down to the region of the lungs of the human body. The vagus nerve traverses down to the chest cavity forming the bronchial branches of the vagus nerve and traverses onto the pulmonary plexus. Breathing operation is controlled by the vagus nerve. The pulmonary plexus refers to the sites of convergence of autonomic fibers which supply the lung. Pulmonary plexus are located proximate the roots of the lungs.
• There are various disorders relating to the operation of the lungs. For example, asthma is a chronic lung condition often characterized by difficulty in breathing. Generally, those with asthma tend to have extra-sensitive or hyper-responsive airways. These airways often react by narrowing or obstructing when they become irritated. This irritation causes air flow obstruction such that movement of air may be restricted in the lungs. This may be exhibited by symptoms such as wheezing, coughing, shortness of breath, and/or chest tightness.
• Bronchial constriction is a common result of asthma. Bronchial constriction refers to muscles that encircle the airways when they tighten or go into a spasm. State-of-the-art treatment for asthma generally includes various drugs, oxygen treatment, respiratory treatment, etc. Unfortunately, an asthma attack can occur at unexpected moments due to various reasons, such as allergies. Patients often carry various medication and inhalants to negate the effect of the hyper responsive reaction in the airways of the lungs.
• Additionally, other breathing disorders, such as chronic obstructive pulmonary disease also affect normal operation of the lungs. Chronic obstructive pulmonary disease (COPD) refers to a progressive disease of the airways. COPD may be characterized by a gradual attenuation of lung function. Various disorders that refer to COPD include chronic bronchitis, chronic obstructive bronchitis, emphysema, or a combination of any two or more of these conditions. COPD can be characterized by a substantially disabling shortness of breath. It is estimated that millions of patients suffer from such lung diseases. Lung disorders are often treated by various drugs. One problem associated with the state-of-the-art treatment includes a resistance that may build up to the drugs that are used to treat lung disorders. Additionally, some known drugs are not effective in certain patients. Besides drug regimens or invasive medical procedures, effective treatment for such diseases and disorders are fairly limited.
• The present disclosure is directed to overcoming, or at least reducing, the effects of one or more of the problems set forth above.
SUMMARY
• In one aspect, the present disclosure includes a method for stimulating a nerve of a patient to treat a pulmonary disorder. At least one electrode is coupled to at least one portion of a vagus nerve of the patient. The portion may include a left vagus nerve and/or a right vagus nerve. An electrical signal is applied to the portion of the vagus nerve using the electrode to treat the pulmonary disorder.
• In another aspect, another method for stimulating a portion of a vagus nerve of a patient to treat a pulmonary disorder is provided. At least one electrode is coupled to at least a portion of a vagus nerve of the patient. The portion may include a left vagus nerve and/or a right vagus nerve. An electrical signal generator is provided. The signal generator is coupled to the at least one electrode. An electrical signal is generated using the electrical signal generator. The electrical signal is applied to the electrode to treat the pulmonary disorder. Applying the electrical signal includes blocking an intrinsic neural activity of the left vagus nerve or the right vagus nerve. The blocking may be performed using a hyperpolarization or a collision stimulation.
• In yet another aspect, another method for stimulating a portion of a vagus nerve of a patient to treat a pulmonary disorder is provided. At least one electrode is coupled to at least a portion of a vagus nerve of the patient. The portion of the vagus nerve may be a left vagus nerve main trunk, a right vagus nerve main trunk, or a branch of the vagus nerve of the patient. The branch of the vagus nerve may include a bronchial branch of the vagus nerve or a pulmonary plexus. An electrical signal is applied to the at least one branch of the vagus nerve using the electrode to treat the pulmonary disorder. Applying the electrical signal includes blocking an intrinsic neural activity of the left vagus nerve or the right vagus nerve. The blocking may be performed using a hyperpolarization or a collision stimulation.
• In yet another aspect, an apparatus for stimulating a portion of a vagus nerve of a patient to treat a pulmonary disorder is provided. The apparatus may include means for coupling at least one electrode to at least one portion of a vagus nerve of the patient. The portion may include a left vagus nerve or a right vagus nerve. The apparatus may also include a means for applying an electrical signal to either of the portion of the vagus nerve using the electrode to treat the pulmonary disorder.
BRIEF DESCRIPTION OF THE DRAWINGS
• The disclosure may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:
• FIG. 1 is a stylized schematic representation of an implantable medical device that stimulates a cranial nerve for treating a patient with a pulmonary disorder, according to one illustrative embodiment;
• FIG. 2 illustrates one embodiment of a neurostimulator implanted into a patient's body for stimulating the vagus nerve of the patient, with an external programming user interface, in accordance with an illustrative embodiment;
• FIG. 3A illustrates a stylized diagram of the lungs, the trachea, the vagus nerve and the bronchial branches;
• FIG. 3B depicts a stylized diagram of the trachea and the left pulmonary plexus;
• FIG. 4A illustrates an exemplary electrical signal of a firing neuron as a graph of voltage at a given location at particular times during firing by the neurostimulator ofFIG. 2, when applying an electrical signal to the vagus nerve, in accordance with one illustrative embodiment;
• FIG. 4B illustrates an exemplary electrical signal response of a firing neuron as a graph of voltage at a given location at particular times during firing by the neurostimulator ofFIG. 2, when applying a sub-threshold depolarizing pulse and additional stimulus to the vagus nerve, in accordance with one illustrative embodiment;
• FIG. 4C illustrates an exemplary stimulus including a sub-threshold depolarizing pulse and additional stimulus to the vagus nerve for firing a neuron as a graph of voltage at a given location at particular times by the neurostimulator ofFIG. 2, in accordance with one illustrative embodiment;
• FIGS. 5A,5B, and5C illustrate exemplary waveforms for generating the electrical signals for stimulating the vagus nerve for treating a pulmonary disorder, according to one illustrative embodiment;
• FIG. 6 illustrates a stylized block diagram depiction of the implantable medical device for treating a pulmonary disorder, in accordance with one illustrative embodiment;
• FIG. 7 illustrates a flowchart depiction of a method for treating a pulmonary disease, in accordance with illustrative embodiment;
• FIG. 8 illustrates a flowchart depiction of an alternative method for treating a pulmonary disease, in accordance with an alternative illustrative embodiment;
• FIG. 9 depicts a more detailed flowchart depiction of performing a detection process ofFIG. 8, in accordance with an illustrative embodiment; and
• FIG. 10 depicts a more detailed flowchart depiction of determining a particular type of stimulation based upon data relating to a particular disorder described inFIG. 8, in accordance with an illustrative embodiment.
• While embodiments disclosed herein are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims.
DETAILED DESCRIPTION
• Illustrative embodiments are described herein. In the interest of clarity, not all features of an actual implementation are described in this specification. In the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the design-specific goals, which will vary from one implementation to another. It will be appreciated that such a development effort, while possibly complex and time-consuming, would nevertheless be a routine undertaking for persons of ordinary skill in the art having the benefit of this disclosure.
• Certain terms are used throughout the following description and claims refer to particular system components. As one skilled in the art will appreciate, components may be referred to by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “comprising” and “including” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” Also, the term “couple” or “couples” is intended to mean either a direct or an indirect electrical connection. For example, if a first device couples to a second device, that connection may be through a direct electrical connection or through an indirect electrical connection via other devices, biological tissues, or magnetic fields. “Direct contact,” “direct attachment,” or providing a “direct coupling” indicates that a surface of a first element contacts the surface of a second element with no substantial attenuating medium therebetween. The presence of substances, such as bodily fluids, that do not substantially attenuate electrical connections does not vitiate direct contact. The word “or” is used in the inclusive sense (i.e., “and/or”) unless a specific use to the contrary is explicitly stated.
• A particular embodiment provides for the treatment of pulmonary disorder(s) by stimulation of nerves, such as the vagus nerves.
