US20030204213A1 - Method and apparatus to detect and monitor the frequency of obstructive sleep apnea - Google Patents

Abstract

The present invention provides a method and apparatus for detecting and monitoring obstructive sleep apnea. The apparatus includes an intracardiac impedance sensor to measure intracardiac impedance, a movement sensor to measure an amount of movement of a patient, and a controller operatively coupled to said intracardiac impedance sensor and said movement sensor, said controller adapted to receive at least one of an intracardiac impedance and the amount of movement of the patient and detect obstructive sleep apnea based upon said intracardiac impedance and said movement.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention[0001]
• This invention relates generally to implantable medical devices, and more particularly, to a method and apparatus to automatically detect and monitor the frequency of obstructive sleep apnea.[0002]
• 2. Description of the Related Art[0003]
• Although the function of sleep is not well understood, one consequence of an inadequate quantity or poor quality of sleep is an inability to maintain adequate wakefulness. The amount of sleep an individual needs is thought to be neurologically determined and is generally stable over time. Among other factors, an insufficient amount of sleep (i.e., quantity of sleep) or a disruption of sleep continuity (i.e., quality of sleep) will result in increased daytime sleepiness. Increased sleepiness in a person may cause a plethora of problems to that person as well as others. Increased sleepiness is a major cause of accidents because people who are sleepy are generally not fully aware of their surroundings. Additionally, because of this decreased awareness, a person who does not receive the adequate quantity and quality of sleep at night may also be prone to decreased efficiency at home and at work. A sleepy person may also require frequent naps during the day to recuperate, thereby reducing productivity in the office as well as in the chores of daily life. As a result, it is important for people generally to receive a good night's rest. However, many people have medical conditions that prevent them from receiving a good night's rest. One such condition is sleep apnea.[0004]
• Sleep apnea is generally defined as the cessation of breathing during sleep. One type of a sleep apnea, obstructive sleep apnea (“OSA”), is caused by repetitive upper airway obstruction during sleep as a result of narrowing of the respiratory passages. Partial obstruction of the passageways may simply lead to hypopnea. Prolonged obstruction of the passageways, however, may lead to nocturnal arousals.[0005]
• OSA is generally characterized by a sleep-related withdrawal of upper airway inspiratory muscle tone superimposed on a narrow, highly compliant pharynx. As a result, the pharynx may during sleep, leading to obstructive apnea.[0006]
• The cause of OSA is thought to be a combination of anatomic characteristics of the upper airway and abnormalities in the neuromuscular control of the muscles in the throat. Sleep apnea is more common in individuals with large tonsils, palate, and tongue, and with a short thick neck. This anatomy may predispose the throat to easily collapse. A badly deviated nasal septum or other nasal obstruction can also worsen OSA because it limits the ability to breathe through the nose. Overweight individuals are also at high risk for OSA. Not all individuals with these anatomic features will have OSA, and OSA occasionally occurs in people with normal-appearing throats.[0007]
• OSA may cause a variety of medical and other problems among patients. Cycles of sleep, snoring, obstruction, arousal, and sleep may occur many times throughout the night. Although such nocturnal arousals may last only a few seconds, they prevent a person from reaching the deep stages of sleep, which the body generally needs to rest and replenish its strength. As a result, patients with OSA may not receive a restful sleep because of multiple nocturnal arousals.[0008]
• Furthermore, multiple arousals with sleep fragmentation are likely to cause excessive daytime sleepiness and fatigue, cognitive impairment, depression, headaches, chest pain, and diminished sexual drive. OSA is generally associated with cardiovascular morbidity, including systemic hypertension, pulmonary hypertension, ischemic heart disease, stroke, and cardiac arrhythmias. OSA is also usually associated with increased mortality by negatively effecting the status, progression, and outcomes of previously existing conditions, such as congestive heart failure (“CHF”).[0009]
• OSA is a disorder which is generally underdiagnosed and undertreated. Because OSA may worsen the effects of a previously existing condition, such as CHF, treatment of OSA may be beneficial to reduce its negative on the previously existing condition. Once OSA has been properly diagnosed, a variety of therapies may be available. Common OSA therapies include non-surgical methods, such as continuous positive airway pressure (“CPAP”), as well as surgical methods, such as uvulopalatopharyngoplasty (“UPPP”). Effective therapy for OSA can often reverse or ameliorate the problems associated with OSA.[0010]
