ABSTRACT
Among the millions of people who fly in aircraft, some will surely have underlying COPD or other diseases that will lower oxygen tensions at sea level. The question of how far arterial oxygen tensions will fall as aircraft cabin pressures decline has been a concern since aircraft flight became popular. This question has been investigated systematically in both actual short-term flights, where cabin pressure becomes equivalent to as high as 8000 ft, and in decompression chambers. The duration of these experiments is always short. In patients with advanced COPD and sea-level hypoxemia, oxygen tensions fall from resting levels of 60-65 torr to about 48-50 torr, values that would be considered an indication for oxygen supplementation in an acutely ill patient at sea level. It is surpris ing to find that in these studies, patients have very few symptoms, probably because of relatively short exposure and lack of physical exertion. At least one study has observed asymptomatic ectopic heart beats. Nomograms have been developed that will predict in a general way the fall of arterial oxygen tensions, depending on the cabin pressure and the preexisting arterial oxygen tension in the individuals.
