Nasal CPAP effect on patterns of sleep apnea.

To evaluate the effect of continuous positive airway pressure via nasal mask (nasal CPAP) on occlusive, mixed, and central apneas (OA, MA, and CA, respectively), we performed nocturnal polysomnography without and with nasal CPAP on 21 patients with sleep apnea. Three patients were unable to tolerate nasal CPAP. The remaining 18 patients had significant reductions in the overall apnea frequency when using nasal CPAP (52.9 +/- 5 per hour slept vs 3.3 +/- 1 per hour slept, mean +/- SE, p less than 0.001). The use of nasal CPAP significantly reduced the frequency of OAs during both nonrapid eye movement (non-REM) and REM sleep (p less than 0.001). It also reduced the frequency of MAs during both non-REM and REM sleep (p less than 0.05). Nasal CPAP did not increase the frequency of CAs in patients who had MAs when sleeping without nasal CPAP indicating that both the "central" and obstructive portions of MA were eliminated. In those patients who had CAs while sleeping without nasal CPAP, the CA frequency was unchanged by nasal CPAP although there was a good deal of interindividual variability. We conclude that nasal CPAP is well tolerated and effective in reducing the frequency of OAs and MAs. The variability of the response of CA to nasal CPAP suggests that the pathogenesis of CA may not be homogeneous.