Induction of general anaesthesia in patients undergoing emergency surgery can be challenging, because of the often suboptimal circumstances under which anaesthesia has to be delivered, as well as potential physiological derangements caused by their underlying illness, especially in elderly patients. Pre-oxygenation is usually achieved using oxygen delivered via a facemask before induction of anaesthesia. In patients undergoing elective surgery, the lungs are normally ventilated with a bag/facemask technique after induction. However, these options for oxygenation are limited. Facemask ventilation has a perceived risk of gastric insufflation of gas, leading to increased intragastric pressure and raised risk of pulmonary aspiration of stomach contents. Nasal cannulae have been recommended as an alternative method of delivering continuous oxygen during induction of anaesthesia. The Aim of this study is to compare the effect of transnasal humidified rapid insufflation ventilatory exchange (THRIVE) oxygenation with facemask oxygenation on extended apnoeic period and postoperative respiratory complications in elderly patients undergoing induction of anaesthesia.

Inclusion Criteria:

• Patients who required induction of general anaesthesia for emergency surgery, whose routine clinical care required arterial blood gas sampling, and who were competent to give consent were recruited.

Exclusion Criteria:

• Patients who had severe respiratory disease.