A process and a device is presented with an electro-impedance 
tomography (EIT) 
system (2), with a computing unit (4) and with a 
respirator (1) for gentle mechanical 
lung ventilation especially in case of atelectases following 
surgical procedures. A first image of the healthy lungs is first recorded prior to anesthetization by means of the EIT 
system (2) and the total area and / or the 
spatial distribution of ventilated 
lung areas are determined from the image values by means of the computing unit (4). Second or additional status images are recorded after assumed 
lung damage and the total area and / or the 
spatial distribution of ventilated lung areas are determined. The total areas and / or the 
spatial distribution of the ventilated lung areas from the first and second or further status images are compared by means of the computing unit (4) and analyzed for the presence of lung areas that have no or reduced ventilation due to atelectases. The information on the presence, the extent and / or the spatial distribution of atelectases is sent by the EIT 
system (2) to the 
respirator (1) so that the 
respiration pressure is increased step by step by the 
respirator (1) as a function of the status image or the currently determined status images until the current image of the lung status corresponds to the first status image or comes close to it with minimal deviations. The 
respiration pressure is subsequently reduced again step by step by the respirator (1) until the computing unit (4) detects a reduction of the ventilated lung areas and the 
respiration pressure is subsequently increased again by means of the respirator (1) to the last value at which no change occurred in the ventilated lung areas.