Initial size of unilateral pleural effusion determines impact of thoracocentesis on oxygenation

BackgroundThere have been contradicting reports in the literature regarding the impact of pleural fluid aspiration on patients’ oxygenation. The aim of this study was to assess the role of the initial size of effusion on post-drainage oxygenation.MethodsWe studied 122 patients, aged (mean±SD) 61.2±16.8 years, with unilateral pleural effusion and no remarkable parenchymal lesion, by determining PaO2, PaCO2 and [A−a] PaO2 just before thoracocentesis (T1), 30 min after its completion (T2) and 48 hours after the procedure (T3). Patients were divided into group A (75 patients) with small and moderate sized effusions and group B (47 patients) with large and massive effusions. The position of the meniscus line on the posteroanterior film, being arbitrarily set at just above the upper costal margin of the sixth anterior rib, was used to divide the two groups. Patients were studied at rest, breathing room air in the sitting position. Repeated measures ANOVA (related samples) and the Friedman test when the normality assumption was violated were used.ResultsIn group A, at T3, PaO2(mm Hg) showed a statistically significant increase versus T1 (p