Prediction of Response to Recruitment Maneuvers in Patients With Acute Respiratory Failure

The investigators will monitor lung ventilation by EIT during the whole protocol and perform P-V curves and arterial blood gas analysis at every step of the protocol.

Participants will be sedated and paralyzed, ventilated in volume-controlled with protective ventilation (tidal volume=6-8 mL/Kg of predicted body weight and respiratory rate set to obtain normal pH) then the protocol will follow 5 steps each lasting 20 minutes to obtain clinical stability:

• PEEP 5 centimeter of water (cmH2O)
• PEEP 10 cmH2O
• Recruitment maneuver followed by PEEP 15 cmH2O
• PEEP 10 cmH2O
• PEEP 5 cmH2O

Inclusion criteria

• Patients with acute hypoxemic respiratory failure defined by recent known clinical insult or worsening of respiratory symptoms and arterial pressure of oxygen to inspired fraction of oxygen ratio (PaO2/FiO2) ≤300 mmHg
• Patient on invasive mechanical ventilation
• Age ≥18 years
• Written informed consent

Exclusion criteria

• Pregnancy
• Unstable hemodynamic condition requiring blood transfusion or adjustment of inotropics more often than every hour
• FiO2 ≥80% or clinical suspicion of pulmonary embolism
• Pneumothorax
• Chronic obstructive pulmonary disease (COPD) with clinical symptoms of lung emphysema as evidenced by chest radiography or computed tomography or autoPEEP > 5 cmH2O
• Intracranial hypertension
• Impossibility to correctly position the EIT belt (e.g., dressings, chest drainage, etc.)
• Contraindications to EIT (e.g., implantable cardiac defibrillator, pacemaker, instable spinal lesions)