• Cranial nerve stimulation has been used successfully to treat a number of nervous system disorders, including epilepsy and other movement disorders, depression and other neuropsychiatric disorders, dementia, coma, migraine headache, obesity, eating disorders, sleep disorders, cardiac disorders (such as congestive heart failure and atrial fibrillation), hypertension, endocrine disorders (such as diabetes and hypoglycemia), and pain, among others. See, e.g., U.S. Pat. Nos. 4,867,164; 5,299,569; 5,269,303; 5,571,150; 5,215,086; 5,188,104; 5,263,480; 6,587,719; 6,609,025; 5,335,657; 6,622,041; 5,916,239; 5,707,400; 5,231,988; and 5,330,515. Despite the recognition that cranial nerve stimulation may be an appropriate treatment for the foregoing conditions, the fact that detailed neural pathways for many (if not all) cranial nerves remain relatively unknown makes predictions of efficacy for any given disorder difficult. Even if such pathways were known, moreover, the precise stimulation parameters that would energize particular pathways that affect the particular disorder likewise are difficult to predict. Accordingly, cranial nerve stimulation, and particularly vagus nerve stimulation, has not heretofore been deemed appropriate for use in treating pulmonary disorders.
• In one embodiment, methods, apparatus, and systems stimulate a cranial nerve, e.g., a vagus nerve, using an electrical signal to a pulmonary disorder. “Electrical signal” on the nerve refers to the electrical activity (i.e., afferent and/or efferent action potentials) that are not generated by the patient's body and environment, rather applied from, an artificial source, e.g., an implanted neurostimulator. Disclosed herein is a method for treating a pulmonary disorder using stimulation of the vagus nerve (cranial nerve X). A generally suitable form of neurostimulator for use in the method and apparatus is disclosed, for example, in U.S. Pat. No. 5,154,172, assigned to the same assignee as the present application. The neurostimulator may be referred to as a NeuroCybernetic Prosthesis (NCP®, Cyberonics, Inc., Houston, Tex., the assignee of the present application). Certain parameters of the electrical stimuli generated by the neurostimulator are programmable, such as be means of an external programmer in a manner conventional for implantable electrical medical devices.
• Particular embodiments provide for an electrical stimulation of a portion of a cranial nerve to treat a pulmonary disorder. A portion of the vagus nerve, such as the bronchial branches of the vagus nerve and/or the pulmonary plexus may be stimulated to affect the functions of the pulmonary system of a patient. Stimulation of a portion of the vagus nerve, which is a parasympathetic nerve system, may be used to modify the hyper-responsive reaction of the airways of the lungs of the patient. For example, a controlled electrical stimulation signal, such as a controlled current pulse, may be applied directly and/or in relative proximity of a portion of the vagus nerve, such as the bronchial branches of the vagus nerve. This stimulation may be used to treat various pulmonary disorders, such as asthma, constrictive pulmonary disorder, cardio pulmonary obstructive disorder, etc.
• Turning now toFIG. 1, an implantable medical device (IMD)100 is provided for stimulating a nerve, such as acranial nerve105 of a patient to treat a pulmonary disorder using neurostimulation, according to one illustrative embodiment. The term “cranial nerve” refers to any portion of the main trunk or any branch of thecranial nerve105 including cranial nerve fibers, a left cranial nerve and a right cranial nerve. TheIMD100 may deliver anelectrical signal115 to anerve branch120 of thecranial nerve105 that travels to thebrain125 of a patient. Thenerve branch120 provides theelectrical signal115 to the pulmonary system of a patient. Thenerve branch120 may be a nerve branch of thecranial nerve105 that is associated with the parasympathetic control of the pulmonary function.
• TheIMD100 may apply neurostimulation by delivering theelectrical signal115 to thenerve branch120 via alead135 coupled to one or more electrodes140 (1-n). For example, theIMD100 may stimulate thecranial nerve105 by applying theelectrical signal115 to thenerve branch120 that couples to the bronchial branches of the vagus nerve and/or the pulmonary plexus using the electrode(s)140(1-n).
• Consistent with one embodiment, theIMD100 may be a neurostimulator device capable of treating a disease, disorder or condition relating to the pulmonary functions of a patient by providing electrical neurostimulation therapy to a patient. In order to accomplish this task, theIMD100 may be implanted in the patient at a suitable location. TheIMD100 may apply theelectrical signal115, which may include an electrical pulse signal, to thecranial nerve105. TheIMD100 may generate theelectrical signal115 defined by one or more pulmonary characteristic, such as an asthma condition, a constrictive pulmonary disorder, a cardiac pulmonary obstructive disorder, etc., of the patient. These pulmonary characteristics may be compared to one or more corresponding values within a predetermined range. TheIMD100 may apply theelectrical signal115 to thenerve branch120 or a nerve fascicle within thecranial nerve105. By applying theelectrical signal115, theIMD100 may treat or control a pulmonary function in a patient.
• Implantablemedical devices100 that may be used include any of a variety of electrical stimulation devices, such as a neurostimulator capable of stimulating a neural structure in a patient, especially for stimulating a patient's cranial nerve such as a vagus nerve. TheIMD100 is capable of delivering a controlled current stimulation signal. Although theIMD100 is described in terms of cranial nerve stimulation, and particularly vagus nerve stimulation (VNS), a person of ordinary skill in the art would recognize that the disclosure is not so limited. For example, theIMD100 may be applied to the stimulation of other cranial nerves, such as the trigeminal and/or glossopharyngeal nerves, or other neural tissue, such as one or more brain structures of the patient.
• In the generally accepted clinical labeling of cranial nerves, the tenth cranial nerve is the vagus nerve, which originates from the stem of thebrain125. The vagus nerve passes through foramina of the skull to parts of the head, neck and trunk. The vagus nerve branches into left and right branches upon exiting the skull. Left and right vagus nerve branches include both sensory and motor nerve fibers. The cell bodies of vagal sensory nerve fibers are attached to neurons located outside thebrain125 in ganglia groups, and the cell bodies of vagal motor nerve fibers are attached toneurons142 located within the gray matter of thebrain125. The vagus nerve is a parasympathetic nerve, part of the peripheral nervous system (PNS). Somatic nerve fibers of the cranial nerves are involved in conscious activities and connect the CNS to the skin and skeletal muscles. Autonomic nerve fibers of these nerves are involved in unconscious activities and connect the CNS to the visceral organs such as the heart, lungs, stomach, liver, pancreas, spleen, and intestines. Accordingly, to provide vagus nerve stimulation (VNS), a patient's vagus nerve may be stimulated unilaterally or bilaterally in which a stimulating electrical signal is applied to one or both the branches of the vagus nerve, respectively. For example, coupling the electrodes140(1-n) includes coupling an electrode to at least one cranial nerve selected from the group consisting of the left vagus nerve and the right vagus nerve. The term coupling may include actual fixation, proximate location, and the like. The electrodes140(1-n) may be coupled to a branch of the vagus nerve of the patient. Thenerve branch120 may be selected from the group consisting of a bronchial brand and the pulmonary plexus.
• Applying theelectrical signal115 to a selectedcranial nerve105 may include generating a response selected from the group consisting of an afferent action potential, an efferent action potential, an afferent hyperpolarization, and an efferent hyperpolarization. TheIMD100 may generate an efferent action potential for treating a pulmonary disorder.
• TheIMD100 may include anelectrical signal generator150 and acontroller155 operatively coupled thereto to generate theelectrical signal115 for causing the nerve stimulation. Theelectrical signal generator150 may generate theelectrical signal115. Thecontroller155 may be adapted to apply theelectrical signal115 to thecranial nerve105 to provide electrical neurostimulation therapy to the patient for treating a pulmonary disorder. Thecontroller155 may direct theelectrical signal generator150 to generate theelectrical signal115 to stimulate the vagus nerve.
• To generate theelectrical signal115, theIMD100 may further include abattery160, amemory165 and acommunication interface170. More specifically, thebattery160 may include a power-source battery that may be rechargeable. Thebattery160 provides power for the operation of theIMD100, including electronic operations and the stimulation function. Thebattery160, in one embodiment, may be a lithium/thionyl chloride cell or, in another embodiment, a lithium/carbon monofluoride cell. Thememory165, in one embodiment, is capable of storing various data, such as operation parameter data, status data, and the like, as well as program code. Thecommunication interface170 is capable of providing transmission and reception of electronic signals to and from an external unit. The external unit may be a device that is capable of programming theIMD100.
• TheIMD100, which may be a single device or a pair of devices, is implanted and electrically coupled to the lead(s)135, which are in turn coupled to the electrode(s)140 implanted on the left and/or right branches of the vagus nerve, for example. In one embodiment, the electrode(s)140(1-n) may include a set of stimulating electrode(s) separate from a set of sensing electrode(s). In another embodiment, the same electrode may be deployed to stimulate and to sense. A particular type or a combination of electrodes may be selected as desired for a given application. For example, an electrode suitable for coupling to a vagus nerve may be used. Theelectrodes140 may include a bipolar stimulating electrode pair. Those skilled in the art having the benefit of the present disclosure will appreciate that many electrode designs could be used.
