Central Sleep Apnea

Unlike with obstructive sleep apnea, 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: Decreased ventilatory drive causes transient decreases and/or pauses in respiration.

• Hyperventilation-related CSA: Increased ventilatory drive during sleep leads to hypocapnia which causes a compensatory fall in ventilation that, if abnormally prolonged, leads to recurrent central apnea with arousals.

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.

Causes of hypoventilation-related CSA with hypercapnia include hypothyroidism, neural lesions (eg, brain stem infarctions, encephalitis

Congenital central hypoventilation syndrome (Ondine curse) is a rare form of idiopathic CSA manifesting in neonates, in some cases associated with Hirschsprung disease. 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 and occasionally during treatment of obstructive apneas.

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 (sometimes called wake-time sleepiness), lethargy, and morning headache.

• Clinical evaluation

• Often polysomnography

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. However, testing may not be necessary if the cause is evident and reversible (eg, travel to high altitude, heart failure) 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.

• Treatment of cause

• Supportive care

Primary treatment of central sleep apnea is optimal management of underlying disorders and avoidance or reduction of opioids, alcohol, and other sedatives (1). 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 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.

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).

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

1. American Thoracic Society: What is Central Sleep Apnea in Adults?: Two page central sleep apnea summary for patients

2. American Academy of Sleep Medicine: Detailed patient information explaining the importance of healthy sleep and treatment options for sleep disorders