The Distribution of Pulmonary Blood Flow in Man during Oxygen Breathing and Breath-Holding

The distribution of pulmonary blood flow was measured in eight normal subjects in the sitting position during two hours with 133Xe-radiospirometry. The perfusion decreased at the lung apices during the first hour but then seemed unchanged. Breath-holding during 40–60 seconds caused a redistri bution towards the apices. The redistribution was less pronounced in the experiments performed during the first hour of sitting than during the second. Breathing 100% oxygen caused an increased perfusion at the lung bases during the second hour but had no effect during the first. Breath-holding during oxygen breathing increased apical perfusion during the first hour but had no effect during the second hour.