Method and apparatus for the treatment of central sleep apnea using biventricular pacing

FIELD OF THE INVENTION

[0001] The present invention generally relates to implantable medical devices. Specifically, the invention relates to the prevention of hypopnia during sleep apnea by stimulating the phrenic nerve with implanted cardiac leads, when the onset of sleep apnea is detected. More specifically, the invention relates to a biventricular pacemaker adapted to provide an automatically adjustable output via a lead preferably located in the coronary sinus.

BACKGROUND OF THE INVENTION

[0002] Sleep apnea is generally associated with the cessation of breathing during sleep. The medical characteristics of sleep apnea have been known for some time. Sleep apnea is terminated by the subject's arousal, followed by hyperventilation. Such arousals from sleep are generally associated with increased sympathetic nervous system activity and blood pressure, which may contribute to the worsening of a patient's cardiac condition.

[0003] Generally, there are two types of sleep apnea. The first is central sleep apnea, which relates to the failure of the body to automatically generate the neuro-muscular stimulation necessary to initiate and control the respiratory cycle at the proper time. The second sleep apnea syndrome is known as obstructive sleep apnea. This generally relates to an obstructive apnea that includes reduction of the size of the superior airways, an increase in their compliance and reduction in the activity of the dilator muscles.

[0004] In the prior art, there are disclosures that suggest various methods and structures to treat events of sleep apnea. For example, in U.S. Pat. No. 6,126,611 to Bourgeois et al., a system is disclosed for stimulating the heart at a higher rate than the heart's natural rate when an apnea event is detected.

[0005] Further examples of pertinent prior art include: U.S. Pat. No. 6,091,973 to Colla et al. discloses a diagnostic system for determining an apneic or hypopneic arousal; U.S. Pat. No. 5,974,340 to Kadhiresan discloses apparatus and method for monitoring respiratory function in heart failure patients to determine the efficacy of therapy; U.S. Pat. No. 5,591,216 to Testerman et al. discloses a method for opening an upper airway of a patient by applying electrical stimulation to the patient's hypoglossal nerve; and U.S. Pat. No. 5,540,733 to Testerman et al. discloses a method and apparatus for detecting and treating obstructive sleep apnea. Electrical stimulation of muscles of the upper airway, including detection of obstructive apnea and stimulation of the muscles of the upper airway in response to the apnea is disclosed.

[0006] Moreover, U.S. Pat. No. 5,540,732 to Testerman discloses method and apparatus for impedance detecting and treating obstructive airway disorders. In this disclosure, an implanted impedance-sensing circuit provides a signal characteristic of transthoracic impedance in the patient. The implanted impedance-sensing circuit allows the inspiratory phase of the patient's respiratory cycle to be identified to apply electrical stimulation during the inspiration phase.

[0007] U.S. Pat. No. 5,540,731 to Testerman discloses a method and apparatus for pressure detection and treating obstructive airway disorders. In this disclosure, muscles of the upper airway are stimulated based on a signal acquired from a pressure sensor thus implanted in the patient. The signal is characteristic of intrathoracic pressure in the patient. The pressure sensor enables the identification of the patient's respiratory cycle, such that the electrical stimulation could be applied during the inspiration phase.

[0008] U.S. Pat. No. 5,483,969 discloses a method and apparatus for providing a respiratory effort waveform for the treatment of an obstructive sleep apnea. In this disclosure, a digital respiratory effort waveform is used to stimulate an upper airway muscle of a patient. Specifically, the waveform is provided by sensing a signal having an output characteristic of respiratory effort of the patient and sampling the sense signal at the predetermined interval.

[0009] Further, U.S. Pat. No. 5,335,657 to Terry Jr. et al. discloses a nervous stimulation system to treat sleep disorder. Specifically, sleep disorder is detected and a predetermined electrical signal to the patient's vegus nerve is applied to alleviate the sleep disorder. The disclosure also relates to sensing the patient's ECG activity in the case of insomniac and hypersomniac patients or detecting a sudden nodding of the head in the case of narcoleptic patients, or sensing the cessation of respiration in the case of sleep apnea patients.

