They say that reaching the summit is only half the climb. And if that’s the case, it’s possible that Melissa Arnot just became the first American woman to climb Mount Everest without using supplemental oxygen.

Arnot reached the summit of the 29,029-foot (8,848-meter) mountain on May 23, achieving a dream that, for her, has been years in the making.

“This has been an emotional journey, to say the least,” said Arnot, according to a press release issued by one of her sponsors. “Climbing Everest without supplemental oxygen has been a goal of mine for a long time.”

Whether Arnot is the first, or second, American woman to successfully climb Everest without oxygen, however, is a debatable point. In 1998, a Hawaiian-born woman named Francys Arsentiev, 40, successfully climbed Everest without oxygen alongside her husband Sergei Arsentiev; however, on the descent, both climbers died in separate events.

To some in the climbing world, Francys is the first American woman to climb Everest without oxygen. To others, the fact that she didn’t make it down alive negates her achievement.

This debate—about whether or not one must survive the descent for their achievement to “count”—has a precedent in Everest’s storied history. For a number of years, climbers speculated on whether or not, in 1924, George Mallory and Andrew Irvine had actually reached the summit of Everest before their ultimate disappearance from high on the Himalayan giant. And if indeed they did summit, shouldn’t they be credited with the mountain’s first ascent—not Edmund Hillary and Tenzing Norgay, who are, of course, officially considered to be the first men to succeed in standing atop Everest?

When asked about this issue sometime in the mid 1980s, Hillary reportedly stated, “If you climb a mountain for the first time and die on the descent, is it really a complete first ascent of the mountain? I’m rather inclined to think, personally, that maybe it’s quite important, the getting down. And the complete climb of a mountain is reaching the summit and getting safely to the bottom again.”

Thankfully, as Arnot is currently safe and sound back in a lower camp, she is the first American woman to climb Everest without oxygen and survive the descent—which, statistically, is when most Everest climbers die.

Climbing Everest without supplemental oxygen is more difficult than climbing with canisters of “Os,” as they’re called. Using supplemental Os effectively makes climbers feel as if they’re 3,000 feet lower than they actually are, which is why many climbers consider using supplemental oxygen to be cheating. However, without oxygen, Everest becomes much more dangerous. More than a third of all deaths on Everest can be linked to people trying to climb without oxygen.

Reinhold Messner and Peter Habeler became the first people to climb Everest without oxygen in 1978, a year in which doctors all but unanimously believed that it would be physically impossible for a human body to function at Everest’s upper altitudes. Messner and Habeler, however, proved everyone wrong, and some climbing purists have even gone so far as to argue that, in a sense, theirs is the first true ascent of the mountain. Either way, choosing to abandon the crutch of supplemental oxygen never really caught on with the Everest crowd. Today, Everest has been climbed by more than 4,000 people, but fewer than 200 have done it without oxygen. This week, America’s best high-altitude female climber added her name to that elite list.

Lydia Bradley, of New Zealand, became the first woman to climb Everest without oxygen in 1988. Since then, six other women have achieved this feat, including Carla Perez, of Ecuador, who summited sans Os this week. Arnot, considered America’s best high-altitude female climber, has added her name to that elite list, which makes her the seventh woman ever to climb Everest without supplemental oxygen.

While this may be Arnot’s first oxygen-less ascent of Everest, it is actually her sixth time successfully climbing the mountain, which is a record for American women. In fact, only one other woman has stood on Everest’s summit more than Arnot, and that is Lakhpa Sherpa, a 42-year-old Nepalese woman who reportedly works at a 7-Eleven in Connecticut. Sherpa, who summited last week, has now climbed Everest seven times.