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

NIV is started and adjusted by the physiotherapist. For the adjustment of PEEP, the ultrasound probe is placed on the thorax, facing the intercostal space having obtained the highest score during the initial LUS (synonym of the worst pulmonary aeration) and the images observed in real time. PEEP is increased until the physiotherapist cannot see any additional benefit on pulmonary aeration or appearance of a patient discomfort or an increasing of air leaks.

"The session will be done via a mouthpiece preferably, or a face mask if it is impossible for the patient to close their mouth properly or to hold the mouthpiece.~The duration of the NIV session will be defined by the prescribing doctor (usually between 30 and 60 minutes), without being able to be less than 30 minutes. The session will be stopped in the event of the appearance of one of the contraindications to NIV mentioned above."

Arterial blood gas will be done at inclusion, at Visit 1 (at the 30th minute from the start of the 1st Non-invasive ventilation session) and at Visit 2 (at the 60th minute from the start of the 1st Non-invasive ventilation session) in both groups of patients in order to calculate the Pa02/Fi02 ratio.

The investigator physiotherapist interviews the participant to measure pain and comfort scores using a visual analogue scale (score from 0 to 10).