Analysis of Altitude Hypoxia Training and In-Flight Hypoxia Events among the Helicopter Aircrews.

Kwo-Tsao Chiang,Yu-Hsin Wen,You-Jin Lin,Sing-Hong Lin,Chung-Yu Lai,Min-Yu Tu,Hsin Chu

doi:10.3390/ijerph18168405

Abstract

All aircrews are required to undertake the altitude hypoxia training and be familiarized with the hypobaric effect on their physiological regulation. Due to the characteristics of the helicopter aircrafts, few researches have reported in-flight hypoxia events among the helicopter aircrews. The main goal of this study was designed to compare the hypoxia symptoms of helicopter aircrews between the altitude hypoxia training and during flight. We developed a questionnaire to collect the details of chamber flights and in-flight hypoxia events in 2019. All data were managed by the SPSS software and two-tailed 0.05 alpha level was considered as a significant level. Of the 213 study participants, there were eight (3.8%) cases that experienced hypoxia symptoms during the flight. The top five symptoms that appeared both in the last and current altitude hypoxia trainings were visual impairment (20.7%), difficulty concentrating (12.7%), tiredness (12.2%), cognitive impairment (8.0%), and air hunger (5.2%). Meanwhile, the frequency of those symptoms above was not significantly different from the last or current training compared with those in-flight hypoxia events. The survey unveiled a series of consistency correlations of hypoxia symptoms between the chamber flights and in-flight environment for the helicopter aircrew group.

Highlights

The human body inhales the air into the lungs
All of them have be qualified by annual health examination and obtained the medical clearance signed by a flight surgeon before the altitude hypoxia training
We used the self-reported questionnaire to obtain the data of hypoxia symptoms between the last and current altitude hypoxia trainings

Summary

Introduction

The human body inhales the air into the lungs. The content of the atmosphere is essentially 21% oxygen which is a vital element for life support. Gas exchange happens in the alveoli based on the pressure gradient. Partial pressure of oxygen decreases by the altitude ascent. If the diffusion rate of oxygen exchange is lower than the consumption rate of the human body due to the reduction of the pressure gradient, people will face the challenge of hypoxia problem when staying at a high-altitude environment [1]. As the military aircrafts have a higher performance ascent to high altitude, aircrews are bound to be threatened by the hypobaric hypoxia. It is generally accepted that the threshold in the aviation medicine is 3048 m (10,000 ft) (so-called physiological altitude) which flight performance is theoretically not impaired [1].

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