Effective Monitoring for Early Detection of Hypoxia in Fighter Pilots

ABSTRACT Objective This study evaluated various biological parameters in subjects exposed to hypoxia, to verify effective monitoring for early hypoxia detection. Background Hypoxic-hypoxia is a life-threatening condition, but no method of early detection in flight has been established. Method Six healthy male subjects underwent 2 experiments at different oxygen concentrations (O2) during hypoxic exposure on different days. Subjects inhaled approximately 21% O2 for 3 minutes, hypoxia using approximately 14% O2 in Experiment 1 and 7% O2 in Experiment 2 for 3.5 minutes using a reduced oxygen breathing device. During the experiments, pupil diameter (PD), cerebral oxygenated hemoglobin (O2Hb), peripheral tissue oxygen saturation (SpO2), heart rate (HR), and blood pressure (BP) were measured. Results All 6 subjects completed both Experiments 1 and 2. ΔO2Hb showed significant correlations with %HR (r = −0.6005, P < .0001), %PD (r = −0.5227, P = .0001), and %SpO2 (r = 0.8281, P < .0001) in Experiment 1. ΔO2Hb also showed significant correlations with %HR (r = −0.7904, P < .0001), %PD (r = −0.7933, P < .0001), and %SpO2 (r = 0.7240, P < .0001) in Experiment 2. Rapid hypoxic exposure caused increase in %PD and decrease in ΔO2Hb, followed by immediate increase in %HR, and then decrease in %SpO2. Conclusion The present study suggested that monitoring of HR, PD, and O2Hb were earlier parameters to detect hypoxia than SpO2.