n 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:

baseline, in supine position under protective ventilation after two minute of recruitment maneuver in pressure controlled ventilation at 1 hour following prone positioning application

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

lung aeration evaluated through ultrasound during protective invasive mechanical in supine position. Lung ultrasound score ranges from a minimum of 0 to a maximum of 36, where 0 is the best lung aeration and 36 is the worst lung aeration

lung aeration evaluated through ultrasound during protective invasive mechanical ventilation in supine position after two minutes of recruiting maneuver in pressure controlled ventilation. Lung ultrasound score ranges from a minimum of 0 to a maximum of 36, where 0 is the best lung aeration and 36 is the worst lung aeration

lung aeration evaluated through ultrasound during protective invasive mechanical ventilation after 1 h from prone position application. Lung ultrasound score ranges from a minimum of 0 to a maximum of 36, where 0 is the best lung aeration and 36 is the worst lung aeration