Journal of Applied Physiology, Vol 78, Issue 2 531-538, Copyright © 1995 by American Physiological Society
Effect of inhibition of prostaglandin synthesis on breathing movements and pulmonary blood flow in fetal sheep
R. D. Savich, F. A. Guerra, C. C. Lee and J. A. Kitterman
Cardiovascular Research Institute, University of California, San Francisco 94143, USA.
During transition from fetal to extrauterine life, respiration increases in
incidence and magnitude as pulmonary blood flow dramatically increases. To
determine whether alterations in pulmonary blood flow in utero are directly
related to alterations in fetal breathing movements (FBM), we studied six
chronically instrumented fetal sheep late in gestation to assess the
effects of continuous FBM caused by a 4-h infusion of meclofenamate, a
prostaglandin synthase inhibitor, on mean pulmonary blood flow to the
fetus. We found a striking increase in FBM from 46 +/- 15% (SD) of the time
during control to > 85% of the time by 1 h (P < 0.001), with the
fetuses exhibiting continuous FBM by the last 1 h of infusion. The mean
pulmonary blood flow also increased significantly during the first 90 min
of the infusion as the incidences of FBM were increasing (26 +/- 14 and 56
+/- 23 ml.min-1.kg-1 for control and infusion, respectively; P < 0.01).
Despite the simultaneous initial increase in FBM and mean pulmonary blood
flow, the increase in left pulmonary artery blood flow was not sustained
and decreased back to baseline by 2 h, even though the incidence of FBM
continued to increase at this time. During the infusion, the mean pulmonary
blood flow was not different between the presence or absence of FBM. There
were no changes in fetal heart rate or pulmonary or systemic blood
pressures during the infusion nor in arterial pH or blood gas tensions. We
conclude that this increase in mean pulmonary blood flow in utero was not
solely related to the increase in breathing movements.
