This article was a finalist for the 2010 National Magazine Awards in the personal service category.

As the highest state in the Lower 48, Colorado sells altitude. It’s what we’ve got that others want—which is why people come from all over to ski down our mountains, camp near our alpine lakes, and climb our fourteeners. Not that we blame them; we dig our state’s God-given natural beauty and well-endowed topography, too. But here’s the rub: There are risks associated with living, playing, or vacationing at altitude. Strange thing is, most people—and way too many Coloradans—don’t realize just how much we’re all affected by our extraordinarily thin air.

Into Thin Air

Demystifying Acute Mountain Sickness.

What is AMS?
A person has acute mountain sickness (AMS) if he has a headache plus at least one other symptom, such as nausea, fatigue, and

dizziness, while at altitude. Researchers don’t know exactly what causes AMS, but many believe that hypoxia (low oxygen) causes blood vessels in the brain to dilate in an attempt to get more oxygen.

The process of dilation causes a headache in most people; the increased blood flow from the dilation also causes swelling in the brain, which may be worse in those that eventually come down with AMS. The brain swelling is thought to be the origin of the other AMS symptoms as well.

How can I prevent AMS?
A gradual ascent to higher altitudes is the key to thwarting AMS. Take your visiting flatlander family too high, too quick, and you’re begging for someone to get sick. Instead of taking them to, say, Breckenridge (9,603 feet above sea level), have them spend their first night in Colorado at an intermediate altitude such as Denver (5,280 feet) or Idaho Springs (7,526 feet) before heading higher into the I-70 corridor. (Some Denver hotels, like the Hotel Teatro, even offer discounted “acclimatization packages” to get you to stay in Denver for a night before heading up the hill.)

Beyond planning a deliberate rate of ascent, you’ll want to keep your lowlanders hydrated—forcing them to down 100 ounces of water a day will help with acclimatizing—and help them avoid overexertion for the first 48 hours at altitude. (That means no crazy hiking at 9,600 feet, folks.) Also, remind your family to stay away from alcohol and sleeping pills in the benzodiazepine family (like Halcion and Restoril), as both suppress breathing and result in lower blood-oxygen levels.

People who know they are susceptible to altitude sickness—meaning they’ve acquired it repeatedly—can ask a doctor to prescribe Diamox. By increasing the amount of bicarbonate excreted in your urine, Diamox makes your blood become more acidic. Acidifying the blood stimulates breathing, which increases the amount of oxygen in the blood. Taken 24 hours before arrival at altitude and every

12 hours for the first two days at altitude, the drug can be up to 75 percent effective in preventing AMS, depending on dose, rate of ascent, and susceptibility.

How can I ID the symptoms of AMS?
The Lake Louise Score is the gold standard for putting a numerical value on the severity of AMS symptoms, such as headache, gastrointestinal distress, and fatigue. A score of four or higher, and you’ve got AMS. Download the Lake Louise Score sheet at

How do I treat AMS?
The best remedy is to descend to lower altitude. But if you can’t go lower or simply want to tough out mild symptoms, the next best treatment is rest, liberal use of ibuprofen or acetaminophen, and time (AMS usually gets better within 24 to 48 hours). If you have AMS symptoms, do not go higher; if you, or someone in your party, is very sick, descend immediately. Of course, if you have access to bottled oxygen, sucking down those Os will decrease AMS symptoms quickly.

Slope Sick

Calculating the cost of altitude illness.

If your most vivid memory from your last getaway to a Colorado ski resort is downing Tylenol and curling up, fetal position-style, in your slope-side condo, you’re not alone. More than 20 percent of Colorado’s ski resort visitors find themselves feeling a bit nauseated�and it’s not from the cafeteria’s $8 bowl of chili. The culprit is, ironically, exactly what people come to Colorado for: the prized geography.

With an average base-village elevation of nearly 9,000 feet, Colorado’s resorts sell the legendary Rocky Mountain High. But while we all covet the spectacular terrain the altitude affords, the thin air takes its toll�and it’s a high price to pay.

Colorado’s high hills attract more than 25 million tourists annually. Of those, more than five million will feel altitude’s effects: nausea, fatigue, headache, weakness, dizziness�all of which lead the affected to reduce their activity level by a whopping 56 percent. Missing a meal, skipping a shopping trip, or passing up a day of skiing may not seem like a tragedy, but according to Telluride’s Institute for Altitude Medicine (IFAM), acute mountain sickness costs the Colorado ski biz upward of $200 million each year.

