Measurements of Pulmonary Capillary Blood Flow and Gas Exchange Throughout the Respiratory Cycle in Man1

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Abstract
By measuring the rate of change of pressure inside an airtight chamber, which had a subject seated within, and with sensitive capacitance manometer attached to it, it was shown that nitrous oxide was absorbed from the lung alveoli at a rate which did not vary significantly between normal inspiration and expiration. It is concluded that pulmonary capillary blood flow does not vary during the normal respiratory cycle. Fluctuations were found with slow breathing. Comparison is made with vascular pressure fluctuations found by other observers to occur during the breathing cycle.