Journal of Applied Physiology, Vol 69, Issue 1 127-135, Copyright © 1990 by American Physiological Society
Changes in lung liquid dynamics induced by prolonged fetal hypoxemia
S. B. Hooper and R. Harding
Department of Physiology, Monash University, Clayton, Victoria, Australia.
Our aim was to determine the effect of prolonged fetal hypoxemia, induced
by reduced maternal uterine blood flow (RUBF), on fetal lung liquid
secretion, flow, and volume. In chronically catheterized fetal sheep, lung
liquid volume (VL) and the secretion rate of lung liquid (Vs) were measured
before and after a 24-h period of either RUBF or normoxemia. Tracheal fluid
flow and the incidence of fetal breathing movements (FBM) were measured
before, during, and after the 24-h period. In normoxic control fetuses Vs
was not significantly altered. After 24 h of RUBF, Vs was significantly (P
less than 0.005) reduced compared with pre-RUBF values. During 24 h of RUBF
the incidence of FBM declined initially but returned to control values
after 12-16 h. In seven of eight fetuses, over the 12- to 24-h period of
RUBF, large amounts of liquid (22.7-62.6 ml) were drawn into the lungs
during FBM, resulting in a net movement of amniotic fluid into the lungs.
During the 18- to 24-h period of RUBF, changes in the incidence of FBM were
found to be significantly and positively correlated (r = 0.86, P less than
0.005) with the changes in VL that occurred over the 24-h period. Thus,
prolonged RUBF can result in the inhalation of large volumes of amniotic
fluid by the fetus, which could be a cause of in utero meconium aspiration.
