Tuberc Respir Dis.  1984 Dec;31(4):176-182. 10.4046/trd.1984.31.4.176.

Role of Intrapleural Pressure in the Positional Effect on Gas Exchange in Unilateral Pleural Effusion


The positional effect on gas exchange is diminished in a large unilateral pleural effusion presumable because of decrease in perfusion and decreased changes in ventilation-perfusion mismatching. We measured intrapleural pressure(Plp) and estimated the volume of effusion(PHt) by measuring height of meniscus on chest P-A in 24 patients with unilateral tuberculous pleural effusion and one patient witn nephrotic syndrome to study the relative role of Plp and PHt in the positional effect of effusion on gas exchange. Plp and PHt were positively correlated(r=0.66, p<0.005). Positional PaO2 differece(Δ paO2) was inversely correlated to PHt(r = -0. 50, p < 0.05). ΔPaO2 was also inversely correlated to Plp but the correlation was not statistically significant(r= -0. 4, P>0.05). The results of this study suggest that intrapleural pressure may be important but that other factors may also be responsible for the positional effect on gas exchange in unilateral effusion .

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