[0010] U.S. Pat. No. 5,146,918 to Kallok et al. discloses a demand apnea control of central and obstructive sleep apnea. The disclosure relates to the use of electrical stimulation on a demand basis. Specifically, sensors monitor the respiration cycle and determine the occurrence of apnea events. More specifically, central apnea is sensed by the passage of an escape interval of time, without the sensing of an aspiratory event and a concurrent decrease in blood oxygen saturation. Obstructive sleep apnea is sensed as an abnormal pressure differential across the airway. The diaphragm is electrically stimulated upon sensing of central apnea and if obstructive sleep apnea is detected, the musculature of the upper airway is electrically stimulated.

[0011] Accordingly, prior art systems typically manage sleep apnea by implanting electrodes in sensors to stimulate the diaphragm and/or musculature of the upper airway. However, most of these apparatus and methods involve complicated implant procedures and appear to be highly invasive. The present invention provides a novel approach that eliminates these complications and the various limitations of the prior art.

SUMMARY OF THE INVENTION

[0012] In one aspect of the present invention, an apparatus for treating sleep apnea is presented. The apparatus includes a control unit and a lead extending from the control unit and having an electrode electrically coupled with the control unit by a conductor, the lead being capable of being implanted proximate a blood-carrying structure within a patient's body. The control unit is capable of outputting a sleep apnea interruption pulse via the conductor and the electrode to stimulate at least one of a phrenic nerve and a diaphragm.

[0013] In another aspect of the present invention, a method for treating sleep apnea is presented. The method includes determining if the patient is experiencing sleep apnea and outputting a sleep apnea interruption pulse to at least one of a phrenic nerve and a diaphragm if the patient is experiencing sleep apnea.

[0014] Yet another aspect of the present invention includes an implanted medical device that delivers therapy to interrupt sleep apnea in conjunction with cardiac therapy that is being delivered. Specifically, a mode switch algorithm changes pacing outputs of a pacemaker, a cardioverter or cardioverter defibrillator. More specifically, a phrenic nerve stimulation threshold is set such that by increasing the pulse widths or increasing the amplitude, or both, phrenic nerve stimulation and cardiac stimulation can be maintained.

[0015] In a further aspect of the present invention, rather than using bipolar leads or stimulating from the LV lead to the RV lead, it is suggested to stimulate from the LV lead to the can. This changes the field that may capture the phrenic nerve. Accordingly, a pacing configuration that captures the phrenic nerve is set in combination with or coordinated with a cardiac pacing scheme. Specifically, when sleep apnea is detected and the need to interrupt it is confirmed, the pacing scheme may be switched to operate under a one pulse delivery made such that both the heart and the phrenic nerve are stimulated. Subsequently, the pacing configuration is switched back to a normal pacing of the heart.

[0016] In yet another aspect of the invention, a pacemaker is implemented having a second mode that allows to pace the phrenic nerve and/or the diaphragm. When sleep apnea is sensed, stimulation of the phrenic nerve may be implemented by either changing the pacing configuration, increasing amplitudes, changing the pacing, changing the electrodes that are used to pace between, changing the number of pulses that are generated by the pacemaker, or implementing a train of pulses rather than a single pulse.

[0017] Yet another aspect of the present invention includes synchronization of the phrenic nerve stimulation pacing with therapeutic pacing that is due to be delivered to the heart. In yet another alternate embodiment, synchronization with the intrinsic heart rate is implemented to trigger phrenic nerve stimulation off a sensed beat.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which the leftmost significant digit(s) in the reference numerals denote(s) the first figure in which the respective reference numerals appear, and in which:

[0019]FIG. 1 is a stylized view of an embodiment of an implantable medical device according to the present invention for use in treating sleep apnea;

[0020]FIG. 2 is a stylized view of an implantable medical device lead according to the present invention that is attached to a myocardium of a heart for use in treating sleep apnea;

[0021]FIG. 3 is a stylized view of a lead according to the present invention having a partial ring electrode for use in treating sleep apnea;

[0022]FIG. 4 is a stylized view of a lead according to the present invention disposed within vasculature proximate a phrenic nerve and a diaphragm;

[0023]FIG. 5 is a flowchart of a first embodiment of a method according to the present invention for treating sleep apnea; and

[0024]FIG. 6 is a flowchart of a second embodiment of a method according to the present invention for pacing a rhythm of a heart and for treating sleep apnea.

