The present pilot randomized controlled clinical trial will test the hypothesis that in patients with ARDS, fixing ventilator settings to the conventional protective ventilatory strategy (VT 6 ml/kg ideal body weight and Pplat ≤ 30 cmH2O, PEEP according the PEEP/FiO2 table), control modes of mechanical ventilation will be associated to a concentration of pulmonary and systemic inflammatory mediators lower than the concentration of inflammatory mediators observed during assisted modes of mechanical ventilation.