title: Pulmonary gas exchange during exercise in athletes. I. Ventilation-perfusion mismatch and diffusion limitation.
abstract: To investigate pulmonary gas exchange during exercise in athletes, 10 high aerobic capacity athletes (maximal aerobic capacity = 5.15 +/- 0.52 l/min) underwent testing on a cycle ergometer at rest, 150 W, 300 W, and maximal exercise (372 +/- 22 W) while trace amounts of six inert gases were infused intravenously. Arterial blood samples, mixed expired gas samples, and metabolic data were obtained. Indexes of ventilation-perfusion (VA/Q) mismatch were calculated by the multiple inert gas elimination technique. The alveolar-arterial difference for O2 (AaDO2) was predicted from the inert gas model on the basis of the calculated VA/Q mismatch. VA/Q heterogeneity increased significantly with exercise and was predicted to increase the AaDO2 by > 17 Torr during heavy and maximal exercise. The observed AaDO2 increased significantly more than that predicted by the inert gas technique during maximal exercise (10 +/- 10 Torr). These data suggest that this population develops diffusion limitation during maximal exercise, but VA/Q mismatch is the most important contributor (> 60%) to the wide AaDO2 observed.
authors.affiliation: Faculty of Medicine, Division of Sports Medicine, University of British Columbia, Vancouver, Canada.
authors.forename: S R
authors.initials: SR
authors.lastname: Hopkins
authors.forename: D C
authors.initials: DC
authors.lastname: McKenzie
authors.forename: R B
authors.initials: RB
authors.lastname: Schoene
authors.forename: R W
authors.initials: RW
authors.lastname: Glenny
authors.forename: H T
authors.initials: HT
authors.lastname: Robertson
mesh_terms: D000328:Adult; D000332:Aerobiosis / Q000502:physiology; D001784:Blood Gas Analysis; D004058:Diffusion; D004912:Erythrocytes / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D011652:Pulmonary Circulation / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology*