The investigators aim to compare four different lung recruitment techniques (described in literature) to Computed tomography scan analysis.

The investigators aim to compare four different lung recruitment techniques (described in literature) to Computed tomography scan analysis:

• stress index technique
• peep test
• recruitment technique used in the EXPRESS study
• recruitment technique used in the LOV study

Inclusion Criteria:

• Clinical diagnosis of acute lung injury/ acute respiratory distress syndrome
• Mechanical ventilation

Exclusion Criteria:

• Clinical diagnosis of chronic obstructive pulmonary disease
• Clinical diagnosis of pneumothorax
• Haemodynamic instability

patients affected by acute lung injury/acute respiratory distress syndrome who are mechanically ventilated