The new definition for acute lung injury and acute respiratory distress syndrome: is there room for improvement?

PURPOSE OF REVIEW: To review the new (Berlin) definition of the acute respiratory distress syndrome (ARDS) and to propose potential improvements. RECENT FINDINGS: The Berlin definition resulted in the following modifications: a criterion of less than 7 days was used to define acute onset; the requirement of pulmonary artery wedge pressure was removed. Clinical judgment for characterizing hydrostatic pulmonary edema suffices, unless there is no apparent ARDS risk factor, in which case an objective evaluation is required; the category of acute lung injury was removed, and ARDS was divided into three categories of severity based on the P/F ratio - mild (from 201 to 300), moderate (from 101 to 200), and severe (≤100  mmHg). A positive end-expiratory pressure value of at least 5  cm H(2)O became required for the diagnosis of ARDS. In this review, we propose that both the use of P/F ratio after some stabilization (first 24  h) and the use of compliance stratified at 0.4  ml/cm H(2)O/kg ideal body weight might improve the stratification of patients. SUMMARY: The Berlin definition brought improvement and simplification over the previous definitions. The use of data over the first 24  h to reclassify the severity of the disease and the use of compliance to stratify each oxygenation category might further improve the definition.