[0025] 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.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0026] 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 developer's 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.

[0027] The present invention encompasses an apparatus and method for managing sleep apnea by stimulating a patient's phrenic nerve and/or diaphragm through the use of one or more electrodes disposed in a patient's body, such as the patient's heart, vasculature, or the like. The one or more electrodes may be placed proximately within the blood-carrying structure or proximately outside the blood-carrying structure. The phrenic nerve includes branches from the C3 through C5 spinal nerves and descends therefrom, through the thorax proximate to the heart, to the diaphragm. Electrical signals are transmitted through the phrenic nerve from the brain to cause the diaphragm to move, thus producing respiration.

[0028]FIG. 1 illustrates an implantable medical device <b>100</b> according to the present invention including a control unit <b>102</b> enclosed in a biocompatible, hermetically sealed can <b>104</b>. The implantable medical device <b>100</b> further includes a first lead <b>106</b> extending from the control unit <b>102</b>, which may be routed through a superior vena cava <b>108</b>, a right atrium <b>110</b>, and into a right ventricle <b>112</b> of a heart <b>114</b>. The first lead <b>106</b> includes a tip electrode <b>116</b> that may be disposed proximate an apex <b>118</b> of the heart <b>114</b> and a ring electrode <b>120</b> that may be disposed within the right ventricle <b>112</b> of the heart <b>114</b>. While FIG. 1 illustrates the tip electrode <b>116</b> disposed proximate the apex <b>118</b> of the heart <b>114</b>, the tip electrode <b>116</b> may be disposed anywhere within the right ventricle <b>112</b> of the heart <b>114</b>.

[0029] The implantable medical device <b>100</b> also includes a second lead <b>122</b> extending from the control unit <b>102</b>, which may be routed through the superior vena cava <b>108</b>, the right atrium <b>110</b>, a coronary sinus <b>124</b>, and into a cardiac vein <b>126</b> (e.g., a middle cardiac vein, a great cardiac vein, or the like). The second lead <b>122</b> includes a tip electrode <b>128</b> and a ring electrode <b>130</b>. The tip electrode <b>128</b> is generally disposed distally within the cardiac vein <b>126</b> from the ring electrode <b>130</b> with respect to the control unit <b>102</b>.

[0030] The implantable medical device <b>100</b> may further include, as illustrated in FIG. 1, a third lead <b>138</b> extending from the control unit <b>102</b>, which may be routed through the superior vena cava <b>108</b> and into the right atrium <b>110</b>. The third lead <b>138</b> includes a tip electrode <b>140</b> and a ring electrode <b>142</b>. The tip electrode <b>140</b> is generally disposed distally from the ring electrode <b>142</b> with respect to the control unit <b>102</b>. The leads <b>106</b>, <b>122</b>, <b>138</b> may be unipolar or multipolar, thus having any number of electrodes (e.g., the electrodes <b>116</b>, <b>120</b>, <b>128</b>, <b>130</b>, <b>140</b>, <b>142</b>, or the like) as desired.

[0031] Generally, electrical pulses may be outputted from the control unit <b>102</b>, via the leads <b>106</b>, <b>122</b>, <b>138</b> to one or more of the electrodes <b>116</b>, <b>120</b>, <b>128</b>, <b>130</b>, <b>140</b>, <b>142</b> so that a portion of body tissue (e.g., a portion of the heart <b>114</b>, a nerve or nerve bundle, a diaphragm <b>136</b>, or the like) may be stimulated. For example, electrical pulses may be outputted from the control unit <b>102</b> via the first lead <b>106</b> to the tip electrode <b>116</b> of the first lead <b>106</b>, wherein the electrical pulses may be useful in stimulating the right ventricle <b>112</b> of the heart <b>114</b>. The electrical circuit is completed, in this example, by returning at least a portion of the electrical energy comprising the pulses via the ring electrode <b>120</b> of the first lead <b>106</b> and the lead <b>106</b> to the control unit <b>102</b>.

