Gasometrical Evaluation (PaO2, PaCO2, pH, PaO2/FiO2, saturometry): Measuring time: before enrollment, 1h and 8h after each administration. In the control group these time are simulated. Ventilatory Evaluation (type of ventilation, V / minute, inspiratory tidal volume, expiratory tidal volume, respiratory rate, I/E, Pr Pico, Paw, FiO2 (default), PEEP, Static lung compliance and oxygenation index): Measuring time: before enrollment, 1h and 8h after each administration. In the control group these time are simulated. Clinical Evaluation (blood pressure (BP), heart rate (HR) and verify if the patient has symptoms of cyanosis (distal or generalized)): Measuring time: before enrollment, 1h and 8h after each administration. In the control group these time are simulated. Radiographic Evaluation (It is measured Chest radiography. They collect the presence or absence of inflammatory infiltrates in the lung fields, and compared with respect to the first assessment, establishing the following scale: Improvement: Decrease or disappearance of pulmonary infiltrates. Stability: Maintenance of pulmonary infiltrates despite treatment. Worsening: Progression with increased pulmonary infiltrates). Measuring time: before the first administration, daily for 3 days of treatment and the fifth day after administration In the control group these time are simulated. Days of stay in the ICU (days between the date of admissions and discharge of the Intensive Care Unit). Measuring time: at the discharge of the ICU. Days of mechanical ventilation (days between the date begins to mechanically ventilated and respiratory support is withdrawn). Measuring time: When the respiratory support is withdrawn Days of endotracheal intubation (days, between the date of the patient is intubated, and the date of the extubation). Measuring time: at the extubation. Complication (description of the complications related to the ARDS and their cause). Measuring time: before enrollment, 1h and 8h after each administration. In the control group these time are simulated. Adverse Events (AE). Measuring time: daily - Description of AE (Name of the AE). - Intensity of AE (Slight, Moderate, Severe) - Severity of the AE(serious, not serious) - Time of the AE (Difference in dates for starting and ending of AE. If the AE begins and end in the same day, then the time is measured in hours and minutes). - Attitude to treatment (no change, modification of dose, Interrupted temporary, interruption ultimately), - Causal relationship (remote, possible, likely, very likely) - Treatment used for the AE (name of treatments)