ABSTRACT
A knowledge and understanding of the physical, physiological and psychological constraints imposed by travel and the flight environment will allow anticipation and prevention of any problems that may otherwise occur during the transfer. As air pressure declines with increasing altitude, less oxygen is available for cellular metabolism and gases trapped within body cavities will expand. Passenger carrying aircraft maintain a cabin pressure which rarely exceeds 6000 ft (1800 m). Although healthy passengers will feel no ill effects, there is a significant decline in alveolar partial pressure of oxygen, from 13.7 kPa (103 mmHg) at sea level to about 10 kPa (75 mmHg) at 6000 ft (1800 m). With ascent from sea level to the same altitude, gas volumes in body cavities will expand by over 25 per cent. There may also be problems with motion sickness, vibration, noise, cold or humidity, not to mention the psychological terror felt by some who can imagine nothing worse than being locked in a flying metal tube!
