ABSTRACT
While a sojourn at altitude can be an enjoyable and at times thrilling experience, brief visits to even modest altitudes quickly remind most of us of our limitations. Most obvious is the breathlessness we experience on climbing a short flight of stairs or navigating a modest incline in a trial. More sinister, though, because it is usually not apparent to us, is the decline in some of our most sophisticated cognitive skills due to the effect of altitude on the function of our brain. In many instances safety in these spectacular yet hazardous environments is dependent upon proper and timely decisions about what courses of action to take and what to avoid. Such decisions depend upon a functioning brain. Some of the tragedies visited upon humans at altitude, such as the events on Everest in 1996, may have resulted from a critical loss of judgment as the result of brain hypoxia (1). That the mortality during the descent from the summit of Everest is three times greater for those who did not use oxygen than in those who did lends credence to this possibility (2).