• Using the electrode(s)140(1-n), theelectrical signal generator150 may apply a predetermined sequence of electrical pulses to the selectedcranial nerve105 to provide therapeutic neurostimulation for the patient with a pulmonary disorder. While the selectedcranial nerve105 may be the vagus nerve, the electrode(s)140(1-n) may include at least one nerve electrode for implantation on the patient's vagus nerve for direct stimulation thereof. Alternatively, a nerve electrode may be implanted on or placed proximate to a branch of the patient's vagus nerve for direct stimulation thereof.
• A particular embodiment of theIMD100 may be a programmable electrical signal generator. Such a programmable electrical signal generator may be capable of programmably defining theelectrical signal115. By using at least one parameter selected from the group consisting of a current magnitude, a pulse frequency, and a pulse width, theIMD100 may treat a pulmonary disorder. TheIMD100 may detect a symptom of the pulmonary disorder. In response to detecting the symptom, theIMD100 may initiate applying theelectrical signal115. For example, a sensor may be used to detect the symptom of a pulmonary disorder. To treat the pulmonary disorder, theIMD100 may apply theelectrical signal115 during a first treatment period and further apply a second electrical signal to thecranial nerve105 using theelectrode140 during a second treatment period.
• In one embodiment, the method may further include detecting a symptom of the pulmonary disorder, wherein the applying theelectrical signal115 to thecranial nerve105 is initiated in response to the detecting of the symptom. In a further embodiment, the detecting the symptom may be performed by the patient. This may involve a subjective observation that the patient is experiencing a symptom of the pulmonary disorder. Alternatively, or in addition, the symptom may be detected by performing a pulmonary disorder test on the patient.
• The method may be performed under a single treatment regimen or under multiple treatment regimens. “Treatment regimen” herein may refer to a parameter of theelectrical signal115, a duration for applying the signal, and/or a duty cycle of the signal, among others. In one embodiment, the applying theelectrical signal115 to thecranial nerve105 is performed during a first treatment period, and may further include the step of applying a second electrical signal to the cranial nerve using theelectrode140 during a second treatment period. In a further embodiment, the method may include detecting a symptom of the pulmonary disorder, wherein the second treatment period is initiated upon the detection of the symptom. The patient may benefit by receiving a first electrical signal during a first, chronic treatment period and a second electrical signal during a second, acute treatment period. Three or more treatment periods may be used, if deemed desirable by a medical practitioner.
• A particular embodiment of theIMD100 shown inFIG. 1 is illustrated inFIG. 2. As shown therein, anelectrode assembly225, which may include a plurality of electrodes such aselectrodes226,228, may be coupled to thecranial nerve105 such asvagus nerve235 in accordance with an illustrative embodiment. Thelead135 is coupled to theelectrode assembly225 and secured, while retaining the ability to flex with movement of the chest and neck. Thelead135 may be secured by a suture connection to nearby tissue. Theelectrode assembly225 may deliver theelectrical signal115 to thecranial nerve105 to cause desired nerve stimulation for treating a pulmonary disorder. Using the electrode(s)226,228, the selected cranial nerve such asvagus nerve235, may be stimulated within a patient'sbody200.
• AlthoughFIG. 2 illustrates a system for stimulating theleft vagus nerve235 in the neck (cervical) area, those skilled in the art having the benefit of the present disclosure will understand theelectrical signal115 for nerve stimulation may be applied to the right cervical vagus nerve in addition to, or instead of, the left vagus nerve, and remain within the scope of the present disclosure. In one such embodiment, lead135 andelectrode225 assemblies substantially as discussed above may be coupled to the same or a different electrical signal generator.
• An externalprogramming user interface202 may be used by a health professional for a particular patient to either initially program and/or to later reprogram theIMD100, such as aneurostimulator205. Theneurostimulator205 may include theelectrical signal generator150, which may be programmable. To enable physician-programming of the electrical and timing parameters of a sequence of electrical impulses, anexternal programming system210 may include a processor-based computing device, such as a computer, personal digital assistant (PDA) device, or other suitable computing device.
• Using the externalprogramming user interface202, a user of theexternal programming system210 may program theneurostimulator205. Communications between theneurostimulator205 and theexternal programming system210 may be accomplished using any of a variety of conventional techniques known in the art. Theneurostimulator205 may include a transceiver (such as a coil) that permits signals to be communicated wirelessly between the externalprogramming user interface202, such as a wand, and theneurostimulator205.
• Theneurostimulator205 having acase215 with an electrically conducting connector onheader220 may be implanted in the patient's chest in a pocket or cavity formed by the implanting surgeon just below the skin, much as a pacemaker pulse generator would be implanted, for example. A stimulatingnerve electrode assembly225, preferably including an electrode pair, is conductively connected to the distal end of an insulated electrically conductivelead assembly135, which preferably includes a pair of lead wires and is attached at its proximal end to the connector on thecase215. Theelectrode assembly225 is surgically coupled to avagus nerve235 in the patient's neck. Theelectrode assembly225 preferably includes a bipolarstimulating electrode pair226,228, such as the electrode pair described in U.S. Pat. No. 4,573,481 issued Mar. 4, 1986 to Bullara, which is hereby incorporated by reference herein in its entirety. Persons of skill in the art will appreciate that many electrode designs could be used. The twoelectrodes226,228 are preferably wrapped about the vagus nerve, and theelectrode assembly225 secured to thenerve235 by aspiral anchoring tether230 such as that disclosed in U.S. Pat. No. 4,979,511 issued Dec. 25, 1990 to Reese S. Terry, Jr. and assigned to the same assignee as the instant application.
• In one embodiment, the open helical design of the electrode assembly225 (described in detail in the above-cited Bullara patent), which is self-sizing and flexible, minimizes mechanical trauma to the nerve and allows body fluid interchange with the nerve. Theelectrode assembly225 conforms to the shape of the nerve, providing a low stimulation threshold by allowing a large stimulation contact area. Structurally, theelectrode assembly225 includes two electrode ribbons (not shown), of a conductive material such as platinum, iridium, platinum-iridium alloys, and/or oxides of the foregoing. The electrode ribbons are individually bonded to an inside surface of an elastomeric body portion of two spiral electrodes, which may include two spiral loops of a three-loop helical assembly.
• In one embodiment, theelectrode assembly225 may include two distinct lead wires or a coaxial cable whose two conductive elements are respectively coupled to one of the conductive electrode ribbons. One suitable method of coupling the lead wires or cable to the electrodes includes a spacer assembly such as that depicted in U.S. Pat. No. 5,531,778 issued Jul. 2, 1996, to Steven Maschino, et al. and assigned to the same Assignee as the instant application, although other known coupling techniques may be used. The elastomeric body portion of each loop is preferably composed of silicone rubber, and the third loop acts as the anchoring tether for theelectrode assembly225.
• In one embodiment, the electrode(s)140 (1-n) of IMD100 (FIG. 1) may sense or detect any target symptom parameter in the patient'sbody200. For example, anelectrode140 coupled to the patient's vagus nerve may detect a factor associated with a pulmonary function. The electrode(s)140 (1-n) may sense or detect a pulmonary disorder condition. For example, a sensor or any other element capable of providing a sensing signal representative of a patient's body parameter associated with activity of the pulmonary functions may be deployed.
• In one embodiment, theneurostimulator205 may be programmed to deliver an electrical biasing signal at programmed time intervals (e.g., every five minutes). In an alternative embodiment, theneurostimulator205 may be programmed to initiate an electrical biasing signal upon detection of an event or upon another occurrence to deliver therapy. Based on this detection, a programmed therapy may be determined to the patient in response to signal(s) received from one or more sensors indicative of corresponding monitored patient parameters.
• The electrode(s)140(1-n), as shown inFIG. 1 may be used in some embodiments to trigger administration of the electrical stimulation therapy to thevagus nerve235 viaelectrode assembly225. Use of such sensed body signals to trigger or initiate stimulation therapy is hereinafter referred to as “active,” “triggered,” or “feedback” modes of administration. Other embodiments utilize a continuous, periodic or intermittent stimulus signal. These signals may be applied to the vagus nerve (each of which constitutes a form of continual application of the signal) according to a programmed on/off duty cycle. No sensors may be used to trigger therapy delivery. This type of delivery may be referred to as a “passive,” or “prophylactic” therapy mode. Both active and passive electrical biasing signals may be combined or delivered by a single neurostimulator.
