Review Board stopped the study after interim analysis reaching stopping rule for efficacy.

• Severe post-traumatic hypoxia is mainly due to lung contusion. The intubation rate of these patients is near 20%.
• Treatment before intubation is needed, is based on pain control with epidural anesthesia and oxygen.
• The investigators' hypothesis is that adding non-invasive mechanical ventilation to the standard treatment can reduce the intubation rate if applied early in the course of the disease.
• As thoracic trauma is often associated with injuries in other body regions that may increase the complications of the technique, specific contraindications have been described.

Inclusion Criteria:

• Age > 18 years.
• Informed consent obtained.
• pO2/FiO2 <200 for more than 8 consecutive hours in the first 48 hours after thoracic trauma.

Exclusion Criteria:

• Orotracheal intubation indicated for any other reason.
• Standard contraindication for non-invasive ventilation (active gastro-intestinal haemorrhage, low level of consciousness, multiorgan failure, airway control problems, lack of cooperation, hemodynamic instability).
• Severe traumatic brain injury.
• Facial trauma with pneumocephalus, skull base fracture, orbit base fracture, any facial fracture involving a sinus.
• Cervical injury with specific treatment contraindicating a facial mask.
• Bronco-pleural fistula.
• Gastro-intestinal trauma.