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Central Sleep Apnea
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 in breathing pattern during sleep. The diagnosis is based on clinical findings and, when necessary, confirmed by polysomnography. Treatment is supportive.
Patients with CSA fall into 2 groups based on their CO 2 level and ventilatory drive.
One group presents with hypercapnia with decreased ventilatory drive. Causes include hypothyroidism and central lesions (eg, brain stem infarctions, encephalitis, Arnold-Chiari malformation).
The other group presents with eucapnia or hypocapnia with increased ventilatory drive but with episodes of apnea, periodic breathing, or both.
Cheyne-Stokes breathing, a discrete pattern of this second form of CSA, is thought to be caused by intrinsic properties of the respiratory control center in the response to hypoxia and acidosis with hyperpnea, causing reoxygenation and alkalosis, leading to hypoventilation by hypopnea and apnea.
High altitude is another cause of recurrent CSA manifesting with hypocapnia.
Chronic use of opioids (eg, patients on methadone maintenance, cancer patients with chronic pain) triggers CSA with an erratic rate and depth of breathing and episodes of apnea; CSA can be hypercapneic or hypocapneic.
Congenital central hypoventilation (a form of Ondine curse) is a rare form of idiopathic CSA in neonates and may be associated with Hirschsprung disease. A mutation in the PHOX2 gene is responsible for 80 to 90% of cases. This mutation produces variable phenotypes, and clinically evident cases are inherited in a dominant pattern.
Diagnosis is suspected on the basis of history and is confirmed by polysomnography. However, testing may not be necessary if CSA causes no symptoms or is clearly related to an identifiable disorder. To diagnose causes of CSA, brain or brain stem imaging may be indicated.
Primary treatment is optimal management of underlying conditions and avoidance of opioids and other sedatives. Secondary treatment of symptomatic patients can be a trial of supplemental O 2 or, in patients with hypercapnic CSA who have symptoms despite other treatments, noninvasive continuous or bilevel positive airway pressure.
For patients who have CSA and Cheyne-Stokes breathing, continuous positive airway pressure may decrease apneic and hypopneic episodes, but effects on clinical outcomes are not clear. Acetazolamide is effective in CSA caused by high altitude.
Electrode pacing of the phrenic nerve and/or diaphragm is an option, such as for children > 2 yr with congenital central hypoventilation syndrome.
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