抄録
Hypoxia inducing visual function deficits have been reported in aircrews at altitude of 10,000 feet
or less, which is not required oxygen supply system. However, there are limited data concerning
effect of lower blood oxygen saturation on visual function. Therefore, we evaluated the contrast
sensitivity changes in mild hypoxia. Eight healthy non-smokers (5 male, 3 female, age range 31 to
51) who had normal vision participated in this study. The participants were exposed to hypobaric
hypoxia for about 50 minutes in a hypobaric chamber at a simulated altitude of 5,000 feet (1,524 m)
and 8,000 feet (3,048 m) on separate days, respectively. Blood oxygen saturation based on pulse
oxymetry (SPO2) and heart rate (HR) were recorded during the hypoxia exposure experiment. The
contrast sensitivity at 1.5, 3, 6, 12, and 18 cycle per degree(cpd) spatial frequencies was measured
before exposure and at both altitudes, using functional acuity contrast test (FACT). The contrast
sensitivity was not significantly impaired at both altitudes, inducing significant SPO2 decrement (91%
at 8,000feet). Although no significant increase was observed in the HR, 50% of the participants
reported feeling warm at the altitude of 8,000 feet. The results suggested that the contrast sensitivity
measured by FACT was not sensitive enough to detect mild hypoxia effect.
