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Does size matter concerning impact of position on oxygenation status in spontaneously breathing patients with
Stylianos A Michaelides1, Avgerinos-Romanos Michailidis1,2, George D Bablekos2
1Department of Occupational Lung Diseases and Tuberculosis, Sismanogleio-Amalia Fleming General Hospital, Athens, Greece.
Background:
Inconsistent and contradictory findings have appeared in the literature concerning the impact of body position on oxygenation in pleural effusion.
Methods:
We attempted to elucidate whether the size of the pleural effusion in patients with no parenchymal disease is the main determinant of posture-induced alterations in oxygenation parameters. We studied 62 spontaneously breathing patients aged 65.3±7.8 years (mean±SD), of whom 36 had large and massive-sized effusions (Group A) and 26 had small and moderate-sized effusions (Group B). Arterial blood gases were determined in four different body positions: sitting (SIT), supine (SUP), ipsilateral (IPS) and contralateral (CON) to the effusion side, after remaining relaxed for at least 20 min in each position. Separation into groups A and B was deliberately set from the position of the fluid meniscus line on a posteroanterior chest film just above the upper costal margin of the sixth anterior rib. A two-way ANOVA model with outcome variables PaO2, PaCO2 and [A-a] DO2 was used.
Results:
In both groups the best oxygenation was found in SIT. The worst oxygenation (highest [A-a] DO2 value) occurred in group A in CON compared with IPS (59.4±7.6 vs 49.0±7.5 mm Hg, p<0.001) and in group B in IPS compared with CON (51.0±8.7 vs 39.5±9.2 mm Hg, p<0.001). Also, PaCO2 showed significant differences in both groups in IPS compared with CON (p=0.002).
Conclusions:
Patients with large-sized effusions exhibit the worst oxygenation when lying on the side contralateral to the effusion, while those with small-sized effusions exhibit the worst oxygenation when lying on the side ipsilateral to the effusion.
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