A method for maintaining ventilation during an oxygen flush in an anaesthetic breathing apparatus (2) is disclosed. The breathing apparatus (2) comprises a breathing circuit (3), a fresh gas section (5), and a ventilator section (7). The fresh gas section (5) comprises an oxygen supply (12), and the ventilator section (7) comprises an expiratory pressure control valve (21). The method (100) comprises steps of: starting a continuous flow of oxygen from the oxygen supply (12) into the breathing circuit (3) interrupting an ongoing ventilation in order to activate the oxygen flush； maintaining the continuous flow of oxygen； and cycling the expiratory pressure control valve (21) between an upper pressure level setting to provide an inspiratory phase of a breathing cycle and a lower pressure level setting to provide an expiratory phase of the breathing cycle.
