The identification of pulmonary capillary permeability from multiple-indicator data: Effects of increased capillary pressure and alloxan treatment in the dog

Abstract

The purpose of this study was to determine the effects of increased intravascular pressure and alloxan treatment of anesthetized dogs on the pulmonary capillary permeability-surface area product (PS) for the tracers [ 14C]urea and 3HOH. 125I-labeled albumin, 51Cr-tagged erythrocytes, [ 14C]urea, and [ 3H]water were injected simultaneously. Values of PS were computed by the integral extraction method, the maximum extraction method, and by two organ-capillary mathematical models. The results indicate that while the extravascular volume is increased by both alloxan and increased pressure, only alloxan increases PS for [ 14C]urea significantly. More detailed calculations of PS based on the mathematical models provide more sensitive and reproducible values of PS. The value of PS for [ 3H]water, generally considered to be flow-limited and therefore insensitive to alterations in PS, was also found to increase slightly with alloxan, but not high pressure. We conclude that multiple-indicator experiments when analyzed by accurate mathematical techniques permit distinction between pulmonary edema caused by high pressure and that caused by increased permeability.