Recruitment manoeuvres, consisting of sustained inflations at high airway pressures, have been advocated as an adjunct to mechanical ventilation in lung protective ventilation strategies to prevent the collapse of the lung.

This study aims to determine the safety and efficacy of a recruitment manoeuvre, by considering its impact on gas exchange, hemodynamics and on the release of systemic inflammatory mediators.

This prospective study will analyse the effects of a single recruitment manoeuvre in critically ill patients. Subjects will be mechanically ventilated patients needing alveolar RMs. After a period of stable lung protective approach ventilation, they will receive the "40/30" RM; lung mechanics, gas exchange, hemodynamics and plasmatic concentration of inflammatory mediators will be obtained before and after the RM. An ultrasound score, established from the lung aeration status of upper and lower parts of anterior and lateral chest wall, will also be calculated before and after the manoeuvre.In selected patients cytokine release in the bronchoalveolar lavage will be measured as well.

Inclusion Criteria:

• Mechanical Ventilation
• Arterial catheter inserted
• Hypoxemic respiratory failure (Pa02/FiO2 <300)
• Radiological evidence of atelectasis or pulmonary infiltrates in the CXR
• Informed consent

Exclusion Criteria:

• Elevated intracranial pressure >25 mmHg
• Bronchopulmonary fistula
• Emphysema
• Kidney or Liver failure