Role of hematocrit in the recruitment of pulmonary diffusing
capacity: comparison of human and dog.
Wu, E. Y., M. Ramanathan, and C. C. W. Hsia.
Department of Internal Medicine, University of Texas Southwestern
Medical Center, Dallas, TX 75235
APStracts 2:0467A, 1995.
In dogs, maximal O2 uptake ( O(V,.)O2max) per kg of body weight is two
to three fold that in humans; the difference cannot be explained
solely by differences in structural features between species. We
compared the functional recruitment of pulmonary diffusing capacity
(DLCO) during exercise in dogs and humans to determine if pulmonary
gas exchange is matched to O(V,.)O2max or the size of the lungs, and
to define the potential role of exercise-induced polycythemia in
producing the superior aerobic capacity of the dogs. We compared the
relationships of DLCO, membrane diffusing capacity (DMCO) and
pulmonary capillary blood volume (Vc) with respect to pulmonary blood
flow ( ) by a rebreathing method during steady state exercise in
adult male human subjects and in conditioned adult male foxhounds.
The slopes and intercepts of the relationships of DLCO and DMCO to c
are significantly greater in dogs than in humans; the slopes of the
relationship of Vc to c are similar. In dogs diffusive pulmonary gas
transport is matched to the higher O2max. The enhanced recruitment of
DLCO and DMCO in dogs during exercise could potentially be explained
entirely by the exercise-induced polycythemia which is seen in dogs
but not in human subjects.
Received 20 April 1995; accepted in final form 16 October 1995.
APS Manuscript Number A432-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95