Table 1.

Inclusion and exclusion criteria of the study

Inclusion criteria	Exclusion criteria
Age ≥ 18 years ASA class 2 or 3 Major abdominal surgery General anaesthesia	Preceding surgery within 30 days Thoracotomy History of lung resection Oxygen therapy at rest Any kind of acute pulmonary morbidity Patient on ventilatory support at surgical admission

ASA American Society of Anaesthesiology