Journal of Applied Physiology, Vol 43, Issue 5 844-851, Copyright © 1977 by American Physiological Society
Effect of SO2 on control of breathing in anesthetized cats
M. M. Grunstein, M. Hazucha, M. H. Sorli and J. Milic-Emili
In seven anesthetized tracheotomized cats we studied the acute respiratory
effects of SO2 inhalation at different steady-state levels of arterial CO2
tension (Paco2). During room air breathing, SO2 (0.05%) addition caused a
progressive reduction in tidal volume (VT) and increases in both
respiratory frequency (f) and pulmonary resistance (RL). Atropine sulfate
abolished the bronchoconstriction response to SO2 and thus permitted the
study of the influence of SO2 on VT and f in the absence of constricted
airways. Despite marked reductions in the VT VS. PaCO2 relationships with
SO2 exposure after atropine, the relationship between pulmonary ventilation
(VE) and PaCO2 was not signifcantly altered. This was the case since SO2
caused solely a reduction in inspiratory duration (Ti), affecting neither
the mean rate of rise of inspiratory activity (i.e., VT/Ti) nor the
relationship between Ti and breath duration. Thus, airways irritation with
SO2 produced rapid, shallow breathing characterized by a shortening of
inspiratory and total respiratory cycle times with no change in the rate of
development of inspiratory activity. The findings suggest an influence
exclusively concerned with the timing of inspiration. Perhaps premature
onset of inspiratory activity accounts for the observed effects.
