Journal of Applied Physiology, Vol 55, Issue 3 851-859, Copyright © 1983 by American Physiological Society
Effect of ketamine on control of breathing in cats
N. Jaspar, M. Mazzarelli, C. Tessier and J. Milic-Emili
We studied minute ventilation, breathing pattern, end-tidal CO2 partial
pressure (PACO2), and tracheal occlusion pressure in cats anesthetized with
ketamine (40 and 80 mg/kg) before and after CO2 inhalation. Before CO2
administration ventilation was reduced and PACO2 increased relative to
unanesthetized cats at both ketamine doses. Breathing pattern was of the
"apneustic" type, being characterized by 1) prolonged inspiratory duration
and relatively short expiratory time and 2) markedly curvilinear (convex
upward) inspiratory volume-time profile. The latter reflected a similar
curvilinearity in the tracheal occlusion pressure waveform. During CO2
inhalation, the ventilatory response to CO2 was similar to that in
unanesthetized cats in spite of a depressed tracheal occlusion pressure
response. This discrepancy was due to the fact that in the presence of a
convex upward inspiratory volume-time profile, the shortening of
inspiratory duration with increasing CO2 results in a marked increase of
mean inspiratory flow, and hence the ventilatory response to CO2 remains
high.
