Patent Application
20050085874
The present invention is generally directed to the application of implantable medical devices in treating physical dysfunctions, and more particularly to method and system for treatment of Obstructive Sleep Apnea (OSA).
Obstructive sleep apnea (OSA) is a common disorder, estimated to affect 4% of middle-aged men and 2% of women. This disorder is characterized by recurrent pharyngeal collapse during sleep leading to repetitive arousals and nocturnal hypoxemia. OSA occurs in individuals with an anatomically small pharyngeal airway. Because of sleep-induced decreases in upper airway muscle tone, the airway collapses necessitating brief arousals from sleep to re-establish airway patency. These recurrent arousals result in sleep fragmentation, excessive daytime sleepiness and decreased quality of life. In addition, the arousals and the nocturnal hypoxemia result in catecholamine surges. Furthermore, there is accumulating evidence that adverse cardiovascular sequelae such as hypertension, arrhythmias, cerebrovascular events, myocardial infarction, and congestive heart failure may result from OSA.
Current methods of therapy are aimed at splinting the airway open during sleep (Continuous Positive Airway Pressure: CPAP) or enlarging the pharyngeal airway through surgery or the use of oral appliances. Nasal CPAP is the most effective and most widely used therapy for obstructive sleep apnea. However, acceptance of and compliance with CPAP creates limitations for its use. Compliance with CPAP is generally reported to be in the range of 50 to 85%. Patients who abandon CPAP therapy typically do so during the first 2 to 4 weeks of treatment because of issues related to mask discomfort, nasal dryness and congestion, and difficulty adapting to the pressure.
Studies demonstrate that compliance with CPAP is poor, although it can be improved with consistent follow-up (e.g. support groups) and when the patient's disease is severe. Untreated, patients with obstructive sleep apnea are at risk of negative sequelae. Thus, there exists a need for an alternative to CPAP for patients with obstructive sleep apnea.
The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims.
The present invention provides a method and system for treating OSA in a patient. As shown in
As indicated above, the present invention is directed to a method and system for treating sleep apnea, and more particularly OSA using at least two small implantable microstimulators, also referred to as BION™ devices. Various features and details associated with the manufacture, operation and use of such implantable microstimulators, or BION devices, may be found in one or more of the following documents, all of which are incorporated herein by reference: U.S. Pat. No. 5,193,539 entitled “Implantable Microstimulator”; U.S. Pat. No. 5,193,540, entitled “Structure and Method of Manufacture of an Implantable Microstimulator”; U.S. Pat. No. 5,312,439 entitled “Implantable Device Having an Electrolytic Storage Electrode”; U.S. Pat. No. 6,164,284, entitled “System of implantable devices for monitoring and/or affecting body parameters; U.S. Pat. No. 6,185,452, entitled “Battery-powered patient implantable device”; U.S. Pat. No. 6,208,894, entitled “System of implantable devices for monitoring and/or affecting body parameters”; U.S. Pat. No. 6,315,721, entitled “System of implantable devices for monitoring and/or affecting body parameters”; U.S. Pat. No. 6,564,807, entitled “System of implantable devices for monitoring and/or affecting body parameters”.
Referring to
By increasing the GGM tone using cyclic/alternating stimulation to the HGNs, the posterior portion of the GGM will be more capable of contracting forward thereby relieving the airway obstruction. By alternating the stimulation of the left and right HGNs, each side of the GGM develops tone while there is a period of rest for the other side's GGM; this results in less chance of GGM fatigue. It is understood that a traditional approach of continuously stimulating and contracting only one side of the GGM results in muscle fatigue because the muscles require a relaxation period in order to allow blood circulation for oxygen and metabolic substances to reach the appropriate muscle fibers and for metabolic by-product to be removed. The alternating stimulation of the HGNs can be performed in equal or varying durations. For example, the right HGN can be stimulated for a first predetermined period of time and the left HGN can be stimulated for a second predetermined period of time. Each HGN stimulation period can be concurrent or sequential and based on distinct inspiratory phases of the patient. For example, it is contemplated to stimulate the first HGN based on the first inspiratory phase and to stimulate the second HGN based on the second inspiratory phase. Furthermore, the first predetermined period of time and the second predetermined period of time can be partially overlapping in time.
