LUNG WATER MEASUREMENT BY NUCLEAR-MAGNETIC-RESONANCE - CORRELATION WITH MORPHOMETRY

Estimates of lung water content obtained from nuclear magnetic resonan ce (NMR) and morphometric and gravimetric measurements were compared i n normal and experimentally injured rats. Average lung water density ( <(rho)over bar>(H2O)) was measured by an NMR technique in excised unpe rfused rat lungs (20 normal lungs and 12 lungs with oleic acid-induced edema) at 0 (full passive deflation) and 30 cmH(2)O lung inflation pr essure and in vivo (4 normal rats and 8 rats with lung injury induced by oleic acid or rapid saline infusion). The <(rho)over bar>(H2O) valu es were compared with morphometric measurements of lung tissue volume density (V-v) obtained from the same lungs fixed at corresponding liqu id-instillation pressures. A close correlation was observed between <( rho)over bar>H2O and V-v in normal and injured excised lungs [correlat ion coefficient (r) = 0.910, P < 0.01]. In vivo <(rho)over bar>(H2O) w as also closely correlated with V-v (r = 0.897, P < 0.01). The correla tion coefficients between <(rho)over bar>H2O and gravimetric lung wate r content (LW(Gr)) were lower in the excised lung group (r = 0.663 and 0.692, respectively, for <(rho)over bar>H2O at 0 and 30 cmH(2)O lung inflation pressure, P < 0.01) than in the in vivo study (r = 0.857, P < 0.01). Our results indicate that NMR techniques, which are noninvasi ve and nondestructive, provide reliable estimates of lung water densit y and that the influence of lung inflation on <(rho)over bar>H2O is im portant (compared with the effect of lung water accumulation in lung i njury) only in the presence of deliberately induced very large variati ons in the lung inflation level.