Ventilation device for ventilating a patient, comprising at least a fluid supply unit and a fluid discharge unit that are suitable for respectively supplying (ZV, ZP) a fluid into at least one airway , i.e., into a lung part or into the lung, of a patient and for discharging (AV, AP) the fluid from this airway ; and further comprising a control device which, at least during a ventilation process for the at least one airway , i.e., during the at least one-time supply of the fluid into the at least one airway and the at least one-time discharge of the fluid from the at least one airway by operating the ventilation device , is configured for setting a profile of a pressure P in the airway , and a profile of a volume V of the fluid supplied to the airway and discharged from the airway according to V = f ZP (P) and V = f AP (P), or according to P = f ZV (V) and P = f AV (V), wherein the ventilation process takes place within a pressure interval and within a volume interval ; characterized in that the ventilation process is set by the control device in such a way that a) over at least 60% of the pressure interval , a ratio - of an absolute value of a measure of the change in the first volume that is present at a pressure P 0 while supplying the fluid , i.e., df AP /d(P) (P0) and - an absolute value of a measure of the change in a second volume that is present at the same pressure P 0 while discharging the fluid , i.e., df ZP /d(P) (P0) or b) over at least 60% of the volume interval , a ratio of - an absolute value of a measure of the change in the first pressure that is present at a volume V 0 while supplying the fluid , i.e., df AV /d(V) (V0) and - an absolute value of a measure of the change in a second pressure that is present at the same volume V0 while discharging the fluid , i.e., df ZV /d(V) (V0), has a value of at least 0.5 and at most 2.0. a) over at least 60% of the pressure interval , a ratio - of an absolute value of a measure of the change in the first volume that is present at a pressure P 0 while supplying the fluid , i.e., df AP /d(P) (P0) and - an absolute value of a measure of the change in a second volume that is present at the same pressure P 0 while discharging the fluid , i.e., df ZP /d(P) (P0) or - of an absolute value of a measure of the change in the first volume that is present at a pressure P 0 while supplying the fluid , i.e., df AP /d(P) (P0) and - an absolute value of a measure of the change in a second volume that is present at the same pressure P 0 while discharging the fluid , i.e., df ZP /d(P) (P0) or b) over at least 60% of the volume interval , a ratio of - an absolute value of a measure of the change in the first pressure that is present at a volume V 0 while supplying the fluid , i.e., df AV /d(V) (V0) and - an absolute value of a measure of the change in a second pressure that is present at the same volume V0 while discharging the fluid , i.e., df ZV /d(V) (V0), has a value of at least 0.5 and at most 2.0. - an absolute value of a measure of the change in the first pressure that is present at a volume V 0 while supplying the fluid , i.e., df AV /d(V) (V0) and - an absolute value of a measure of the change in a second pressure that is present at the same volume V0 while discharging the fluid , i.e., df ZV /d(V) (V0), <EOS>