Journal of Applied Physiology, Vol 42, Issue 4 630-635, Copyright © 1977 by American Physiological Society
Ventilatory response in the fetal lamb following peripheral chemodenervation
D. E. Woodrum, T. A. Standaert, C. R. Parks, D. Belenky, J. Murphy and W. A. Hodson
Carotid infusions of sodium cyanide solution and perfusions of hypoxemic or
hypercapnic fetal blood were done before and after peripheral chemoreceptor
denervation. Step changes in PaO2 ranged from -11 to -22 Torr; step changes
in PaCO2 ranged from +17 to +42 Torr. The cyanide dose was 0.2 mg/kg per
loop system. Control perfusions consisted of 25 ml of fetal blood without
changes in pH and blood gases. A ventilatory response occurred in the
majority of all experimental perfusions regardless of innervation status of
the peripheral chemoreceptors. No response occurred with control
perfusions. There was a marked variability in the time of onset of
ventilatory activity with a delay of greater than 10 s occurring following
most perfusions. These studies demonstrate that the fetus has an attenuated
ventilatory response to chemical stimuli and that hypoxia stimulates
ventilation in the absence of peripheral chemoreceptors.
