Optimization of Positive End Expiratory Pressure by Use of Pulmonary Ultrasound for Patients With Blunt Chest Trauma Treated by Non-Invasive Ventilation (Opti-PEP).

Inclusion Criteria: * Patients aged 18 or more * Admitted to intensive care or continuing care for 72 hours or less for blunt chest trauma, defined by the presence of at least one of the following elements on the initial CT scan: fracture(s) of rib(s) / fracture(s) of the sternum / pulmonary contusion / hemothorax * Acute hypoxemic respiratory failure defined by the administration of oxygen at least 3 L/min with nasal cannula or FiO2≥30% if high flow oxygen therapy. * Patient with a functional arterial catheter for blood tests Exclusion Criteria: * Acute respiratory distress, defined by the presence of at least one of the following clinical signs: respiratory rate ˃ 35 / use of accessory inspirators / paradoxal abdominal or thoracic motion * Imminent need for invasive mechanical ventilation * Usual contraindication to non-invasive ventilation (undrained pneumothorax, trauma to the face, vigilance disorders, digestive bleeding, hemodynamic instability, intolerance) * Hypercapnia (PaCO2˃45mmHg) * Patient unable to cooperate, communicate * Therapeutic limitation * Expected length of stay ≤ 48h * Severe head trauma * Pregnant or breastfeeding women * Participation in other clinical research related to respiratory failure/respiratory therapy * Vulnerable people * Protected adults, under guardianship or curatorship, or unable to give consent * Non-affiliated person or beneficiary of a social security scheme * Absence of free, informed and written consent, signed by the participa…