Journal of Applied Physiology, Vol 65, Issue 1 283-287, Copyright © 1988 by American Physiological Society
Microvascular pressures during hypoxia in isolated lungs of newborn rabbits
C. D. Fike, S. J. Lai-Fook and R. D. Bland
Department of Pediatrics, University of California, San Francisco.
The purpose of this study was to determine the sites of hypoxic
vasoconstriction in lungs of newborn rabbits. We isolated and perfused with
blood the lungs from 19 rabbit pups, 7-23 days old. We maintained blood
flow constant, continuously monitored pulmonary arterial and left atrial
pressures, and alternated ventilation of the lungs with 95% O2-5% CO2
(control), and 95% N2-5% CO2 (hypoxia). Using micropipettes and a
servonulling device, we measured pressures in 20-60-micron-diam subpleural
arterioles and venules during control and hypoxic conditions. We inflated
the lungs to a constant airway pressure of 5-7 cmH2O and kept left atrial
pressure greater than airway pressure (zone 3) during micropuncture. In
eight lungs we measured microvascular pressures first during control and
then during hypoxia. We reversed this order in four lungs. In seven lungs
we measured microvascular pressures only during hypoxia. We found a
significant increase in pulmonary arterial pressure with no change in
microvascular pressures. These results indicate that the site of hypoxic
vasoconstriction in lungs of newborn rabbits is arteries greater than 60
micron in diameter.
