The invention relates to a ventilation device for ventilating a patient, comprising at least a fluid supply unit or, additionally, a fluid discharge unit which can be used to guide a fluid into at least one airway, that is part of a lung or in a lung, of a patient or for discharging the fluid from said airway； and to a control device which, during the ventilation of at least one airway of the patient, can be used to guide a fluid into the at least one airway and/or discharge the fluid from at least one airway by operating the ventilation device, for determining or also for estimating a path of at least one region of a compliance curve of the at least airway by guiding and/or discharging the fluid from the at least one airway and by determining at least one value of the compliance. The invention also relates to a method for operating a ventilation device.
