Intermittent Hypoxic Exposure Improves Mean Reaction Time (MRT) Upon Rapid Ascent to High Altitude

Abstract

Intermittent Hypoxic Exposure (IHE) may attenuate negative affects of rapid ascent to high altitudes. Currently, there is little data to quantitatively or systematically determine the potential benefit IHE may provide to unacclimatized people living near sea level (SL) upon rapid ascent to high altitudes. Physical and intellectual demands may be intense during the first few days of high altitude exposure if people are expected to perform well immediately upon ascent to high altitude (e.g. military personnel making tactical decisions or mountaineers, safeguarding the lives of expeditionary members). PURPOSE: To determine the effect of IHE on cognitive performance decrement upon subsequent exposure to 4300 m. METHODS: On day 1, 12 informed healthy female and male volunteers (M ±SEM: 20.2 ±0.3 yr) were exposed to a simulated altitude of 4300 m while resting in a normobaric hypoxic chamber for 4 hours. During d2-4, subjects remained at 3600 m for 3h (IHE; n=6) or at SL as control subjects (SL; n=6). On d5 all subjects repeated exposure to 4300 m for 4h. Volunteers completed the Automated Neuropsychological Assessment Metrics (ANAM, a battery of cognitive skills tests) 5-7 times during familiarization and once again at the beginning of and once after each altitude exposure. Test modules known to be sensitive to altitude were utilized for the ANAM battery. Included modules are the Stanford Sleepiness Scale; Mood Scale-R; Simple Reaction Time; Running Memory Continuous Performance; Logical Reasoning-Symbolic; Code Substitution Learning: Immediate and Delayed Memory; Matching to Sample; and 4-Choice Reaction Time. RESULTS: Differences were found only for the 4-Choice Reaction Time module. There was no MRT difference between groups prior to altitude exposure on d1 or d5. All subjects increased MRT (IHE: 618.0±14.3 to 678.3±22.9 ms; P=0.023; SL: 639.5±28.2 to 713.4±36.5 ms; P=0.038) after 4h of altitude exposure on d1. SL controls increased MRT on d5 (576.3±5.1 to 682.7±20.8 ms; P=0.003) while IHE subjects had no change (567.2±29.0 to 596.5±25.9 ms; P=0.348). CONCLUSION: IHE for 1d at 4300m for 4h and 3d at 3600 m ameliorates the negative alterations in MRT seen after a subsequent 4h exposure to 4300 m. Supported by: The Borgenicht Program; Jeffress Memorial Trust; and The Foundation for Aging Studies and Exercise Science Research