The next step in this development will add the capability to create simple representations of aircrew stations for man in the loop evaluations. Top of page Current Understanding of High Altitude Physiology and Hypoxia Len S. Goodman Hypoxia is a significant aeromedical problem in civilian and military aviation, and is prevalent at altitudes as low as 5,000 ft. Hypoxia in flight is caused by the decrease in total atmospheric pressure as altitude increases, compromising blood oxygenation. Hypoxia symptoms can mimic other non hypoxic conditions. Symptoms may first arise as subtle impairments in behaviour, but will increase in severity as altitude level and duration of exposure increases.
Symptoms vary among aircrew populations, but can also vary in the same person between exposures.
Up to altitudes of 40,000 ft, inadvertent exposure to the ambient air due to failure of either the oxygen system or decompression of the cabin can result in significant hypoxia. The peak PPB level currently available in most military aircraft is 30 mm Hg, which provides emergency hypoxia protection at altitudes up to 50,000 ft. However, tolerance to higher levels of PPB has been studied in the laboratory. The research to date has focused on extending the altitude protection limits. This margin ensures aircrew protection during emergency descent to a safe altitude within 45 s.