These Climbers Summited Mount Everest in Record Time. Did Inhaling Xenon Help?

Scientific American

6 days ago

Last week a quartet of British climbers made it to the top of Mount Everest —and spent less than a week on the total round trip from London. That's weeks fewer than it usually takes to acclimate to the high elevation, scale the world's highest peak and head home.
Their guide, speaking to the New York Times, credited their accomplishment to a secret advantage: prior to the trip, the climbers inhaled xenon gas, which may have made their acclimatization to the low-oxygen environment of Everest easier. But experts on the medical uses of xenon are uncertain that it was a decisive factor.
'Maybe there is something there. We just don't know,' says Andrew Subudhi, a professor of human physiology and nutrition at the University of Colorado Colorado Springs, who studies human performance in low-oxygen environments. 'From the scientific evidence, I can't see anything that is definitive or even proof-of-concept yet.'
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How does xenon work in the body?
Xenon is a noble gas—colorless, odorless, inert. But it does affect the body. It's been used as an anesthetic on occasion since the 1950s, says Robert Dickinson, a senior lecturer in medicine at Imperial College London. Dickinson has long studied another intriguing aspect of xenon: the gas has shown neuroprotective effects after a brain injury such as a stroke or a traumatic blow to the head. This protective quality has been demonstrated in many animal studies and a handful of small human trials, Dickinson says.
Both the anesthetic and potential neuroprotective effects occur because xenon can bind to brain receptors called N-methyl-D-aspartate (NMDA) receptors. Activating these receptors has an excitatory effect on neurons, but xenon tamps down NMDA activity. After a brain injury, NMDA receptors can become overexcited, causing further cell death, so quieting these receptors might prevent additional damage.
Those are xenon's best-studied effects on human health. But the gas has also piqued interest in the sports medicine world because it can increase the production of erythropoietin (EPO), a hormone that is known to stimulate the bone marrow to increase its production of red blood cells. Red blood cells carry oxygen, which is, of course, in short supply on the icy slopes of Mount Everest.
Can xenon really acclimate someone to high elevations?
Before attempting Everest's summit, climbers must hang out in Kathmandu, Nepal, and then Everest Base Camp for weeks, lest they fall prey to altitude sickness, which is marked by fatigue, headache, nausea and confusion. In serious cases, the lungs fill with fluid or the brain swells, which can quickly lead to death. The air at Everest Base Camp contains about half the oxygen as is present at sea level, and the air at the summit contains a mere 33 percent.
Xenon's potential to increase the production of red blood cells, thus increasing the blood's ability carry oxygen, raises the question of whether it might provide a performance boost or prevent altitude sickness in the athletes climbing the world's highest peaks. The problem is: no one really knows if the EPO boost provided by xenon is enough to make a real difference in how someone handles a high elevation. Davide Cattano, an anesthesiologist at the McGovern Medical School at the University of Texas Health Science Center at Houston, did some of the animal research that has shown that xenon increases a blood factor called hypoxia-inducible factor 1–alpha (HIF-1α), which in turn can increase EPO. He's skeptical that the recent Everest climbers saw much benefit. 'The level of HIF that you're inducing does not justify this superhuman capability,' Cattano says.
One 2019 study published in the Journal of Applied Physiology tested 12 runners who were randomly assigned to inhale air that contained 70 percent xenon or a sham gas for two minutes each day for several weeks before they ran three kilometers. The runners who inhaled xenon saw an increase in EPO in their blood, but they didn't show any improvement in fitness or athletic performance, as measured by their running speed and their heart rate and respiration during exercise.
Even dosing people with EPO directly with injections may not prevent altitude sickness or improve performance at high elevation, Subudhi says. In a study that is currently in review for publication in a scientific journal, he and his colleagues tested EPO injections on a small group of mountain-climbing athletes, and these subjects didn't see any benefits. It's possible a different dose or a longer course of treatment might make a difference, Subudhi says, but 'my enthusiasm for chasing that is much less when I didn't see anybody have a measurable benefit.'
Why did the recent Everest climbers reach the peak so quickly?
It is possible xenon improved the climbers' oxygen-carrying capacity by boosting their EPO, experts say. It's also possible the anesthetic and analgesic effects of the gas ameliorated the climbers' aches and pains or the fatigue from altitude, Cattano speculates. Just the act of breathing a heavy gas like xenon might also result in some change to lung capacity, he says, even if the EPO effect is small.
But the athletes also did something else: they slept in hypoxic tents for weeks before traveling to the mountain. These tents create a low-oxygen environment, which definitely increases EPO and red blood cell production. This preacclimatization, plus the climbers' intensive training regime, may have done the trick. Whether the xenon added any benefit on top of the hypoxic tents is unclear, Dickinson says.
Xenon is expensive, which has limited its use as an anesthetic and in athletics. But more people will probably shell out for the gas, given that the baseline cost of climbing Mount Everest is so expensive and the stakes are so high, Subudhi says.
'People are literally fighting for their lives at high altitudes, and if you're doing things that may give you a small chance of improving your rate of success, yeah, it might be worth it to some people,' he says. 'Not everybody is going to sit there and make a completely scientific decision about their life.'