Introduction: Intermittent hypoxic exposure (IHE) prior to ascent to high altitude is postulated as a beneficial pre-conditioning strategy in the prevention of high altitude illness. Variations in arterial stiffness and endothelial function (vascular tone) may also be important in the pathogenesis of altitude related illness. The influence of IHE pre-conditioning on cardiovascular adaptations (notably arterial stiffness and vascular tone) to altitude is less clear. This study explored the impact of normobaric IHE pre-conditioning on acute cardiovascular adaptations to high altitude. Method: Participants were assigned to one of three intervention groups: control (no IHE), IHE at rest (IHE-rest) or IHE with training (IHE-training) matched for fitness, age and sex. In the 14- day period prior to a high altitude expedition IHE groups completed 10×2 hour hypoxic exposures in an environmental chamber (12.2% O2 equivalent to 4300 m), at rest (IHE-rest) or rest plus 20 minutes running at 80% heart rate reserve (calculated from individual predetermined VO2max at altitude). Arterial stiffness (SI) and vascular tone (RI) responses were recorded using a non-invasive finger photoplethysmography technique at sea-level (baseline), pre and post IHE intervention period, 12 and 72 hours post arrival at altitude (Lukla, Nepal, 2800 m). Results: Thirty apparently healthy participants (18 male, 12 female, age range 20-62 years) free from cardiovascular disease were recruited (n = 10 per condition). Two-way repeated measures (intervention x time) ANOVA revealed no main effect for intervention for SI (control_1.07±1.41 m.s-1, IHE-rest _0.50±0.65 m.s-1, IHE-training_1.07±0.81 m.s-1; P = 0.083) or RI (control_3.3±4.4%, IHE-rest_7.6±25.6%, IHE-training 7.2±18.1%; P = 0.174). There were no between-group interaction effects for any cardiovascular measurements (P = 0.059 for RI; P = 0.112 for SI) Conclusion: Intermittent hypoxic exposure prior to ascent to high altitude does not significantly alter vascular tone or arterial stiffness in apparently healthy adults. The impact of IHE preconditioning on endothelial function at higher altitudes and in the prevention of altitude related illness remains to be elucidated.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)