In the Pulmonary Arteries, Capillaries, and Veins
Longitudinal Distribution of Vascular Resistance in the Pulmonary Arteries, Capillaries, and Veins JEROME S. BRODY, EDWARD J. STEMMLER, and ARTHu B. DuBois From the Department of Physiology, Division of Graduate Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104 A B S T R A C T A new method has been described monary artery pressure averaged 20.4 cm H2O, for measuring the pressure and resistance to blood and pulmonary vein pressure averaged 9.2 cm flow in the pulmonary arteries, capillaries, and H2O. These techniques also provide a way of ana- veins. Studies were performed in dog isolated lyzing arterial, capillary, and venous responses to lung lobes perfused at constant flow with blood various pharmacologic and physiologic stimuli. from a donor dog. Pulmonary artery and vein volume and total lobar blood volume were mea- INTRODUCTION sured by the ether plethysmograph and dye- dilution techniques. The longitudinal distribution The arterioles are the major resistance vessels in of vascular resistance was determined by analyzing the systemic vascular bed (1, 2), but it is uncer- the decrease in perfusion pressure caused by a tain whether the greatest resistance to blood flow bolus of low viscosity liquid introduced into the in the lungs is in the arteries, capillaries, or veins vascular inflow of the lobe. (1, 3, 4). The pulmonary arteries were responsible for Piiper (5), in 1958, reasoned from Poiseuille's 46% of total lobar vascular resistance, whereas law that, during constant perfusion, injection into the pulmonary capillaries and veins accounted for the bloodstream of a bolus of fluid with viscosity 34 and 20% of total lobar vascular resistance different from that of blood would cause a per- respectively.
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