Journal of Applied Physiology, Vol 60, Issue 3 861-867, Copyright © 1986 by American Physiological Society
Intravenous acid infusion without lowering arterial pH stimulates breathing
J. A. Orr, D. F. Erichsen, H. W. Shirer, P. L. Allen and P. A. Payne
The aim of this study was to determine whether increases in ventilation
would occur during intravenous acid infusion even if systemic arterial pH
was held constant. In six awake ponies, HCl (500 ml, approximately 0.312 M)
was infused into the right atrium at a total dose of 1.0 meq/kg over 18 min
while an equivalent dose of NaOH was infused into the left heart to restore
systemic arterial pH to normal. Total ventilation increased at the onset of
the infusion and remained elevated although systemic arterial pH was normal
to slightly alkaline. The increase in ventilation during the initial 2 min
of the infusion coincided with an increase in pulmonary arterial PCO2 and
decrease in pulmonary arterial pH. As the infusion progressed, however,
pulmonary arterial pH and PCO2 returned to near control values due to the
recirculation of systemic arterial blood with an acid-base status that had
been altered consequent to the hyperventilation. Pulmonary arterial blood
pressure was increased significantly during the entire infusion. Infusion
of equivalent doses of hypertonic saline led to only minor alterations in
the variables that were measured. These experiments demonstrate that this
dose of intravenous HCl can increase ventilation independent of reductions
in systemic arterial pH. Because increases in ventilation and pulmonary
arterial H+ were not well correlated throughout the entire infusion, and
pulmonary arterial blood pressure was increased, it is not clear if the
mechanism for this ventilatory response is due to stimulation of pulmonary
chemoreceptors, pulmonary vascular mechanoreceptors, or some other
mechanism unrelated to increases in systemic arterial H+ concentration.
