Effects of exhaustive endurance exercise on pulmonary gas exchange and airway
function in women.
Wetter, Thomas J., Claudette M. St. Croix, David F. Pegelow, David A. Sonetti, and
Jerome A. Dempsey.
Department of Preventive Medicine, John Rankin Laboratory of Pulmonary
Medicine, University of Wisconsin, Madison, Wisconsin 53705
APStracts 8:0267A, 2001.
Seventeen fit women ran to exhaustion (14 ± 4 min) at a constant speed and grade,
reaching 95 ± 3% of maximal O2 consumption. Pre- and postexercise lung function,
including airway resistance [total respiratory resistance (Rrs)] across a range of
oscillation frequencies, was measured, and, on a separate day, airway reactivity was
assessed via methacholine challenge. Arterial O2 saturation decreased from 97.6 ± 0.5%
at rest to 95.1 ± 1.9% at 1 min and to 92.5 ± 2.6% at exhaustion. Alveolar-arterial O2
difference (A-aDo2) widened to 27 ± 7 Torr after 1 min and was maintained at this level
until exhaustion. Arterial «po2» («pao2») fell to 80 ± 8 Torr at 1 min and then increased
to 86 ± 9 Torr at exhaustion. This increase in «pao2» over the exercise duration occurred
due to a hyperventilation-induced increase in alveolar «po2» in the presence of a constant
A-aDo2. Arterial O2 saturation fell with time because of increasing temperature (+2.6 ±
0.5°C) and progressive metabolic acidosis (arterial pH: 7.39 ± 0.04 at 1 min to 7.26 ±
0.07 at exhaustion). Plasma histamine increased throughout exercise but was inversely
correlated with the fall in «pao2» at end exercise. Neither pre- nor postexercise Rrs,
frequency dependence of Rrs, nor diffusing capacity for CO correlated with the exercise
A-aDo2 or «pao2». Although several subjects had a positive or borderline
hyperresponsiveness to methacholine, this reactivity did not correlate with exercise-
induced changes in Rrs or exercise-induced arterial hypoxemia. In conclusion, regardless
of the degree of exercise-induced arterial hypoxemia at the onset of high-intensity
exercise, prolonging exercise to exhaustion had no further deleterious effects on A-aDo2,
airway resistance, or function.
Received 18 December 2000; accepted in final form 10 April 2001
APS Manuscript Number A1217-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 18 June 2001