Central Sleep Apnea

Unlike with obstructive sleep apnea Obstructive Sleep Apnea (OSA) Obstructive sleep apnea (OSA) consists of multiple episodes of partial or complete closure of the upper airway that occur during sleep and lead to breathing cessation (defined as a period of... read more , in which airway obstruction restricts airflow, central sleep apnea (CSA) is caused by alterations in respiratory drive, which during sleep is highly dependent on carbon dioxide levels. Two mechanisms are distinguished:

Hypoventilation-related CSA usually occurs in patients with a central nervous system or neuromuscular disorder that directly impairs ventilation, resulting in high CO2 levels (hypercapnia). Rarely, patients have an impaired chemoreceptor response to hypercapnia (primary alveolar hypoventilation).

Paradoxically, most CSA involves periods of hyperventilation. Transient increases in ventilation for any reason may overshoot the target carbon dioxide level, causing hypocapnia. In most people, compensatory mechanisms restore normal ventilation despite the hypocapnia. In patients with CSA, compensatory mechanisms do not respond quickly enough, and the hypocapnia causes periods of hypoventilation and/or apnea resulting in hypercapnia. Patients may cycle periodically between hyper- and hypoventilation, as in Cheyne-Stokes breathing, in which patients have brief periods of apnea followed by progressively faster and deeper breathing, which then becomes slower and shallower until they become apneic again and repeat the cycle.

Disturbed ventilation occurs primarily during sleep because during wakefulness there are additional external stimuli for respiration.

CSA can interfere with sleep enough to cause excessive daytime sleepiness Insomnia and Excessive Daytime Sleepiness (EDS) Many sleep disorders manifest with insomnia and usually excessive daytime sleepiness (EDS). Insomnia is difficulty falling or staying asleep, early awakening, or a sensation of unrefreshing... read more .

Causes of hypoventilation-related CSA with hypercapnia include hypothyroidism Hypothyroidism Hypothyroidism is thyroid hormone deficiency. Symptoms include cold intolerance, fatigue, and weight gain. Signs may include a typical facial appearance, hoarse slow speech, and dry skin. Diagnosis... read more , neural lesions (eg, brain stem infarctions, encephalitis Encephalitis Encephalitis is inflammation of the parenchyma of the brain, resulting from direct viral invasion or occurring as a postinfectious immunologic complication caused by a hypersensitivity reaction... read more , Chiari II type malformation), and certain drugs (most commonly opioids—including methadone).

Congenital central hypoventilation syndrome (Ondine curse) is a rare form of idiopathic CSA manifesting in neonates, in some cases associated with Hirschsprung disease Hirschsprung Disease Hirschsprung disease is a congenital anomaly consisting of a failure of neuronal colonization (and thus a failure of innervation) of the lower intestine, usually limited to the colon, resulting... read more . A mutation in the PHOX2 gene is responsible for 80 to 90% of cases. This mutation produces variable phenotypes. Clinically evident cases are inherited in a dominant pattern. Sleep hypoventilation can be found in the parents.

An extremely rare condition that can cause CSA is a syndrome of Rapid-Onset obesity (marked weight gain in < 1 year) with Hypothalamic dysfunction, Hypoventilation, and Autonomic Dysregulation (ROHHAD); cause is multifactorial. Patients present in their second or third decade, often after a stress such as infection or surgery.

Hyperventilation-related CSA occurs at high altitude in healthy people as a consequence of hypobaric hypoxia. It also occurs in patients with heart failure Heart Failure (HF) Heart failure (HF) is a syndrome of ventricular dysfunction. Left ventricular (LV) failure causes shortness of breath and fatigue, and right ventricular (RV) failure causes peripheral and abdominal... read more and occasionally during treatment of obstructive apneas Treatment Obstructive sleep apnea (OSA) consists of multiple episodes of partial or complete closure of the upper airway that occur during sleep and lead to breathing cessation (defined as a period of... read more .

Central sleep apnea may be asymptomatic, detected by caretakers or bed partners who notice long, quiet respiratory pauses and shallow breaths followed by hyperpnea, or restless sleep.

When symptoms occur, patients may experience excessive daytime sleepiness Insomnia and Excessive Daytime Sleepiness (EDS) Many sleep disorders manifest with insomnia and usually excessive daytime sleepiness (EDS). Insomnia is difficulty falling or staying asleep, early awakening, or a sensation of unrefreshing... read more (sometimes called wake-time sleepiness), lethargy, and morning headache.

Diagnosis of CSA is based on clinical findings and, when necessary, confirmed by sleep testing at home with portable equipment or in a sleep laboratory using polysomnography Testing Almost half of all people in the US report sleep-related problems. Disordered sleep can cause emotional disturbance, memory difficulty, poor motor skills, decreased work efficiency, and increased... read more . However, testing may not be necessary if the cause is evident and reversible (eg, travel to high altitude, heart failure Heart Failure (HF) Heart failure (HF) is a syndrome of ventricular dysfunction. Left ventricular (LV) failure causes shortness of breath and fatigue, and right ventricular (RV) failure causes peripheral and abdominal... read more ) or in asymptomatic patients.

To diagnose central nervous system causes of apnea with hypercapnia, brain or brain stem imaging may be indicated. Arterial blood gases and bicarbonate levels during wakefulness are helpful to distinguish hypercapnic from hypocapnic pathophysiology.

Primary treatment of central sleep apnea is optimal management of underlying disorders and avoidance or reduction of opioids, alcohol, and other sedatives (1 Treatment references Central sleep apnea (CSA) is a heterogeneous group of conditions characterized by changes in ventilatory drive without airway obstruction. Most of these conditions cause asymptomatic changes... read more ). Secondary treatment of symptomatic patients can be a trial of supplemental oxygen or, in patients with hypercapnic CSA who have symptoms despite other treatments, noninvasive positive airway pressure ventilation Noninvasive positive pressure ventilation (NIPPV) Mechanical ventilation can be Noninvasive, involving various types of face masks Invasive, involving endotracheal intubation Selection and use of appropriate techniques require an understanding... read more may be indicated.

For patients who have CSA and Cheyne-Stokes breathing, supplemental oxygen may decrease apneic and hypopneic episodes; positive airway modalities have been used, but efficacy is not clear.

Acetazolamide, which causes metabolic acidosis and stimulates respiration, is effective for CSA caused by high altitude and is useful in some patients with heart failure.

Electrical pacing of the diaphragm, typically done by transvenous phrenic nerve stimulation, is an option, such as for children > 2 years with congenital central hypoventilation syndrome, or for adults with symptomatic recurrent CSA. Programmable phrenic nerve or diaphragm stimulation systems can produce a rhythmic breathing pattern that stabilizes tidal volume, airflow, and oxygenation, entrains breathing during sleep, and potentially alters disease progression (2 Treatment references Central sleep apnea (CSA) is a heterogeneous group of conditions characterized by changes in ventilatory drive without airway obstruction. Most of these conditions cause asymptomatic changes... read more ).

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