The present invention relates to a kind of pressure-sensitive breathings for applying the normal pressure from pressure source to users air flue, and the air flue for allowing breathable gas to enter user from air inlet flows out air from the respiratory system of user to exhalation vents in air-breathing and expiration tidal volume. The conveying that the present invention makes re-breathing exhalation and optimizes pressurized breathable gas by the way that gas is only discharged during expiration, and users consideration that addressing is important, including reduction noise, pressure change and size to the maximum extent.
