Abstract: A system for reducing central sleep apnea (CSA) is described in which certain methods of increasing a patient's rebreathing during periods of the sleep cycle are used. By increasing rebreathing during periods of overbreathing, the over-oxygenation which typically results from the overbreathing period can be reduced, thus reducing the compensating underbreathing period and effectively reducing the loop gain associated with the central sleep apnea. Nasal occlusion and a leak resistant oral interface provide control for gas leaks from a patent interface.