Evaluation of V/Q Mismatch as Predictor of Pulmonary Postoperative Complications in Patients Undergoing Major Surgery

Pulmonary postoperative complications (PPC) are among the main causes of surgical complications affecting both postoperative morbidity and mortality. Little is known about the effect of intraoperative VQ mismatch on the occurrence of PPC. PPC are classically considered associated to the occurrence of intraoperative atelectasis, and therefore to the development of a certain amount of shunt, but this concept have been recently questioned. Recent studies showed indeed that, despite age is one of the main determinants of PPCs, increasing age is not associated to the increase of intraoperative shunt. Shunt therefore may not be the main determinant of PPC. In this trial the investigators will evaluate if other causes of intraoperative VQ mismatch (e.g. low V/Q, high V/Q, dead space) may predict PPC in a population of patients undergoing major surgery.