Application of lung ultrasonography on evaluating extravascular lung water and prognosis in patients with acute respiratory distress syndrome

Abstract

To evaluate the value of lung ultrasonography score (LUS) on assessing extravascular lung water (EVLW) and prognosis in patients with acute respiratory distress syndrome (ARDS). The clinical data of 46 patients meeting ARDS Berlin definition admitted to intensive care unit (ICU) of Ningbo Yinzhou People's Hospital from July 2016 to December 2019 were retrospectively collected. The general data, vital signs, blood lactic acid (Lac), oxygenation index (OI), LUS, extravascular lung water index (EVLWI), sequential organ failure assessment (SOFA) score, clinical pulmonary infection score (CPIS) and the length of ICU stay were collected. According to the prognosis of patients during ICU treatment, the patients were divided into survival group and non-survival group, and the clinical characteristics between the two groups were compared. The correlation between LUS and OI, EVLWI, SOFA, and CPIS were analyzed by Pearson correlation analysis. Receiver operator characteristic (ROC) curve was plotted to determine the prognostic value of LUS for ARDS patients during ICU treatment. Forty-six patients were enrolled in the analysis, of whom 32 patients survived (69.6%), and 14 patients died (30.4%) during ICU treatment. There was no significant difference in gender, age, left ventricular ejection fraction (LVEF) or heart rate (HR) between the two groups. Compared with the survival group, the mean arterial pressure (MAP) and OI in the non-survival group were significantly lowered [MAP (mmHg, 1 mmHg = 0.133 kPa): 57.48±33.34 vs. 85.45±19.56, OI (mmHg): 74.50±18.40 vs. 233.06±28.28, both P < 0.05], while Lac, LUS, EVLWI, SOFA and CPIS were significantly increased [Lac (mmol/L): 6.78±2.56 vs. 2.21±1.42, LUS score: 23.57±2.03 vs. 15.58±2.24, EVLWI (mL/kg): 22.93±2.56 vs. 12.96±2.18, SOFA score: 20.21±3.35 vs. 12.43±2.97, CPIS score: 8.07±1.38 vs. 4.59±1.04, all P < 0.01], and the length of ICU stay was significantly shortened (days: 9.33±3.28 vs. 16.89±4.12, P < 0.05]. Pearson correlation analysis showed that a significant negative linear correlation was found between LUS and OI (r = -0.823, P < 0.01), and positive linear correlations were found between LUS and EVLWI, SOFA, CPIS (r values were 0.745, 0.614, 0.757, respectively, all P < 0.01). ROC curve analysis showed that both LUS and EVLWI could predict the prognosis of ARDS patients during ICU treatment, and the areas under ROC curve (AUC) of LUS and EVLWI were 0.936 and 0.991, respectively. When the cut-off of LUS score was 20.5, the sensitivity and specificity were 85.7% and 81.2% respectively. LUS score has a good correlation with EVLWI monitored by pulse index continuous cardiac output (PiCCO), which can reflect lung water content. LUS score can be used as an early prognostic indicator for ARDS patients.