[0032] In another example, electrical pulses may be outputted from the control unit <b>102</b> via the first lead <b>106</b> to the tip electrode <b>116</b> of the first lead <b>106</b>, wherein the electrical circuit is completed by returning at least a portion of the electrical energy comprising the pulses via the can <b>104</b> to the control unit <b>102</b>. Other configurations and modes of operation may be employed, such that electrical pulses are emitted from certain ones of the electrodes <b>116</b>, <b>120</b>, <b>128</b>, <b>130</b>, <b>140</b>, <b>142</b> and returned to the control unit <b>102</b> via other ones of the electrodes <b>116</b>, <b>120</b>, <b>128</b>, <b>130</b>, <b>140</b>, <b>142</b> and/or the can <b>104</b>.

[0033] Still referring to FIG. 1, a right phrenic nerve <b>132</b> extends proximate a right side of the heart <b>114</b> and a left phrenic nerve <b>134</b> extends proximate a left side of the heart <b>114</b>. As discussed above, each of the right phrenic nerve <b>132</b> and the left phrenic nerve <b>134</b> extends to the diaphragm <b>136</b>. It has been found that, under certain circumstances, electrical pulses emitted from electrodes (e.g., the electrodes <b>116</b>, <b>120</b>, <b>128</b>, <b>130</b>, <b>140</b>, <b>142</b>, or the like) disposed within and/or proximate blood-carrying structures, such as the heart <b>114</b>, vasculature, or the like, may stimulate one or both of the right phrenic nerve <b>132</b> and the left phrenic nerve <b>134</b>. Such stimulation may result in stimulation of the diaphragm <b>136</b>. Further, the electrical pulses may stimulate the diaphragm <b>136</b> directly. Accordingly, the scope of the present invention encompasses the direct stimulation of the diaphragm <b>136</b> by such electrical pulses as well as stimulation of the diaphragm <b>136</b> via the phrenic nerves <b>132</b>, <b>134</b>. Thus, according to the present invention, one or more electrical pulses may be outputted from the control unit <b>102</b>, transmitted via one or more of the leads <b>106</b>, <b>122</b>, <b>138</b>, and emitted from one or more electrodes (e.g., the electrodes <b>116</b>, <b>120</b>, <b>128</b>, <b>130</b>, <b>140</b>, <b>142</b> or the like) disposed proximate a blood-carrying structure to stimulate one or both of the phrenic nerves <b>132</b>, <b>134</b> to stimulate the diaphragm <b>136</b>.

[0034] The control unit <b>102</b> may, in one embodiment, also include a sleep apnea detection device <b>142</b> for determining whether the patient is experiencing sleep apnea. Sleep apnea detection device <b>142</b> may be incorporated with implantable medical device (IMD) or can <b>104</b>. In an alternate embodiment, sleep apnea detection device <b>142</b> is in wireless/telemetry communication T with can <b>104</b>. The sleep apnea detection device <b>142</b>, <b>144</b> may operate by any means known in the art. For example, sleep apnea may be detected by cycle breath analysis, heart rate variability, bradycardia sensing, minute ventilation sensing; pressure/impedance sensing, inspiratory function sensing, diaphragm contraction sensing, airflow sensing via nostrils or a mouth, and/or the like.

