[Central sleep apnea syndrome]

Central sleep apnea syndrome (CSAS) is a disorder characterized by repeated apneic events during sleep with no associated ventilatory effort. CSAS is classified as either hypercapnic or non-hypercapnic. In the hypercapnic form of CSAS, increases in PaCO(2) generally result from reductions in ventilation or outright apneas due to an underlying depression of respiratory drive. Hypercapnic CSAS is common in central hypoventilation syndromes which may be primary (idiopathic) or secondary to other disorders that cause damage to the respiratory center. Non-hypercapnic CSAS is not associated with either a primary reduction in respiratory drive or respiratory muscle weakness. Non-hypercapnic CSAS can be a primary disorder or can occur secondary to high altitude, other medical illnesses such as congestive heart failure and central nervous system disease.