A ventilation drive (10) for an anesthesia device and a method for operating such a ventilation drive (10) are provided. The ventilation drive includes a blower unit (12), a pressure chamber (14) and a flexible bag (16) located in the pressure chamber (14). An internal volume of the bag (16) is coupled to an inspiratory branch (20) of a ventilation line. The blower unit (12) can be coupled to the internal volume of an outlet side and to an air inlet (26) for feeding ambient air on an inlet side. Further, a flow sensor (36) is provided between the outlet side of the blower unit (12) and the pressure chamber (14).
