Journal of Applied Physiology, Vol 47, Issue 6 1212-1217, Copyright © 1979 by American Physiological Society
Central chemical regulation of respiration in term newborn
M. A. Bureau, R. Begin and Y. Berthiaume
The role of the medullary H+-sensitive chemoreceptors on the drive of
breathing was studied in 10 unanesthetized newborn animals (8 lambs and 2
kids). The experiment consisted of sequential measurements of ventilation
(VE) during a progressive change in the arterial pH (pHa) and in the pH of
the cisternal cerebrospinal fluid (pHCSF), induced by intravenous infusion
of hydrochloric acid (HCl) followed after an 8-h steady state of acidosis
by rapid bicarbonate [HCO3-] infusion. It is shown that a rapid change in
[HCO3-]CSF occurs during the infusion of HCl or NaHCO3. As a consequence
both CSF and arterial pH change in the the same direction and large changes
in pHCSF (from 7.331 to 7.227) were observed. Such CSF acidosis did not
contribute to further increase VE beyond the level by hyperventilation
induced by the initial fall of pHa. The ventilatory response to the
decrease in pHa was found to fall off with moderate to severe acidosis (pHa
less than 7.20). In conclusion, this study demonstrates an instability of
the pHCSF during neonatal metabolic acidosis and it suggests an immaturity
of both the H+-sensitive medullary and peripheral chemoreceptors in the
8-day-old newborns.
