Severity scoring of lung oedema on the chest radiograph is associated with clinical outcomes in ARDS

Background There is no accurate, non-invasive measurement to estimate the degree of pulmonary oedema in acute respiratory distress syndrome (ARDS). We developed the Radiographic Assessment of Lung Oedema (RALE) score to evaluate the extent and density of alveolar opacities on chest radiographs. After first comparing the RALE score to gravimetric assessment of pulmonary oedema in organ donors, we then evaluated the RALE score in patients with ARDS for its relationship to oxygenation and clinical outcomes. Methods We compared radiographs with excised lung weights from 72 organ donors (derivation cohort) and radiographs with clinical data from 174 patients with ARDS in the ARDSNet Fluid and Catheter Treatment Trial (validation cohort). To calculate RALE, each radiographic quadrant was scored for extent of consolidation (0-4) and density of opacification (1-3). The product of the consolidation and density scores for each of the four quadrants was summed (maximum score=48). Results Agreement between two independent reviewers for RALE score was excellent (intraclass correlation coefficient=0.93, 95% CI 0.91 to 0.95). In donors, pre-procurement RALE score correlated with height-adjusted total lung weight (rho= 0.59, p<0.001). In patients with AR DS, higher RALE scores were independently associated with lower PaO2/fractional inspired oxygen and worse survival. Conservative fluid management significantly decreased RALE score over 3 days compared with liberal fluid management. Conclusions The RALE score can be used to assess both the extent of pulmonary oedema and the severity of AR DS, by utilising information that is already obtained routinely, safely and inexpensively in every patient with AR DS. This novel non-invasive measure should be useful for assessing AR DS severity and monitoring response to therapy.