Am. J. Respir. Crit. Care Med., Vol 151, No. 4, 04 1995, 1018-1026.
Alveolar air/tissue interface and nuclear magnetic resonance behavior of normal and edematous lungs
AG Cutillo, KC Goodrich, K Ganesan, S Watanabe, DC Ailion, AH Morris and CH Durney
Department of Internal Medicine, University of Utah, Salt Lake City.
The alveolar air/tissue interface markedly affects the NMR properties of
lungs by causing an NMR signal loss as a result of internal (tissue-
induced) magnetic field inhomogeneity. The signal loss can be measured as
the difference in NMR signal intensity (difference signal delta) between a
pair of images obtained using temporally symmetric and asymmetric spin-echo
sequences. Previous data indicate that the difference signal measured at an
asymmetry time of 6 ms (delta 6ms) is very low in degassed lungs and
increases markedly with alveolar opening. Theoretically, the NMR behavior
of edematous lungs is expected to differ from that of normal nondegassed
lungs because alveolar flooding and collapse are equivalent to partial
(regional) degassing. To test this prediction, we measured delta 6ms in
normal and edematous (oleic acid-injured) excised unperfused rat lungs at
5, 10, 20, 30, and 0 (full passive deflation) cm H2O inflation pressure
(PL). Lung volume changes were estimated from NMR lung water density (pH2O)
measurements. In normal lungs, delta 6ms did not vary with PL. In edematous
lungs delta 6ms was, as predicted, significantly lower than normal at 5 and
10 cm H2O PL but rose markedly (to about normal) as PL was further
increased. Upon subsequent deflation from 30 to 0 cm H2O PL, delta 6ms did
not vary significantly or decreased. On the basis of our theoretical
models, the data could be interpreted as reflecting the loss of alveolar
air/tissue interface as a result of alveolar flooding and the relative
contributions of airspace recruitment and distension to the lung volume
changes. Histologic and morphometric data obtained from the same lungs
supported this interpretation.(ABSTRACT TRUNCATED AT 250 WORDS)
