Comparison of Different Oxygen Flow Rates During Preoxygenation Using High-Flow Nasal Oxygen

In this study, we will use high-flow nasal oxygen for preoxygenation in patients undergoing elective anaesthesia. Preoxygenation with high-flow nasal oxygen is most often performed at flow rates of \<50 l/min. In this study, patients will be randomised to preoxygenation using high-flow nasal oxygen and flow rates of 45 l/min, 70 l/min or 95 /min.