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New Report Shows the Best Ways to Prevent Altitude Sickness

Outdoor Hiking
by Tim Wenger Jul 25, 2019

Few things ruin a session in the outdoors faster than a splitting headache. Toss in a bit a nausea and dizziness, and you’ll be spending the day bedside in the hotel room while your crew bags a peak without you. Many who come from low elevation to places like Colorado or Montana, and even people from higher altitudes who venture into the high alpine, are familiar with the symptoms of acute mountain sickness, or AMS. But new research provides insight into what you can do both before you travel and while at high elevation to prevent or at least minimize the condition.

In its recent report on acute altitude sickness published in the Wilderness and Environmental Medicine journal, the Wilderness Medical Society outlines its latest findings on how to prevent and treat the condition. The full report is about as entertaining as watching a silent movie with your eyes closed, so here are the basics distilled for easy reference.

Know your mountain sickness specs.

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The Wilderness Medical Society defined four types of mountain sickness in its report. The first, AMS, occurs when you ascend rapidly to an elevation that your body isn’t used to. Chronic mountain sickness, on the other hand, affects people who live at high elevation.

The two other types are more critical conditions that can evolve out of extreme cases of AMS. High-altitude cerebral edema (HACE) is an extreme form of AMS wherein the person experiences extreme dizziness to the point that even standing up straight is a tall order. High-altitude pulmonary edema (HAPE) happens when damaged capillaries leak fluid into the lungs, a rare but extremely serious condition that can be fatal if not treated promptly. Both necessitate medical treatment and are cause for an immediate descent from the mountains.

It’s less common to experience altitude sickness below 6,500 feet. In general, AMS, which is the main focus of the report, affects the average mountain climber once they hit 8,200 feet. Here are the basics you need to know before a high-altitude trip:

  • The air is thinner at altitude, meaning your body has to breathe harder to meet its needs, and AMS occurs when the body doesn’t react well to this. Common symptoms include dizziness, light to moderate headache, and, if your stomach is on the weak side, a bout of vomiting.
  • Dehydration is only going to amplify these signifiers, so drink plenty of water and keep yourself well-fed because mountain climbing burns calories at a rapid rate. AMS is no fun to deal with, but in itself is generally not cause for major concern beyond treating, resting, and adjusting, and potentially descending in you’ve worked your way up a mountain.
  • In general, AMS is the primary threat for hikers, climbers, mountain bikers, and other relatively fit travelers ascending into the mountains, and the symptoms will recede once your body adjusts to the thinner air.
  • The risk of getting AMS varies greatly by individual. If you have experienced symptoms of AMS before and ascend to above 9,100 feet in one day, your risk increases greatly, while it is lower for those who have never had symptoms or who allow one-two days to adjust. Anyone ascending to above 11,400 feet in one day runs a high risk.

What to do when you have symptoms of acute mountain sickness

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According to the report, the first thing to do once that headache or nausea kicks in is to stop climbing and rest. This might seem like an obvious statement, but when you’re out in the field with a group of people and you’re the only one feeling sick, the temptation to just suck it up and keep going tends to creep in.

When this happens, remember one of the key pillars of backcountry travel: the consensus of the group is driven by the weakest link. While no one wants this to be their descriptor, the intention is that the group operates as a whole and thus when someone is feeling ill, the group must accommodate. There’s no shame in needing to take a pause. Additionally, follow these steps:

  • If rest doesn’t cut it, the WMS recommends descending 1,000 to 3,000 feet.
  • Tylenol and Ibuprofen can be effective in countering the headache but should be taken in addition to the prior steps, not in place of them. The report cites that 600 milligrams of Ibuprofen taken three times per day is more effective at combating AMS than doing nothing.
  • Acetazolamide, commonly sold as Diamox, was also cited by the report as being an effective combattant. For optimal results, begin taking Diamox the day before you ascend to higher altitudes and continue until two days after you finish.
  • Also noted is the practice of chewing coca leaves, common among South American mountaineers, farmers, and others who spend ample time working at high altitude. (If you’re hiking in the Andes, you may be able to purchase coca leaves or coca leaf tea.)
  • Dexamethasone and ginkgo biloba, available in over-the-counter soft gel tabs, can be effective agents in warding off the symptoms, as well.

Steps to prevent altitude sickness

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Acclimatization is king when it comes to proper planning and preparation for a high altitude ascent. This should take multiple forms, beginning with allowing a full day for your body to acclimatize to an elevation slightly higher than you’re used to:

  • If you live at sea level, try spending the first night in a city or town at the base of the mountains before you begin your ascent, and allow 24 hours to adjust.
  • If you’re traveling to trek in the Himalayas, spend a night or two in Kathmandu, elevation 4,592 feet, before taking off on your trek. Going skiing in Colorado? Spend a night at 5,280 feet in Denver before driving up to Summit County.
  • If you’re undertaking a multi-day trek or climb that steadily ascends in altitude, the study recommends allowing periodic rest and acclimatization days. “Above an altitude of 3,000 meters [about 10,000 feet], individuals should not increase the sleeping elevation by more than 500 meters [1,600 feet] per day and should include a rest day (ie, no ascent to higher sleeping elevation) every three to four days,” the report said.
  • A portable oxygen cylinder can help to offset the lack of oxygen you’re breathing from the thinner air.

Among the clearest recommendations is to climb up the mountain slowly. Even if you’re a trail runner who spends a lot of time in the high country, ascending to an elevation higher than what your body is accustomed to should be done at a slow pace.

“Controlling the rate of ascent, in terms of the number of meters gained per day, is a highly effective means of preventing acute altitude illness,” the report notes. As noted above, at elevations above 10,000 feet, try to keep your ascent to no more than 1,600 feet per day.

But even more important is the altitude at which a person sleeps. Because you will spend multiple hours at the same elevation overnight, it’s critical that you plan your ascent so that your body can be properly adjusted before you hit the hay.

“The increase in sleeping elevation should be less than 500 meters [1,600 feet] for any given day of a trip,” said the report. In cases where this isn’t possible, the use of a rest day becomes even more important.

Minimizing its impact while on the hill

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In general, you can minimize the effects of AMS symptoms by following the precautions we’ve listed here. But in the interest of safety and proper trip planning, follow these tips:

  • Lest we forget the importance of water: Pack it. Drink it. And then drink more of it.
  • Get yourself a water filter from an outdoors store such as REI — the best for high altitudes is Life Straw because you can pull water from flowing streams and other sources quickly and safely in case your personal supply runs out.
  • On the gear front, run through this list of basics to ensure you’re properly prepared.
  • When climbing, keep your head down to the mountain as much as possible. This minimizes vertigo-induced nausea.
  • Alcohol furthers dehydration, whether you’re at sea level or 12,000 feet. So while summiting a peak is a revelrous accomplishment, maybe wait until you’re back at the trailhead to crack open that celebratory beer.

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