[0035] Those skilled in the art will appreciate that electrical pulses are conventionally used to pace one or more chambers (e.g., the right ventricle <b>112</b>, the right atrium <b>110</b>, or the like) of the heart <b>114</b>. Generally, such electrical pulses are effective only on the portion of the heart proximate to the electrode or electrode from which the electrical pulses are being emitted, due to the amplitude, shape, and/or duration of the pulses. Conventionally, this is generally a desirable situation, since it may be undesirable to stimulate other body tissue proximate the heart <b>114</b>. However, in the treatment of sleep apnea, it may be generally desirable, according to the present invention, to stimulate one or both of the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b>, either alone or in combination with a portion of the heart <b>114</b>. Thus, according to one embodiment of the present invention, the amplitude and/or duration of the pulses is modified from the pulses generally used in cardiac pacing therapies to stimulate one or both of the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b> and, in certain circumstances, a portion of the heart <b>114</b>.

[0036] For example, in conventional cardiac pacing therapies, the amplitude of the electrical pulses may fall within a range of about 0.5V to about 5.0V. By comparison, the amplitude of the electrical pulses useful in stimulating one or both of the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b>, according to the present invention, may fall within a range of about 0.5V to about 10V. Thus, when stimulating one or both of the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b>, the portion or portions of the heart <b>114</b> proximate the electrode or electrodes being used to stimulate the phrenic nerves <b>132</b>, <b>134</b> may also be stimulated. Accordingly, according to one embodiment of the present invention, the electrical pulses used to stimulate the phrenic nerves <b>132</b>, <b>134</b> are timed to coincide with a desirable time for stimulating the portion or portions of the heart <b>114</b> proximate the electrode or electrodes being used to stimulate the phrenic nerves <b>132</b>, <b>134</b>. For example, the electrical pulses may be timed to coincide with an intrinsic heartbeat, a planned cardiac pacing pulse, or may be timed based on a previous intrinsic heartbeat or cardiac pacing pulse. In this way, normal cardiac function may be maintained without inducing arrhythmia in the heart <b>114</b>.

[0037] Further, in conventional cardiac pacing therapies, the duration of the electrical pulse may generally fall within a range of about 0.05 ms to about 0.5 ms. However, to effectively stimulate one or both of the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b>, according to the present invention, the duration of the electrical pulse may fall within a range of about 0.5 ms to about 1.5 ms. As described above, such electrical pulses used to stimulate one or both of the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b> may also stimulate the portion or portions of the heart <b>114</b> proximate the electrode or electrodes being used to stimulate the phrenic nerves <b>132</b>, <b>134</b>. Thus, it may be desirable, as described above, to time the stimulation of the phrenic nerves <b>132</b>, <b>134</b> to coincide with a desirable point in time to stimulate the portion or portions of the heart <b>114</b> proximate the electrode or electrodes being used to stimulate the phrenic nerves <b>132</b>, <b>134</b>.

[0038] While specific voltage and duration ranges are provided above, the scope of the present invention encompasses any pulse voltage or duration, or any series of pulse voltages and durations, which are effective in stimulating one or both of the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b>. The amplitude and/or duration of the electrical pulse required to stimulate the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b> may depend upon where the electrode is positioned relative to one of the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b>. For example, in general, the more distally the electrode is positioned from the phrenic nerve <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b>, the greater the pulse amplitude and/or the pulse duration required to stimulate the phrenic nerve <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b>. Many features of the human anatomy, such as locations of the coronary veins, position of the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b> with respect to a blood-carrying structure, are quite variable from patient to patient. Thus, it may be desirable to position the electrode or electrodes and to determine the amplitude and/or duration of the pulse to be used to stimulate one or both of the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b> in an iterative fashion. For example, it may be desirable to position the electrode then output a pulse to determine if the phrenic nerve <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b> may be stimulated at that electrode position, pulse amplitude, and pulse duration. If stimulation is accomplished, the amplitude and/or duration of the pulse may be reduced to determine if the phrenic nerve <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b> may still be stimulated. If stimulation is not accomplished at the first electrode position, pulse amplitude setting, and pulse duration setting, the electrode may be repositioned or the pulse amplitude and/or pulse duration may be increased to determine if the phrenic nerve <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b> may be stimulated.

