Pulmonary capillary permeability in man and a canine model of chemical pulmonary edema

Abstract

Pulmonary capillary permeability-surface products (PSP) for sucrose and water have been calculated in normal, awake man and in anesthetized dogs using multiple indicator dilution data and a numerical deconvolution technique to estimate maximal extraction. In man and control animals the PSP for sucrose was found to be 9.1 and 7.1 cm 3/sec, respectively, while PSPs for water were found to be 34.0 and 30.9 cm 3/sec. The effects of flow and choice of the reference tracer (red blood cells or albumin) were examined. With the exception of water in man, the PSPs for sucrose and water did not change significantly with an increased cardiac output, regardless of the reference tracer chosen. Pulmonary capillary damage induced by the infusion of 75 mg/kg of alloxan in dogs increased the PSPs for sucrose and water by 35 and 52%, respectively, when red cells formed the reference tracer material. This change was eliminated for sucrose when albumin formed the reference tracer and reduced the magnitude of the change for water from 52 to 34%. The permeability increases in the alloxan damaged dogs occurred in the presence of normal pulmonary artery and wedge pressures. We conclude that the exchange of water is not flow-limited at physiologic or higher rates of perfusion and that albumin is misleading as a reference tracer in multiple indicator dilution studies of pulmonary edema.