EFFECT OF OXYGEN CONCENTRATION IN INSPIRED GAS UPON PULMONARY ARTERIAL BLOOD FLOW

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Abstract
Radioisotope perfusion scanning of the lungs was used to assess the effects of unilateral hypoxia and hypercapnia on the distribution of the pulmonary arterial blood flow of 15 patients in a supine position, who had pulmonary tuberculosis of minimal extent. The distribution of the pulmonary arterial blood flow was regulated by O2 concentration in the inspired gas. If the O2 concentration was less than that of air in 1 lung while the other lung was breathing pure O2, the distribution of the pulmonary arterial blood flow in the hypoxic lung was reduced gently in S-shaped fashion, with the steepest gradient between 8-12% O2, although there was a fairly wide range in the reduction ratio. Unilateral hypercapnia did not affect the distribution of the pulmonary arterial blood flow when the O2 concentration in the inspired gas was kept at the level of that of air. This might be due to the bilateral effect of increased CO2 tension in the circulating blood.