Climbers who ascend higher than 26,000 feet on Mount Everest enter the “death zone.”
In this area, oxygen is so limited that body cells begin to die and judgment becomes impaired.
Climbers can also experience heart attacks, strokes or severe altitude sickness.
Human bodies function best at sea level. Down here, oxygen levels are adequate for our brains and lungs. At much higher altitudes, our bodies cannot function properly.
But if climbers want to scale Everest, the world’s highest peak at 29,029 feet (8,848 meters or 5.5 miles) above sea level, they must brave what’s known as the “death zone.” This is the area with an altitude above 8,000 meters, where there is so little oxygen that the body begins to die, minute by minute and cell by cell.
In the Death Zone, climbers’ brains and lungs are starved of oxygen, their risk of heart attack and stroke increases, and their judgment is rapidly impaired.
“Your body is deteriorating and essentially dying,” Shaunna Burke, a climber who summited Everest in 2005, told Business Insider. “It becomes a race against time.”
In 2019, at least 11 people died on Everest, nearly all of whom spent time in the death zone. It became one of the deadliest seasons on Everest in recent memory.
Some expedition companies have attributed these deaths to crowding, noting that the peak became so choked with climbers during a rare period of good weather that people became stranded in the death zone for too long. On May 22, 2019, 250 climbers attempted to reach the summit, The Kathmandu Post reported, and many climbers had to wait in line to ascend and descend.
These extra, unplanned hours in the death zone may have put the 11 people who died at risk, though it’s difficult to determine the specific causes of each death.
A climber said climbing Everest is like “running on a treadmill and breathing through a straw”
At sea level, the air contains about 21% oxygen. But at altitudes above 12,000 feet, oxygen levels are 40 percent lower.
Jeremy Windsor, a doctor who climbed Everest in 2007 as part of the Caudwell Xtreme Everest Expedition, told Everest blogger Mark Horrell that blood samples taken from four climbers in the death zone revealed the climbers survived with only a quarter of the oxygen they needed at sea level.
“These were comparable to the figures found in patients on the verge of death,” Windsor said.
Five miles above sea level, the air is so low in oxygen that even with supplemental air tanks, it can feel like “running on a treadmill and breathing through a straw,” according to climber and filmmaker David Breashears.
Climbers must acclimate to the lack of oxygen
Lack of oxygen comes with a myriad of health risks. When the amount of oxygen in the blood drops below a certain level, the heart rate rises up to 140 beats per minute, increasing the risk of heart attack.
Climbers must give their bodies time to acclimate to the lung-crushing conditions of the Himalayas before attempting the summit of Everest. Expeditions generally make at least three trips up the mountain from Everest Base Camp (which is higher than almost any mountain in Europe at 17,600 feet), climbing a few thousand feet higher with each successive trip before pushing on to the top.
Over the course of those weeks at high altitudes, the body starts making more hemoglobin (the protein in red blood cells that helps carry oxygen from the lungs to the rest of the body) to compensate. But too much hemoglobin can thicken the blood, making it harder for the heart to pump blood around the body. This can lead to a stroke or fluid buildup in the lungs.
On Everest, a condition called high-altitude pulmonary edema (HAPE) is common: a quick check with the stethoscope can reveal a clicking sound as the fluid that has leaked into the lungs churns up. Other symptoms include fatigue, a feeling of imminent choking at night, weakness, and a persistent cough that comes out of a white, watery, or frothy liquid. Sometimes the cough is so severe that it can break or separate the ribs.
Climbers with HAPE are always short of breath, even when resting.
In the death zone, your brain can start to swell, which can lead to nausea and a form of psychosis
Acclimatization to death zone altitudes is simply not possible, high-altitude expert and physician Peter Hackett told PBS.
One of the biggest risk factors at 26,000 feet is hypoxia, a lack of adequate oxygen circulation to organs such as the brain. If the brain doesn’t get enough oxygen, it can start to swell, causing a condition called high-altitude cerebral edema (HACE). Essentially, it’s HAPE for the brain.
This swelling can trigger nausea, vomiting, and difficulty thinking and reasoning.
An oxygen-starved brain can cause climbers to forget where they are and enter a delirium that some experts consider a form of high-altitude psychosis. Hypoxic climbers’ judgment becomes impaired and they are known to do strange things like start taking off their clothes or talking to imaginary friends.
Other possible dangers include insomnia, snow blindness and vomiting
Burke said he suffered from a constant and relentless cough while climbing.
“Every second or third breath your body gasps for air and you wake up,” she said.
The air was so thin that he couldn’t sleep well.
“Humans will start to deteriorate,” Hackett added. “Sleep becomes an issue. Muscle wasting takes place. Weight loss takes place.”
Nausea and vomiting caused by altitude-related illnesses, including HAPE and HACE, also cause a decrease in appetite. The glare from endless snow and ice can cause snow blindness: temporary loss of vision or ruptured blood vessels in the eye.
Temperatures in the Death Zone never go above zero degrees Fahrenheit. “Any exposed skin freezes instantly,” Burke said.
A loss of blood circulation to the climbers’ fingers and toes can cause frostbite and, in severe cases, if the skin and underlying tissue die, gangrene. The gangrenous tissue often has to be amputated.
All of this physical weakening and impaired vision can lead to accidental falls. Fatigue is always present, according to Burke.
“It takes everything to put one foot in front of the other,” she said.
Poor decision-making can also lead to climbers forgetting to attach a safety rope, veering off the route, or not properly packing life-saving equipment such as oxygen tanks.
Climbers scale the death zone in a day, but can end up waiting in line for hours
Climbing in the death zone is “a living hell,” as Everest climber and 1998 NOVA expedition member David Carter told PBS.
Typically, climbers attempting to reach the summit try to ascend and descend in a single day, spending as little time as possible in the death zone before returning to safer altitudes. But this frantic push to the finish comes at the end of weeks of climbing.
Lhakpa Sherpa, who has summited Everest nine times (more than any other woman on Earth) previously told Business Insider that the day a group attempts to climb Everest is by far the hardest time of the trip.
To successfully reach the top, everything has to go right. At around 10pm, the climbers leave Camp Four at 26,000 feet. The first part of their climb is done in the dark, illuminated by starlight and headlights.
About seven hours later climbers typically reach the summit. After a short rest filled with celebrations and photography, the expeditions turn back, safely back for the 12-hour journey, and arrive (ideally) before sunset.
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