Accurate characterization of extravascular lung water in acute respiratory distress syndrome*

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Abstract
Objectives: Measurements of extravascular lung water (EVLW) correlate to the degree of pulmonary edema and have substantial prognostic information in critically ill patients. Prior studies using single indicator thermodilution have reported that 21% to 35% of patients with clinical acute respiratory distress syndrome (ARDS) have normal EVLW (p < .0001). In all patients, EVLW increased an average of 1.1 ± 2.1 mL/kg when indexed to AdjBW and 2.0 ± 4.1 mL/kg when indexed to PBW. Indexing EVLW to PBW or AdjBW increased the proportion of ARDS patients with elevated EVLW (each p < .05) without increasing the frequency of elevated EVLW in non-ARDS patients. EVLW indexed to PBW had a stronger correlation to Lung Injury Score (r2 = .39 vs. r2 = .17) and Pao2/Fio2 ratio (r2 = .25 vs. r2 = .10) than did EVLW indexed to ActBW. Conclusions: Indexing EVLW to PBW or AdjBW reduces the number of ARDS patients with normal EVLW and correlates better to Lung Injury Score and oxygenation than using ActBW. Studies are needed to confirm the presumed superiority of this method for diagnosing ARDS and to determine the clinical treatment implications.