AJP - Heart and Circulatory Physiology, Vol 257, Issue 4 1287-H1291, Copyright © 1989 by American Physiological Society
Mathematical model of edema in the isolated rabbit lung perfused with oleic acid
H. G. Hempling and S. A. Katz
Department of Physiology, Medical University of South Carolina, Charleston 29425.
The development of edema by the isolated, perfused rabbit lung in response
to oleic acid was analyzed with the equations of Kedem and Katchalsky
(Biochim. Biophys. Acta 27: 229-246, 1958). A perfused cylinder and annulus
surround was chosen as a model. Isolated lungs, perfused with an isosmotic
solution containing dextran as an oncotic agent, received a bolus injection
of oleic acid into the pulmonary artery, resulting in marked edema without
a rise in mean pulmonary arterial pressure. Hydrostatic pressure was kept
constant and in the model was converted to its equivalent concentration of
osmotically active impermeant solute, with a reflection coefficient (sigma)
of 1. Fluid changes could be analyzed with three principal components as
follows: the capillary permeability to solute (Pk), the hydraulic
coefficient (Lp), and sigma. The equations were solved using Euler's method
for integration, and the values for the three coefficients were adjusted to
fit the data. The analysis indicated that the edema measured experimentally
could be simulated by a progressive increase in Lp at constant or
increasing values of Pk and decreasing values for sigma but not after
selective increases in Pk and/or decreases in sigma alone. The analysis
suggests that an expanding hydraulic conductivity may be the rate-limiting
factor in oleic acid-induced pulmonary edema in the isolated, perfused
rabbit lung.
