Mechanical ventilation can induce pulmonary lesions called ventilator induced lung injury (VILI). High levels of Transpulmonary pressure is one of the most important mechanism of VILI during the use of mechanical ventilation. The use of bilevel pressure ventilator modes like APRV could generate high levels of transpulmonary pressure.

The aim of this study is to evaluate the variations of transpulmonary pressure during the use of APRV by clinicians

Inclusion Criteria:

• Adult
• Patient mechanically ventilated for more than 48 H for acute respiratory failure
• Decision to use of the APRV mode by clinicians in charge of the patient

Exclusion Criteria:

- Contraindication for the use of a nasogastric tube