Significance of extravascular lung water index, pulmonary vascular permeability index, and intrathoracic blood volume index in the differential diagnosis of burn-induced pulmonary edema

Objective To appraise the significance of extravascular lung water index (EVLWI), pulmonary vascular permeability index (PVPI), and intrathoracic blood volume index (ITBVI) in the differential diagnosis of the type of burn–induced pulmonary edema. Methods The clinical data of 38 patients, with severe burn hospitalized in our burn ICU from December 2011 to September 2014 suffering from the complication of pulmonary edema within one week post burn and treated with mechanical ventilation accompanied by pulse contour cardiac output monitoring, were retrospectively analyzed. The patients were divided into lung injury group (L, n=17) and hydrostatic group (H, n=21) according to the diagnosis of pulmonary edema. EVLWI, PVPI, ITBVI, oxygenation index, and lung injury score (LIS) were compared between two groups, and the correlations among the former four indexes and the correlations between each of the former three indexes and types of pulmonary edema were analyzed. Data were processed with t test, chi–square test, Mann–Whitney U test, Pearson correlation test, and accuracy test [receiver operating characteristic (ROC) curve]. Results There was no statistically significant difference in EVLWI between group L and group H, respectively (12.9±3.1) and (12.1±2.1) mL/kg, U=159.5, P>0.05. The PVPI and LIS of patients in group L were respectively 2.6±0.5 and (2.1±0.6) points, and they were significantly higher than those in group H [1.4±0.3 and (1.0±0.6) points, with U values respectively 4.5 and 36.5, P values below 0.01]. The ITBVI and oxygenation index of patients in group L were respectively (911±197) mL/m² and (136±69) mmHg (1 mmHg=0.133 kPa), which were significantly lower than those in group H [(1 305±168) mL/m² and (212±60) mmHg, with U values respectively 21.5 and 70.5, P values below 0.01]. In group L, there was obviously positive correlation between EVLWI and PVPI, or EVLWI and ITBVI ( with r values respectively 0.553 and 0.807, P<0.05 or P<0.01), and there was obviously negative correlation between oxygenation index and EVLWI, or oxygenation index and PVPI (with r values respectively –0.674 and –0.817, P values below 0.01). In group H, there was obviously positive correlation between EVLWI and ITBVI ( r=0.751, P <0.01) but no obvious correlation between EVLWI and PVPI, oxygenation index and EVLWI, or oxygenation index and PVPI (with r values respectively –0.275, 0.197, and 0.062, P values above 0.05). The total area under ROC curve of PVPI value for differentiating the type of pulmonary edema was 0.987 [with 95% confidence interval (CI) 0.962–1.013, P<0.01], and 1.9 was the cutoff value with sensitivity of 94.1% and specificity of 95.2%. The total area under ROC curve of ITBVI value for differentiating the type of pulmonary edema was 0.940 (with 95% CI 0.860–1.020, P<0.01), and 1 077.5 mL/m² was the cutoff value with sensitivity of 95.2% and specificity of 88.2%. Conclusions EVLWI, PVPI, and ITBVI have an important significance in the differential diagnosis of the type of burn–induced pulmonary edema, and they may be helpful in the early diagnosis and management of burn–induced pulmonary edema.