Reconsideration of Hypoxic Chamber Flight Training through a Pulse Oximetry Monitoring Study in ROKAF

ABSTRACT

Hypoxia is a serious aviation problem and can always be a source of dangerous aerospace accidents. Hypoxic chamber flight training used to evaluate hypoxia tolerance via TUC (time of useful consciousness) and to become aware of hypoxic symptoms. Because TUC depends on subjective symptoms and lacks strict objectivity, pulse oximetry monitoring has become useful in the aviation environment. In this study, we monitored arterial oxygen saturation (SaO2) by pulse oximetry in the ROKAF subjects (n=33) experiencing hypoxia at the simulated altitude of 25,000 ft. The duration from mask-off to mask-on (TUC), the duration from mask-off to the time of SaO2 of 90% (T90), the duration from 90% to 70% of SaO2(T70), and the SaO2 value at mask-on (bottom SaO2) were examined. The mean bottom SaO2 and TUC were 64.5% and 180 sec, respectively. The subjective hypoxic symptoms were facial flushing, thinking impairment, dyspnea, sweating, anxiety, and so on, in descending order. The majority of the subjects put on their mask before 70% of SaO2 was reached or before they felt any severe symptoms. In comparison with the data of JASDF (Yoneda, 2000), TUC, T90, and T70 were longer in JASDF, but bottom SaO2 and pulse increasing rate during hypoxia (PR/TUC) were higher in ROKAF. Also, TUC in the subjects of this study was much shorter than those of 10 years ago. These may be due to different training protocols, but not enough data exists to explain such difference. The need for the reconsideration of the hypoxic training from the various viewpoints is raised.