Benefits of High Flow Nasal Cannula Oxygen for Preoxygenation During Intubation in Non Severely Hypoxemic Patients

Inclusion Criteria: * Adults older than 18 years regardless of the gender * Requiring orotracheal intubation in intensive care unit * "No severely hypoxemic respiratory failure" defined as Oxygen Pression (Pa02)/FI02 \> 200 mmHg measured in the 4 hours before inclusion Exclusion Criteria: * Not the first Intubation during this stay in intensive care unit * Contraindication to oro-tracheal intubation * Intubation without anaesthesic rapid sequence induction * Intubation during cardiac arrest * Real emergency (as asphyxia) with immediate intubation needed (without time enough for randomization) * Nasopharyngeal obstacle with contraindication to use Optiflow device * Patients with a documented Cormack IV exposition before inclusion * Protected adult * Pregnancy or breastfeeding * Lack of consent * Patient already enrolled in another study that could interfere with the primary objective of this study