RESUMO
BACKGROUND: Hypobaric hypoxia is a stressful emergency situation that can cause a degradation of the sensory, motor, and higher cognitive functions necessary for safe flight. METHODS: We studied the salivary cortisol and dehydroepiandrosterone-sulfate (DHEA-S) concentrations of 12 healthy male military aviators (AV) exposed to an altitude-induced hypoxia challenge in a hypobaric chamber. A matched control group (C) of eight flight physiology instructors wearing oxygen masks during the challenge was studied. Salivary samples were collected every 2 h on 3 experimental days (the day before, the day of, and the day after the hypobaric chamber challenge). RESULTS: In the AV group, salivary cortisol concentrations showed a statistically significant increase from 5.42 +/- 0.15 measured at 08:30 to 11.37 +/- 1.86 ng ml(-1) during the hypobaric chamber challenge and a statistically significant increase in DHEA-S was also measured (from 3.15 +/- 0.42 ng x ml(-1) at 08:30 to 5.99 +/- 0.15 ng x ml(-1)). The day after the challenge, the concentrations of both hormones were comparable to those measured the day before; neither C nor AV showed any disturbances of the physiological diurnal fluctuations of cortisol and DHEA-S. No differences were found among the cortisol/DHEA-S ratios measured during the 3 experimental days in the AV group. DISCUSSION: In spite of having experienced a psycho-physical stress, the AVs did not show any dysregulation of the diurnal fluctuations of cortisol and DHEA-S, thus presenting a good level of stress resilience. Data presented in this paper are consistent with recent literature suggesting a stress-buffering role of DHEA-S.
