The prognostic value of extravascular lung water index in patients with acute respiratory distress syndrome

Abstract

To evaluate the relationship between extravascular lung water index (EVLWI), pulmonary vascular permeability index (PVPI) and the severity categories defined by the Berlin definition, and investigate the prognostic value of EVLWI in patients with acute respiratory distress syndrome (ARDS). Fifty-four patients with ARDS who received pulse index continuous cardiac output (PiCCO) monitoring were analyzed retrospectively. The patients were divided into mild, moderate and severe groups according to oxygenation index (OI) at admission. Characteristics and acute physiology and chronic health evaluation II (APACHEII) score in mild, moderate and severe groups were recorded, and the differences in EVLWI and PVPI among the severity categories of ARDS patients were analyzed. The correlation between EVLWI and intrathoracic blood volume index (ITBVI), PVPI and OI was analyzed. The receiver operating characteristic curve (ROC curve) was used to evaluate the prognosis accuracy of these indicators. Of 54 patients, there were 18 ARDS patients in mild group, 22 in moderate group and 14 in severe group. The 28-day mortality rate was gradually increased with severity categories of ARDS, and mortality in moderate and severe groups were significantly higher than that in mild group [54.5% (12/22), 57.1% (8/14) vs. 22.2% (4/18), both P<0.05]. 216 independent evaluation were measured in 54 patients within 72 hours, EVLWI was increased with severity categories of ARDS [EVLWI in mild, moderate and severe groups were 11 (10, 13) mL/kg, 14 (11, 16) mL/kg, 17 (12, 23) mL/kg, U=15.556, P=0.000], as well as the change tendency in PVPI [PVPI in mild, moderate and severe groups were 2.0 (1.8, 2.5), 2.7 (2.0, 3.9), 3.7 (2.1, 4.8), U=16.552, P=0.000] . The negative correlation between EVLWI and OI was found (r=-0.599, P=0.000), as well as between PVPI and OI (r=-0.541, P=0.000). The positive correlation between EVLWI and PVPI was found (r=0.811, P=0.000), as well as between EVLWI and ITBVI (r=0.168, P=0.041). The area under ROC curve (AUC) for EVLWI evaluating the prognosis at 0, 24, 48, 72 hours was 0.639 ± 0.082, 0.642 ± 0.082, 0.702 ± 0.078, 0.719 ± 0.076 respectively, 95% confidence interval (95%CI) was 0.479-0.799, 0.483-0.802, 0.551-0.852, 0.570-0.869 respectively, AUC for APACHEII was 0.783 ± 0.068, and 95%CI was 0.648-0.918. As EVLWI>13 mL/kg at 72 hours, the sensitivity and the specificity of accurate judgment were 81.8% and 61.5%. Combining the Berlin definition with EVLWI and PVPI, the severity of ARDS can be assessed accurately. Dynamic observation of EVLWI can be one of prognostic factors in the patients with ARDS.