The blood chemistry of team leader Wally Berg is analyzed as part of the 1998 research expedition. In 1999 Yale Medical School is sending a team of doctors to conduct further medical research and test medical telemetry equipment for NASA.

When climbers reach the summit of Mount Everest, few feel as if they’re on top of the world. The thin air at this extreme altitude offers only a third of the oxygen available at sea level. Lack of oxygen, or hypoxia, starts a chain of reactions that can result in altitude sickness.

Climbers also battle against frostbite, hypothermia, and snow blindness.

Climbers risk altitude sickness any time they venture above 8,000 feet (2,400 meters). The region above 25,000 feet (7,600 meters) is called the death zone.

Starved for oxygen, climbers’ bodies overcompensate by breathing more vigorously. Consequently, they exhale too much carbon dioxide, which in turn upsets the blood’s pH balance. With their blood more alkaline than usual, mountaineers can grow dizzy or nauseated. Other symptoms of acute mountain sickness (AMS) include headaches, appetite loss, insomnia, and extreme fatigue.

AMS ranges from common discomfort to a severe condition called high-altitude cerebral edema (HACE). Because of the low air pressure, the body overcompensates and speeds up its blood circulation. The brain can swell from too much blood, causing disorientation. HACE can kill within a few hours.

Also, fluid may gather in the lungs, creating high-altitude pulmonary edema (HAPE). A climber stricken with HAPE usually has a cough (sometimes accompanied by pink froth), tightness in the chest, tinges of blue on lips or fingers, and an extremely accelerated heart rate.

The cure for the potentially fatal edemas: oxygen and rapid descent.

This spring about a dozen doctors from Yale University will set up a medical tent at Everest Base Camp—17,600 feet (5,400 meters) up. They will monitor the climbers’ vital signs via data from “biopacks” worn while ascending.

The climbers will also face scrutiny from another hemisphere. At 7:30 a.m. ET each morning doctors back at Yale will make rounds at Mount Everest through telecommunications links.

A crucial focus for the doctors will be the climbers' brain activity. Recent studies have suggested that too little oxygen for too long can shut down parts of the brain forever.