EVEREST BASE CAMP, Tibet—On the high reaches of Mount Everest, the air is so thin that the human body begins to shut down.
Blood thickens and becomes sluggish. Dehydration is a constant threat. Delirium can strike rapidly. A desire to sit down and fall asleep, even in severe cold, can intensify.
Survival is the paramount concern in the "death zone" above 26,000 feet, and illness can strike with the lightning speed of changing Himalayan weather.
"At that altitude, your digestion doesn't really work. You're basically living on fumes," said David Tait, a British climber who spoke before returning to Everest this year, making the summit on May 15. "Most people don't really want to eat, and they don't hold it down very well."
It can take hours for simple tasks such as lighting a stove, getting dressed and putting iron-tipped crampons on boots to walk on the icy terrain, New Zealand guide Mark Woodward said.
For those climbers who don't use bottled oxygen to cope with the thin air, the challenges are greater. Without sufficient oxygen, the blood congeals and slows, leaving climbers more prone to the extreme cold. Using bottled oxygen can help warm distressed or ailing climbers.
Moreover, at extreme altitude, climbers are prone to cerebral edema, a potentially lethal swelling of the brain, or a sudden buildup of fluid in the lungs.
"It's an extremely tough environment," said Duncan Chessell, an Australian expedition leader on Everest.
"Every step is undeniable murder," Tait added.
The extraordinary stress forces most individuals to turn into primitive selves, focused only on their survival.
"At 8,000 meters (26,247 feet), you turn into an animal," said Charlie Buffet, a French journalist who's written several books about high-altitude climbing.
Inexperienced climbers sometimes can't even make it to the "death zone."
"Some people are very fit but can only go to advanced base camp (at 6,300 meters, or 20,350 feet) and nothing more. They get headaches. They vomit. They don't have energy," said Kari Kobler, a veteran Swiss guide on Everest.
Even experienced climbers struggle with losing weight and muscle mass at high altitude, able to hold down only candy, chocolate and soups.
The actual summit attempt is particularly grueling, often involving prolonged periods without sleep. From a final high camp, where they rest for a few hours, climbers depart for the summit at about 11 p.m. or midnight, beginning a long climb in the dark, when icy terrain is firmest, wearing headlamps. If they're lucky, and slower climbers don't clog the route, they arrive at the summit before noon, then begin the descent, which some consider the most perilous period because of fatigue.
(c) 2007, McClatchy-Tribune Information Services.
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