Am. J. Respir. Crit. Care Med., Vol 149, No. 5, 05 1994, 1276-1285.
Effects of pulmonary fibrosis on the distribution of edema. Morphometric analysis
MP Zwikler, D Iancu and RP Michel
Department of Pathology, McGill University, Montreal, Quebec, Canada.
We tested the hypothesis that in advanced pulmonary fibrosis, edema is
redistributed away from the relatively noncompliant interstitium and
predominantly floods alveoli. Severe left lung fibrosis was produced in six
dogs with radiation and intratracheal bleomycin and, 24 mo later,
hydrostatic edema was induced by infusing 20% body weight Ringer's lactate.
Previously we had found, by computed tomography scanning and gravimetry,
that similar amounts of water per unit volume accumulated in control and
fibrotic lungs; semiquantitative light microscopic grading showed less
interstitial and more alveolar edema in the fibrotic lungs. In the present
study, we extended these observations with detailed morphometric assessment
of volume fractions and absolute volumes of the pulmonary compartments, and
we examined the lungs with electron microscopy. We found a twofold rise in
the volume fractions of connective tissue and alveolar edema (p < 0.05)
and a 50% reduction of air and of interstitial edema in fibrotic lobes (p
< 0.05). There was a marked reduction in the absolute volume of edema,
paralleling the reduction in lung volume in fibrosis, and minimal
gravity-dependent edema gradients in both control and fibrotic lungs. In
the latter, evidenced by electron microscopy, the interstitial edema was
randomly distributed, whereas in the control lungs, it was found primarily
around extra-alveolar vessels and airways, not in the alveolo-capillary
septa. We conclude that fibrosis profoundly affects the distribution of
edema in the lung.