• Theelectrical signal generator150 may be programmed using programming software of the type copyrighted by the assignee of the instant application with the Register of Copyrights, Library of Congress, or other suitable software based on the description herein. A programming wand (not shown) may be used to facilitate radio frequency (RF) communication between the externalprogramming user interface202 and theelectrical signal generator150. The wand and software permit noninvasive communication with theelectrical signal generator150 after theneurostimulator205 is implanted. The wand may be powered by internal batteries, and provided with a “power on” light to indicate sufficient power for communication. Another indicator light may be provided to show that data transmission is occurring between the wand and theneurostimulator205.
• Theneurostimulator205 may provide vagus nerve stimulation (VNS) therapy upon a vagus nerve branch. Theneurostimulator205 may be activated manually or automatically to deliver the electrical bias signal to the selected cranial nerve via the electrode(s)226,228. Theneurostimulator205 may be programmed to deliver theelectrical signal115 continuously, periodically or intermittently when activated.
• Turning now toFIGS. 3A and 3B, a stylized diagram of the lungs, the trachea, the vagus nerve is illustrated. TheIMD100 may be used to stimulate a portion of the vagus nerve, such as a portion of the bronchial branches to treat various disorders, such as asthma, constrictive pulmonary disorder, cardiopulmonary destructive disorder, etc. The diagrams illustrated inFIGS. 3A and 3B have been simplified for ease and clarity of description, however, those skilled in the art would appreciate that various details have been simplified for the sake of clarity.
• Referring simultaneously toFIGS. 3A and 3B, the left pulmonary plexus may merge from the bronchial branches of the left vagus nerve. The pulmonary plexus refer to sites of convergence of autonomic fibers that supply the lung. The pulmonary plexus are generally sighted anterior and posterior relative to each lung root. The parasympathetic nerve, which includes the right vagus nerve and the left vagus nerve, may be stimulated to affect the operation of various portions of the pulmonary system of a patient. The pulmonary plexus may provide for parasympathetic and sympathetic stimulation.
• The right vagus nerve generally descends posteroinferiorly on the trachea. The right vagus nerve divides posterior to the trachea onto the pulmonary plexus. The pulmonary plexus passes anteriorly to the root of the lung. The left vagus nerve descends anteriorly to the arch of the aorta. The left vagus nerve gives off the recurrent laryngeal branch and then the fibers diverge anteriorly to supply the left pulmonary arterial plexus. Embodiments provide for placing an electrode on a portion of the right vagus nerve and/or the left vagus nerve. Additionally, an electrode may be placed in proximity to the pulmonary plexus. Therefore, the electrode(s) become operatively coupled to one or more portions of the vagus nerve and/or to the pulmonary plexus. This way, an electrical signal sent to the electrodes may be directed to affect a reaction in the pulmonary plexus and/or the bronchial branches of the vagus nerve.
• In one embodiment, a stimulation may be applied in an efferent manner, which refers to signals being carried away on a nerve from the central nervous system. Therefore, a “blocking” type stimulation signal may be employed using theIMD100 such that afferent fibers are not stimulated, while efferent fibers are stimulated. The blocking function provided by the stimulation may relate to inhibiting the conduction of action potential by performing hyperpolarization and/or performing collision blocking. Collision blocking may relate to performing high-frequency or rapid stimulation to prevent an action potential in a tissue. The blocking action provides for blocking an intrinsic neural activity on a target portion of a tissue. An appreciable amount of blockage of signals sent back to the brain via the vagus nerve is achieved while employing an efferent type stimulation to affect the operation of portions of the body proximate to the pulmonary plexus and/or the bronchial branches of the vagus nerve. In this way, various disorders may be treated, including asthma, constrictive pulmonary disorder, cardiopulmonary obstructive disorders, etc. For example, by providing efferent stimulation, hyper-responsiveness of the airways may be attenuated in a parasympathetic manner to reduce pulmonary disorders, such as asthma.
• In addition to efferent fiber stimulation, additional stimulation may be provided in combination with the blocking type of stimulation described above. Efferent blocking may be realized by enhancing the hyper polarization of a stimulation signal, as described below. Embodiments may be employed to cause theIMD100 to perform stimulation in combination with signal blocking, in order to treat pulmonary disorders. Using stimulation from theIMD100, parasympathetic nerve portions are be inhibited such that stimulation blocking is achieved, wherein the various portions of the parasympathetic nerve may also be stimulated to affect the pulmonary mechanism in a patient's body. In this way, afferent as well as efferent stimulation may be performed by theIMD100 to treat various pulmonary disorders.
• FIG. 4 provides a stylized depiction of an exemplary electrical signal of a firing neuron as a graph of voltage at a given location at particular times during firing, in accordance with one embodiment. A typical neuron has a resting membrane potential of about −70 mV, maintained by transmembrane ion channel proteins. When a portion of the neuron reaches a firing threshold of about −55 mV, the ion channel proteins in the locality allow the rapid ingress of extracellular sodium ions, which depolarizes the membrane to about +30 mV. The wave of depolarization then propagates along the neuron. After depolarization at a given location, potassium ion channels open to allow intracellular potassium ions to exit the cell, lowering the membrane potential to about −80 mV (hyperpolarization). About 1 msec is required for transmembrane proteins to return sodium and potassium ions to their starting intra- and extracellular concentrations and allow a subsequent action potential to occur. Particular embodiments may raise or lower the resting membrane potential, thus making the reaching of the firing threshold more or less likely and subsequently increasing or decreasing the rate of fire of any particular neuron.
• Referring toFIG. 4B, an exemplary electrical signal response is illustrated of a firing neuron as a graph of voltage at a given location at particular times during firing by the neurostimulator ofFIG. 2, in accordance with one illustrative embodiment. As shown inFIG. 4C, an exemplary stimulus including a sub-threshold depolarizing pulse and additional stimulus to thecranial nerve105, such as thevagus nerve235 may be applied for firing a neuron, in accordance with one illustrative embodiment. The stimulus illustrated inFIG. 4C depicts a graph of voltage at a given location at particular times by the neurostimulator ofFIG. 2.
• The neurostimulator may apply the stimulus voltage ofFIG. 4C to thecranial nerve105, which may include afferent fibers, efferent fibers, or both. This stimulus voltage may cause the response voltage shown inFIG. 4B. Afferent fibers transmit information to the brain from the extremities; efferent fibers transmit information from the brain to the extremities. Thevagus nerve235 may include both afferent and efferent fibers, and theneurostimulator205 may be used to stimulate either or both.
• Thecranial nerve105 may include fibers that transmit information in the sympathetic nervous system, the parasympathetic nervous system, or both. Inducing an action potential in the sympathetic nervous system may yield a result similar to that produced by blocking an action potential in the parasympathetic nervous system and vice versa.
• Returning back toFIG. 2, theneurostimulator205 may generate theelectrical signal115 according to one or more programmed parameters for stimulation of thevagus nerve235. In one embodiment, the stimulation parameter may be selected from the group consisting of a current magnitude, a pulse frequency, a signal width, on-time, and off-time. An exemplary table of ranges for each of these stimulation parameters is provided in Table 1. The stimulation parameter may be of any suitable waveform; exemplary waveforms in accordance with one embodiment are shown inFIGS. 5A-5C. Specifically, the exemplary waveforms illustrated inFIGS. 5A-5C depict the generation of theelectrical signal115 that may be defined by a factor related to at least one of an asthma condition, constrictive pulmonary disorder, and a cardiac pulmonary obstructive disorder of the patient relative to a value within a defined range.
• According to one illustrative embodiment, various electrical signal patterns may be employed by theneurostimulator205. These electrical signals may include a plurality of types of pulses, e.g., pulses with varying amplitudes, polarity, frequency, etc. For example, the exemplary waveform5A depicts that theelectrical signal115 may be defined by fixed amplitude, constant polarity, pulse width, and pulse period. The exemplary waveform5B depicts that theelectrical signal115 may be defined by a variable amplitude, constant polarity, pulse width, and pulse period. The exemplary waveform5C depicts that theelectrical signal115 may be defined by a fixed amplitude pulse with a relatively slowly discharging current magnitude, constant polarity, pulse width, and pulse period. Other types of signals may also be used, such as sinusoidal waveforms, etc. The electrical signal may be controlled current signals.

