Quality of Preoxygenation in Emergency Surgery

Factors, that are associated with compromised preoxygenation will be determined during our study. Pulse oximetry data and end-tidal oxygen concentration values will be evaluated in association with risk factors for insufficient anaesthesia face mask seal, difficult intubation, preoxygenation techniques used, comorbidities, physical status, hemodynamic and laboratory measures. Parameters analysed: * Preoperative: medical history, physical examination, laboratory findings, anthropometric data * Intraoperative: preoxygenation equipment and method used (defined by anaesthesiologist in charge of the case), oxygenation and haemodynamic values recorded during preoxygenation and induction of anaesthesia, intraoperative laboratory values (if obtained)