Association between Different Indexations of Extravascular Lung Water (EVLW) and PaO2/FiO2: A Two-Center Study in 231 Patients

Background: Variability of body weight (BW) and height calls for indexation of volumetric hemodynamic parameters. Extravascular lung water (EVLW) has formerly been indexed to actual BW (BWact) termed EVLW-index (EVLWI). In overweight patients indexation to BWact might inappropriately lower indexed EVLWIact. Several studies suggest indexation of EVLWI to predicted BW (EVLWIpred). However, data regarding association of EVLWIact and EVLWpred to mortality and PaO2/FiO2 are inconsistent. Two recent studies based on biometric database-analyses suggest indexation of EVLWI to height (EVLWIheight). Therefore, our study compared the association of un-indexed EVLW, EVLWIheight, EVLWpred and EVLWIact to PaO2/FiO2 and Oxygenation index (OI = mean airway pressure*FiO2*/PaO2). Methods: A total of 2119 triplicate transpulmonary thermodilutions (TPTDs; PiCCO; Pulsion Medical-Systems, Germany) were performed in 50 patients from the evaluation, and 181 patients from the validation groups. Correlations of EVLW and EVLWI to PaO2/FiO2, OI and ROC-AUC-analyses regarding PaO2/FiO2 10 were performed. Results: In the evaluation group, un-indexed EVLW (AUC 0.758; 95%-CI: 0.637-0.880) and EVLWIheight (AUC 0.746; 95%-CI: 0.622-0.869) provided the largest ROC-AUCs regarding PaO2/FiO2 10” (0.778; 95%-CI: 0.713–0.842) compared to 0.739 (95%-CI: 0.669–0.810) for EVLWIact and 0.756 (95%-CI: 0.688–0.824) for EVLWIpred. Conclusions: Indexation of EVLW to height (EVLWIheight) improves the association of EVLW(I) to PaO2/FiO2 and OI compared to all other indexations including EVLWIpred and EVLWIact. Also considering two recent biometric database analyses, EVLWI should be indexed to height.