• 	TABLE 1
  	PARAMETER	RANGE

  	Output current	0.1-6.0	mA
  	Pulse width	10-1500	μsec
  	Frequency	0.5-250	Hz

  	On-time	1 sec and greater
  	Off-time	0 sec and greater

  	Frequency Sweep	10-100	Hz
  	Random Frequency	10-100	Hz

• On-time and off-time parameters may be used to define an intermittent pattern in which a repeating series of signals may be generated for stimulating thenerve105 during the on-time. Such a sequence may be referred to as a “pulse burst.” This sequence may be followed by a period in which no signals are generated. During this period, the nerve is allowed to recover from the stimulation during the pulse burst. The on/off duty cycle of these alternating periods of stimulation and idle periods may have a ratio in which the off-time may be set to zero, providing continuous stimulation. Alternatively, the idle time may be as long as one day or more, in which case the stimulation is provided once per day or at even longer intervals. Typically, however, the ratio of “off-time” to “on-time” may range from about 0.5 to about 10.
• In one embodiment, the width of each signal may be set to a value not greater than about 1 msec, such as about 250-500 μsec, and the signal repetition frequency may be programmed to be in a range of about 20-250 Hz. In one embodiment, a frequency of 150 Hz may be used. A non-uniform frequency may also be used. Frequency may be altered during a pulse burst by either a frequency sweep from a low frequency to a high frequency, or vice versa. Alternatively, the timing between adjacent individual signals within a burst may be randomly changed such that two adjacent signals may be generated at any frequency within a range of frequencies.
• In one embodiment, at least one electrode may be coupled to each of two or more cranial nerves. (In this context, two or more cranial nerves means two or more nerves having different names or numerical designations, and do not refer to the left and right versions of a particular nerve). In one embodiment, at least oneelectrode140 may be coupled to each of thevagus nerve235 and/or a branch of the vagus nerve. The electrode may be operatively coupled to bronchial brand of the vagus nerve and/or to the pulmonary plexus. The term “operatively” coupled may include directly or indirectly coupling. Each of the nerves in this embodiment or others involving two or more cranial nerves may be stimulated according to particular activation modalities that may be independent between the two nerves.
• Another activation modality for stimulation is to program the output of theneurostimulator205 to the maximum amplitude which the patient may tolerate. The stimulation may be cycled on and off for a predetermined period of time followed by a relatively long interval without stimulation. Where the cranial nerve stimulation system is completely external to the patient's body, higher current amplitudes may be needed to overcome the attenuation resulting from the absence of direct contact with thevagus nerve235 and the additional impedance of the skin of the patient. Although external systems typically require greater power consumption than implantable ones, they have an advantage in that their batteries may be replaced without surgery.
• Other types of indirect stimulations may be performed in conjunction with embodiments. In one embodiment, noninvasive transcranial magnetic stimulation (TMS) may be provided to thebrain125 of the patient along with using theIMD100 of the present information to treat the pulmonary disorder. TMS systems include those disclosed in U.S. Pat. Nos. 5,769,778; 6,132,361; and 6,425,852. Where TMS is used, it may be used in conjunction with cranial nerve stimulation as an adjunctive therapy. In one embodiment, both TMS and direct cranial nerve stimulation may be performed to treat the pulmonary disorder. Other types of stimulation, such as chemical stimulation to treat pulmonary disorders may be performed in combination with theIMD100.
• Returning to systems for providing direct cranial nerve stimulation, such as that shown inFIGS. 1 and 2, stimulation may be provided in at least two different modalities. Where cranial nerve stimulation is provided based solely on programmed off-times and on-times, the stimulation may be referred to as passive, inactive, or non-feedback stimulation. In contrast, stimulation may be triggered by one or more feedback loops according to changes in the body or mind of the patient. This stimulation may be referred to as active or feedback-loop stimulation. In one embodiment, feedback-loop stimulation may be manually-triggered stimulation, in which the patient manually causes the activation of a pulse burst outside of the programmed on-time/off-time cycle. The patient may manually activate theneurostimulator205 to stimulate thecranial nerve105 to treat the acute episode of a pulmonary disorder, such as an asthma attack. The patient may also be permitted to alter the intensity of the signals applied to the cranial nerve within limits established by the physician. For example, the patient may be permitted to alter the signal frequency, current, duty cycle, or a combination thereof. In at least some embodiments, theneurostimulator205 may be programmed to generate the stimulus for a relatively long period of time in response to manual activation.
• Patient activation of aneurostimulator205 may involve use of an external control magnet for operating a reed switch in an implanted device, for example. Certain other techniques of manual and automatic activation of implantable medical devices are disclosed in U.S. Pat. No. 5,304,206 to Baker, Jr., et al., assigned to the same assignee as the present application (“the '206 patent”). According to the '206 patent, means for manually activating or deactivating theelectrical signal generator150 may include a sensor such as piezoelectric element mounted to the inner surface of the generator case and adapted to detect light taps by the patient on the implant site. One or more taps applied in fast sequence to the skin above the location of theelectrical signal generator150 in the patient'sbody200 may be programmed into the implantablemedical device100 as a signal for activation of theelectrical signal generator150. Two taps spaced apart by a slightly longer duration of time may be programmed into theIMD100 to indicate a desire to deactivate theelectrical signal generator150, for example. The patient may be given limited control over operation of the device to an extent which may be determined by the program dictated or entered by the attending physician. The patient may also activate theneurostimulator205 using other suitable techniques or apparatus.
• In some embodiments, feedback stimulation systems other than manually-initiated stimulation may be used. A cranial nerve stimulation system may include a sensing lead coupled at its proximal end to a header along with a stimulation lead and electrode assemblies. A sensor may be coupled to the distal end of the sensing lead. The sensor may include a temperature sensor, a breathing parameter sensor, a heart parameter sensor, a brain parameter sensor, or a sensor for another body parameter. The sensor may also include a nerve sensor for sensing activity on a nerve, such as a cranial nerve, such as thevagus nerve235.
• In one embodiment, the sensor may sense a body parameter that corresponds to a symptom of pulmonary disorder. If the sensor is to be used to detect a symptom of the medical disorder, a signal analysis circuit may be incorporated into theneurostimulator205 for processing and analyzing signals from the sensor. Upon detection of the symptom of the pulmonary disorder, the processed digital signal may be supplied to a microprocessor in theneurostimulator205 to trigger application of theelectrical signal115 to thecranial nerve105. In another embodiment, the detection of a symptom of interest may trigger a stimulation program including different stimulation parameters from a passive stimulation program. This may entail providing a higher current stimulation signal or providing a higher ratio of on-time to off-time.
