Oro-tracheal intubation in intensive unit care(ICU) in acute hypoxemic respiratory failure after crash induction remains a critical event.

The aim of this study is to determine whether Nasal High Flow Therapy (HFT) Optiflow ® is more efficient than the face mask for preoxygenation before orotracheal intubation after crash induction in acute hypoxemic respiratory failure

This study will be designed as followed : Patients will be randomized in 2 groups :"PREOXYFLOW" or "STANDARD FACE MASK".

Patients randomized in "PREOXYFLOW" group will received a four minutes preoxygenation period with Nasal High Flow Therapy (HFT) (60 l/mn FIO2 = 1) before orotracheal intubation under laryngoscopy after crash induction. Patients randomized in "STANDARD FACE MASK" group will received a four minutes preoxygenation period with standard face mask (15 l/mn) before orotracheal intubation under laryngoscopy after crash induction

Inclusion Criteria:

• Adults older than 18 years regardless of the gender
• Acute hypoxemic respiratory failure defined as :

Respiratory rate > 30/mn AND Hypoxemia with SpO2 <90% with oxygen supply > FiO2 0,5 AND PaO2/FiO2 <300 mmHg

Exclusion Criteria:

• Contraindication to oro-tracheal intubation
• Intubation without anesthetic delivery
• Intubation during cardiac arrest
• Asphyxia with immediate intubation needed
• Nasopharyngeal obstacle with contraindication to use Optiflow device
• Patients with a documented Cormack IV exposition before inclusion
• Protected adult
• Pregnancy
• Lack of consent
• Patient already enrolled in an other randomized study.