Journal of Applied Physiology, Vol 48, Issue 1 188-196, Copyright © 1980 by American Physiological Society
Direct pulmonary vascular responses in the conscious newborn lamb
J. E. Lock, F. Hamilton, H. Luide, F. Coceani and P. M. Olley
Electromagnetic flow probes were placed around the right and left pulmonary
arteries (RPA and LPA) of nine newborn lambs. Preliminary in vitro and in
vivo experiments delineated the accuracy and limitations of this method of
flow measurement and the value in vivo of a balloon occlusive zero. Six to
nine days after surgery, catheters were placed in the aorta and a branch
pulmonary artery permitting simultaneous measurements of RPA and LPA flow,
pulmonary arterial pressure, and aortic pressure. Vasoactive agents were
injected into one lung, and a shift in blood flow distribution reflected
direct active vasoconstruction or vasodilation in that lung. With a normal
arterial oxygen tension, acetylcholine had no direct effect on the
pulmonary vessels, but indirectly lowered pulmonary resistance via its
systemic effects. Histamine was a potent direct pulmonary vasoconstrictor,
bradykinin was a weak direct dilator, norepinephrine was a direct
constrictor, prostaglandin E1 was a direct dilator, and prostaglandin F2a
was a direct constrictor. These results demonstrate the feasibility of
isolating the direct pulmonary vascular effects of certain pharmacologic
agents using a double pulmonary artery flow probe preparation, agents using
a double pulmonary artery flow probe preparation, without the use of
anesthetics or extracorporeal perfusion circuits.
