Worthe S. Holt*

The discussion of high-pressure environments in Chapter 8 noted that humans function well only within a narrow range of barometric pressures. Ascent to altitude places workers in an adverse environment and exposes them to multiple stressors—decreased barometric pressure, reduced oxygen levels (hypoxia), ionizing and nonionizing radiation, and low temperatures. Most workers are acclimated to sea-level or near-sea-level pressures; reduced barometric pressures and oxygen levels will produce a range of symptoms ranging from mild discomfort to severe disease or even death.


It was estimated that more than 140 million people worldwide permanently resided above 2440 m (8000 ft). Tourism to mountainous regions of the Western United States exposed an estimated 35 000 000 people to the hypobaric environment.1 Occupationally, pilots and flight attendants have the greatest potential exposure, although actual incidents in commercial aviation are infrequent due to cabin pressurization. Inside observers in hypobaric pressure chambers and scientists at research laboratories located at high altitudes routinely perform duties at decreased barometric pressures. Individuals who travel to mountainous regions as employees of the construction or travel industries are also at risk, depending on the altitude reached and the time taken to reach that altitude. Rescue workers and the military may also be at risk. ...

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