Reinhold Messner and Peter Habeler were the first people to climb Mount Everest without supplemental oxygen, reaching the summit on May 8, 1978. At the time, most physiologists believed the feat was impossible, that the human body simply could not function at 8,849 meters with only the thin ambient air to breathe. Since that breakthrough, fewer than 250 people have repeated it, out of the thousands who have stood on the summit.
The 1978 First Ascent
Messner, an Italian, and Habeler, an Austrian, climbed the South Col route, pushing through the Western Cwm, the Icefall, and a series of camps before launching their final summit bid from Camp V at 8,500 meters. The physical toll was extraordinary. Simply getting dressed that morning took them two hours. They switched to hand signals because speaking wasted too much breath.
As they climbed higher, progress slowed to a crawl. Every few steps, they leaned on their ice axes and gasped. Messner recorded into a tape recorder that “breathing becomes such a serious business we scarcely have strength to go on.” By 8,800 meters they were no longer roped together and collapsed every 10 to 15 feet, lying in the snow before dragging themselves forward. Habeler suffered headaches and double vision. Messner described feeling like his mind was dead, that only his soul compelled him to keep crawling. Sometime between 1 and 2 p.m., they reached the top.
What Happens to the Body Without Bottled Oxygen
Above roughly 8,000 meters, often called the “death zone,” the air holds about a third of the oxygen available at sea level. Arterial blood samples taken from climbers at 8,400 meters showed average blood oxygen levels around 24.6 mmHg. For context, a healthy person at sea level measures around 75 to 100 mmHg. The brain, muscles, and every organ are essentially starving for oxygen.
The most dangerous consequence is high-altitude cerebral edema, a condition where low oxygen triggers fluid leakage in the brain, raising pressure inside the skull. Early signs include unsteady walking and impaired coordination, particularly in fine motor control. Without descent or treatment, it can progress from confusion to coma to death within 24 hours, with a fatality rate reaching 50%. Even survivors of severe cases sometimes experience lasting problems with memory, attention, and executive function. Climbers without bottled oxygen spend more time in this danger zone and face these risks at much higher intensity.
The numbers reflect this. Between 1978 and 1999, climbers who summited Everest without supplemental oxygen died at a rate of 8.3%, compared to 3.0% for those using oxygen. On K2, the world’s second-highest peak, the gap is even starker: 18.8% versus 0%.
Ang Rita Sherpa: The Record Holder
No one has matched what Ang Rita Sherpa accomplished. Born in Nepal in 1948, he summited Everest 10 times without supplemental oxygen between 1983 and 1996. Guinness World Records recognizes this as the most oxygen-free ascents of Everest by any person. While many elite climbers have managed the feat once, Ang Rita did it repeatedly across 13 years, a testament to both his physical gifts and the remarkable high-altitude adaptation found among Sherpa populations who have lived at elevation for generations.
First Woman: Lydia Bradey
In 1988, just a decade after Messner and Habeler’s breakthrough, New Zealand climber Lydia Bradey became the first woman to summit Everest without supplemental oxygen. Her achievement was initially disputed by members of her own expedition, leading to years of controversy before it was broadly accepted. Bradey went on to climb Everest six times and remains the only New Zealander to have reached the summit without oxygen. As of the 2024 climbing season, only about 10 women total have accomplished the feat, with Slovakian climber Lenka Polackova becoming the tenth.
Speed Records and Modern Feats
Spanish-born mountain runner Kilian Jornet pushed the concept further in 2017 by summiting Everest twice in a single week without supplemental oxygen. His first ascent, from a monastery at 5,100 meters, took roughly 26 hours. Dissatisfied, he went back up five days later from Advanced Base Camp and reached the summit in 17 hours. No other mountain runner had achieved two oxygen-free summits in such a compressed timeframe.
The 2024 season saw a handful of notable oxygen-free summits. Polish climber Piotr Jerzy Krzyzowski became the first person to summit both neighboring Lhotse and Everest without supplemental oxygen in a single push, combining two 8,000-meter peaks in one effort. Indian climber Skalzang Rigzin also summited without oxygen that season.
Why So Few Have Done It
Out of the more than 6,000 people who have summited Everest, the oxygen-free climbers represent a tiny fraction. The reason is straightforward: the margin between survival and death narrows dramatically. Climbers move far more slowly without bottled oxygen, which means more hours spent in the death zone, more exposure to storms, more time for cerebral and pulmonary edema to develop. Decision-making deteriorates as the brain loses oxygen, making it harder to recognize when to turn back.
Most commercial expeditions today treat supplemental oxygen as standard equipment, not a luxury. The climbers who go without it tend to be elite alpinists with years of high-altitude experience and specific physiological advantages, whether genetic or built through long acclimatization. Even among that group, the success rate is low and the risks remain severe. The 8.3% death rate for oxygen-free summiters means roughly 1 in 12 who reached the top did not make it home.