Journal of Applied Physiology, Vol 59, Issue 3 941-946, Copyright © 1985 by American Physiological Society
Hypoxia potentiates, oxygen attenuates deflation-induced reflex tracheal constriction
E. H. Vidruk
The reflex tracheomotor responses of in situ isolated segments of the
extrathoracic trachea of anesthetized, paralyzed, and ventilated dogs were
monitored. Reflex tracheal constriction was evoked by passive lung
deflation. The purpose of this study was to determine whether the
prevailing state of oxygenation altered the magnitude of this reflex.
Compared with the magnitude of the response during normoxia [arterial O2
tension (PaO2) = 78 Torr], that during hypoxia (PaO2 = 44 Torr) was nearly
threefold larger while that during hyperoxia (PaO2 greater than 250 Torr)
was about 50% smaller. The isocapnic changes in oxygenation by themselves
usually had no effect on tracheomotor tone. The deflation-induced reflex
tracheal constriction was eliminated by complete denervation of the
tracheal segment but usually only diminished by partial denervation.
Bilateral vagotomies or bilateral carotid body denervation also usually
decreased the magnitude of the reflex. It appears that the magnitude of
this reflex is dependent on the prevailing state of oxygenation and that a
pulmonary stretch receptor-carotid body chemoreceptor interaction accounts
for the exaggerated reflex tracheal constriction during hypoxia and the
attenuated response during hyperoxia.
