ALTERATIONS OF SOME PULSE WAVE PARAMETERS ON VIETNAMESE MILITARY AIRCREWS AT SIMULATED 5,000 METERS ALTITUDE

Abstract

SUMMARY Objectives: To evaluate alterations of some arterial stiffness and arterial pulse wave time indices in military aircrews under simulating hypoxic conditions at altitude of 5,000 meters. Subjects and methods: The interventional study was conducted on 97 male military aircrews; Hypobaric Oxygen Chamber HPO 6+2 (AMST, Republic of Austria) was used to mimic hypoxia at 5,000m altitude in 20 minutes; and AngioScan M01 (Angio Electronic, Russian), a device was used to perform a noninvasive examination of arteries by assessing some pulse wave parameters. Results: As compared with ground conditions, there was a statistically significant increase in stiffness index at 5,000m (median comparison: 7.9 m/s vs 7.4 m/s; p < 0.001); a decrease in augmentation index (AIp) and augmentation index normalized to heart rate of 75 beats per minute (AIp75): AIp: -22.74 ± 14.75% vs 0.11 ± 14.34%; AIp75: -13.93 ± 11.75 vs -1.34 ± 12.42% (p < 0.001). The decrease of reflection index (RI) was statistically significant: 16.52 ± 7.03% vs 34.31 ± 10.61% (p < 0.001). Paired comparisons on some stiffness parameters at 5,000m altitude: 72.1% with increased stiffness index; 92.8% with decreased AIp; 92.8% with decreased AIp75; 98.97% with decreased RI; statistical significance with p < 0.001. In comparison with ground condition, the duration of the pulse wave (PD): PD was decreased: 646.90 ± 85.46 ms vs 846.13 ± 103.57 ms (p < 0.01). The ejection duration (ED) and percentage of ejection duration (%ED): ED was decreased: 258.05 ± 12.69 ms vs 279.05 ± 14.26 ms; %ED was increased: 40.51 ± 4.46% vs 33.46 ± 3.31% with statistical significance (p < 0.01). This time parameter dTpp (ms) was decreased: 91.06 ± 14.91 ms vs 98.66 ± 15.9 ms, with statistical significance (p < 0.01). Conclusions: The alterations of arterial stiffness index and time parameters of arterial pulse wave at simulated 5,000m altitude reflected a physiological stress and cardia burden in military aircrews exposed to acute hypobaric hypoxia.