Hypoxic Pulmonary Vasoconstriction

Abstract

Hypoxic pulmonary vasoconstriction (HPV) is a homeostatic mechanism that, in the adult animal, diverts desaturated, mixed venous blood from poorly ventilated (hypoxic) areas of the lung to other, better ventilated (normoxic) areas of lung. Because of the relatively small amount of actively metabolizing tissue in the lungs, the proximity of the small resistance pulmonary arteries to the alveoli, and the presence of the bronchial circulation, which brings highly oxygenated blood to the lungs, the resistance pulmonary arteries are exposed to a relatively high oxygen tension, close to alveolar levels. This is particularly true in comparison with systemic resistance arteries, for instance, in the kidneys, or in skeletal or cardiac muscle, which are exposed to much lower oxygen tensions and also to the vasoactive products of metabolism. It may be useful to distinguish between the responses to hypoxia of arteries in these oxygen-consuming organs and those relating to oxygen supply, such as the pulmonary arteries and the ductus arteriosus. This chapter discusses cellular mechanism involved in hypoxia-induced constriction in pulmonary arteries and dilation in the ductus arteriosus.