Redox Homeostasis in Humans Exposed to Intermittent Hypoxia-Normoxia and to Intermittent Hypoxia-Hyperoxia

Exposure to hypoxia is known to increase oxidative stress and to impair antioxidant defenses in humans. The aim of the study was to measure oxidative stress and antioxidant capacity in healthy humans after being acutely exposed to both intermittent hypoxia-normoxia (IHN) and intermittent hypoxia-hyperoxia (IHH). Twenty-one healthy, young male participants were exposed to both IHN and IHH (fraction of inspired oxygen [FIO₂] 0.11 for up to 7 minutes followed by 3-5 minutes of exposure to normoxia (room air) or hyperoxia, FIO₂ 0.3-0.35) in a crossover design study. In each participant, oxidative stress and antioxidant capacity were measured before and after each exposure in both experimental conditions. After IHN, compared with baseline, neither oxidative stress (289.1 ± 63.2 vs. 262.2 ± 85.2 UCarr) nor antioxidant capacity (2376.1 ± 452.9 vs. 2525.0 ± 400.7 UCor) was significantly different. After IHH, neither oxidative stress (285.1 ± 94.2 vs. 277.5 ± 86.7 UCarr) nor antioxidant capacity (2653.6 ± 492.7 vs. 2568.4 ± 427.4 UCor) was significantly different compared with baseline. When the two studied exposure modalities were compared, there was no significant difference between groups with respect to both oxidative stress and antioxidant capacity. These data suggest that exposing healthy individuals to short-term IHN and IHH does not increase oxidative stress and it does not impair antioxidant defenses.