[Lung circulation in emphysema].

Pulmonary emphysema is regularly complicated by pulmonary hypertension which is, however, mostly of minor degree. As long as pulmonary capillary pressure and cardiac output remain within normal limits, the elevated pressure in the pulmonary artery is due to an increase of vascular resistance for which hypoxia is responsible in the first place, while rarefaction of vascular ramifications due to the emphysematic destructive process in the pulmonary parenchyma plays only a secondary role. Breathing of oxygen decreases pulmonary hypertension, an effect which is reinforced by combination of oxygen with IPPB. Phentolamine lowers both vascular resistance and pressure in the pulmonary artery in short-term administration. The effect of hemodilution on pulmonary hypertension in emphysematic patients with hypoxic polycythemia is, however, somewhat disappointing if the hematocrit value remains below 60%. Some rheological causes for this therapeutic failure are discussed.