RESUMO
OBJECTIVES: A recent update of the definition of acute respiratory distress syndrome (ARDS) proposed an empirical classification based on ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (PaO2/FiO2) at ARDS onset. Since the proposal did not mandate PaO2/FiO2 calculation under standardised ventilator settings (SVS), we hypothesised that a stratification based on baseline PaO2/FiOv would not provide accurate assessment of lung injury severity. DESIGN: A prospective, multicentre, observational study. SETTING: A network of teaching hospitals. PARTICIPANTS: 478 patients with eligible criteria for moderate (100