Journal of Applied Physiology, Vol 45, Issue 3 385-391, Copyright © 1978 by American Physiological Society
Effects of pulmonary congestion and of left atrial distention on breathing in dogs
T. C. Lloyd Jr
Prior experiments showed that pulmonary congestion may initiate tachypnea
from lung receptors and that left atrial distention has no significant
effect on breathing, but in those experiments secondary reflexes could have
determined the results. In this study we separately distended the entire
pulmonary vascular bed, the arterial compartment, and the left atrium in
dogs perfused and oxygenated by an external system while ventilating and
while not ventilating the lungs. Distending pressures ranged from 20 to 70
Torr, and as output variables we measured the initial rate of inspiration,
peak inspiratory magnitude, inspiratory duration, expiratory duration, and
breathing frequency from the diaphragmatic electromyogram. Total vascular
congestion caused prolongation of expiration and lowering of frequency
without effect on inspiratory duration, its rate or magnitude. A smaller
depression was induced from the arterial compartment. Left atrial
distention, which failed to occur sufficiently often to be attributable to
dogs in general, had much less effect. However, when a related change in
breathing did occur, it was limited to a shortening of inspiratory
duration.