• One method of diagnosis for OSA is nocturnal polysomnography. In nocturnal polysomnography, multiple physiological parameters are measured while the patient sleeps in a laboratory. Typical parameters in a nocturnal polysomnography include eye movement observations (to determine whether a patient has reached REM sleep), an electroencephalogram (to determine arousals from sleep), chest wall monitors (to document respiratory movements), nasal and oral air-flow measurements, and an electrocardiogram, among other parameters. A combination of these and other factors are used by doctors and other qualified sleep specialists to determine whether a patient has OSA. However, nocturnal polysomnography is generally expensive and time-consuming. Furthermore, many patients experience the symptoms of OSA (e.g., nocturnal arousals, snoring) while they are asleep, and therefore, never recognize that they may have a sleeping disorder. As a result, many patients with OSA may not seek proper diagnosis or treatment of their sleeping disorder from a doctor or other qualified sleep specialist. Even if a patient is diagnosed with OSA, frequent laboratory monitoring of the patient is generally not feasible due to the expense and time involved in a nocturnal polysomnography.[0011]
• The technology explosion in the implantable medical devices industry has resulted in many new and innovative devices and methods for analyzing and improving the health of a patient. The class of implantable medical devices now includes pacemakers, implantable cardioverters, defibrillators, neural stimulators, and drug administering devices, among others. Today's state-of-the-art implantable medical devices are vastly more sophisticated and complex than early ones, capable of performing significantly more complex tasks. The therapeutic benefits of such devices have been well proven.[0012]
• There are many implementations of implantable medical devices that provide data acquisition of important physiological data from a human body. Many implantable medical devices are used for cardiac monitoring and therapy. Often these devices comprise sensors that are placed in blood vessels and/or chambers of the heart. Often these devices are operatively coupled with implantable monitors and therapy delivery devices. For example, such cardiac systems include implantable heart monitors and therapy delivery devices, such as pacemakers, cardioverters, defibrillators, heart pumps, cardiomyostimulators, ischemia treatment devices, drug delivery devices, and other heart therapy devices. Most of these cardiac systems include electrodes for sensing and gain amplifiers for recording and/or driving sense event signals from the inter-cardiac or remote electrogram (“EGM”).[0013]
• Many patients who use implantable medical devices may be at risk for OSA.[0014]
• However, patients are generally left with traditional forms of diagnosis for OSA, such as nocturnal polysomnography. As mentioned, nocturnal polysomnography may be an expensive and time-consuming procedure. Furthermore, many patients may not recognize that they have symptoms relating to OSA, such that they would seek diagnosis and treatment for the disorder. Nocturnal polysomnography is generally an infrequent procedure that does not provide long term monitoring of the patient's condition after he has been diagnosed. The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.[0015]
SUMMARY OF THE INVENTION
• In one aspect of the present invention, an apparatus is provided for detecting and monitoring obstructive sleep apnea. The apparatus includes an intracardiac impedance sensor to measure intracardiac impedance, a movement sensor to measure an amount of movement of a patient, and a controller operatively coupled to said intracardiac impedance sensor and said movement sensor, said controller adapted to receive at least one of an intracardiac impedance and the amount of movement of the patient and detect obstructive sleep apnea based upon said intracardiac impedance and said movement.[0016]
• In another aspect of the present invention, a method is provided for detecting and monitoring obstructive sleep apnea. The method includes measuring an intracardiac impedance to detect a change in the intracardiac impedance, measuring an amount of movement of a patient, and determining the presence of obstructive sleep apnea based upon the change in the intracardiac impedance and the movement of the patient.[0017]
BRIEF DESCRIPTION OF THE DRAWINGS
• The invention 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:[0018]
• FIG. 1 is a simplified diagram of an implementation of an implantable medical device, in accordance with one illustrative embodiment of the present invention;[0019]
• FIG. 2 illustrates a simplified block diagram representation of an implantable medical system in accordance with one illustrative embodiment of the present invention;[0020]
• FIG. 3 illustrates a more detailed block diagram representation of the implantable medical device of FIGS. I and[0021]2, in accordance with one illustrative embodiment of the present invention; and
• FIG. 4 illustrates a more detailed block diagram representation of a plurality of sensors and its associated data interfaces of FIG. 3, in accordance with one illustrative embodiment of the present invention.[0022]
