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

To see whether a multiple-indicator dilution technique would measure lung vascular permeability and extravascular lung water (EVLW) in humans, we did indicator studies during cardiac catheterization in 18 patients with various degrees of stable heart failure. A mixture of “Cr-erythrocytes, '”I-albumin, 'H-water, and uC-urea was injected into the right atrium, and serial blood samples were taken from an arterial catheter. From the time-concentration curves we calculated cardiac output, 14C-urea permeability-surface area product (PS) (by both integral extraction and a Krogh-convolution model), and EVLW (by both mean transit time and a Krogh-convolution model). We also calculated 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), carbon monoxide-diffusing capacity, and alveolar volume (VA). 14C-urea PS correlated well with VA 1/S (r = 0.62, (p = 0.019). Urea PS/VA l / l did not correlate with Pmv (r-0.36, (p = NS), 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 even better with Pmv-plasma oncotic pressure (r = 0.63, (p = 0.007). We therefore conclude that “C-urea PS is a measure of lung vascular permeability in humans, and that, as in animals, permeability is unaffected by PmT. EVLW may be a more useful measure of lung water in humans than previously thought, when interpreted in light of the measurable forces affecting fluid exchange. Circ Res 44: 523-530, 1979