Although the effect of permissive hypercapnia on hemodynamics and right ventricular function was previously reported in patients with acute respiratory distress syndrome, the effects of acute controlled hypercapnia on right ventricular function during one-lung ventilation have not yet been investigated systematically. Experimental evidence is conflicting concerning the pulmonary vasodilatory or vasoconstrictive effect of hypercapnic acidosis. The final effect of hypercapnic acidosis on physiological functions depends on the level of hypercapnia and the context of the individual (healthy vs. diseased).