Ever since ARDS was defined, we continue defining the pathophysiology and the pathophysiological interaction mechanisms, acute or exudative initial phase is of quick onset and consists in dyspnea, hypoxemia, respiratory failure and pulmonary edema.The onset of respiratory failure requires mechanical ventilation and this respiratory failure is given by arterial hypoxemia associated with pulmonary edema due to filtration of proteins, decrease of compliance by alveolar edema and surfactant dysfunction, in- AbstractAcute respiratory distress syndrome (ARDS) is a common syndrome in intensive care units, proper diagnosis and understanding of pathophysiology with the corresponding management positively affect the outcomes of patients with ARDS.The pathophysiology of ARDS is complex and involves a series of multiple biomolecular agents.There are multiple definitions of ARDS, the last assigned being the Berlin definition.There are some unknown aspects regarding ARDS that will be recognized within a few years of research.The purpose of this review is refresh some aspects as pathophysiology and classification about ARDS.