Effects of Body Position and Recruiting Maneuver on Lung Aeration Assessed Through Ultrasound in Patients Intubated for Acute Respiratory Failure Related to Novel Coronavirus 19 Disease

"In patients undergoing invasive mechanical ventilation with an arterial oxygen tension on inspired oxygen fraction ratio \< 200 mmHg requiring recruitment maneuver and prone positioning as a rescue therapy, lung aeration will be evaluated at:~1. baseline, in supine position under protective ventilation~2. after two minute of recruitment maneuver in pressure controlled ventilation~3. at 1 hour following prone positioning application"