Pulmonary gas exchange during exercise in highly trained cyclists with arterial hypoxemia

1 Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, South Australia 5000; 2 Department of Medicine, University of California San Diego, La Jolla, California 92093; 3 Australian Institute of Sport, Belconnen, Australian Capital Territory 2616; and 4 Department of Physiology, University of Adelaide, Adelaide, South Australia 5000, Australia The causes of exercise-induced hypoxemia (EIH) remain unclear. We studied the mechanisms of EIH in highly trained cyclists. Five subjects had no significant change from resting arterial P O 2 (Pa O 2 ; 92.1 ± 2.6 Torr) during maximal exercise (C), and seven subjects (E) had a >10-Torr reduction in Pa O 2 (81.7 ± 4.5 Torr). Later, they were studied at rest and during various exercise intensities by using the multiple inert gas elimination technique in normoxia and hypoxia (13.2% O 2 ). During normoxia at 90% peak O 2 consumption, Pa O 2 was lower in E compared with C (87 ± 4 vs. 97 ± 6 Torr, P