Brad Johnson (left), “Blues” Voisard and a climbing Sherpa on the summit of Ama Dablam, Nepal. (Photo courtesy of Brad Johnson)

Dr. Peter Hackett is the global guru of high altitude medicine, a leading authority on illness and high-elevation climbing. Hackett developed the Himalayan Rescue Association and established a medical clinic on the trek to Everest Base Camp in Pheriche, Nepal, in 1975. He summited Everest in 1981, soloing from the South Col before fixed ropes adorned the route for clients. He was responsible for creating and operating the Denali Medical Research Project at a high altitude camp on the mountain that treats climbers and seeks to understand altitude physiology.  

Hackett ran the ER at Telluride Regional Medical Center for 15 years, and continues to lecture around the world on health and performance at altitude. He also advises friends from his adopted town of Ridgway as they travel and climb across the globe.

Visitors to Telluride are often challenged by exercise in a place where the elevation can range from about 8,750 feet on Main Street to over 14,000 feet above town (to a physiologist, “high altitude” begins at 5,000 feet).

The first of two critical things one needs to keep in mind when traveling to elevations above 5,000 feet is what Hackett refers to as the Four Day Window. That’s the amount of time it takes, on average, for the body to reach its maximum oxygen level, and to get past the danger for altitude illness.

“It’s very important, and how well you adjust is mostly genetically determined,” he said.

For example, Hackett has observed that good athletes at low altitude don’t necessarily do well at high altitude. It doesn’t matter whether you are a top-flight marathoner at sea level; once you arrive in Telluride, your body requires time to adjust. According to Hackett’s website, “25 percent of those visiting from a lower elevation will experience Acute Mountain Sickness (AMS). The barometric pressure is one-third as dense at Mountain Village than it is at sea level. The main problem is lower air pressure, which means less oxygen. The air (is composed of) 21 percent oxygen whether you are in Death Valley or on the summit of Everest, but it’s got fewer molecules when you go to high altitude because of the lower air pressure. The most important and immediate response to altitude is increasing the breathing.”

Hackett also notes an increase in intestinal gasses with the pressure change. “People fart more,” he said.

And if you have a sinus infection or a tooth abscess, those situations can create “significant pain” after a quick ascent, say, from Montrose Regional Airport to Mountain Village.

The second thing to understand is the 9,000-foot threshold. Hackett states emphatically that “AMS goes up dramatically over 9,000.’”

The 9,000-foot marker is significant for Telluride because town is at 8,750 feet and Mountain Village is 9,547 feet, which puts visitors at even greater risk for the headaches, nausea and lack of appetite from AMS.

Ideally, Hackett suggests sleeping below 9,000 feet for the first 48 hours while adjusting. Instead of making the jump from, say, an elevation of 3,000 feet or lower to 9,000-plus feet at Mountain Village, travelers might consider a stop in a location with an elevation like that of Denver (5,280 feet) or Ridgway (6,985 feet) for a night to give the body a chance to adapt. A single night at these altitudes “can change your response (to high elevation) significantly,” Hackett said.

Ski resort base areas in Colorado range from between 6,000 feet and 9,000 feet. So merely arriving at a base area in Colorado — before you head up the mountain — puts you well up in the zone where your body can be affected by altitude. Riding the gondola to its high point at San Sophia Station at 10,540 feet provides you with less than 29 percent of the oxygen that you’d get at sea level. If you decide to hike up a fourteener in the summer months, you will be working with 43 percent less oxygen than you would have at sea level.

Hackett says the VO2 Max is the body’s greatest ability to extract oxygen from the air and deliver it to the tissues so you can be active and feel well. The thing to remember is that over 5,000 feet, your VO2 Max decreases by three percent for every 1,000 feet of elevation you climb.

“Even with acclimatization, (the VO2 Max) only improves a little bit” as you go up, Hackett said, “and a person can never perform as well at altitude as they can at sea level.”

In addition to acclimating, taking in fluids is critical to adapting to high elevation.

“This is a very dry, dehydrating environment,” Hackett pointed out. Most visitors to Telluride are involved in some form of athletic activity, whether it is skiing, mountain biking or hiking. Hackett’s website notes that athletes can sweat 0.5 to 1.5 liters per hour. In addition, the lungs must humidify the incoming dry air (which also requires water from the body). It is a high-demand scenario for bodies unaccustomed to high altitude.

