AJP - Regulatory, Integrative and Comparative Physiology, Vol 249, Issue 1 39-R43, Copyright © 1985 by American Physiological Society
Pulmonary vascular resistance during unilateral pulmonary arterial occlusion in ducks
F. L. Powell, R. H. Hastings and R. W. Mazzone
We measured mean pulmonary arterial pressure (Ppa) during temporary
unilateral pulmonary arterial occlusion (TUPAO) in 10 ducks. Ppa increased
from 11.4 +/- 0.8 mmHg during control conditions to 18.8 +/- 1.8 during
TUPAO. In 5 of the 10 ducks we also measured mean left atrial pressure
(Pla) and cardiac output (Q). In these ducks Ppa significantly increased
with TUPAO from 13.9 +/- 0.4 to 22.0 +/- 1.2 mmHg, whereas Pla and Q did
not change significantly. Pulmonary vascular resistance (PVR) increased
from 10.6 +/- 1.3 to 24.1 +/- 5.3 mmHg X min X 1(-1) on TUPAO. By assuming
equal vascular resistance in either lung it can be calculated that the
vascular resistance in only one lung was 22.5 +/- 3.5 mmHg X min X 1(-1)
during control conditions. Thus doubling flow resulted in no significant
change in one lung's vascular resistance. A morphometric study of both
lungs of a domestic goose that were rapidly frozen during TUPAO indicated
very little compliance in pulmonary blood capillaries. The relative volume
of exchange tissue occupied by blood capillaries was 0.28 in the occluded
lung and 0.36 in the perfused lung. Surface-to-volume ratios of blood
capillaries were 12,524 cm-1 in the occluded lung and 11,056 cm-1 in the
perfused lung. We conclude that PVR in birds is relatively insensitive to
changes in Q, in contrast to mammals.
