Complex Sleep Apnea (CompSA) is a less common type of sleep apnea seen in patients with OSA.  When treatment with PAP therapy is used, the respiratory center of the brain fails to send a signal to the body to breathe causing central apnea.  This may happen immediately when PAP is started, or later when PAP is at higher pressures.

CompSA can develop as a responce to CPAP and Bi-PAP therapies, and thus usually requires treatment with more specialized PAP therapies.