On the topic of fluids, there is also some good news: Hackett’s a proponent of drinking coffee, because it “stimulates your cardiovascular system and counter-effects lassitude.” This is contrary to what you might read. Hackett says he’s seen visitor guides in Summit County that counsel guests “to stop drinking caffeine when you go to high altitude because of unrealistic and unfounded fears of dehydration.” When he ran the medical center in Telluride, he said, “People would come in with caffeine withdrawal headaches and bad mountain sickness after stopping their caffeine. The altitude headache and the caffeine headache are the same. They are the blood vessels engorging too much in the brain. The data shows that caffeine is metabolized differently at high altitude than at low altitude, so you might even need a little more. It leaves your body quicker.”   

In contrast to coffee, which is a stimulant, certain substances can depress respiratory function.

“People might read it’s important to avoid alcohol at altitude, and that’s not really accurate,” Hackett said, “and most people are going to ignore that advice anyway. One beer or one glass of wine is not enough to depress the breathing. The first night at altitude is critical — the first two nights, really. On the second or third night, you can have three or four drinks. You don’t have to worry about it.

“With any drug, you want to know how it affects breathing,” he added. When it comes to cannabis, “Marijuana does not depress breathing. If anything, it slightly stimulates breathing … Marijuana hasn’t really been studied for (its effects on) acclimatization, but what little research is available suggests it does not interfere with acclimitiaztion and it would not lead to mountain sickness. The same goes for drugs with codeine, or any opiate. The usual one-pill dosage of Vicodin or Tylenol with codeine is not going to depress your breathing, but two or three doses will. Opiates or benzodiazepines, plus alcohol, are a bad idea at high altitude.”

There is no vitamin or supplement that enhances the body’s ability to manage thinner air, even ginko biloba, although Hackett mentioned one test group that did show improved results with it. But the challenge is getting the herb with the actual potency and quality that was used in the studies. It is quite difficult, since supplements can vary in quality so radically. He hears folks extol antioxidants for adjusting, but says they also don’t help. “CBDs aren’t tested,” Hackett said. Aspirin and Tylenol help with headaches, and are useful for children and infants. “If an infant is fussy, it is often because of the discomfort of altitude change.” A dosage that is the same as for fever should help settle them down.    

The only reliable medication is the pharmaceutical Diamox, which has been used for 50 years. It can decrease symptoms of altitude illness by 75 percent. The downside of Diamox is in its potential side effects, which can include tingling in fingers and toes, malaise, fatigue, nausea, and headache. It has the additional bonus of altering the taste of carbonated beverages, including beer.

AMS can cause headache, nausea, shortness of breath, fatigue and loss of appetite. “But it is not life threatening,” Hackett said. He recommends 600 milligrams of Advil (ibuprofen) three times a day to reduce the symptoms of AMS. It does not speed up acclimatization like Diamox, but helps with the discomfort while the body adjusts during the four day window.

Other things to note on arrival at altitude are that it is normal for blood pressure to go up. Respirations and heart rate usually increase in an effort to deliver O2 to all the sites in the body, especially in the first of the four days window when your body is getting to its “maximal oxygen level.”

Interestingly, “Asthmatics often do better at altitude because of a lack of dust mites. There are fewer allergens,” Hackett said. “We don’t have cockroaches. There are camps in the mountains where kids go in the summer to alleviate their asthma.”

Hackett’s website states that for athletes doing aerobic activities over 5,000 feet, “10 to 20 days of acclimation at the performing altitude is ideal.” To perform your best in Telluride, you might want to stay awhile. “You’ll feel better and enjoy yourself more,” Hackett said. For more information, go to


Brad Johnson and Bill Liske both reside in Ridgway and have spent the last 30-plus years guiding and climbing throughout High Asia, Africa and Peru. Their work has taken them from Huaraz, Peru at 10,000 feet to Kilimanjaro to Nepal. Johnson, for example, has summited Cho Oyo (26,906 feet) and Mt. Everest; he leaves for a fourth attempt on 27,825 feet Mount Makalu this Saturday.

They go about their work with a quiet confidence, but there is nothing common about the physiological challenges each must face at altitude. It’s one thing to figure out the quirks of your own body’s response, and something else to be responsible for the welfare of companions and clients.

Johnson’s strategies are well developed. “I always try to get legs and lungs in shape with a lot of uphill training,” he said. “I know there are certain elevations I have to stop and spend a few days at. For example, 14,000 feet is one. When I first arrive, I get dizzy easily. When I bend down to put in a tent stake and then stand up, I’m whirly and lightheaded. Sometimes I have a headache the first night there.”

