Heart rate, blood pressure, and <scp>SpO</scp> ₂ responses to simulated 5000 m hypobaric exposure in healthy male Vietnamese pilots

This study was motivated by the limited high-altitude physiology data available for Asian military aviators, especially in Vietnam. To characterize acute heart rate (HR), blood pressure (BP), and oxygen saturation (SpO₂) responses in healthy Vietnamese pilots during simulated 5000 m hypobaric exposure. Seventy-five healthy male military pilots underwent 30-min exposure in a hypobaric chamber simulating 5000 m altitude. HR, systolic/diastolic BP (SBP/DBP), and SpO₂ were recorded at baseline (0 m), peak altitude, and post-exposure. HR increased from 80.0 ± 9.0 to 91.9 ± 11.0 bpm, SBP/DBP rose by 10.4/6.5 mmHg, and SpO₂ decreased from 98.4 ± 1.0% to 77.7 ± 6.0% (all p < 0.001). All changes were transient, returning to baseline within 5 min after exposure, and no adverse events occurred. Higher baseline HR and older age predicted smaller HR increases. Acute 5000 m hypobaric hypoxia caused transient tachycardia, hypertension, and hypoxemia. Response variability correlated with baseline hemodynamic status and age. This safe, reproducible model can serve as a noninvasive cardiovascular stress test in clinical and aerospace medicine.