Dispatches from the roof of the world
Dispatch #39 May 18, 2012
To Os or Not to Os
Andy Bardon
The North Face athlete Sam Elias learns to use an oxygen mask system.

Everest is not technically the hardest mountain in the world, nor the most remote, nor necessarily the most beautiful. Everest can’t even lay claim to having the tallest base-to-summit elevation gain. Everest is merely our highest mountain—that paramount point on the planet that can peer over all others.

Its height is what makes it hard to climb. Everest Base Camp, at 17,500 feet (5,334 meters), is higher than most mountains on earth. At this elevation there is but 50 percent of the oxygen available at sea level, and when you first arrive you get winded just tying your shoelaces. On the summit of Everest, 29,035 feet (8, 850 meters), there is only 33 percent of the oxygen at sea level.

In short, the one thing that distinguishes climbing Everest from climbing other mountains is the extreme lack of oxygen. The remedy, since the earliest attempts on the peak, has been supplementary oxygen: oxygen compressed into a bottle fitted with a regulator with a tube that runs from the regulator to an oxygen mask fitted tightly over the climber’s face. Not surprisingly, the use of oxygen, or “Os,” has been a topic of contention for almost a century.

J. B. Noel
The 1924 Everest Expedition.

In June, 1924, during the third British Everest expedition, the expedition leader, Edward Norton, reached 28,126 feet (8,573 meteres) on the North Face—without supplementary oxygen—before turning back to rescue a teammate. Just a few days later, George Mallory and Sandy Irvine, using Os, famously disappeared on the mountain. Norton, in tweeds, was less than a thousand feet from the top. Had he summited, sans Os, the history of Everest would have been radically different.

On the fourth British expedition in 1933 three mountaineers—again climbing without oxygen—managed to reach Norton’s high point before turning back. And yet, 20 years later, during the first ascent of Everest, the notion of climbing the mountain without oxygen was abandoned. Everest finally succumbed to siege tactics, the labor of hundreds of humans, and dozens of bottles of oxygen. Ten years afterward, utilizing the same siege tactics and lots of Os, Everest was climbed by Americans.

Despite the fact that the early British expeditions proved humans could go almost to the summit of Everest without supplementary oxygen, the idea languished until accomplished mountaineers Reinhold Messner and Peter Habeler, defying critics who claimed they would either die or become vegetables, climbed Everest via the South Col route without Os in 1978 (54 years after Norton almost pulled it off). Given that supplementary oxygen changes the physiological height of the mountain, there are those who view the Messner/Habeler ascent as the first true ascent of Everest. Two years later Messner climbed Everest solo, without oxygen—perhaps the greatest ascent ever.

Interestingly, although Mallory himself used oxygen, he found it aesthetically unappealing: “When I think of mountaineering with four cylinders of oxygen on one’s back and a mask over one’s face—well, it loses its charm.” The taciturn British mountaineer H.W. Tilman said that climbing with Os was not climbing by “fair means.” Recently, veteran American alpinist Steve House has called climbing Everest with Os cheating, while others have even likened it to blood doping.

Today more than 3,500 people have reached the summit of Everest, but only 5 percent, or 161 people, have done so without oxygen: 35 Sherpas with no deaths, 117 Westies with 10 deaths. The late, great Russian climber Anatoli Boukreev, author of The Climb: Tragic Ambitions on Everest, made three ascents of Everest without Os, and super-Sherpa Ang Rita from Yilajung, Nepal, made ten oxygenless ascents.

Barry Bishop
Thomas Hornbein demonstrates use of an oxygen tank to Sherpas during the 1963 expedition.

So how much does using oxygen help the Everest climber? I posed this question to Dr. Thomas Hornbein, famed summiter from the ’63 American Everest expedition, before coming on this anniversary expedition. To my surprise, Hornbein was enthusiastic, and said he and professor Ray Huey at the University of Washington would do some research on the subject.

Recently, here at Base Camp, Tom wrote me with his fascinating results, never before published. “To answer your question Mark, I derived a formula enfolding a number of variables: altitude, volume of ventilation/minute, oxygen flow rates, and an efficiency factor that states how much of the oxygen flowing continuously into the reservoir bladder is actually utilized during inhalation. That fraction is low at low breathing volumes and increases to 95-97 percent at high minute ventilations and positive-negative pressure swings within the mask.”

Hornbein goes on to say that the efficiency of different brands of oxygen masks may vary a bit, and that the actual breathing volumes while climbing from the South Col to the summit are estimations, but the graph (below) provides a very good idea of the altitude-lowering effect of using oxygen.

Thomas F. Hornbein
As oxygen flow increases, perceived altitude decreases.

“For example,” writes Tom, “for climbers resting on the summit and breathing O2 at 3 liters per minute, Everest’s physiological height is roughly half its actual height. For climbers doing light work, Everest’s physiological height is about two-thirds its true height. With heavier work, like just before topping out, the physiological altitude would be near a 7,000 meter equivalent.”

Ted Wood
The oxygen mask worn by Hornbein in 1963.

Although there is considerable variation, Everest climbers typically sleep at Camp 3, 23,000 feet (7010 meters), breathing one liter of Os per minute, climb to Camp 4, 26,000 feet (7,925 meters), on two liters of Os per minute, and ascend from the South Col to the summit on three liters per minute.

Reinhold Messner notoriously said that climbing Everest with oxygen is like climbing a 6,000-meter peak, not an 8,000-meter peak, and Hornbein notes that “he’s in the ball park.” (Just for reference, there are only 14 8,000-meter peaks, almost 200 7,000-meter peaks, and over a thousand 6,000-meter peaks.)

So if using oxygen actually lowers the physiological elevation of Everest, putting it beneath dozens of other peaks, why do climbers use Os? Safety. In a 2000 American Alpine Journal report, Dr. Ray Huey points out that when summiting Everest sans Os, an individual climber is over two times more likely to die than a climber on Os. Furthermore, because oxygen helps the blood flow out to the extremities, oxygen use dramatically decreases the chances of frostbite. There have also been some studies that suggest there is at least some short-term memory loss—brain damage—caused by climbing Everest without oxygen. (Also, because only the fittest climbers in the world could ever attempt Everest without oxygen, all commercial guiding of Everest would end instantly without the use of Os.)

For almost everyone, after two months of hardship, just getting to the top of Everest by sucking on Os is an achievement of a lifetime. But among elite mountaineers, the oxygen debate will likely continue for another century.

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