Preoxygenation is routinely performed before endotracheal intubation. In the intensive care unit, preoxygenation is often accomplished using a nose-mouth mask. It seems probable that high flow nasal cannula oxygen, which is used in the treatment of patients with hypoxemic respiratory failure, is equally effective in preventing the development of hypoxemia during intubation. In this prospective randomized study preoxygenation using high flow nasal cannula oxygen is compared with preoxygenation via nose-mouth mask in patients with hypoxemic respiratory failure.

Inclusion Criteria:

• patients treated in an intensive care unit
• indication for intubation
• presence of hypoxemic (SaO2/fraction of inspired oxygen(FiO2): 300 or less) respiratory failure
• informed consent

Exclusion Criteria:

• blocked nasopharynx
• contraindications for nose-mouth mask or high flow nasal cannula oxygen
• expected difficult airway