A thorax drainage device for aspirating fluids from a pleural cavity of a patient using underpressure has a fluid collection container for collecting the aspirated fluids and a drainage tube for connecting the fluid collection container to the pleural cavity of the patient. The fluid collection container is connectable to a vacuum source, in order to generate an underpressure in the fluid collection container. The thorax drainage device has an adjustable mechanism for attenuating pressure differences during the respiration of the patient, this mechanism being adjustable independently of a suction capacity of the vacuum source. This device permits a gradual expansion of the lung without risk of injury and thus prepares the lung for the completion of the drainage.
