Inclusion Criteria:  Age equal to or greater than 18 years Availability of a family member or legal representative capable of understanding and signing the informed consent Patient admitted to the intensive care unit requiring invasive mechanical ventilation, who shows: Hemodynamic stability: MAP ≥ 65 mmHg and norepinephrine requirements ≤ 0.5 µg / kg / min, and Respiratory stability: PaO2 / Fraction of Inspired Oxygen (FiO2)> 100 and stable oxygen requirements in the previous 6 hours. In case is considered to start phase of "weaning" or awakening, the level of sedation should allow adequate triggering of the inspiratory trigger, in a patient with improvement of respiratory failure and / or radiological image.  Exclusion Criteria:  Age under 18 years Weight less than 50 kg Body weight greater than 120 kg Height greater than 1,90 m Presence of barotrauma (pneumothorax) or pleural fistula Hemodynamic instability (MAP < 65 mmHg or norepinephrine requirements > 0,5 µg /kg / min) Neurocritical patient Obstetric patient