Flying High. Voice Stress Analysis to Detect Pre-symptomatic Acute Hypobaric Hypoxia at 25000 Ft

Previous research showed that Acute Hypobaric Hypoxia (AHH) induced pre-symptomatic compensatory voice markers at 20000 ft but not at 25000 ft. These studies were conducted in an intermittent design with pauses in between. Since AHH evolves more rapidly at higher altitudes, compensation might have occurred in theses pauses. Hence, we studied voice reactivity of 16 subjects to AHH at 25000 ft in a hypobaric chamber in a continuous speech design. We analyzed fundamental frequency-range (F0-range) and voice onset time (VOT) in function of the hypoxic symptoms as indicated by the subjects. We did not find the pre-symptomatic compensation (i.e., decreased F0-range and VOT). We found increased F0-range and decreased VOT. We hypothesize that at higher altitudes, voice reactivity to AHH is the output of physiological processes of both compensation and control loss. Voice stress detection is a promising future tool and the role of breathing in regulatory compensation processes should be examined.