It’s a problem that disproportionately affects Colorado’s ski areas. Ever wonder why you don’t hear about sickly skiers in the high mountains of Switzerland or Italy? Can’t figure out why nearby Park City has tall peaks and fewer issues? The answer lies not in the elevation of the highest ski lift (which is the Imperial Express SuperChair at Breckenridge, by the way), but in the altitude of the base village.

Colorado’s resorts, unlike most European ones, have very high-altitude villages. “People don’t typically get altitude sickness in Europe,” says Dr. Peter Hackett, one of the world’s leading experts in altitude medicine and the founder of IFAM. “European base villages are tucked into lower-elevation valleys, which means people are sleeping at lower altitudes.” And it’s the sleeping altitude�the elevation where your body spends the most time acclimatizing�that often determines whether you will acquire acute mountain sickness. Anything higher than 8,000 feet could mean a very bad ski vacation; go even higher and your chances of illness increase exponentially.

Of course, Colorado’s ski resorts aren’t exactly clamoring to get the word out on AMS�after all, scaring off tourists never seems like a good business move. “I understand the ski industry not wanting a headline that says ‘Avoid Altitude Sickness,’ ” Dr. Hackett says, “but it’s irresponsible for ski areas to not talk about it.” Resorts like Breckenridge and Vail have information about AMS on their Web sites, while others provide information when asked.

“Climb high, sleep low” is a maxim used by experienced mountaineers, and it’s a good guideline for travelers�and even those from the comparably “low” altitude of Denver�who know they are susceptible to altitude sickness. Not every resort offers base-village accommodations�in which case it’s a good idea to shack up at a much lower altitude. Before you, or your sea-level-dwelling friends, book your next Colorado ski vacation, take the numbers below into consideration.

Resort Base Peak
Arapahoe Basin 10,780 13,050
Aspen Highlands 8,040 11,675
Aspen Mountain 7,945 11,212
Beaver Creek 8,100 11,440
Breckenridge 9,600 12,998
Buttermilk 7,870 9,900
Copper Mountain 9,712 12,313
Crested Butte 9,375 12,162
Durango Purgatory 8,793 10,822
Echo Mountain 10,050 10,650
Eldora 9,200 10,800
Howelsen 6,696 7,136
Keystone 9,300 12,408
Loveland Ski Area 10,600 13,010
Monarch 10,790 11,961
Powderhorn 8,200 9,850
Silverton 10,400 13,487
Ski Cooper 10,500 11,700
Ski Hesperus 8,200 8,880
Snowmass 8,104 12,510
SolVista 8,202 9,202
Steamboat 6,900 10,568
Sunlight 7,885 9,895
Telluride 8,750 12,570
Vail 8,120 11,570
Winter Park/Mary Jane 9,000 12,060
Wolf Creek 10,300 11,904

Got Oxygen?

A low O2 environment forces the body to try to adjust. Here’s what happens when you head for the hills.

At the first hint of hypoxia, or lack of oxygen, oxygen-sensing nerves in the neck tell the body to breathe faster and deeper, allowing increased oxygen intake. Hyperventilation means you’re off-gassing carbon dioxide more quickly, too. The lower level of CO2 can lead to a feeling of lightheadedness.

An increased heart rate, which you may be able to feel for the first day or two at altitude, speeds oxygenated blood to the tissues. People who are born and raised at altitude often have larger hearts with more blood vessels.

Many people who venture into the thin air complain about a dry, sometimes debilitating cough. The hacking may be caused by cold, dry air, but studies also have shown that receptors in the airways that incite cough may simply be more sensitive at altitude.

Carotid Bodies
Located where the carotid arteries split into the internal and external carotid arteries, these nerve bundles sense low oxygen in the blood and cause increased respiration. People who have had a carotid endarterectomy, a surgical procedure that removes plaque from the lining of the carotid artery, may have a decreased ability to acclimatize because of damage to the carotid bodies.

Blood picks up oxygen as it flows through the lungs. In situations where a part of the lung isn’t well-oxygenated (say, pneumonia), blood vessels in the less-oxygenated part of the lung constrict to allow more blood flow to areas where oxygen is available. At altitude, all areas of the lung can have reduced oxygenation; all of the blood vessels can tighten, which results in high blood pressure in the lung. That, in turn, may cause high altitude pulmonary edema (HAPE), a life-threatening condition in which fluid fills up air pockets in the lungs and prevents oxygen from getting into the blood. HAPE occurs in about one in every 10,000 Colorado skiers.

