Treatment of complex sleep apnea syndrome.

Patients with complex sleep apnea syndrome (CompSAS) present with features of obstructive sleep apnea syndrome but demonstrate not only instability of upper airway tone (leading to classic obstructive apneas and hypopneas) but also unstable, chemosensitive ventilatory control leading to repetitive central apneas or periodic breathing during sleep. The central apneas often become most apparent after application of continuous positive airway pressure (CPAP) to alleviate upper airway obstruction; patients continue to have fragmented sleep and repetitive desaturations as a result of central apneas and hypopneas. In some patients, central apneas appear to abate over time as a result of some form of adaptation to CPAP. How often this occurs is uncertain, however, and many patients with CompSAS require treatment that combines stabilization of the upper airway obstruction with treatment of respiratory center dysfunction. Adaptive servo-ventilation, which provides both a minimum pressure to hold the airway open and a precisely calculated ventilatory assist to minimize cyclic hypoventilation and hyperventilation, has emerged as a leading treatment. Noninvasive ventilation using bilevel positive airway pressure in the spontaneous-timed mode also may regulate ventilation in some patients with CompSAS. There is anecdotal evidence that CompSAS may be successfully treated using combined PAP therapy with oxygen, carbon dioxide, or the addition of dead space, but data are not sufficient to routinely recommend these methods.