Dynamic Range of Luminance Perception in Acute Hypobaric Hypoxia

The effects of acute hypobaric hypoxia, as potentially experienced in high altitude flight, on the detection of low contrast targets within a high dynamic range (DR) of luminance were investigated. The tests were performed after 10 minutes of adaptation to an ambient luminance level of 0.2 lx. Twenty-four individuals were exposed to hypobaric hypoxia at an altitude of 18,000 ft (5,490 m) inside a hypobaric chamber and were asked to identify the darkest one perceived from a grid of progressively less luminous patches. The results were compared with those obtained by the same subjects at sea level. The results indicate a global reduction of the DR perception during hypoxia, with a mean decrease of 0.023 cd/m2 (standard deviation ±0.064), which resulted statistically significant (p < 0.05). No significant correlations with oxygen saturation levels were observed. These findings might have practical applications in the design of cockpit's instruments, especially those dedicated to night-time flight missions at high altitudes.