• While the invention is 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 invention 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 invention as defined by the appended claims.[0023]
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
• Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.[0024]
• There are many discrete processes involving the operation of implantable medical devices (e.g., pacemakers, cardio defibrillators, the like). The operation of an implantable medical device includes collecting, storing, and analyzing physiological data relating to a patient, and/or delivering therapy (e.g., cardiac therapy) to a portion of a patient's body. Often, these tasks are performed by an implantable medical system, which includes an implantable medical device. Based upon the analysis performed by the implantable medical system, one or more therapies may be delivered to a particular portion of a patient's body. One example of such a therapy is a cardiac therapy, which is delivered to a patient's heart.[0025]
• Embodiments of the present invention may be utilized to detect and monitor the common symptoms and conditions related to patients with Obstructive Sleep Apnea (OSA). It should be appreciated that the present invention may be included in an implantable device capable of collecting data other than data used to diagnose or monitor OSA. The data may be collected by sensors in the implantable device and may be used by doctors and other sleep experts to judge the severity of apneas and to determine the efficacy of apnea therapy, without the use of nocturnal polysomnography.[0026]
• Turning now to FIG. 1, one embodiment of implementing an implantable medical device into a human body is illustrated. A sensor device[0027]210 (e.g., devices attached to leads114) placed upon theheart116 of thehuman body105 is used to acquire and process physiological data. In one embodiment, thesensor device210 may also be a therapy delivery device (described in greater detail below). An implantablemedical device220 collects and processes a plurality of data acquired from thehuman body105. In one embodiment, the implantablemedical device220 may be a cardiac pacemaker or an implantable cardiovertor defibrillator (“ICD”). The data acquired by the implantablemedical device220 can be monitored by an external system, such as theaccess device240 comprising aprogramming head122, which remotely communicates with the implantablemedical device220. Theprogramming head122 is utilized in accordance with medical device programming systems known to those skilled in the art having the benefit of the present disclosure, for facilitating two-way communication between the implantablemedical device220 and theaccess device240.
• In one embodiment, a plurality of[0028]access devices240 can be employed to collect a plurality of data, including OSA data, processed by the implantablemedical device220 in accordance with embodiments of the present invention. The implantablemedical device220 is housed within a hermetically sealed, biologically inert outer canister orhousing113, which may itself be conductive so as to serve as an electrode in the implantablemedical device220 pacing/sensing circuit. One or more sensors/leads, collectively identified withreference numeral114 in FIG. 1, are electrically coupled to the implantablemedical device220 and extended into the patient'sheart116 via avein118. Disposed generally near a distal end of theleads114 are one or more exposed conductive electrodes (i.e., sensor device210) for receiving electrical cardiac signals or delivering electrical pacing stimuli to theheart116. The leads114 may be implanted with their distal end situated in either the atrium or ventricle of theheart116. In an alternative embodiment, thesensor device210, or theleads114 associated with thesensor device210, may be situated in a blood vessel on theheart116, such as avein118.
• Turning now to FIG. 2, a[0029]system200, in accordance with one embodiment of the present invention, is illustrated. Thesystem200 comprises a plurality of sensor devices, collectively identified withreference numeral210 in FIG. 2, an implantablemedical device220, anaccess device240, and aninterface230 that provides a communication link between the implantablemedical device220 and theaccess device240. Embodiments of the present invention provide a plurality of physiological data from thesensor devices210, which are then processed and stored in the implantablemedical device220. In one embodiment, thesensor devices210 may collect data that is used to detect and monitor OSA in a patient.
• As mentioned, based upon physiological data and other factors, the implantable[0030]medical device220 may deliver a therapy to a portion of the patient's body, via thesensor devices210. Theaccess device240 can then be used to monitor and analyze the organized data from the implantablemedical device220 via theinterface230 and view results from delivered therapy. Theaccess device240 can be used to monitor the efficiency of the therapy delivered by the implantablemedical device220. Theaccess device240 can be used to determine, based upon data stored by the implantablemedical device220, whether a therapy delivered was of proper energy intensity.
