Systemic Blood Pressure Variation During a 12-Hour Exposure to Normobaric Hypoxia (4500 m)

This study was aimed at evaluating a potential association between blood pressure variation and acute mountain sickness (AMS) during acute exposure to normobaric hypoxia. A total of 77 healthy subjects (43 males, 34 females) were exposed to a simulated altitude of 4500 m for 12 hours. Peripheral oxygen saturation, heart rate, systemic blood pressure, and Lake Louise AMS scores were recorded before and during (30 minutes, 3, 6, 9, and 12 hours) hypoxic exposure. Blood pressure dips were observed at 3-hour mark. However, systolic blood pressure fell more pronounced from baseline during the initial 30 minutes in normobaric hypoxia (-17.5 vs. -11.0 mmHg, p = 0.01) in subjects suffering from AMS (AMS⁺; n = 56) than in those remaining unaffected from AMS (AMS^-; n = 21); values did not differ between groups over the subsequent time course. Our data may suggest a transient autonomic dysfunction resulting in a more pronounced blood pressure drop during initial hypoxic exposure in AMS⁺ compared with AMS^- subjects.