title: Low chemoresponsiveness and inadequate hyperventilation contribute to exercise-induced hypoxemia.
abstract: Is inadequate hyperventilation a cause of the exercise-induced hypoxemia observed in some athletes during intense exercise? If so, is this related to low chemoresponsiveness? To test the hypothesis that exercise-induced hypoxemia, inadequate hyperventilation, and chemoresponsiveness are related, 36 nonsmoking healthy men were divided into hypoxemic (Hyp; n = 13) or normoxemic (Nor; n = 15) groups based on arterial oxygen saturation (SaO2; Hyp < or = 90%, Nor > 92%) observed during maximum O2 uptake (VO2max). Men with intermediate SaO2 values (n = 8) were only included in correlation analysis. Ventilatory parameters were collected at rest, during a treadmill maximal oxygen consumption (VO2max) test, and during a 5-min run at 90% VO2max. Chemoresponsiveness at rest was assessed via hypoxic ventilatory response (HVR) and hypercapnic ventilatory response (HCVR). VO2max was not significantly different between Nor and Hyp. SaO2 was 93.8 +/- 0.9% (Nor) and 87.7 +/- 2.0% (Hyp) at VO2max. End-tidal PO2 and the ratio of minute ventilation to oxygen consumption (VE/VO2) were lower while PETCO2 was higher for Hyp (P < or = 0.01). End-tidal PO2, end-tidal PCO2, and VE/VO2 correlated (P < or = 0.05) to SaO2 (r = 0.84, r = -0.70, r = 0.72, respectively), suggesting that differences in oxygenation were due to differences in ventilation. HVR and HCVR were significantly lower for Hyp. HVR was related to VE/VO2 (r = 0.43), and HCVR was related to the ratio of VE to CO2 production at VO2max (r = 0.61).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Kinesiology, Indiana University, Bloomington 47405, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Harms
authors.forename: J M
authors.initials: JM
authors.lastname: Stager
mesh_terms: D000328:Adult; D001784:Blood Gas Analysis; D002628:Chemoreceptor Cells / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D006985:Hyperventilation / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology