PULMONARY VASOCONSTRICTION IN RESPONSE TO PRECAPILLARY HYPOXEMIA*

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Abstract
The present study was concerned with the relationship between pulmonary vascular resistance and the oxygen tension of blood perfusing pulmonary precapillary vessels in dogs. It involved either the intravenous administration of dinitrophenol or the breathing of a mixture of carbon monoxide in air to reduce the oxygen tension of mixed venous blood without affecting either the alveolar oxygen tension or the pulmonary venous oxygen tension. It was found that a decrease in the oxygen tension of the mixed venous blood evoked an increase in pulmonary arterial pressure and in pulmonary vascular resistance. Evidence was also provided to indicate that the pressor response originated in a direct effect of the lowered oxygen tension of the mixed venous blood on the precapillary vessels, rather than in either the pharmacologic effects of dinitrophenol or carbon monoxide, changes in blood pH or carbon dioxide tension, or changes in the oxygen tension at some extra-pulmonary site.