Exercise-induced hypoxemia: fact or fallacy?
Whereas the prevalence of exercise-induced hypoxemia (EIH) in endurance athletes is commonly reported as approximately 50%, most previous studies have not corrected PaO2 for exercise-induced hyperthermia. Furthermore, although a detrimental effect on aerobic performance has been assumed, no study has measured arterial oxygen content (CaO2) in this context.


OBJECTIVE
To determine the effect of temperature-correcting PaO2 values for rectal, arterial blood, esophageal, and exercising muscle temperatures during exercise on CaO2 and the prevalence of EIH.


METHODS
Twenty-three trained males (age 26 +/- 5 yr; VO2peak 65.2 +/- 1.6 mL x kg-1 x min-1) performed incremental treadmill exercise to exhaustion with PaO2 corrected for simultaneous temperature measurements at all four sites. EIH was defined as DeltaPaO2 >or= 10 mm Hg.


RESULTS
: With no temperature correction, DeltaPaO2 was -20.8 +/- 5.0 mm Hg and prevalence was 96% (n = 23), but when corrected for rectal temperature, DeltaPaO2 was -14.7 +/- 7.8 mm Hg and prevalence was 73% (n = 20); for arterial blood temperature, DeltaPaO2 was -7.7 +/- 6.5 mm Hg and prevalence was 35% (n = 20); and for esophageal temperature, DeltaPaO2 was -8.1 +/- 7.7 mm Hg and prevalence was 48% (n = 23), although when corrected for active muscle temperature, DeltaPaO2 was +8.2 +/- 7.8 mm Hg and prevalence was 0% (n = 10). There were no significant changes in CaO2 except for uncorrected values, and there was no correlation between DeltaPaO2 and VO2peak.


CONCLUSIONS
Although the prevalence of EIH depends on the temperature correction applied to PaO2 values, in no case is there a significant change in CaO2 or any relationship with maximal aerobic power.
Scroop
Garry C
GC
Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, Australia.
Shipp
Nicholas J
NJ
D000328:Adult; D000704:Analysis of Variance; D001784:Blood Gas Analysis; D001831:Body Temperature / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000453:epidemiology / Q000503:physiopathology*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D015995:Prevalence