In 1994, the Acute Respiratory Distress Syndrome (ARDS) was defined by the American European Consensus Conference (AECC) as an acute onset of hypoxemia (arterial partial pressure of oxygen to fraction of inspired oxygen [PaO2/FIO2] ≤200 mm Hg) with bilateral infiltrates on chest radiograph with no evidence of left atrial hypertension. While the above criteria improved clinicians ability to care for patients with ARDS, the lack of explicit criteria for defining acute, sensitivity of PaO2/FIO2 to different ventilator settings, the poor reliability of the chest radiograph criterion, and difficulties distinguishing hydrostatic edema were all reasons to revise the definition.1
Using a consensus process, a panel of experts developed the Berlin definition in 2011.2 The definition proposed 3 categories of ARDS based on degree of hypoxemia: mild (200 mm Hg
The definition was tested using patient level meta-analysis of 4188 patients with ARDS from 4 multicenter clinical data sets and 269 patients with ARDS from 3 single-center data sets containing physiologic information. The results of the testing demonstrated that the four variables of the definition did not contribute to the predictive validity of severe ARDS for mortality. Therefore, they were removed from the proposed definition and only the four stages of hypoxemia remained.
Using the Berlin definition compared with the older definition, stages of mild, moderate and severe ARDS were associated with higher mortality [27% (95%CI: 24%-30%); 32% (29%-34%); and 45% (42%-48%), respectively; P<0.001)] and increased median duration of mechanical ventilation in survivors (5 days; [IQR], 2-11; 7 days; IQR, 4-14; and 9 days; IQR, 5-17, respectively; P<0.001).
The authors highlight the importance of linking consensus discussions with empirical evaluation which could serve as a model to create more accurate evidence based recommendations.
Bernard GR, Artigas A, Brigham KL, et al. The American-European Consensus Conference on ARDS: definitions, mechanisms, relevant outcomes, and clinical trial coordination. AmJ Respir Crit Care Med
. 1994;149(3 pt 1):818-824.
2. Ranieri VM, Rubenfeld GD, Thompson BT, et al. ARDS Definition Taskforce. Acute respiratory distress syndrome: The Berlin Definition. JAMA. 2012;307(23):2526-2533.