Johnson usually spends three nights acclimating before his next move to a higher camp, a technique that closely mirrors Hackett’s Four Day Window. The next crucial elevation for his body is between 17,000 and 18,000 feet, where “I have to stay another two to three nights.” With his body caught up, Johnson stops feeling dizzy and the stair-stepping continues until he hits 20,000 or 21,000 feet, which is where he has found “in my older years” — Johnson is 64 — “that my body doesn’t acclimate as fast as it used to. I really notice that sleeping above 21,000 feet I get Cheyne-Stokes breathing.”

With Cheyne-Stokes, your respiratory rate slows down and “each consecutive breath gets shallower and shallower until finally you might not take a breath for 30 or 40 seconds. And then, all of a sudden, you take a really deep breath and it wakes you up. So all night long you are waking yourself up and freaking your partner out.” The solution Johnson uses is taking 60 to 125 milligrams of the altitude drug Diamox before going to sleep, which dramatically reduces his Cheyne-Stokes breathing.

“The thing is, nobody knows how they are going to do at altitude until they go there. And everyone’s body acclimatizes differently,” Johnson said.

He bases his client’s acclimatization on his own process, with three nights at 10,000 feet and another three at 14,000 feet, doing easy hikes. After that, they can make their way to 18,000-to-20,000 feet summits. “I believe in the credo climb high, sleep low,” he said. “When everyone is feeling good, we can go to 20,000 feet.”

The risk is pushing too hard, too soon. “I’ve seen lots of companies base itineraries around American’s two-week vacations, trying to squeeze a 17-day trip into a 14-day trip, and at least one of their clients got altitude sickness and had to go home.” Specifically, the client would get HAPE (High Altitude Pulmonary Edema). “When they rush the schedule, they have one less day at 14 — and each day puts you a step closer to HAPE. It is cumulative for sure,” Johnson said.

Liske has observed the same push to decrease the time taken to get clients to the summit of Kilamanjaro, the highest peak on the African continent at 19,341 feet. “It’s a good example of climbers and guide services moving too fast,” he said. Guides “run people up the Coca-Cola route, the standard route, and they will gain 4,000 feet in a day, and another 3,000 to 4,000 feet the next day.” Perhaps unsurprisingly, “They have a very low success rate.” By contrast, “going up the Shira Plateau, taking your time, having a rest day, works really well. It’s an eight-day trip instead of a four or five day trip, with a 95 percent success rate.”

Johnson recalls, “In my 30-plus years of guiding hundreds of clients, I can only remember three people who weren’t able to acclimatize with my schedule and had to return to the city. They were the people that fell in that category of just not being able to adapt to altitude.”

Liske and Johnson share attitudes about designing treks. Liske says, “I always tried to have sleeping locations that were lower; no matter how high we went during the day, I wanted to sleep low. It is preferable to keep the daily gains to 1,500 to 2,000 feet. And once a week it is nice to have a rest day or even a flat day, or one where you finish at the same altitude. I’ve always adhered to this standard and I’ve had good results.”

Liske warns that, “over 14,000 feet” you never want to exhaust yourself, because at those altitudes your body just doesn’t recover, or at least doesn’t recover well. “Going to Huaraz in Peru at 10,000 feet is a good example, because you fly into Lima at sea level and take a bus to Huaraz and you had better not try to do something right away. You need at least three nights in Huaraz.” Like Johnson, Liske uses a pulse oximeter to monitor his clients’ health. It only takes seconds and tells you what your oxygen saturation is in a number. Ideally, we want to be in the 90s (the higher the better). Readings in the 70s and 80s are an indication that you are not doing well at altitude. (The device also measures a person’s pulse, and is an excellent diagnostic tool.) Liske uses O2 meter readings as a guideline throughout, in order to avoid getting a client into an oxygen deficit, at which point they have to descend and abandon the trip.

“It’s harder for the person involved to argue against going back down, because the O2 saturation numbers on the meter are tangible evidence of how effective your oxygen transfer is,” Liske said. “I don’t care how fit you are; the oximeter doesn’t lie. We are going down.”

Taking your time, acclimating slowly, are techniques for staying healthy and enjoying your experience at altitude not only in the high peaks of the world but also in the San Juans.

“Before the 20th century, we didn’t have altitude sickness,” Hackett said. “Altitude problems are symptoms of a hurried society.”