The volumes of the extraparenchymal segment (Vpa(EP)) and intraparenchymal segment (Vpa(IP)) of the pulmonary arterial tree were determined in intact anesthetized dogs during room air breathing and acute hypoxia. Total pulmonary arterial blood volume (Vpa(total)) was calculated as the product of pulmonary blood flow and pulmonary arterial circulation time. An angiographic technique was used to estimate Vpa(EP). Vpa(IP) was calculated by subtracting Vpa(EP) from Vpa(total). During room air breathing at functional residual capacity, mean ±SD of Vpa(EP) was 17.1±5.1 ml and of Vpa(IP) was 31.7±20.8 ml, representing 40% and 60%, respectively, of Vpa(total). Vpa(total) increased 22.2 ± 10.5 ml during lung inflation, with proportional increases in Vpa(IP) and Vpa(EP). Vpa(EP) was found to be influenced equally by changes in transmural pulmonary arterial and transpulmonary pressure. Acute hypoxia was accompanied by an increase in pulmonary vascular resistance and a decrease in volume distensibility of the extraparenchymal segment. Vpa(total) increased 76% without changes in the relative volume distribution of Vpa(EP) and Vpa(IP). These findings can be best explained by active vasomotion with an increase in downstream pulmonary vascular resistance.
|Title of host publication||J.APPL.PHYSIOL.RESPIR.ENVIRON.EXERCISE PHYSIOL.|
|Number of pages||6|
|State||Published - Jan 1 1977|
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