[0039] In certain circumstances it may be possible to directly stimulate the diaphragm <b>136</b> by emitting stimulation pulses from an electrode disposed proximate a blood-carrying structure within a patient's body. For example, the tip electrode <b>116</b> of the first lead <b>106</b> may be disposed close enough to the diaphragm <b>136</b> such that stimulation pulses emitted from the tip electrode <b>116</b> may capture the diaphragm <b>136</b>. Thus, such pulses may stimulate the diaphragm <b>136</b> directly with little or no interaction with the phrenic nerves <b>132</b>, <b>134</b>.

[0040] While a plurality of leads <b>106</b>, <b>122</b>, <b>138</b> are illustrated in FIG. 1, the present invention encompasses an implantable medical device <b>100</b> having only one of the leads <b>106</b>, <b>122</b>, <b>138</b>. Further, the scope of the present invention includes an implantable medical device <b>100</b> having one or more leads (e.g., the leads <b>106</b>, <b>122</b>, <b>138</b>, or the like) extending from the control unit <b>112</b> to areas proximate blood-carrying structures other than as shown in FIG. 1. For example, the present invention encompasses an implantable medical device <b>100</b> having a lead <b>202</b>, as illustrated in FIG. 2, having a tip electrode <b>204</b> and extending from the control unit <b>102</b> (shown in FIG. 1) to a pericardium <b>206</b> of the heart <b>114</b>. The phrenic nerve <b>134</b> and/or the diaphragm <b>136</b> may be stimulated either via the tip electrode <b>204</b> or via an optional ring electrode <b>206</b>.

[0041] Further, it may be possible to stimulate one or both of the phrenic nerves <b>132</b>, <b>134</b> and/or the diaphragm <b>136</b> while reducing the likelihood of stimulating the heart <b>114</b>. FIG. 3 illustrates a lead <b>302</b> that may be used for either of the leads <b>122</b>, <b>202</b> shown in FIGS. 1 and 2, respectively, and the like. The lead <b>302</b> includes a conductor set <b>304</b> having one or more conductors extending from the control unit <b>102</b> (shown in FIG. 1) to a tip <b>5</b> electrode <b>306</b> and a partial ring electrode <b>308</b>. The partial ring electrode <b>308</b> extends only partway around a circumference of the lead <b>302</b>. Thus, the lead <b>302</b> may be positioned proximate the heart <b>114</b> or within the cardiac vein <b>126</b> or the like such that the partial ring electrode <b>308</b> faces away from the heart <b>114</b>. Accordingly, upon emitting a stimulation pulse from the partial ring electrode <b>308</b>, the pulse is directed away from the heart <b>114</b>, which may reduce the likelihood of stimulating a portion of the heart <b>114</b> proximate the partial ring electrode <b>308</b>.

[0042] As indicated above, the scope of the present invention encompasses an electrode disposed within vasculature that is capable of stimulating one or more phrenic nerves and or the diaphragm of the patient. FIG. 4 illustrates a lead <b>402</b> having an electrode <b>404</b> and being disposed within a blood vessel <b>406</b> proximate a phrenic nerve <b>408</b> such that an electrical pulse or pulses, emitted from the electrode <b>404</b>, may stimulate the phrenic nerve <b>408</b>. Further, in one embodiment, the electrode <b>404</b> may be disposed within the blood vessel <b>406</b> proximate a diaphragm <b>410</b> such that an electrical pulse or pulses, emitted from the electrode <b>404</b>, may directly stimulate the diaphragm <b>410</b>.

[0043]FIG. 5 illustrates a first embodiment of a method according to the present invention for treating sleep apnea. From a starting point (block <b>502</b>), the method includes determining if the patient is experiencing sleep apnea (block <b>504</b>). If the patient is not experiencing sleep apnea (block <b>506</b>), the method returns to the starting point (block <b>502</b>). If the patient is experiencing sleep apnea (block <b>506</b>), however, the method includes outputting one or more sleep apnea interruption pulses to one or both of the phrenic nerves (e.g., the phrenic nerves <b>132</b>, <b>134</b> shown in FIGS. 1 and 2) and/or to the diaphragm (e.g., the diaphragm <b>136</b> shown in FIGS. 1 and 2), as illustrated by block <b>508</b>. In one embodiment, the one or more sleep apnea interruption pulses may be outputted (block <b>508</b>) proximate a heart (e.g., the heart <b>114</b>). In one embodiment, the pulses may be timed from a previously scheduled pacing pulse or triggered from an intrinsic beat of the heart <b>114</b>, timed coincident with an intrinsic heartbeat, or timed to coincide with a cardiac pacing pulse. The method then returns to the starting point (block <b>508</b>).

