Effect of Sitting, Hypoxia, and Breath-holding on the Distribution of Pulmonary Blood in Man

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Abstract
The distribution of pulmonary blood flow and ventilation was measured in 8 normal subjects in the sitting position with 133Xe-radiospirometry. The perfusion and ventilation were found to decrease in the lung apices with time. The inhalation of 10 per cent oxygen in nitrogen during one minute shifted more blood towards the apices in 16 experiments of 18. Breath-holding during 40–60 seconds caused the same redistribution towards the apices, even if the mean arterial oxygen tension still was 74 mm Hg in these experiments. General and local hypoxia thus counteracts the influence of gravity in the distribution of pulmonary blood in normal subjects.