Exercise-induced cerebral deoxygenation among untrained trekkers at moderate altitudes.

Publisher: Heldref Publications Country of Publication: United States NLM ID: 0212627 Publication Model: Print Cited Medium: Print ISSN: 0003-9896 (Print) Linking ISSN: 00039896 NLM ISO Abbreviation: Arch Environ Health Subsets: MEDLINE

Publication: Washington, DC : Heldref Publications
Original Publication: Chicago, American Medical Assn.

Acclimatization* ; Altitude*; Altitude Sickness/*metabolism ; Altitude Sickness/*physiopathology ; Exercise/*physiology ; Hypoxia, Brain/*metabolism ; Hypoxia, Brain/*physiopathology; Acute Disease ; Adult ; Blood Gas Analysis ; Brain Chemistry ; Exercise Test ; Female ; Hemodynamics ; Humans ; Lactic Acid/blood ; Male ; Oxygen/blood ; Spectroscopy, Near-Infrared ; Time Factors

The pathophysiology of altitude-related disorders in untrained trekkers has not been clarified. In the present study, the effects of workload on cardiovascular parameters and regional cerebral oxygenation were studied in untrained trekkers at altitudes of 2700 m and 3700 m above sea level. We studied 6 males and 4 females at each altitude, and their average ages were 31.3+/-7.1 y at 2700 m and 31.2+/-6.8 y at 3700 m, respectively. The resting values of heart rate and mean blood pressure were not significantly different at 2700 m and 3700 m than at sea level. However, increases in these values after exercise were more prominent at high altitudes (heart rate increase = 51.6% at 2700 m and 70.4% at 3700 m; mean blood pressure increase: 19.0% at 2700 m and 17.2% at 3700 m). In addition, post-exercise blood lactate concentration was significantly higher at 3700 m than at sea level or at 2700 m (i.e., 7.6 mM at 3700 m, 3.8 mM at 2700 m, and 4.17 mM at 0 m, respectively). Exercise induced an acute reduction in the arterial oxygen saturation value (SpO2) at 2700 m and 3700 m (i.e., 11.2% reduction at 2700 m and 9.4% at 3700 m), whereas no changes were observed at sea level. The resting values of regional oxygen saturation (rSO2)--measured by a near infra-red spectrophotometer at sea level, 2700 m, and 3700 m-were nearly identical. Exercise at sea level did not reduce this value. In contrast, we observed a decrease in rSO2 after subjects exercised at 2700 m and 3700 m (i.e., 26.9% at 2700 m and 48.1% at 3700 m, respectively). The rSO2 measured 2 min and 3 min after exercise at 3700 m was significantly higher than the preexercise value. From these observations, we concluded that alterations in cardiovascular parameters were apparent only after an exercise load occurred at approximately 3000 m altitude. Acute reduction in cerebral regional oxygen saturation might be a primary cause of headache and acute mountain sickness among unacclimatized trekkers.

33X04XA5AT (Lactic Acid)
S88TT14065 (Oxygen)

Date Created: 19990805 Date Completed: 19990812 Latest Revision: 20161219

20240627

10.1080/00039899909602485

10433186