Preoxygenation With a High-flow Nasal Cannula or a Simple Mask Before General Anesthesia in Head and Neck Surgery

Apply high flow heated (34 °C) and humidified nasal oxygen with the OptiFlow System (Thrive, Fisher \& Paykel®, Aukland New Zealand) using a flow of 30 liter/minute and an inspiratory oxygen fraction (FiO2) of 1.0. Increase the oxygen flow to 60 liter/minute over the course of the first minute. Ask the patients not to speak during anesthesia induction and keep the mouth closed.

Perform standard preoxygenation by oxygen insufflation via a face mask using the standard anesthesia ventilators (semicircular system) with 100% oxygen flow of 12 liter/minute. The patients breathe with tidal volume.