Distributions of vascular volume and compliance in the lung

The ether- and dye-dilution methods were used to estimate the arterial, capillary, and venous volumes and compliances in isolated dog lung lobes. In the range of arterial pressure from approximately 7 to 14.5 Torr and venous pressure of 1.4 to 10.8 Torr, the total lobar blood volume ranged from approximately 2 to approximately 2.6 ml/kg body wt. About 19% of the lobar vascular volume was in the arteries, approximately 59% was in the capillaries, and approximately 22% was in the veins. The lobar vascular compliance was approximately 0.065 ml.Torr-1.kg body wt-1 with an arterial-capillary-venous distribution of approximately 30:49:21. These results suggest that the largest fractions of the intralobar blood volume and compliance are in the capillary bed. The segmental compliances along with outflow occlusion data were used to place lower and upper bounds on the arterial, capillary, and venous resistances. These bounds were 13.6 and 61.4% of the total vascular resistance for the arteries, 0 and 59.4% for the capillaries, and 5.5 and 64.9% for the veins, respectively. These bounds are rather broad, but they help to put the information content of the occlusion data under the conditions of these experiments into perspective.