Journal of Applied Physiology, Vol 39, Issue 6 969-975, Copyright © 1975 by American Physiological Society
Effect of ventilation on pulmonary blood volume of the fetal lamb
A. M. Walker, D. G. Alcorn, J. C. Cannata, J. E. Maloney and B. C. Ritchie
Blood volume changes in the fetal lung following the onset of ventilation
were studied by isotopic measurement of red blood cell and plasma volume in
rapidly frozen lungs of ten near term fetal lambs. Total pulmonary blood
volumes of fetal lambs ventilated with 3% O2 and 7% CO2 in nitrogen (so
that blood gas levels were little changed from fetal values), or with air,
were compared with measurements in unventilated lambs. Regional
correlations of blood volume and blood flow (measured with isotope-labeled
microemboli) within the lungs were also examined. Total pulmonary blood
volume averaged 5.6 ml/kg body weight in unventilated fetal lambs and was
approximately 43% greated in fetal lambs after 5-20 min of air ventilation,
but not significantly different in lambs ventilated with 3% O2 and 7% CO2
in nitrogen. Thus it is ventilation with air, rather than the introduction
of gas into the alveoli, which enlarges the fetal pulmonary vascular bed.
Regional pulmonary blood volume and blood flow were correlated, though
poorly, in air-ventilated lungs, but not in lungs ventilated with 3% O2 and
7% CO2 in nitrogen; this suggests that a common factor may operate to
increase both blood flow and blood volume in the fetal lung following the
introduction of air.