[0044] In certain situations, as described previously, it may be desirable to incorporate a method for treating sleep apnea into the pacing of a heart (e.g., the heart <b>114</b>). Thus, a second embodiment of a method according to the present invention for treating sleep apnea, as illustrated in FIG. 6, includes, from a starting point <b>602</b>, determining if cardiac pacing is desirable (block <b>604</b>) and determining if the patient is experiencing sleep apnea (block <b>606</b>). If cardiac pacing is not needed (block <b>608</b>) and the patient is not experiencing sleep apnea (block <b>610</b>), the method returns to the starting point (block <b>602</b>). However, if the patient is experiencing sleep apnea (block <b>610</b>), the method includes detection of intrinsic heart beat (block <b>611</b>) and outputting one or more sleep apnea interruption pulses to one or both of the phrenic nerves (e.g., the phrenic nerves <b>132</b>, <b>134</b> shown in FIGS. 1 and 2) and/or to the diaphragm (e.g., the diaphragm <b>136</b> shown in FIGS. 1 and 2), as illustrated by block <b>612</b>. The method then returns to the starting point (block <b>602</b>).

[0045] However, if cardiac pacing is needed (block <b>608</b>) and the patient is not experiencing sleep apnea (block <b>614</b>), the method includes outputting one or more cardiac pacing pulses (block <b>616</b>). The method then returns to the starting point (block <b>602</b>). If cardiac pacing is needed (block <b>608</b>) and the patient is experiencing sleep apnea (block <b>614</b>), the method includes detection of intrinsic heart beat (block <b>617</b>) outputting one or more cardiac pacing pulses and outputting one or more sleep apnea interruption pulses to one or both of the phrenic nerves and/or the diaphragm (block <b>618</b>). The method then returns to the starting point (block <b>602</b>). In one embodiment, the one or more sleep apnea interruption pulses may be outputted (blocks <b>612</b>, <b>618</b>) proximate a heart (e.g., the heart <b>114</b>).

[0046] While the method embodiment illustrated in FIG. 6 is described as having steps performed in a particular order, the present invention is not so limited. For example, determining if the patient is experiencing sleep apnea (block <b>606</b>) may be performed prior to determining if cardiac pacing is desirable (block <b>604</b>), or these steps may be performed simultaneously. Further, the decision of whether cardiac pacing is needed (block <b>608</b>) may be performed after the decision of whether sleep apnea has been detected <b>5</b> (blocks <b>610</b>, <b>614</b>), or these steps may be performed simultaneously. Other variations of the method illustrated in FIG. 6 as will be appreciated to one skilled in the art are also encompassed by the present invention. Further, outputting the sleep apnea interruption pulses (blocks <b>612</b>, <b>618</b>) may also be used as the outputted cardiac pacing pulses (blocks <b>616</b>, <b>618</b>).

[0047] As indicated previously, the presence of a sleep apnea condition may be determined by any means known in the art. For example, sleep apnea may be detected by cycle breath analysis, heart rate variability, bradycardia sensing, minute ventilation sensing; pressure/impedance sensing, inspiratory function sensing, diaphragm contraction sensing, airflow sensing via nostrils or a mouth, and/or the like. Further, the desirability of cardiac pacing may be determined by any means known in the art, such as by analyzing one or more electrocardiograms, or the like. Thus, the specific means by which sleep apnea is detected and the specific means by which the desirability of cardiac pacing is determined are not material to the practice of the invention.

[0048] 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. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood as referring to the power set (the set of all subsets) of the respective range of values, in the sense of George Cantor. Accordingly, the protection sought herein is as set forth in the claims below.