Journal of Applied Physiology, Vol 54, Issue 4 997-1002, Copyright © 1983 by American Physiological Society
Ventilatory changes associated with changes in pulmonary blood flow in dogs
J. F. Green and M. I. Sheldon
To examine the influence of pulmonary blood flow (Qp) on spontaneous
ventilation (VE), we isolated the systemic and pulmonary circulations and
controlled the arterial blood gases and blood flow (Q) in each circuit as
we measured VE. Each dog was anesthetized with ketamine and maintained with
halothane. Systemic Q was drained from the right atrium and pumped through
an oxygenator and heat exchanger and returned to the aorta. An identical
bypass was established for the pulmonary circulation, draining blood from
the left atrium and pumping it to the pulmonary artery. The heart was
fibrillated, all cannulas were brought through the chest wall, and the
median sternotomy was closed. The dog was then allowed to breathe
spontaneously. The arterial O2 partial pressure (PO2) of both circuits was
maintained greater than 300 Torr. Systemic Q was maintained at 0.080 l X
min-1 X kg-1. Initially the arterial CO2 partial pressure (PCO2) of both
circuits was set at 40 Torr as Qp was varied randomly between approximately
0.025 and 0.175 l X min-1 X kg-1. The average VE-Qp relationship was linear
with a slope of 1.45 (P less than 0.0005). Increasing the arterial PCO2 of
both circuits to 60 Torr elevated VE an average of 0.37 l X min-1 X kg-1 at
each level of Qp (P less than 0.0005). Vagotomy abolished the effect of Qp
on VE. Increasing Qp affected the systemic arterial PCO2-VE response curve
by shifting it upward without altering its slope. These results demonstrate
that increases in Qp are associated with increases in VE. This phenomenon
may contribute to exercise hyperpnea.
