Journal of Applied Physiology, Vol 52, Issue 6 1535-1544, Copyright © 1982 by American Physiological Society
Measurement of lung water in dog lobes using inhaled C15O2 and injected H215O
A. J. Swinburne, C. G. MacArthur, C. G. Rhodes, J. D. Heather and J. M. Hughes
Indicator-dilution analysis was used in a recirculation-free isolated dog
lobe preparation to compare an inhaled water tracer (C15O2) and an injected
water tracer (H215O) with direct weighing as a measure of total lung water.
Residue detection (counting over the lung) was compared with outflow
detection (counting over the venous effluent). With outflow detection,
inhaled C15O2 measured 74% and injected H215O 90% of the gravimetric lung
water. In hemodynamic edema, the increase in lung water measured by residue
detection of both tracers correlated well with increases in weight (r =
0.92, slope = 1.03). However, outflow detection of both tracers
underestimated the lung water increase by 53% in edema (r = 0.88, slope =
0.47). Thus, in edema, equilibration of both tracers within the lung water
volume is rapid, but clearance from the lung is delayed because slowly
clearing water pools develop. The errors caused by inhomogeneity of
perfusion distribution were investigated after pulmonary arterial injection
of 34-, 50-, and 175-micrometers spheres. For the same lung weight, C15O2
transit was delayed and H215O transit accelerated greatly by the
175-micrometers spheres and slightly by the 50-micrometers spheres.
