Role of ventilatory response to exercise in determining exercise
capacity in copd.
Bauerle, Otto, and Magdy Younes.
Respiratory Investigation Unit, Department of Medicine, Faculty of
Medicine, University of Manitoba
APStracts 2:0323A, 1995.
The progression of chronic obstructive pulmonary disease (COPD) is
generally associated with decreased exercise capacity. Differences in
FEV1 among patients account for only a fraction of the variability in
maximal oxygen consumption (VO2max). We hypothesized that variability
in ventilatory response to exercise and in inspiratory mechanics and
body mass index (BMI) contribute importantly to variability in VO2max
in this disease. We analyzed the files of 53 patients with
established diagnosis of COPD who underwent a recent symptom limited
exercise test. We used inspiratory capacity (IC) and maximum
inspiratory flow (MIF) as measures of variability in inspiratory
mechanics. The VE at the subject's VO2max was divided by the
predicted in a normal subject at the same VO2 to obtain a ratio
(VEmax/VEpred). The ventilatory response during exercise provided the
best correlation with peak VO2 (r = 0.62). FEV1 and IC, also
correlated with peak oxygen consumption, but not as well as the
ventilatory response (r = 0.49, 0.46). MIF and BMI showed only weak
positive correlations (r = 0.23, NS). The stepwise analysis generated
the following equation: VO2max (% predicted) = (77.26 x VEpred/VEmax)
+ (0.45 x FEV1 % predicted) - 23.66; r = 0.76, p < 0.001. We
conclude that variability in the ventilatory response during exercise
is one of the main determinants of variability in exercise capacity
in COPD patients.
Received 10 January 1995; accepted in final form 5 July 1995.
APS Manuscript Number A29-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.