• In response to the afferent action potentials, the detection communicator may detect an indication of change in the symptom characteristic. The detection communicator may provide feedback for the indication of change in the symptom characteristic to modulate theelectrical signal115. In response to providing feedback for the indication, theelectrical signal generator150 may adjust the afferent action potentials to enhance efficacy of a drug in the patient.
• Theneurostimulator205 may use thememory165 to store disorder data and a routine to analyze this data. The disorder data may include sensed body parameters or signals indicative of the sensed parameters. The routine may include software and/or firmware instructions to analyze the sensed hormonal activity for determining whether electrical neurostimulation would be desirable. If the routine determines that electrical neurostimulation is desired, then theneurostimulator205 may provide an appropriate electrical signal to a neural structure, such as thevagus nerve235.
• In certain embodiments, theIMD100 may include aneurostimulator205 having acase215 as a main body in which the electronics described inFIGS. 1-2 may be enclosed and hermetically sealed. Coupled to the main body may be theheader220 designed with terminal connectors for connecting to a proximal end of the electrically conductive lead(s)135. The main body may include a titanium shell, and the header may include a clear acrylic or other hard, biocompatible polymer such as polycarbonate, or any material that may be implantable into a human body. The lead(s)135 projecting from the electricallyconductive electrode assembly225 of the header may be coupled at a distal end to electrodes140(1-n). The electrodes140(1-n) may be coupled to neural structure such as thevagus nerve235, utilizing a variety of methods for operatively coupling the lead(s)135 to the tissue of thevagus nerve235. Therefore, the current flow may take place from one terminal of thelead135 to an electrode such as electrode226 (FIG. 2) through the tissue proximal to thevagus nerve235, to a second electrode such aselectrode228 and a second terminal of thelead135.
• Turning now toFIG. 6, a block diagram depiction of theIMD100, in accordance with an illustrative embodiment is provided. TheIMD100 may include acontroller610 capable of controlling various aspects of the operation of theIMD100. Thecontroller610 is capable of receiving internal data and/or external data and generating and delivering a stimulation signal to target tissues of the patient's body. For example, thecontroller610 may receive manual instructions from an operator externally, or may perform stimulation based on internal calculations and programming. Thecontroller610 is capable of affecting substantially all functions of theIMD100.
• Thecontroller610 may include various components, such as aprocessor615, amemory617, etc. Theprocessor615 may include one or more microcontrollers, microprocessors, etc., that are capable of performing various executions of software components. Thememory617 may include various memory portions where a number of types of data (e.g., internal data, external data instructions, software codes, status data, diagnostic data, etc.) may be stored. Thememory617 may include random access memory (RAM), dynamic random access memory (DRAM), electrically erasable programmable read-only memory (EEPROM), flash memory, etc.
• TheIMD100 may also include astimulation unit620. Thestimulation unit620 is capable of generating and delivering stimulation signals to one or more electrodes via leads. A number of leads122,134,137 may be coupled to theIMD100. Therapy may be delivered to the leads122 by thestimulation unit620 based upon instructions from thecontroller610. Thestimulation unit620 may include various circuitry, such as stimulation signal generators, impedance control circuitry to control the impedance “seen” by the leads, and other circuitry that receives instructions relating to the type of stimulation to be performed. Thestimulation unit620 is capable of delivering a controlled current stimulation signal over the leads122.
• TheIMD100 may also include apower supply630. Thepower supply630 may include a battery, voltage regulators, capacitors, etc., to provide power for the operation of theIMD100, including delivering the stimulation signal. Thepower supply630 includes a power-source battery that in some embodiments may be rechargeable. In other embodiments, a non-rechargeable battery may be used. Thepower supply630 provides power for the operation of theIMD100, including electronic operations and the stimulation function. Thepower supply630 may include a lithium/thionyl chloride cell or a lithium/carbon monofluoride cell. Other battery types known in the art of implantable medical devices may also be used.
• TheIMD100 also includes acommunication unit660 capable of facilitating communications between theIMD100 and various devices. In particular, thecommunication unit660 is capable of providing transmission and reception of electronic signals to and from anexternal unit670. Theexternal unit670 may be a device that is capable of programming various modules and stimulation parameters of theIMD100. In one embodiment, theexternal unit670 is a computer system that is capable of executing a data-acquisition program. Theexternal unit670 may be controlled by a healthcare provider, such as a physician, at a base station in, for example, a doctor's office. Theexternal unit670 may be a computer, preferably a handheld computer or PDA, but may alternatively include any other device that is capable of electronic communications and programming. Theexternal unit670 may download various parameters and program software into theIMD100 for programming the operation of the implantable device. Theexternal unit670 may also receive and upload various status conditions and other data from theIMD100. Thecommunication unit660 may be hardware, software, firmware, and/or any combination thereof. Communications between theexternal unit670 and thecommunication unit660 may occur via a wireless or other type of communication, illustrated generally byline675 inFIG. 6.
• TheIMD100 also includes adetection unit695, which is capable of detecting various conditions and characteristics of the pulmonary functions of a patient. For example, thedetection unit695 may include hardware, software, or firmware that is capable of determining a respiratory rate, a heart rate, a pulse oxygen level, an oxygen saturation factor in the blood, a carbon dioxide factor in the blood, and the like. Thedetection unit695 may include means for deciphering data from various sensors that are capable of measuring respiratory rates, heart rate, RSA, pulse oxygen, etc. Additionally, thedetection unit695 may decipher data from external sources, wherein data from theexternal unit670 may be provided to theIMD100. External inputs may include data such as results from breathing testing, external pulse oxygen measurements, heart rate monitors, respiratory rate monitors, etc. Thedetection unit695 may also detect an input from the patient or an operator indicating that an onset of breathing difficulty, such as an asthma attack. Based upon data deciphered by thedetection unit695, theIMD100 may deliver stimulation to a portion of the vagus nerve to affect the pulmonary functions in the patient.
• TheIMD100 may also include astimulation target unit690 that is capable of directing a stimulation signal to one or more electrodes that is proximate to the various portions of the vagus nerve, such as the left pulmonary plexus and/or the bronchial branches of the vagus nerve. In this way, thestimulation target unit690 is capable of targeting a predetermined portion of the pulmonary region, such as the left pulmonary plexus. Therefore, for a particular type of data detected by thedetection unit695, thestimulation target unit690 may stimulate a selected portion of the pulmonary system to perform an afferent, efferent, and/or an afferent in combination with an efferent stimulation, to treat a breathing disorder. Therefore, upon an onset of an asthma attack, for example, theIMD100 may select various portions of the vagus nerve, specifically the bronchial branches, or a portion of the pulmonary plexus to stimulate to perform an efferent and/or an afferent-efferent combination stimulation, in order to alleviate the asthma attack.