• Turning now to FIG. 3, a more detailed block diagram depiction of one embodiment of the implantable[0031]medical device220 is illustrated. The implantablemedical device220 comprises aprocessor310, acontrol logic320, amemory unit330, adata acquisition controller340, atelemetry interface350, and a plurality ofdata interfaces360,370,380,390. The plurality ofsensor devices210 of FIG. 2 provide various physiological data to the implantablemedical device220. Theprocessor310 controls the operation of the implantablemedical device220. Theprocessor310 utilizes thecontrol logic320 to perform a plurality of operations, including memory access and storage operations. Theprocessor310 communicates with thecontrol logic320 and thedata acquisition controller340 via abus line325. Thecontrol logic320 sends control signals to thememory unit330 for controlling and installing thememory unit330, and to thedata acquisition controller340, which controls the acquisition of physiological data and drives output signals to thetelemetry interface350.
• The[0032]telemetry interface350 can facilitate real-time access of physiological data acquired by thedata acquisition controller340. Therefore, a physician can view physiological data on a real time basis by accessing thedata acquisition controller340, via thetelemetry interface350. Thedata acquisition controller340 can prompt the data interfaces360,370,380,390 to retrieve physiological data from thesensor device210, process such data, and deliver physiological data to thedata acquisition controller340. The data interfaces360,370,380,390 can perform a number of analog-to-digital conversions and time-interval conversions, known to those skilled in the art, upon the acquired physiological data. The data interfaces360,370,380,390 can acquire, condition, and process physiological data and forward them to thedata acquisition controller340.
• It should be appreciated that, in an alternate embodiment, the functionality of the data interfaces[0033]360,370,380,390 may be combined with thesensor devices210, such that information gathered by thesensor devices210 may be readily utilized by the implantablemedical device220 without further processing by another device or interface. It should also be appreciated that, although thesensor devices210 are separated from the implantablemedical device220 for illustrative purposes in FIGS. 2 and 3, the implantablemedical device220 may further comprise thesensor devices210.
• Turning now to FIG. 4, one embodiment of the[0034]sensor device210 and the implantablemedical device220 of FIGS. 1, 2, and3, in accordance with the present invention, is shown. In the illustrated embodiment of FIG. 4, four sensors are shown. However, it should be appreciated that the implantablemedical device220 may comprise of more or less sensors than the illustrated embodiment of FIG. 4, such that OSA may be properly diagnosed on a patient. It should also be appreciated that the functionality of each sensor described below may be combined into one or more sensors, such that OSA may be properly diagnosed on a patient.
• The implantable[0035]medical device220 comprises four sensors, which individually and in combination may be used to detect OSA in a patient. An intracardiac impedance sensor210-1 measures impedance between an intracardiac atrial electrode and an intracardiac ventricular electrode. An intrathoracic impedance sensor210-2 measures impedance across the thorax. In one embodiment, the intrathoracic impedance sensor210-2 may include pacemaker sensors, which measure impedance between a pacemaker and an intracardiac electrode. The impedance between the pacemaker and the intracardiac electrode may be used to estimate in minute ventilation (“MV”). A movement sensor210-3 detects movement in a patient during sleep. The movement sensor210-3, in one embodiment, may be a piezo crystal or an accelerometer. An electrical sensor210-4 detects cardiac depolarizations.
• Using the four sensors[0036]210-1,210-2,210-3,210-4, a plurality of information can be gathered to properly diagnosis OSA on a patient. The information gathered by the sensors210-1,210-2,210-3, and210-4 is processed by anintracardiac data interface360, an intrathoracicimpedance data interface370, amovement data interface380, and anelectrical data interface390, respectively, before the information is forwarded to thedata acquisition controller340. Although sensors can be used individually to diagnose OSA, combinations of two or more sensors may form a basis for diagnosis of OSA. For example, a large decrease in impedance between atrial and ventricular electrodes (i.e., a decrease in the intracardiac impedance sensor210-1) occurring when a patient is not exercising (i.e., a low reading from the movement sensor210-3) may be a factor towards diagnosis of OSA. As a patient attempts to breath while his airway is obstructed, negative intrathoracic pressure may increase, which overfills the right side of the heart. This overfilling of the right side of the heart increases the diameter of the atrium and the ventricle. Although the volume of the heart does not change, the shape of the heart becomes shorter and wider. As a result, a drop in atrial-to-ventricular impedance may be observed during OSA because the wider blood pool will cause a reduced impedance. The wider blood pool may also be a result vigorous exercise from the patient. Therefore, the intracardiac impedance sensor210-1 may be read in conjunction with the movement sensor210-3. In one embodiment, a low reading from the movement sensor210-3 indicates the patient is not exercising or in some other physical activity. A decrease in the intracardiac impedance sensor210-1 and a low reading from the movement sensor210-3 indicates a possibility that the patient has OSA.
