A recent large observational study published on JAMA showed that acute respiratory distress syndrome (ARDS) is associated with high mortality and developed in 10.4% of 29,144 patients admitted to the intensive care unit from 50 countries across 5 continents. Mechanical ventilation is the cornerstone for lung treatment during ARDS. Lung protective ventilation improved ARDS outcome significantly. However, it is still unclear what method should be used to select levels of positive end- expiratory pressure (PEEP).