(CNN) 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.

Photos: Journey to the roof of the world "Standing on the summit of Everest is the most beautiful and the most hideous experience of my life," said British TV personality Ben Fogle.

Click through the gallery to follow his journey up the world's highest mountain. Hide Caption 1 of 11 Photos: Journey to the roof of the world Fogle set off to summit Everest with former British Olympian, Victoria Pendleton in April 2018 in support of the British Red Cross. Hide Caption 2 of 11 Photos: Journey to the roof of the world Fogle and Pendleton began the expedition by trekking to Everest Base Camp, 5400m above sea level. Hide Caption 3 of 11 Photos: Journey to the roof of the world To acclimatize to the ever-decreasing levels of oxygen, the team did several rotations to Camp 1 and 2, reaching an elevation of 6,400m. Hide Caption 4 of 11 Photos: Journey to the roof of the world But the expedition was dogged by problems along the way. Pendleton, who struggled with altitude sickness, was advised to cut her trip short.

Hide Caption 5 of 11 Photos: Journey to the roof of the world "It is a dangerous mountain and the reality is that a lot of it is a bit of a gamble," said Fogle, who also suffered from setbacks at extreme altitude. Hide Caption 6 of 11 Photos: Journey to the roof of the world At about 8,500 meters, well into the Death Zone, Fogle's oxygen regulator and tank exploded. "Up at that height, the air is very thin and most of us need supplementary oxygen," said Fogle. "You can imagine the fear and the terror when that suddenly explodes."

Hide Caption 7 of 11 Photos: Journey to the roof of the world Fogle said it was the selflessness of the Sherpas that saved him. "Ming Dorjee, one of our Sherpas, gave me his regulator and his oxygen tank and he returned down to a lower level." Hide Caption 8 of 11 Photos: Journey to the roof of the world After six weeks on the mountain, Fogle managed to summit on May 16. He dedicated his Everest expedition to his son who was delivered stillborn in 2014. Hide Caption 9 of 11 Photos: Journey to the roof of the world "When you hold a little life that was never able to be. The breath was never -- he never had a breath. I think I resolved then and there that I wanted to live my life brightly." Hide Caption 10 of 11 Photos: Journey to the roof of the world "In many ways, I feel I'm living a life for two now," said Fogle. "I was never lonely when I was out there bizarrely, even in the dead of night when we were traipsing through the very dangerous Khumbu Icefall. I felt his presence and it was very powerful." Hide Caption 11 of 11

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

To explore the biology behind human oxygen efficiency on Everest, Dhillon took part in two scientific expeditions to Everest in 2007 and 2013

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.

Photos: Everest is the tallest mountain in the world, at 8,847 meters above sea level. Low oxygen at that altitude pushes human endurance to its limits. Pictured, Sherpa mountaineer Pemba Dorje Sherpa and others on Everest, 2009. Hide Caption 1 of 9 Photos: Having lived in the Himalayas for centuries, Sherpas have adapted to easily breathe the thin air. Hide Caption 2 of 9 Photos: In 2013, the Xtreme Everest research team conducted experiments on Sherpas and other volunteers at high altitudes to discover how Sherpas thrive at such heights. Hide Caption 3 of 9 Photos: Researchers set up their laboratory at the highest altitude possible -- Mount Everest base camp. Hide Caption 4 of 9 Photos: The secret behind this ability lies in their cells; Sherpas have differences in their mitochondria, which means they use oxygen very efficiently. Hide Caption 5 of 9 Photos: Nepalese climber Apa Sherpa is the joint world record for most successful climbs of Mount Everest with 21 ascents. Another Sherpa, Phurba Tashi, is the other joint record holder. Hide Caption 6 of 9 Photos: For the research, 116 healthy volunteers living in lowland locations and 64 Sherpas were tested before, during and after a climb to Everest base camp. Hide Caption 7 of 9 Photos: The goal was to understand more about hypoxia -- when not enough oxygen reaches the body's organs -- a condition that affects many intensive care patients. Hide Caption 8 of 9 Photos: Having collected genetic information from the individuals who took part in the study, the next phase of research will look at genetic reasons behind the Sherpas' adaptations to high altitudes.

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'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

Photos: Your body on Everest Dr. Luanne Freer founded Everest ER, a nonprofit medical clinic, in 2003. The clinic is open every year during climbing season at Everest Base Camp. Hide Caption 1 of 7 Photos: Your body on Everest They provide medical services and preventative education to climbers and locals alike. Hide Caption 2 of 7 Photos: Your body on Everest Each year, Everest ER treats an average of 500 people from April 1 to the end of May. Hide Caption 3 of 7 Photos: Your body on Everest Before Everest ER, there was no medical presence on Everest. Only a couple of operational helicopters were capable of airlifting people with injuries to clinics. Hide Caption 4 of 7 Photos: Your body on Everest Jon Kedrowski says that skiing in Colorado is a good way to prepare for climbing high peaks in Nepal like Everest. Hide Caption 5 of 7 Photos: Your body on Everest Kedrowski crosses a crevasse in the Khumbu Icefall on a ladder. Teaching clients how to walk in crampons and using other equipment in icy conditions is key to helping them acclimate. Hide Caption 6 of 7 Photos: Your body on Everest Fellow climber Sandra LeDuc captured this photo of a triumphant and relieved Kedrowski reaching the summit of Mount Everest on May 26, 2012. Hide Caption 7 of 7

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."