Journal of Applied Physiology, Vol 53, Issue 2 324-329, Copyright © 1982 by American Physiological Society
Pulmonary interstitial compliance: a function of the osmotic constituents of the interstitium
P. D. Snashall, S. J. Keyes, B. M. Morgan and K. F. Chung
We have attempted to dehydrate the lung interstitium to determine the
nature of forces holding water in that compartment. We administered
furosemide with and without bovine albumin intravenously to rabbits (n =
21) 18-24 h before they were anesthetized with pentobarbital sodium. Renal
pedicels were ligated and 51Cr-labeled EDTA was injected to estimate lung
interstitial water volume. After a period of equilibration the thorax was
rapidly opened, and left atrial pressure was measured by direct puncture.
125I-labeled albumin was injected to label the lung vascular volume, and
the rabbits were killed 3 min later. Lungs were removed and drained of
blood, and extravascular water volume, interstitial volume, and dry weight
were determined. Results from these rabbits were compared with a group of
normal (n = 4) and overhydrated (n = 6) rabbits. We have found that lung
interstitial water is removed in proportion to the change in intravascular
forces. We estimate interstitial compliance to be 1.76% cmH2O-1. Our
results are compatible with the hypothesis that removal of water is opposed
by an increase in interstitial colloid osmotic pressure and not by a fall
of hydrostatic pressure. This implies that in the normally hydrated state
interstitial hydrostatic pressure is ambient.
