Minimal redistribution of pulmonary blood flow with exercise in
racehorses.
Bernard, Susan L., Robb W. Glenny, Howard H. Erickson, M. Roger Fedde,
Nayak Polissar, Randall J. Basaraba, Michael P. Hlastala.
Department of Physiology and Biophysics and Department of Medicine,
University of Washington, Seattle, Washington and Department of
Anatomy and Physiology and Department of Diagnostic
Medicine/Pathobiology, Kansas State University, Manhattan, Kansas
APStracts 3:0260A, 1996.
We determined the spatial distribution of pulmonary blood flow at rest
and during increasing levels of exercise (34, 59 and 90% maximum
oxygen consumption) in Thoroughbred racehorses (n=4) using 15 micron
fluorescent microspheres. After euthanasia, the lungs were flushed
free of blood, removed, air-dried at TLC, sliced into
isogravitational planes, which were sampled in a systematic fashion
for three-dimensional reconstruction. The fluorescence was measured
for quantification of blood flow. Mean pulmonary blood flow
heterogeneity (expressed as coefficient of variation) did not change
with increasing exercise levels (36.2 16.4% (rest) to 26.9 6.8%
(gallop) p=ns). Greater than 70% of pulmonary blood flow variation
across rest to high exercise states is determined by a fixed, spatial
pattern. Thirty percent of the variation of pulmonary blood flow
variation seen in horses over rest and exercising states is due to
redistribution. The majority of flow redistribution was due to flow
increasing to the dorsal region of the lung during exercise at 90%
O2max (a flow gradient of 0.20 ml[beta]min-1[beta]cm-1 up the lung,
p=.04).
Received 30 November 1995; accepted in final form 30 April 1996.
APS Manuscript Number A239-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96