Journal of Applied Physiology, Vol 52, Issue 6 1591-1597, Copyright © 1982 by American Physiological Society
Effect of changing lung mass on lung water and permeability-surface area in sheep
J. R. Snapper, T. R. Harris and K. L. Brigham
The effects of changing cardiac output and lung mass on pulmonary capillary
surface area, lung water, and hemodynamics were studied in eight sheep.
51Cr-erythrocytes, 125I-albumin, 3H2O, and [14C]urea were injected into the
right atrium, and timed samples were collected from the aorta for the
calculation of cardiac output (CO), extravascular lung water (EVLW), and
permeability-surface area product (PS) for [14C]urea. CO was varied by
opening and closing arteriovenous shunts, and lung mass was decreased by
first tying off the left lung followed by tying off the right lower lobe.
Pulmonary arterial pressure (r = -0.741) and pulmonary vascular resistance
(r = -0.700) increased as lung mass was decreased. CO decreased slightly (r
= -0.470 while left atrial pressure was not changed (r = -0.144) by
decreasing lung mass. There was a close correlation between EVLW and lung
mass (r = 0.944) and between [14C]urea PS and lung mass (r = 0.672). We
were able to demonstrate that [14C]urea behaves as a diffusion-limited
tracer in a single pass through the lungs, since [14C]urea extraction
decreased as flow per unit mass increased. These results support the
clinical use of multiple-tracer studies to measure EVLW and [14C]urea PS.
