[Pathophysiological reactions of the pulmonary circulation in airway and lung diseases]

Hypoxic pulmonary vasoconstriction (HPV) is a physiological phenomenon in healthy lungs and a regulatory mechanism in alveolar hypoventilation by which blood flow is diverted from poorly ventilated areas to better ventilated alveolar regions. Maintained alveolar hypoxia (related either to respiratory diseases or to high altitude) results in a persistent activation of HPV. The latter mechanism is involved in the development of pulmonary vasoconstriction and right heart failure (Cor pulmonale) in chronic airway diseases. Compared to other species, especially the bovine and the porcine lung is highly susceptible to develop pulmonary hypertension because of anatomical and physiological pecularities. Consequently, therapeutic support of the heart is indicated in cattle and pigs suffering from respiratory diseases. In contrast, non-selective vasodilators are not recommended because they override the compensatory effect of hypoxic vasoconstriction and impair pulmonary gas exchange.