Examination of Normobaric Hypoxia Training using Reduced Oxygen Breathing Device (ROBD)

Abstract

Hypobaric hypoxia is a serious threat facing pilots and may cause in fatal accidents. Hypobaric hypoxia induces cognitive decline and a loss of consciousness. Pilots regularly receive hypobaric chamber training to prepare for emergency procedures in case of hypoxia and rapid decompression. In the US Air Force Physiological Training Program, the reduced oxygen breathing device (ROBD) is used as an alternative to the hypobaric chamber for refresher hypoxia training. The ROBD produces normobaric hypoxia situation by delivering a mixture of air and nitrogen gas through an oxygen mask. The Japan Air Self-Defense Force is considering introducing ROBD training. The purpose of this study is to estimate the training effectiveness of two training profiles which make use of ROBD. One profile simulated an outward leakage of oxygen from a mask and the other profile simulated a continuous flow oxygen hose disconnects. Subjects included six healthy males on a volunteer basis. During each participant’s profiling, subjective hypoxia symptoms and the timing of their occurrence were recorded. In addition to physiological monitoring, cerebral levels of oxy-hemoglobin (oxy-Hb), deoxy-hemoglobin (deoxy-Hb) and total-hemoglobin (total-Hb), saturation pulse O2 (SpO2) , and heart rate (HR) were all measured. For detecting cognitive decline, the required time for achieving Trail Making Test type B (TMT-B) is compared at sea level and at 24,000 ft. Across both profiles, all subjects felt subjective hypoxia symptoms, with some participants noting air hunger as the most serious concern. The deoxy-Hb and total-Hb significantly increased during both profiles, in contrast, oxy-Hb decreased significantly. The SpO2 level at 24,000 ft was significantly lower than that at sea level for both profiles. HR levels at 24,000 ft were also significantly higher than that at sea level for both profiles. The required time for achieving TMT-B at 24,000 ft was significantly longer than for that at sea level. These two profiles could cause various hypoxia symptoms, physiological variables and cognitive decline to all subjects. These results suggest that both profiles can be useful for normobaric hypoxia training via the use of ROBD.