Inclusion Criteria:  Patients with community acquired pneumonia requiring invasive mechanical ventilation Bilateral pulmonary infiltrates on chest imaging not fully explained by fluid overload in the opinion of the attending physician One of the criteria below: Oxygen inspired fraction above 50% with a positive end-expiratory pressure of at least 8 cmH2O to main peripheral oxygen saturation above 93%, OR Arterial partial pressure of oxygen divided by inspired fraction of oxygen lower than 200 with PEEP values of at least 5 cmH2O  Exclusion Criteria:  Patients with inclusion criteria for more than 36 hours Refusal of the patient´s legal representative Acute neurologic disease (stroke, brain trauma, or any disease that may cause intracranial hypertension) Patients with current airway fistula or barotrauma Patients on chronic home use of oxygen due to underlying lung disease Patients younger than 18 years Patients not on full code status