Kai Schommer and Peter Bartsch said some tourists make climbs of almost 7,000 yards -- such as Mount Kilimanjaro -- without any prior experience at high altitudes, and the excessively rapid ascent can result in sudden vomiting and intractable headache, the first signs of high-altitude cerebral edema.
Climbers who spend 48 hours or more above about 4,000 yards can suffer an impairment of consciousness that may progress within hours to coma, which can be fatal if untreated.
A noticeable loss of physical performance ability during ascent and a dry cough are early manifestations of high-altitude pulmonary edema, and those who fail to heed warning signs and continue to ascend might develop high-altitude cerebral edema as well, Schommer and Bartsch said.
The findings, published in Deutsches Arzteblatt International, said there are no validated tests to assess susceptibility to altitude sickness.
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