Indicator dilution lung water and vascular permeability in humans. Effects of pulmonary vascular pressure.

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Abstract
A multiple-indicator dilution technique to measure lung vascular permeability and extravascular lung water (EVLW) in humans was studied using an indicator during cardiac catheterization in 18 patients with various degrees of stable heart failure. A mixture of 51Cr-erythrocytes, 125I-albumin, H3O, and 14C-urea was injected into the right atrium, and serial blood samples were taken from an arterial catheter. From the time-concentration curves cardiac output, 14C-urea permeability-surface area product (PS) (by integral extraction and a Krough-convolution model), and EVLW (by mean transit time and a Krogh-convolution model) were calculated with lung microvascular pressure (Pmv) from pulmonary artery and pulmonary artery wedge or left atrial pressures, and measured hematocrit, plasma protein concentration, lung vital capacity, total lung capacity (TLC), CO-diffusing capacity, and alveolar volume (VA). 14C-urea PS correlated well with VA2/3 (r = 0.62, P = 0.019). Urea PS/VA2/3 did not correlate with Pmv (r = 0.36, P = NS [not significant]), hematocrit (r = -0.07, P = NS) or cardiac output (r = 0.36, P = NS). EVLW/TLC correlated with Pmv (r = 0.51, P = 0.02) and with Pmv-plasma oncotic pressure (r = 0.63, P = 0.007). 14C-urea PS is a measure of lung vascular permeability in humans and in animals, permeability is unaffected by Pmv. EVLW may be a more useful measure of lung H2O in humans than previously thought, when measurable forces affecting fluid exchange are accounted for.