Oxygen tension and the regulation of local pulmonary blood flow

The effect of hypoxia on pulmonary blood vessels was not really established until 1946 when Von Euler and Liljestrand reported that: 'An increase of the pulmonary arterial pressure was invariably observed if the animal (cat) was made to breathe a mixture containing 10-11% oxygen in nitrogen'. Several groups of workers have shown that hypoxic gas mixtures introduced into one lung or lobe in animals, or into one lung in man, result in a diversion of flow to the opposite lung. Nevertheless, during air breathing it is impossible to maintain the oxygen tension of the arterial blood constant (to exclude central mechanisms), and proof of the Von Euler and Liljestrand hypothesis requires hypoxia to be introduced locally and confined to a small portion of the lung. The authors found a preparation in which this could be done and devised a method for measuring local blood flow and alveolar gas tensions.