Background It has been suggested that hyperbaric oxygen preconditioning (HBOP) can improve pilot acceleration endurance, and the mechanism may be related to improvement of autonomic function, but there are few researches on this.
Objective To investigate the effect of HBOP on lower body negative pressure (LBNP) endurance in pilots with poor acceleration endurance, and detect autonomic function-related indexes such as cardiac quantum spectrum (CQS) and reactive hyperemia index (RHI), so as to explore the mechanisms by which HBOP improves acceleration endurance. Methods Pilots with poor acceleration tolerance at the Air Force Specialized Medical Center from February to July in 2021 were selected as subjects for a multi-person HBO chamber and a 3-times HBO exposure protocol. Oxygen inhalation was performed for a total of 95 min, once a day (fixed at 14:30-16:05 in the chamber), for 3 days. Using the subjects' own before-and-after control design method, their LBNP endurance, CQS and RHI were measured before and after HBOP.
Results Twenty pilots were identified with poor acceleration tolerance. The cumulative stress index (CSI) was (-894.00 ± 232.88) min·mmHg in subjects before HBOP and (-1310.50 ± 349.23) min·mmHg in subjects after HBOP (t=6.546, P<0.001), which suggested that the LBNP endurance increased significantly. The CQS index was (5.05 ± 1.35) before HBOP and (4.30 ± 1.26) after HBOP, which indicated a significant improvement in myocardial function indexes (t=2.680, P=0.015). The RHI values were (1.46 ± 0.43) before HBOP and (1.78 ± 0.54) after HBOP, indicating a significant improvement in vascular endothelial function indexes (t=-2.524, P=0.021).
Conclusion HBOP can improve myocardial function and vascular endothelial function in pilots with poor acceleration tolerance, thereby improving their LBNP tolerance.
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