• Another possible indication that a patient has OSA may be provided by the intrathoracic impedance sensor[0037]210-2. In one embodiment, the intrathoracic impedance sensor210-2 may measure impedance between an implantable device housing, such as a can electrode, and an endocardial electrode, such as an atrial electrode or a ventricular electrode. A decrease in intrathoracic impedance during attempted inspiration may be a factor in determining whether a patient has OSA. As a patient attempts to breathe while his airway is obstructed, the circumference of his thorax may expand. As the patient's thorax expands, the diaphragm pushes the heart and lungs upward. As the lungs are pushed upward, the lungs do not change volume, but instead become shorter and wider. The shorter and wider shape of the lungs may reduce intrathoracic impedance. In addition, as a patient attempts to breath while his airway is obstructed, negative intrathoracic pressure may increase, which overfills the right side of the heart. As the right side of the heart overflows, a wider blood pathway forms, thereby reducing intrathoracic impedance. Furthermore, upward movement of the diaphragm pushes the heart closer to the implantablemedical device220, thereby reducing impedance. A decrease in the intrathoracic impedance sensor210-2 indicates the possibility that the patient has OSA.
• Another possible indication that a patient has OSA comes from a rapid increase in impedance minute ventilation (“MV”) followed by a slower decrease in impedance MV. A person who does not have sleep apnea breathes normally during rest. A patient who has OSA usually cannot breathe normally during rest because of an obstruction in the airway. While the patient's heart is attempting to pump blood into the lungs, the obstruction is preventing the patient from breathing. As a result, the patient's heart begins to pump faster to compensate for the lack of blood flow. After an arousal event, the patient begins to breathe again, but because the heart was pumping fast before the arousal event, the patient goes through a hyperpneic phase, which is a period of abnormally rapid or deep breathing. Studies have shown that during the hyperpneic phase there may be an immediate rise in MV followed by a more gradual drop in MV over a period of time.[0038]
• An arousal event each time an obstruction is relieved may cause brief periods of movement detectable by the movement sensor. As mentioned, in one embodiment, the movement sensor may be a piezo crystal or an accelerometer. During the hyperpneic phase following the release of an obstruction, there is usually a brief arousal which can cause body movement detectable by movement sensors. A brief period of movement during sleep coinciding with the dramatic increase in respiration (i.e., a rapid increase in impedance MV followed by a slower decrease in impedance MV), as described above, may indicate the patient has OSA. An immediate rise in MV followed by a more gradual drop in MV, coupled with a brief of movement of sleep, indicates the possibility that the patient has OSA.[0039]
• Yet another possible indication that a patient has OSA may be provided by the electrical sensor[0040]210-4. OSA can cause bradycardia during an obstruction. Bradycardia is an abnormally slow or unsteady heart rhythm (usually less than 60 beats per minute) that causes symptoms such as dizziness, fainting, fatigue, and shortness of breath. Release of the obstruction is generally accompanied by sinus tachycardia and possibly increased atrial-ventricular conduction. Sinus tachycardia is a fast heartbeat (usually more than 150 beats per minute) because of rapid firing of the sinoatrial (i.e., sinus) node. Both sinus tachycardia and increased atrial-ventricular conduction can be detected by intracardiac electrodes and electrical sensing amplifiers or by subcutaneous electrodes and electrical sensing amplifiers.
• Referring back to FIG. 3, as the sensors[0041]210-1,210-2,210-3,210-4 collect data, the data interfaces360,370,380,390 process the data, in accordance with conventional practice, and forwards the data to thedata acquisition controller340. Theprocessor310 then utilizes thecontrol logic320 to provide the data from the data acquisition controller to thememory unit330. In addition, a doctor or another qualified sleep professional may use thetelemetry interface350 to facilitate real-time access to the data on the data acquisition controller. The doctor or another qualified sleep specialist may analyze the collected data to determine whether the patient has OSA.
• The particular embodiments disclosed above are illustrative only, as the invention 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 invention. Accordingly, the protection sought herein is as set forth in the claims below.[0042]

