Atelectasis develops after the induction of anaesthesia, even in healthy subjects, and is associated with an increase in intraoperative shunt leading to impairment of gas exchange (4). It is well known that in patients, who have undergone mechanical ventilation with high oxygen concentration levels, oxygen replaces the less insoluble nitrogen. Partial oxygen pressure increases with the implementation of oxygen in high concentrations, and the oxygen flow into the blood increases. But when the gas flow into the blood is more than inspired, absorption atelectasis develops in lungs - due to appliance of high oxygen concentration. Atelectasis may also develop due to different reasons such as failure in secretion clearance during the surgery, replacement of nitrogen with inhalation anaesthetics and appliance of pneumoperitoneum.