Density Detection in Dependent Left Lung Region Using Transesophageal Echocardiography

Abstract

Background Densities in dependent lung regions worsen oxygenation in patients with acute respiratory distress syndrome. Identification of these densities requires examination using computed tomography (CT). In this study, the authors evaluated the use of transesophageal echocardiography (TEE) to estimate densities in the dependent lung. Methods Forty consecutive patients with acute lung injury or acute respiratory distress syndrome who underwent CT and TEE examination were included in this study. Densities in the lower left lung area were detected through the descending aorta by TEE. Density areas observed by TEE were compared with those obtained by CT. The effect of positive end-expiratory pressure (PEEP) application on density area was also evaluated. Results Density areas in the dependent lung region measured by TEE were 12.0+/-6.1 cm2 (mean +/- SD) at mid esophageal position. Density areas evaluated using TEE in the left lung correlated significantly with those estimated with CT in the left and right lungs (P < 0.01 in both lungs). In addition, the authors observed a significant correlation between PaO2/FIO2 and density areas estimated using TEE (P < 0.05). During positive end-expiratory pressure application, the area of density estimated with TEE decreased and PaO2 improved. Conclusions The authors clearly demonstrated that it is possible to estimate the density area of the dependent left lung regions in patients with acute lung injury or acute respiratory distress syndrome using TEE. It is also possible to observe the changes of density areas during application of positive end-expiratory pressure.