Journal of Applied Physiology, Vol 50, Issue 2 421-427, Copyright © 1981 by American Physiological Society
Respiratory reflexes evoked by tracheal distension
S. V. Rao, F. B. Sant'Ambrogio and G. Sant'Ambrogio
In 13 dogs that were anesthetized and ventilated through an endotracheal
tube, segments of either the intrathoracic (ITT) or extrathoracic trachea
(ETT) were distended by over-inflating the sealing cuff within the first
half of an inspiration and maintaining this overinflation for two breathing
cycles. ITT distension caused a significant prolongation of the expiratory
duration (TE) of the first challenged breath in 12 of the 13 dogs. ETT
distension prolonged the TE in only 5 of the 13 dogs. An inhibition of
inspiration resulting in shortened inspiratory time and reduced peak
phrenic amplitude (PPA) was measured in three experiments. In six other
experiments, there was only a transient decrease in phrenic discharge,
which immediately resumed. In the remaining four experiments, the
inspiratory burst was unaffected. After vagotomy, ITT distension shortened
TE in 8 of the 13 dogs. ETT distension was ineffective in 10 out of 11
experiments; in the remaining experiment TE was significantly lengthened.
No significant effects were elicited on TI and PPA by either ITT or ETT
distension. These results could be explained by the known behavior of
tracheal receptors and could indicate the presence of extravagal
influences.
