Efficacy of Non-Invasive Mechanical Ventilation in Early Hypoxia Secondary to Thoracic Trauma

* 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.