Relationship Between Orthostatic Stress Response And Acute Mountain Sickness Susceptibility At High Altitude: Pilot Study

PURPOSE: To determine whether there is a difference in hemodynamic responses to head-up tilt (HUT) subjects who do, and do not, experience acute mountain sickness (AMS) during exposure hypobaric hypoxia. We also aimed if those variables altered HUT correlated with AMS severity. METHODS: Fifteen participants completed three testing sessions: 1) VO2max test workload at 50% for hypoxia exposure; 2) consisted of supine rest 20 min followed by 70° upright ≤40 min; 3) six hours hypoxic simulating 4572 m where performed two, 30-min cycling bouts rested when not exercising. During HUT, continuous blood pressure (BP) monitoring was used assess systolic diastolic (SBP, DBP); mean arterial (MAP); variability SBP, DBP, MAP; heart rate. scores were reported before after exposure. Statistical analysis included mixed effects ANOVA changes between end scored ≥ 3 positive (AMS+) < negative (AMS-) groups. Correlations linear regression determined associations scores. significance set p 0.05. RESULTS: Systolic, diastolic, (BPV) increased from (BPV ± SD AMS+ & AMS- groups: SBP = 3.5 3.0, 1.2 1.9: DBP 1.7 1.5, 0.6 0.9: MAP 2.8 2.9, 1.1 1.4; 0.004, 0.006, respectively). Those higher tended have greater magnitude change the (r 0.65, 0.64, 0.60, CONCLUSIONS: Increased BPV indicates BP dysregulation, suggesting that individuals may disruptions control could be observable postural prior promising predictive variable but further research needed. In future, researchers should consider using sea-level residents range simulated elevations predictability susceptibility BPV.