• One or more blocks illustrated in the block diagram ofIMD100 inFIG. 6 may include hardware units, software units, firmware units and/or any combination thereof. Additionally, one or more blocks illustrated inFIG. 6 may be combined with other blocks, which may represent circuit hardware units, software algorithms, etc. Additionally, any number of the circuitry or software units associated with the various blocks illustrated inFIG. 6 may be combined into a programmable device, such as a field programmable gate array, an ASIC device, etc.
• Turning now toFIG. 7, a flowchart depiction of a method for treating a pulmonary disorder, in accordance with one illustrative embodiment is provided. An electrode may be coupled to a portion of a vagus nerve to perform a stimulation and/or a blocking function to treat a breathing disorder. In one embodiment, a plurality of electrodes may be positioned in electrical contact or proximate to a portion of the vagus nerve to deliver a stimulation to the portion of the vagus nerve (block710). TheIMD100 may then generate a controlled electrical signal, based upon one or more characteristic relating to the breathing condition of the patient (block720). This may include a predetermined electrical signal that is preprogrammed based upon a particular condition of a patient, such as an asthma condition, a constrictive pulmonary disorder condition, a cardiopulmonary obstructive condition, etc. For example, a physician may pre-program the type of stimulation to provide (e.g., efferent stimulation and/or afferent-efferent stimulation), in order to treat the patient based upon the type of breathing disorder of the patient. TheIMD100 may then generate a signal, such as a pulse signal, to affect the operation of one or more portions of the pulmonary system of a patient.
• TheIMD100 may then deliver the stimulation signal to the portion of the vagus nerve as determined by the factors such as an asthma condition, a constrictive pulmonary disorder condition, a cardiopulmonary obstructive condition, a pulse-oxygen percentage, etc. (block730). The application of the electrical signal may be delivered to the main portion of the vagus nerve, to the bronchial branches of the vagus nerve, and/or to the pulmonary plexus. Application of the stimulation signal is designed to promote a blocking effect relating to a signal that is being sent from the brain to the various portions of the pulmonary system to treat the breathing disorder. For example, the hyper-responsiveness may be diminished by blocking various signals from the brain to the various portions of the lungs. This may be accomplished by delivering a particular type of controlled electrical signal, such as a controlled current signal to the pulmonary plexus. Additionally, afferent fibers may also be stimulated in combination with an efferent blocking to treat a pulmonary disorder.
• Additional functions, such as a detection process, may be alternatively employed with the embodiment. The detection process may be employed such as an external detection or an internal detection of a bodily function to adjust the operation of theIMD100.
• Turning now toFIG. 8, a block diagram depiction of a method in accordance with an alternative embodiment is illustrated. TheIMD100 may perform a database detection process (block810). The detection process may encompass detecting a variety of types of characteristics of the pulmonary activity, such as respiratory rates, heart rate, pulse oxygen levels, etc. A more detailed depiction of performing the detection process is provided inFIG. 9, and accompanying description below. Upon performing the detection process, theIMD100 may determine whether a detected disorder is sufficiently severe to treat based upon the measurements performed during the detection process (block820). For example, the respiratory rate may be detected to see if an asthma attack is present. Upon a determination that the disorder is insufficient to treat by theIMD100, the detection process is continued (block830).
• Upon a determination that the disorder is sufficient to treat using theIMD100, a determination as to the type of stimulation based upon data relating to the disorder, is made (block840). The type of stimulation may be determined in a variety of manners, such as performing a look-up in a look-up table that may be stored in thememory617. Alternatively, the type of stimulation may be determined by an input from an external source, such as theexternal unit670 or an input from the patient. Further, determination of the type of stimulation may also include determining the location as to where the stimulation is to be delivered. Accordingly, the selection of particular electrodes, which may be used to deliver the stimulation signal, is made. A more detailed description of the determination of the type of stimulation signal is provided inFIG. 10 and accompanying description below.
• Upon determining the type of stimulation to be delivered, theIMD100 performs the stimulation by delivering the electrical signal to one or more selected electrodes (block850). Upon delivery of the stimulation, theIMD100 may monitor, store, and/or compute the results of the stimulation (block860). For example, based upon the calculation, a determination may be made that adjustment(s) to the type of signal to be delivered for stimulation, may be performed. Further, the calculations may reflect the need to deliver additional stimulation. Furthermore, data relating to the results of a stimulation may be stored inmemory617 for later extraction and/or further analysis. Additionally, real time or near real time communications may be provided to communicate the stimulation result and/or the stimulation log to anexternal unit670.
• Turning now toFIG. 9, a more detailed block diagram depiction of performing the detection process ofblock810 inFIG. 8 is illustrated. TheIMD100 may monitor one or more vital signs relating to the pulmonary functions of the patient (block910). For example, the breathing rates, the pulmonary obstruction level, asthma related activity, etc., may be detected. Other factors, such as breathing testing, heart rate, RSA, pulse oxygen levels, etc., may also be tested. This detection may be made by sensors residing inside the human body, which may be operatively coupled to the IMD. These factors may be also provided by an external device via thecommunication unit660.
• Upon acquisition of various vital signs, a comparison may be performed comparing the data relating to the vital signs to predetermined, stored data (block920). For example, the respiratory rates may be compared to various predetermined thresholds to determine whether aggressive action would be needed, or simply further monitoring would be sufficient. Based upon the comparison of the collected data with theoretical, stored thresholds, theIMD100 may determine whether a disorder exists (block930). For example, various vital signs may be acquired in order to determine afferent and/or efferent stimulation fibers are to be stimulated. Based upon the determination described inFIG. 9, theIMD100 may continue to determine whether the disorder is sufficiently significant to perform treatment, as described inFIG. 8.
• Turning now toFIG. 10, a more detailed flowchart depiction of determining the type of stimulation indicated inblock840 ofFIG. 8 is illustrated. TheIMD100 may determine a quantifiable parameter of a breathing disorder (block1010). These quantifiable parameters, for example, may include a frequency of occurrence of various symptoms of a disorder, e.g., tightening of the passageways, the severity of the disorder, a binary type of analysis as to whether a disorder or a symptom exists or not, a physiological measurement or detection, or other test results, such as a breathing test. Based upon these quantifiable parameters, a determination may be made whether a parasympathetic or a sympathetic response/stimulation is appropriate (block1020). For example, as illustrated in Table 2, a matrix may be used to determine whether a parasympathetic or a sympathetic response for stimulation is appropriate. This determination may be overlaid by the decision regarding whether a blocking type of stimulation or a non-blocking type of stimulation should be performed.

