The invention relates to a respirator (10) for the at least supportive respiration of living beings (12), wherein the respirator comprises the following: a connection formation for connection to a breathing gas supply； a breathing gas conduit arrangement (30)； a pressure change arrangement (16) for changing the pressure in the breathing gas conduit arrangement (30)； a flow sensor (44), which provides a flow signal (50) representing a breathing gas volume flow in the breathing gas conduit arrangement (30), a control unit (18) controlling the operation of the respirator (10). Said control unit is designed to trigger a transition from an expiratory to an inspiratory operation of the respirator (10), whenever an increase in the steepness of a flow signal curve (50) exceeds a steepness change threshold value (58). According to the invention, the control unit (18) is configured to detect the steepness change threshold value (58) depending on an expiratory time constant of the respective patient (12) to be ventilated, and to trigger the transition from an expiratory to an inspiratory operation of the respirator (10), whenever the increase in the steepness of the flow signal curve (50) exceeds the steepness change threshold value (58) determined in accordance with the expiratory time constant.
