Figure 17-36 Mongrel dogs anesthetized with pentobarbital (bottom axis), placed in a lateral decubitus position, and subjected to progressive extracellular fluid expansion (top axis) have a marked decrease in the PO₂ (left vertical axis) of blood draining the dependent lung (solid circles) and a smaller, much slower decrease in the PO₂ of blood draining the nondependent lung (open circles). The pulmonary arteriovenous shunt (right vertical axis) rises progressively (triangles). (Redrawn from Ray JF, Yost L, Moallem S, et al: Immobility, hypoxemia, and pulmonary arteriovenous shunting. Arch Surg 109:537, 1974.)