A breathing apparatus has an expiratory flow sensor unit, an expiratory pressure sensor unit, an expiratory pressure regulator, and an expiratory control unit operatively connected to the expiratory pressure sensor unit for a feedback control of an expiratory pressure during an expiratory phase of a breathing cycle. The expiratory control unit is adapted to provide a real time target pressure value during the expiratory phase to the expiratory pressure regulator for adjusting a desired positive end expiratory pressure (PEEP) level (PEEPset) based on an inspiratory tidal volume of an inspiratory phase of the same breathing cycle and a currently accumulated expiratory tidal volume measured by the expiratory flow sensor unit. In this manner advantageous regulation of PEEP with minimized work of breathing is obtained.