During hypoxia the kidneys release erythropoietin (EPO), a protein that stimulates red blood cell production. Also, typically noticeable on the second day at altitude, the kidneys react to lower CO2 levels—and the resulting alkaline blood—by increasing urination. (Which is why you always feel like you have to pee just as you get on the chairlift.)

Bone Marrow
EPO produced in the kidneys tells the bone marrow to up the production of oxygen-carrying red blood cells.

Increased red blood cells deliver more oxygen to the tissues.

Some altitude researchers believe that mild swelling in the brain may be a root cause of acute mountain sickness (AMS, see page 97). One percent of people that ascend above 13,000 feet will experience a build-up of fluid on the brain (high altitude cerebral edema, or HACE); this condition is life-threatening and requires immediate descent to low altitude. Traveling to extreme altitude, like climbing Mt. Everest, can cause temporary decline in cognitive and speaking abilities.

Muscles use oxygen and sugars to create energy. In situations where oxygen isn’t readily available, energy is created using a process called anaerobic metabolism. The by-product of anaerobic metabolism is lactic acid, a substance that produces that burning sensation you feel in your thighs after only the second run of the day.

Increased stress hormones and lower oxygen levels in body tissues at altitude (starting around 14,000 feet) can delay wound healing. Even the smallest cut can take a long time to heal, and can become infected more easily.

Study groups

Colorado’s cutting-edge research aims to lower the risk of altitude sickness.

In an unassuming white building on Aurora’s Anschutz Medical Campus, researchers toil away in front of computers and charts and vials of unrecognizable substances, but these scientists look more like the high school soccer team than the math club. That’s no coincidence: The researchers who work at the University of Colorado’s Altitude Research Center (ARC) labor over their experiments because it’s their job, but also because many of them have a personal interest in the results.

“Most of us are here because we figured out a way to combine our interests in science and outdoor recreation,” says Jason Chapman, a former research associate at ARC and a regular marathoner. “Plus, we get to use the information we learn here to help us perform better at altitude.” The center, which has been around in various incarnations for more than 15 years, is one of the few research organizations

of its kind in the world. With a mission to improve life through research on how hypoxia affects health and performance, ARC strives to generate science that will help both an experienced mountaineer climb higher without consequence and an oxygen-starved ICU patient heal more quickly.

Dr. Robert Roach, ARC’s research director and an avid mountain climber, has been consumed with the desire to allow people to have more fun at altitude for three decades. “We want to be a place where people can bring their problems with altitude and hypoxia,” he says, adding that the center offers workshops and seminars for the public as well as for health-care providers. “But we also want to radically advance the field of high-altitude biology.” That means conducting groundbreaking experiments—things like determining whether intracranial pressure causes altitude headache, figuring out if there’s a genetic susceptibility for altitude illness, and sussing out the basic mechanism behind acute mountain sickness. On any given day at ARC you’ll see research subjects furiously exercising in the hypobaric chamber, scientists peering at brain scans,

and Roach and company pounding out grant proposals. Of course, ARC’s crack team of scientists isn’t

the only Colorado-based group interested in altitude medicine.

“We’re dedicated to research at ARC,” says Roach, “but Peter Hackett is the best person in the world for clinical work.” So if you’re in good shape but you still suck serious wind trying to climb Mt. Massive, your best bet for figuring out why you can’t summit is Hackett. Considered one of the planet’s foremost experts on altitude medicine, Hackett operates the Institute for Altitude Medicine (IFAM) in Telluride. IFAM, founded in 2007, has an affiliation with ARC but exists for a very different reason: Effective clinical consultations and treatment for altitude-related illness are not widely available. “People come to me for a variety of reasons,” says Hackett, “but mostly it’s, ‘I had a problem on Everest last time and need to know why,’ or ‘My blood pressure is simply too high at altitude,’ or ‘I just can’t catch my breath past a certain elevation.’ And, fortunately, almost all of these issues can be dealt with.”

It may not be surprising that Colorado fields a rather large brain trust of high-altitude researchers. After all, the state’s mountainous backbone serves as a natural laboratory and a vast reservoir for anecdotal evidence. What is surprising, though, is how far-reaching the results of this clinical and laboratory research could one day be. “If we can figure out what causes high-altitude headache,” says Roach, “we might be able to expand that research and help figure out what causes the common, everyday headache. Furthermore, if we can determine the basic mechanisms of hypoxia, we may come to a better understanding of diseases like stroke, which affect millions of Americans.”