Abstract
BackgroundVariability 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).MethodsA 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<200 mmHg (primary endpoint) and OI>10 were performed.ResultsIn 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<200 mmHg. The AUC for EVLWIpred was smaller (0.713). EVLWIact provided the smallest AUC (0.685). This was confirmed in the validation group: EVLWIheight provided the largest AUC (0.735), EVLWIact (0.710) the smallest. In the merged data-pool, AUC was significantly greater for EVLWIheight (0.729; 95%-CI: 0.674–0.784) compared to all other indexations including EVLWIact (ROC-AUC 0.683, p = 0.007) and EVLWIpred (ROC-AUC 0.707, p = 0.015). The association of EVLW(I) was even stronger to OI compared to PaO2/FiO2. In the merged data-pool, EVLWIheight provided the largest AUC regarding “OI>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.ConclusionsIndexation 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.
Highlights
Extravascular lung water (EVLW) is a measure of the interstitial, alveolar and lymphatic fluid content of the lungs
In the Antwerp-validation-group mean values of EVLWIpred, EVLWIadj and EVLWIid were higher than mean the EVLWIact
Impact of indexation according to different weight correctionformulas for the classification of EVLWI: Distribution of EVLWIvalues classified as normal (EVLWI,7 ml/kg), moderately elevated (7 ml/kg#EVLWI,10 ml/kg) and markedly elevated EVLWI (EVLWI$10 ml/kg) significantly varied among the patients with a body mass index (BMI)$30 kg/m2 as well as in the total patient groups depending on the weight used for indexation of EVLWI (Fig. 1)
Summary
Extravascular lung water (EVLW) is a measure of the interstitial, alveolar and lymphatic fluid content of the lungs. Based on a better correlation to mortality, a number of studies have suggested indexation of EVLW to predicted BW (EVLWIpred) (see Table 1) [12: 14]. This study demonstrated that height was the only biometric parameter independently associated to EVLW These data were recently confirmed by Wolf et al, using a similar approach in a surgical group [19]. Despite these conclusive data, both studies did not investigate, if indexation of EVLW to height (EVLWIheight) provides better association to pulmonary function and outcome. Both studies did not investigate, if indexation of EVLW to height (EVLWIheight) provides better association to pulmonary function and outcome
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