Claims (26)

What is claimed:

1. A method of detecting and monitoring obstructive sleep apnea, comprising:

measuring an intracardiac impedance to detect a change in the intracardiac impedance;

measuring an amount of movement of a patient; and

determining the presence of obstructive sleep apnea based upon the change in the intracardiac impedance and the movement of the patient.

2. A method ofclaim 1, wherein measuring the intracardiac impedance further comprises measuring the intracardiac impedance between an intracardiac atrial electrode and an intracardiac ventricular electrode.

3. A method ofclaim 1, wherein measuring the intracardiac impedance further comprises detecting a decrease in the intracardiac impedance.

4. A method ofclaim 1, wherein measuring the amount of movement of the patient further comprises detecting a low amount of movement of the patient.

5. A method of detecting and monitoring obstructive sleep apnea, comprising:

measuring the intrathoracic impedance to detect a change in the intrathoracic impedance; and

determining the presence of obstructive sleep apnea based upon the change in the intrathoracic impedance.

6. A method ofclaim 5, wherein measuring the intrathoracic impedance further comprises measuring the intrathoracic impedance between an endocardial electrode and a pacemaker housing.

7. A method ofclaim 5, wherein measuring the intrathoracic impedance further comprises detecting a decrease in the intrathoracic impedance.

8. A method of detecting and monitoring obstructive sleep apnea, comprising:

measuring impedance minute ventilation to detect a change in the impedance minute ventilation;

measuring an amount of movement of a patient; and

determining the presence of obstructive sleep apnea based upon the change in the impedance minute ventilation and the movement of the patient.

9. A method ofclaim 8, wherein measuring impedance minute ventilation further comprises detecting an increase in impedance minute ventilation followed by a decrease in impedance minute ventilation.

10. A method ofclaim 8, wherein measuring impedance minute ventilation further comprises detecting an immediate increase in impedance minute ventilation followed by a more gradual decrease in impedance minute ventilation.

11. A method ofclaim 8, wherein measuring the amount of movement of the patient further comprises detecting a low amount of movement of the patient.

12. A method of detecting and monitoring obstructive sleep apnea, comprising:

detecting sinus tachycardia;

measuring an atrial-ventricular conduction to detect a change in the atrial-ventricular conduction; and

determining the presence of obstructive sleep apnea based upon detecting sinus tachycardia and the change in the atrial-ventricular conduction.

13. A method ofclaim 12, measuring the atrial-ventricular conduction further comprises detecting an increase in the atrial-ventricular conduction.

14. A medical device for detecting and monitoring obstructive sleep apnea, comprising:

means for measuring an intracardiac impedance to detect a change in the intracardiac impedance;

means for measuring an amount of movement of a patient; and

means for determining the presence of obstructive sleep apnea based upon the change in the intracardiac impedance and the movement of the patient.

15. A medical device for detecting and monitoring obstructive sleep apnea, comprising:

means for measuring the intrathoracic impedance to detect a change in the intrathoracic impedance; and

means for determining the presence of obstructive sleep apnea based upon the change in the intrathoracic impedance.

16. A medical device for detecting and monitoring obstructive sleep apnea, comprising:

means for measuring impedance minute ventilation to detect a change in the impedance minute ventilation;

means for measuring an amount of movement of a patient; and

means for determining the presence of obstructive sleep apnea based upon the change in the impedance minute ventilation and the movement of the patient.

17. A medical device for detecting and monitoring obstructive sleep apnea, comprising:

means for detecting sinus tachycardia;

means for measuring an atrial-ventricular conduction to detect a change in the atrial-ventricular conduction;

means for determining the presence of obstructive sleep apnea based upon detecting sinus tachycardia and the change in the atrial-ventricular conduction.

18. A medical device for detecting and monitoring obstructive sleep apnea, comprising:

an intracardiac impedance sensor to measure an intracardiac impedance;

a movement sensor to measure an amount of movement of a patient; and

a controller operatively coupled to said intracardiac impedance sensor and said movement sensor, said controller adapted to receive at least one of an intracardiac impedance and the amount of movement of the patient and detect obstructive sleep apnea based upon said intracardiac impedance and said movement.

19. The medical device ofclaim 18, wherein the movement sensor further comprises a piezo crystal.

20. The medical device ofclaim 18, wherein the movement sensor further comprises an accelerometer.

21. The medical device ofclaim 18, further comprising an intrathoracic impedance sensor operatively coupled to said controller to measure an intrathoracic impedance, said controller adapted to receive the intrathoracic impedance and to detect said obstructive sleep apnea based upon said intrathoraic impedance.

22. The medical device ofclaim 18, further comprising an electrical sensor operatively coupled to said controller to measure electrical activity in a heart, said controller adapted to receive the electrical activity and to detect said obstructive sleep apnea based upon said electrical activity.

23. The medical device ofclaim 22, wherein the electrical sensor detects cardiac depolarizations.

24. The medical device ofclaim 22, wherein the electrical sensor comprises an electrical sensing amplifier and at least one of a cardiac electrode and a subcutaneous electrode.

25. The medical device ofclaim 22, wherein at least one of the intracardiac impedance sensor, the intrathoracic impedance sensor, the movement sensor, and the electrical sensor is implantable.

26. The medical device ofclaim 18, further comprising a telemetry interface adapted to facilitate real-time access to the data on the controller.

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