Journal of Applied Physiology, Vol 48, Issue 5 794-798, Copyright © 1980 by American Physiological Society
Failure of tracheal distension to inhibit breathing in anesthetized dogs
T. C. Lloyd Jr and J. A. Cooper
Using anesthetized spontaneously breathing dogs, we compared the
respiratory effects of tracheal distension with the effects of changes in
lung volume before and after vagotomy. We used an endotracheal tube with a
long cuff to distend the trachea to pressures of 10, 20, and 40 cmH2O. Lung
volume increases were imposed by expiratory threshold loading, and volume
was decreased by abdominal compression, both of which caused outward rib
cage displacement. During expiratory loading, the tidal volume was
unchanged but respiratory frequency and minute volume fell and an active
expiratory effort appeared; whereas frequency and minute volume rose, but
tidal volume fell during abdominal compression. Tracheal distension evoked
no discernible change in breathing. Following vagotomy, tidal volume and
minute volume fell, and frequency rose slightly, during expiratory loading
but abdominal compression was without effect. After vagotomy, 40 cmH2O
tracheal distension caused a slight frequency increase. We concluded that
the potential role of tracheal deformation in the reflex control of
breathing is insignificant in comparison with the other airways.
