Journal of Applied Physiology, Vol 45, Issue 2 212-218, Copyright © 1978 by American Physiological Society
Reflex effects of lung inflation and inhalation of halothane, ether, and ammonia
T. C. Lloyd Jr
Anesthetized dogs were perfused at constant pressure from an external
oxygenator after removing their hearts. Systemic vascular resistance (SVR)
and spontaneous breathing effors were monitored while the lungs were
ventilated briefly at a low frequency with several tidal volumes and at a
low volume with several frequencies. Inflation depressed respiratory
activity and transiently lowered SVR to a minimum from which it
spontaneously partially recovered. The transient and sustained SVR changes
were directly related to peak inflating pressure, independent of the mode
of ventilation. Pressurization of the sublaryngeal extrapulmonary airways
and addition of ammonia to lung inspirate were without effect. Ventilation
with 7% ether had no effect, but at 13% it occasionally increased
respiratory activity. Ventilation with 7% halothane depressed SVR and
stimulated respiration, whereas 13% caused vasodilation and apnea. The
magnitudes of SVR responses to halothane and to inflation were
uncorrelated. All effects of inflation and inhalants were eliminated by
vagotomy. We condluded that the systemic vessels appear to respond to
changes in respiratory minute volume; that this is brought about by
intrapulmonary receptors, perhaps of more than one type; that two classical
"irritants" have little effect in dogs; and that halothane has effects on
breathing and SVR consistent with stimulation of J-receptors.
