Journal of Applied Physiology, Vol 49, Issue 2 287-293, Copyright © 1980 by American Physiological Society
Effect of vagal stimulation on collateral flow resistance in dog lungs
L. E. Olson and N. E. Robinson
Vagal effects on steady-state resistance of pathways within a segment of
lung (Rss) were studied in open-chest dogs using a wedged catheter
technique. To prevent adrenergic bronchodilation, dogs were pretreated with
propranolol. Rss was determined with vagi intact or sectioned and during
electrical stimulation of right and left vagi. Following determination of
Rss, gas flow into the segment was arrested, segmental pressure decay
recorded, and the time for 90% decay (T90) measured. Stimulation of the
vagus supplying the lung with the wedged catheter (ipsilateral) increased
Rss and T90 at low (2-4 cmH2O) transpulmonary pressures (Pao) and T90 at
high (5-9 cmH2O) Pao. Vagal sectioning and contralateral stimulation had
minimal effects. Atropine abolished vagal effects. We modeled the segment
as two series compartments, one with a rapid time constant and one with a
longer time constant. At both low and high Pao, vagal stimulation prolonged
the slow time constant. If the fast compartment represents small airways
and the slow compartment collateral pathways, collaterals may not be
effective in maintaining ventilation to lung segments distal to a vagally
constricted bronchus.