• 	TABLE 2
  	BLOCKING	NON-BLOCKING

  	PARASYMPATHETIC	Yes	No
  	SYMPATHETIC	No	Yes

• The example illustrated in Table 2 shows that a blocking parasympathetic stimulation is to be provided in combination with a sympathetic non-blocking stimulation for a particular treatment. A determination may be made that for a particular type of quantifiable parameter that is detected, the appropriate treatment may be to perform a parasympathetic blocking signal in combination with a sympathetic non-blocking signal. Other combinations relating to Table 2 may be implemented for various types of treatments. Various combinations of matrix, such as the matrix illustrated in Table 2 may be stored in the memory for retrieval by theIMD100.
• Additionally, external devices may perform such calculation and communicate the results and/or accompanying instructions to theIMD100. TheIMD100 may also determine the specific batch of the nerve to stimulate (block1030). For example, for a particular type of stimulation to be performed, the decision may be made to stimulate the pulmonary plexus and/or the bronchial branches of the vagus nerve. TheIMD100 may also indicate the type of treatment to be delivered. For example, an electrical treatment alone or in combination with another type of treatment may be provided based upon the quantifiable parameter(s) that are detected (block1040). For example, a determination may be made that an electrical signal by itself is to be delivered. Alternatively, based upon a particular type of disorder, a determination may be made that an electrical signal, in combination with a magnetic signal, such as transcranial magnetic stimulation (TMS) may be performed. The determination ofblock1040 may also include a decision to perform a blocking function that may include performing an electrical blocking and/or a chemical blocking (e.g., using a pharmaceutical compound, such as an anesthetic or steroid compound).
• In addition to electrical and/or magnetic stimulation, a determination may be made whether to deliver a chemical, biological, and/or other type of treatment(s) in combination with the electrical stimulation provided by theIMD100. In one example, electrical stimulation may be used to enhance the effectiveness of a chemical agent. Therefore, various drugs or other compounds may be delivered in combination with an electrical stimulation or a magnetic stimulation. Based upon the type of stimulation to be performed, theIMD100 delivers the stimulation to treat various pulmonary disorders.
• Utilizing the embodiments, various types of stimulation may be performed to treat pulmonary disorders. For example, asthma, constrictive pulmonary disorder, cardiopulmonary obstructive disorders, etc, may be treated by the performing vagus nerve stimulation described herein. Embodiments provide for performing pre-programmed delivery of stimulation and/or real time decisions relating to delivering stimulation. For example, various detections of parameters, such as respiratory rate, external input relating to physiological data, breathing testing, heart rate, RSA, pulse oxygen results, etc., may be used to determine whether a stimulation is needed and/or the type of stimulation to be delivered. Parasympathetic, sympathetic, blocking, non-blocking afferent, and/or efferent delivery of stimulation may be performed to treat pulmonary disorders.
• All of the methods and apparatus disclosed and claimed herein may be made and executed without undue experimentation in light of the present disclosure. While the methods and apparatus have been described in terms of particular embodiments, it will be apparent to those of skill in the art that variations may be applied to the methods and apparatus and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the disclosure as defined by the appended claims. It should be especially apparent that the principles of the disclosure may be applied to selected cranial nerves other than the vagus nerve to achieve particular results.
• The particular embodiments disclosed above are illustrative only, as the embodiments may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the disclosure. Accordingly, the protection sought herein is as set forth in the claims below.

Claims (20)

1. A method comprising:

positioning an electrode in a patient's body at a location proximate a branch of a vagus nerve, the branch of the vagus nerve including at least one of a bronchial branch of the vagus nerve and a pulmonary plexus; and

activating the electrode such that energy is delivered from the electrode to the branch of the vagus nerve so as to block intrinsic neural activity in the branch of the vagus nerve to treat a pulmonary disorder.

2. The method ofclaim 1, wherein the pulmonary disorder comprises asthma and delivering the energy attenuates hyper-responsiveness of an airway of the patient.

3. The method ofclaim 1, wherein the pulmonary disorder comprises chronic obstructive pulmonary disease.

4. The method ofclaim 1, wherein the electrode is placed in proximity to the pulmonary plexus near a root of a lung of the patient.

5. The method ofclaim 1, wherein signals to a brain of the patient via the vagus nerve are blocked.

6. The method ofclaim 5, wherein blocking intrinsic neural activity comprises blocking signals in both afferent and efferent nerve fibers in the branch of the vagus nerve.

7. A method comprising:

positioning an electrode outside of a bronchial airway within a subject; and

activating the electrode to deliver energy to nerve tissue positioned along the bronchial airway so as to block neural activity in the nerve tissue to treat a pulmonary disorder.

8. The method ofclaim 7, wherein the electrode is configured to deliver electrical energy to nerve tissue of a vagus nerve.

9. The method ofclaim 7, wherein the electrode is configured to deliver energy to a branch of a vagus nerve including at least one of a bronchial branch of the vagus nerve and a pulmonary plexus.

10. The method ofclaim 7, wherein the electrode is placed within the subject in proximity to a bronchial branch of a vagus nerve or in proximity to a pulmonary plexus of the subject and near a root of a lung of the subject.

11. The method ofclaim 7, wherein the electrode is placed within the subject proximate to a root of a lung of the subject.

12. An apparatus for treating a patient having a pulmonary disorder, the apparatus comprising:

an electrode positionable in a patient's body on or in proximity to a branch of a vagus nerve such that the electrode is operatively coupled thereto, the branch including at least one of a bronchial branch of the vagus nerve and a pulmonary plexus; and

a generator configured to be coupled to the electrode to deliver electrical energy thereto;

wherein the electrode is configured to deliver the electrical energy to the branch of the vagus nerve so as to block intrinsic neural activity in the branch of the vagus nerve to treat the pulmonary disorder.

13. The apparatus ofclaim 12, wherein the electrode is configured to be positioned in proximity to the pulmonary plexus near a root of a lung of the patient.

14. The apparatus ofclaim 12, wherein the electrode is configured to be positioned outside a bronchial airway of the patient.

15. The apparatus ofclaim 12, wherein the electrode is configured to be indirectly coupled to the branch of the vagus nerve.

16. The apparatus ofclaim 12, further comprising a sensor adapted to sense a parameter in the patient's body, the generator being configured to deliver the electrical energy in response to data received from the sensor.

17. The apparatus ofclaim 16, wherein the parameter comprises a symptom of the pulmonary disorder.

18. The apparatus ofclaim 16, further comprising a means for modulating the electrical energy based on the data received from the sensor.

19. The apparatus ofclaim 12, wherein the generator is configured to modulate the electrical energy based on an impedance detected at the electrode.

20. The apparatus ofclaim 12, wherein the generator is configured to be implanted in the patient's body.

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