According to the present invention, the stimulation duration of each HGN based on the inspiratory phase is about 5 seconds, which is produced by the burst counter 114 and communicated to the microprocessor 118. Moreover, the frequency of the each stimulation pulse is the range of about 20 to 100 Hz (preferably about 30 Hz) and the pulse width is about 200 microseconds. The stimulation current is in the range of about 0.5 to 5 milliamps depending on the proximity of the microstimulator to the desired HGN. As shown in
The stimulation timing of both HGNs can be either by a closed-loop feedback from sensors or an open-loop method. In an embodiment of an open-loop method, a patient's breathing pattern is monitored while asleep. The monitoring is accomplished either with another person present or through any known medical monitoring equipment that may be connected to the patient. The phase of the breathing cycle/respiratory function of the patient may be monitored by a monitoring unit in the form of sensor such as a nasal flow probe 111, thermocouple, a pulse oxygen sensor, or with force sensitive bands on the thorax, or with any other monitoring means known to those skilled in the art. After the monitoring of the patient's breathing pattern, a determination is made as to the length and frequency of the patient's inspiratory effort/pattern. Having the aforementioned information available, then alternating stimulation to each HGN to cause alternating contraction of each side of the GGM according to the inspiratory pattern is performed.
In an embodiment of a closed-loop method, a sensor or a group of sensors are utilized to monitor the patient's respiratory function similar to those sensors utilized in the open-loop method. The sensors can be any conventional sensors (e.g. those positioned on the nose or surface of the skin of the thorax/abdomen of a patient) capable of monitoring parameters of a patient indicative of the respiratory function. Hence, utilizing the sensors the respiratory function of the patient is monitored such that based on the determination of the inspiratory pattern one or both of the HGNs of the patient are stimulated. A feedback control signal is provided from the sensors monitoring the respiratory cycle/function of the patient to the controller, which in turn controls the operation of the stimulation function of the microstimulators.
In an aspect of the present invention, it is contemplated that instead of alternating/cycling, both microstimulators would stimulate the left and the right HGNs concurrently. When both sides of the GGMs contract at the same time, each side would then need less contraction than when one side is used. This will be advantageous in providing a lower amount of stimulation current to each HGN than the total amount of stimulation current applied to a single HGN in a traditional OSA treatment, and possibly provide a more symmetrical opening of the pharynx. This mode of simultaneous HGN stimulation could be during inspiratory phases only or during both inspiratory and expiratory phases of a sleeping patient.
In normal individuals (i.e., non-apneic), the level of activity of the GGM is the same during sleep as it is during wakefulness. In individuals with OSA, the level of activity of the GGM is increased approximately three times normal during wakefulness to compensate for their structurally small pharyngeal airway. When asleep, individuals with OSA experience a large reduction in genioglossus activity from the elevated levels seen when they are awake. In the present invention, it is contemplated that an afferent stimulation of the HGN is provided, which is set at a sub-motor threshold level. This is intended to cause an increase in the excitability of the hypoglossal nucleus (brain stem) resulting in an increase in firing of motor axons down the HGN producing an increase in tone of GGM muscles, thereby leading to a sustained increase in the pharyngeal airway and thus alleviating the main problem of OSA.
In the present invention, it is contemplated that the afferent fibers of the left and right HGN(s) are stimulated concurrently or in an alternate fashion. Furthermore, it is contemplated in the present invention that a motor-threshold level stimulation of the efferent fibers of the HGN(s) is provided as an excitatory input to the GGM(s). This is intended to produce an opening of the airway, thereby relieving an obstruction of the OSA.
The various operations and stimulation methods according to the present invention are described below with reference to the relevant figures—
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It must be noted that the aforementioned operations and stimulation methods may be effected utilizing a closed-loop or an open-loop method as described above.
For a more clear visualization of the positioning of the microstimulators with respect to the HGN,
The descriptions of the invention, the specific details, and the drawings mentioned above, are not meant to limit the scope of the present invention. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes, which come within the meaning and range of equivalency of the claims, are to be embraced within their scope.
This application claims the benefit of U.S. Provisional Application No. 60/512,245 filed on Oct. 17, 2003.
| Number | Date | Country | |
|---|---|---|---|
| 60512245 | Oct 2003 | US |
