Journal of Applied Physiology, Vol 61, Issue 2 603-610, Copyright © 1986 by American Physiological Society
Effect of chronic pulmonary denervation on ventilatory responses to exercise
P. S. Clifford, J. T. Litzow, J. H. von Colditz and R. L. Coon
To assess the role of intrapulmonary receptors on the ventilatory responses
to exercise we studied six beagle dogs before and after chronic pulmonary
denervation and five dogs before and after sham thoracotomies. Each
exercise challenge consisted of 6 min of treadmill exercise with
measurements taken during the third minute at 3.2 km/h, 0% grade, and
during the third minute at 5.0 km/h, 0% grade. Inspiratory and expiratory
airflows were monitored with a low-dead-space latex mask and
pneumotachographs coupled to differential pressure transducers. Both pre-
and postsurgery, all dogs exhibited a significant arterial hypocapnia and
alkalosis during exercise. Denervation of the lungs had no significant
effect on minute ventilation at rest or during exercise, although there was
a lower frequency and higher tidal volume in the lung-denervated dogs at
all measurement periods. Breathing frequency increased significantly during
exercise in lung-denervated dogs but to a lesser magnitude than in the
control dogs. The changes that occurred in breathing frequency in all
animals were due predominantly to the shortening of expiratory time.
Inspiratory time did not shorten significantly during exercise following
lung denervation. We conclude from these data that intrapulmonary receptors
which are deafferented by sectioning the vagi at the hilum are not
responsible for setting the level of ventilation during rest or exercise
but are involved in determining the pattern of breathing.
