By the time it became clear the altitude was killing her, it was already too late

ASPEN, Colo. – In some ways, Susanna Deforest was typical of those who suffer from Colorado’s thinner air after arriving from a low elevation. A 20-year-old from Pennsylvania, she felt sluggish when hiking up a trail to the popular Conundrum Hot Springs near Aspen, lacking much energy. She had to stop frequently for rest.

But in critical ways, her personal physiology masked what was happening as her case of high-altitude pulmonary edema, serious in its own right, turned deadly. She wasn’t breathing hard, nor did she cough. She didn’t turn blue. There were no obvious telltale signs to tell her and her companions on Aug. 18 that her blood oxygen saturation was dropping dangerously low.

When she died early the next morning at an elevation of 10,367 feet, the oxygen saturation in her blood was at about what is commonly found in climbers who at between 22,000 and 28,000 feet in elevation unaided by oxygen.

Dr. Steve Ayers, the corner of Pitkin County, said Friday that her cause of death was high altitude pulmonary edema and high altitude cerebral edema. The former, HAPE, is more common and can precede the latter, HACE, which is exceedingly rare. However, HACE can occur without HAPE.

This was an extreme case of dangers of hypoxia, or the effect of oxygen deprivation on human tissues. It also poses questions for those who survive whether they could have done anything differently to prevent the death. In this case, the answer is probably not.

Mountain sickness is relatively common, afflicting about a quarter of all visitors to Colorado resorts of above 8,000 feet in elevation who arrive from sea level. Young men most commonly suffer. They eat heavy, drink too much alcohol, and still plow forward, skiing with gusto. The usual advice is to take it easy for a few days, stay hydrated, and get plenty of rest.

High-altitude pulmonary edema, or HAPE, ordinarily doesn’t show up until the second or third day. It can affect people at elevations of as low at 6,000 feet, but it’s more common at about 8,000 feet.

Aspen and Vail are both a little above 8,000 feet. Telluride is at 8,750, but most people visiting there stay at Mountain Village, elevation 9,545 feet. Mt. Crested Butte, the slope-side town, is 9,380 feet. Most lodges in Summit County are 9,000 feet or above.

The cases of HAPE are relatively rare. Just one visitor in every 5,000 to 10,000 visitors to Colorado mountain resorts will suffer HAPE, according to Dr. Peter Hackett. A physician, Hackett made hypoxia, or oxygen deprivation, a central part of both his research and his mountain climbing career. He summited Mt. Everest in 1981 and in later years ministered to climbers at the 18,000-foot base camp.

At Aspen Valley Hospital, physicians see HAPE victims one or twice a month although, on at least one occasion, there were three cases within a 24-hour period. Victims of the condition, also called acute mountain sickness, invariably arrive on their third night at altitude after their afflictions have worsened. Ayers says they complain about trouble with breathing and they can’t sleep. Sometimes they can hear fluid gurgling in their chests, and the sound worries them.

“It should worry them,” says Ayers. It’s a telltale symptom of HAPE.

These cases of HAPE are invariably remedied with the simple prescription of supplemental oxygen, about three liters a minute. The patients can return to their hotel rooms, oxygen cannulas in their nostrils.

Fatalities resulting from HAPE used to be more common in Colorado, the nation’s highest state with an average elevation of 6,800 feet. But travelers have become better educated and clinics in high-mountain valleys better able to respond.

Still, fatalities do occur. Several years ago, a visitor to Mt. Crested Butte died of HAPE. A hunter in the San Juan Mountains also died.

More rare and more deadly is cerebral edema, or HACE in which fluids built up in the brain. Rapid response can make all the difference. Ayers remembers a case several years ago of a young woman staying in Snowmass Village suffering from HACE. The lodge was probably at about 9,400 feet, the base elevation for which cerebral edema occurs. In that case, she was given oxygen immediately at Aspen Valley Hospital and put on a helicopter to a level-one trauma center in Denver, where neurologists are on staff around the clock. She didn’t need them, though. Getting off the helicopter in Denver, she had recovered.

In the case of Suzanne Deforest, supplemental oxygen would have made all the difference. But her symptoms were atypical.

She had flow to Denver on Aug 13, spending the night in Golden, elevation 5,675 feet. The next day she traveled to Dillon, elevation 9,111 feet, where she lingered for two days and probably started developing HAPE, according to the report of Ayers, the coroner.

The next day, on Aug. 17, she and companions set out from Aspen to hike up the Conundrum Hot Springs trail. It starts out at 8,700 feet and, 8.5 miles later, ends up at the hot springs, just below treeline at 11,200 feet in elevation.

Ayers says she struggled up the trail, needing frequent stops for rest, but companions said she did not exhibit obvious signs of breathing distress.

Her symptoms were subtle and atypical, as is true in 10 to 15 percent of cases. A healthy person at sea level has an oxygen saturation of 96 to 98 percent in their blood, says Hackett. Oxygen saturations typically drop to 89 or 90 when people are at 9,000 feet in elevation.

For a normal person standing on top of Mt. Everest, unaided by supplemental oxygen, it would be 40 or 50.

As the young woman struggled up the Conundrum trail, her oxygen saturation levels probably dropped to the level of the world’s highest peaks. As you develop HAPE, your oxygen level continues to drop, even if you are not ascending in elevation. HAPE, in this case, then continued into HACE. “It’s no mystery that she had high-altitude cerebral edema,” says Hackett.

Had the woman breathed heavily instead of just feeling lousy, she or her companions might have figured out that rapid descent was necessary. Instead, they hunkered down in a tent, sort of waiting out the storm. That was a fatal if understandable decision.

Arriving at 1:30 a.m., the rescue helicopter was unable to land, because of its weight. Instead, the helicopter had to burn off fuel. It didn’t land until 5:30 a.m. By then, she was dead.

But from the testimony of a key witness and a timeline put together by the Pitkin County deputy coroner, it almost certainly would have made no difference had the helicopter been able to land the first time. When the tent companion returned to the tent after shining her lights to the helicopter, she found the woman had stopped breathing.

There may be cases of victims of HACE brought back from the brink of death, but Ayers says he’s unaware of any. Victim of cardiac arrhythmia can be brought back from the brink of death. But when the brain has swollen to the point it is causing cardiac arrest, it can’t be reversed.

Had the victim and her companions carried a book of “Wilderness Medicine,” the text that Ayers carries with him on his travels around the world, they might have diagnosed her HAPE and then HACE. But few of us carry such books when backpacking or any place else.


This story was originally published on Sept. 8 in Mountain Town News.
Photo by Allen Best. 


  1. Colorado climate altitude in general,even in the cities, ~5,000 feet, made me sick. Nothing major, but it was a slow pull on my health. But I did not really understand until I moved to a lower altitude and more humid climate. Within 6 months, my skin was fuller, my mild occassionally dizziness left, my general mild pain left, and I had so much more energy!! To note, I am mid 30s, healthy, a runner, and very slender. 5’6″ and 118 lbs. The climate is NOT for everyone and someone like me who is fit but with a gentle composition will suffer. I have increased the quality of my life simply by moving!

  2. Which Wilderness Medicine? There seem to be many different ones, would love to know which is best, which one Dr. Ayers carries around…

  3. I second the person above ^^^^ which version of Wilderness Medicine , by which author? Amazon has many different ones

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