On the peak of Everest, it can take minutes just to catch your breath. That’s because, at an elevation of 8,848 meters (29,029 feet), each breath contains one-third of the oxygen found at sea level.
In May, British TV personality Ben Fogle was put to the test when his oxygen regulator exploded a few hundred meters from the summit.
One of his mountain guides, Ming Dorjee Sherpa, was able to sacrifice his oxygen mask, regulator and cylinder and descend to a lower camp without supplemental oxygen.
Then, on the Hillary Step, less than 50 meters from the summit, Fogle’s second regulator and bottle exploded on his back.
“It was pretty terrifying. My heart just sank, because I couldn’t really see a way out,” Fogle said.
“It’s a bit like going to Mars in a space suit and imagining what happens when you unzip it.”
Thanks to the heroic acts of the Sherpas and expedition leader Kenton Cool, who gave Fogle his oxygen supply, the team reached the summit on May 16.
Journey to the roof of the world
But time on top of Everest is short-lived, as the body is rapidly deteriorating, and you’re more exposed than ever to the elements. If luck is on your side, you might get about 20 minutes to take it all in before it becomes intolerable, explains high-altitude medical expert Sundeep Dhillon.
“You are constantly reminded that you shouldn’t be there,” Dhillon said. “Most people can’t survive more than a day or two at those altitudes with or without oxygen.”
An accomplished mountaineer in his own right, Dhillon worked closely with Fogle and former Olympic track cyclist Victoria Pendleton ahead of their Everest expedition to raise funds for the British Red Cross.
Though physically fit and strong, Pendleton struggled with oxygen deficiency at high altitude. After complications at camp two, 6,400 meters above sea level, she was advised to pull out of the summit bid.
“Altitude is extremely humbling, and although we tested both of them in the lab, there is no sea-level predictor for how you’re going to do,” Dhillon said. “Victoria won’t be the only world record holder or Olympian that’s struggled on Everest.”
According to Dhillon, fitness does not affect how efficiently the body performs in a low-oxygen environment.
Endurance at altitude is all down to genetics.
Surviving Everest is in your genes
At 8,000 meters above sea level, on the balcony of Everest, Dhillon and the Caudwell Xtreme Everest team collected the least-oxygenated human blood samples ever recorded in “healthy” humans.
“We effectively had to drop our trousers and stick needles in each other’s groins to get arterial blood,” Dhillon said.
The oxygen levels recorded in the first expedition in 2007 were on par with those collected from critically ill patients close to death.
The team went back in 2013 to test the “superhuman” physiology of the Sherpa population of the Himalayas, who have lived at high altitude for centuries.
Among other findings, they discovered that the Sherpas’ mitochondria – the part of human cells that respire to generate energy – were much more efficient at using oxygen.
The aim of this research was to identify how different people adapt to low oxygen levels – or hypoxia – at high altitude and to apply this understanding to critically ill patients.
A similar study in 2014 analyzed the genetic adaptations for high altitude found in residents of the Tibetan plateau.
The biological secrets that make Sherpas superhuman mountaineers
‘Rotting whilst trying to acclimatize’
Much of the Caudwell Xtreme Everest research was done at base camp at an elevation of 5,400 meters, which is above the highest altitude where humans can permanently live, Dhillon said.
“All the time you’re there, you’re rotting whilst trying to acclimatize.”
Most people don’t realize that a two- or three-month Everest trip only involves 15 to 20 days of actual climbing, he says. “The rest of the time, you’re waiting for your body to acclimatize to the ever-decreasing levels of oxygen.”
This is when acute mountain sickness kicks in, a result of the slight swelling of the brain.
Much like a hangover, acute mountain sickness manifests in the form of headache, dizziness, nausea, trouble sleeping and loss of appetite, according to the Institute for Altitude Medicine.
Your body on Everest
If untreated, it can morph into high-altitude cerebral edema once you reach extreme altitude.
“Your brain is now swelling because of the hypoxia, and it has nowhere to go because it’s constrained by your skull,” Dhillon said. “The only exit out of your skull is where your spinal cord comes down, so your brain is being squeezed out of your skull.”
A person with high-altitude cerebral edema resembles a drunkard: confused, hallucinating and vomiting, with impaired judgment.
Another severe form of altitude sickness is high-altitude pulmonary edema, the accumulation of fluid in the lungs. Symptoms include shortness of breath, coughing, chest congestion and severe weakness.
If untreated, both cerebral and pulmonary edema can lead to coma and death.
Dangers of the Death Zone
Climbers who make it above 8,000 meters – into the Death Zone, as it’s known – need to keep their wits about them.
The simplest task like sitting up out of bed will leave you short of breath, making you pant for a few minutes, Dhillon said.
A lack of oxygen to the brain affects your mental performance, too. If you were to try think of words that begin with the letter “T,” at extreme altitude, you would be able to think of only two or three.
If climbers are sensible and have enough oxygen in reserve, they can get back down the mountain quickly as the air “literally gets thicker every few hundred meters,” he said.
But perhaps the biggest danger is when climbers treat the summit as the journey’s end point. According to Dhillon’s estimates, “you’ve probably got a one in 10 chance of dying on the way down.”
“People are perfectly capable of exerting themselves beyond their capabilities whilst underestimating the demands that those extreme altitudes place on you. They forget they’re in the Death Zone.”