Hypoxia awareness training for aircrew: a comparison of two techniques

Major hazards associated with hypoxia awareness training are the risks of decompression sickness, barotrauma, and loss of consciousness. An alternate method has been developed which combines exposure to a simulated altitude of 10,000 ft (3048 m) with breathing of a gas mixture containing 10% oxygen and 90% nitrogen. The paradigm, called Combined Altitude and Depleted Oxygen (CADO), places the subjects at a physiological altitude of 25,000 ft (7620 m) and provides demonstration of symptoms of hypoxia and the effects of pressure change. CADO is theoretically safer than traditional training at a simulated altitude of 25,000 ft (7620 m) due to a much lower risk of decompression sickness (DCS) and has greater fidelity of training for fast jet aircrew (mask-on hypoxia). This study was conducted to validate CADO by comparing it with hypobaric hypoxia.

There were 43 subjects who were exposed to two regimens of hypoxia training: hypobaric hypoxia (HH) at a simulated altitude of 25,000 ft (7620 m) and CADO. Subjective, physiological, and performance data of the subjects were collected, analyzed, and compared.

There were no significant differences in the frequency and severity of the 24 commonly reported symptoms, or in the physiological response, between the two types of hypoxia exposure.

CADO is similar to HH in terms of the type and severity of symptoms experienced by subjects, and appears to be an effective, useful, and safe tool for hypoxia training.