Clinical epidemiology of acute lung injury and acute respiratory distress syndrome: incidence, diagnosis, and outcomes.

Acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) are clinical syndromes characterized by the sudden onset of severe hypoxemia and diffuse bilateral pulmonary infiltrates in the absence of left atrial hypertension. Although advances have been made in the understanding of the etiology, pathophysiology, and epidemiology of both entities, many questions remain regarding their incidence, diagnosis, and outcomes. This article reviews the currently used definition of ARDS and ALI, different studies that have advanced the understanding of the epidemiology and outcomes of these entities, and several diagnostic issues that are important for both clinicians and researchers.