Fig. 14

A schematic illustration of the effects of the lateral decubitus position upon pulmonary circulatory hemodynamics in healthy subjects. The dependent lung receives the majority of blood flow at the expense of a decrease in flow to the non-dependent lung, as illustrated by the thickness of the black bifurcating arrow in the main pulmonary artery (MPA) to the respective pulmonary arteries (PA). The pulmonary veins (V) in the dependent lung are more distended compared to those in the non-dependent lung, as illustrated by the greater diameter of the red veins coming from the dependent lung compared to those coming from the non-dependent lung. By comparison, there is no difference in vessel distension on the arterial side, as illustrated by the equal diameters of the two pulmonary arteries (PA). The vascular distensibility, as illustrated by the dotted contours and the horizontal arrows, is much higher in the non-dependent lung in particular in the non-dependent veins, and this is related to the lesser pulmonary venous distension in the non-dependent lung