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What does altitude sickness feel like? Recognition, prevention, and treatment advice from a WFR instructor.

By Philip M, CPR Seattle Lead WFA & WFR Instructor

(True story, though names have been changed).

"We're back," I called out, dropping my pack in the grass as the sunset cast orange light over our basecamp in the Peruvian Andes.  Dean and I had been out scouting our mountaineering route for the following day on Yanamarey, an easy 17,000' glacier climb in the Cordillera Blanca.  Dean and I had been climbing in Peru for a few weeks already.  We’d planned this particular outing to help our recently arrived climbing partner Jon acclimatize to the altitude.  He had flown then bussed in to Huaraz, Peru (elevation 10,013') from his sea level home in New England a few days earlier.  He planned to hang out for a day at our 14,000’ high base camp before trying to climb higher the following morning.

Normally cheery Jon just growled from inside the tent, "Are we even going to talk about going down?"  I looked at Dean.  Our plans had changed.

Patient Assessment

We discovered that after hiking up from the trailhead the day before and sleeping poorly at 14,000', Jon hadn't come out of the tent all day.  He was complaining of nausea and a severe headache and was uncharacteristically irritable as we discussed the situation.  On assessment, we found him to be alert and oriented to person and place but confused about the time of day and what was happening around him.  His had an elevated heart rate and respiratory rate and looked pale.  He denied having any allergies, was not taking any medications, had no pertinent medical issues, and hadn't eaten or drank more than a few sips of water all day due to lack of appetite.  We found nothing else significant on a head-to-toe physical examination, but he was a little wobbly while trying to walk around camp.

Assessment and Plan

Based on Wilderness First Responder training, we determined that Jon was suffering from a case of Acute Mountain Sickness.  We worried about the possible onset of High Altitude Cerebral Edema due to his changes in mental status.  We agreed that the best course of action was to immediately descend to lower elevation before his symptoms became worse.  So we encouraged Jon to drink whatever as he could keep down and broke camp.  Dean and I took Jon's pack and I lent him a pair of trekking poles to aid in balance.  We then stumbled a few miles down the valley, descending a thousand vertical feet by headlamp and moonlight.  He vomited once as we hiked but as we neared the trailhead his mental status improved and he even started cracking a few jokes.  We caught a few hours of sleep and by the time the sun rose, Jon still had a headache but was feeling much better.  He drank some herbal tea and ate a pancake with Peruvian dulce de leche as we waited for a ride back to town with a local herder and his flock of sheep.  Back in Huaraz, Jon had a full recovery after a few days rest and climbed to 19,000' without incident a few weeks later.

Acute Mountain Sickness

The most common type of altitude sickness is Acute Mountain Sickness (AMS).  AMS typically occurs when higher than 7,000' above sea level and is more common at higher elevations.  I've treated many patients with AMS symptoms at between 12,000' and 14,000' in the Colorado mountains.  Anyone ascending to higher elevations may suffer altitude sickness, but rapid ascent puts you at greater risk.  Flying or driving from low elevation to a mountain town then going on a strenuous hike to higher elevation without rest is a great way to learn firsthand how altitude sickness feels!

What are the signs and symptoms of AMS?

Here is a list of possible symptoms of Acute Mountain Sickness:

  • Headache
  • Nausea
  • Loss of Appetite
  • Shortness of breath
  • Insomnia
  • Weakness
  • Increased Urination
  • Lassitude (lack of energy)
  • Elevated Heart Rate
  • Elevated Respiratory Rate

Headache and nausea are the most common symptoms of AMS, often accompanied by loss of appetite, difficulty sleeping, weakness, increased urination, and lack of energy.  These symptoms along with breathing dry mountain air often lead to dehydration as well. Heart rate and respiratory rate will usually be elevated to help the body meet oxygen demand while blood pressure stays about the same as normal.  Mental status changes such as becoming disoriented, irritable, and combative, decreases in level of responsiveness, or intense coughing (especially if producing pinkish saliva or mucus) are possible indications of less common but more serious conditions like High Altitude Cerebral Edema (HACE) and High Altitude Pulmonary Edema (HAPE).  Treat these as serious medical emergencies.

How to avoid AMS?

The best treatment for altitude sickness is prevention.  Our bodies can adjust to higher elevations over time.  Mountaineers have a rule of thumb to "climb high, sleep low."  Exposing your body to altitude during the day and then returning to lower elevation to sleep helps with acclimatization.  Stay hydrated.  Don't go to high elevations if you have cold or flu symptoms.  The US Centers for Disease Control and Prevention recommend the following guidelines:

  • Ascend gradually.
  • Avoid going directly from low elevation to >9,000 ft (2,750 m) sleeping elevation in 1 day.
  • Once above 9,000 ft (≈2,750 m), move sleeping elevation by no more than 1,600 ft (≈500 m) per day and plan an extra day for acclimatization every 3,300 ft (≈1,000 m).
  • Consider using acetazolamide to speed acclimatization if abrupt ascent is unavoidable.
  • Avoid alcohol for the first 48 hours at elevation.
  • If a regular caffeine user, continue using to avoid a withdrawal headache that could be confused with an altitude headache.
  • Participate in only mild exercise for the first 48 hours at elevation.
  • A high-elevation exposure (> 9,000 ft [≈2,750 m]) for ≥2 nights, within 30 days before the trip, is useful, but closer to the trip departure is better.

Treatment for AMS

If you find yourself or a partner feeling symptoms of AMS, stop ascending.  Give your body time to adjust to the elevation. Stay hydrated and watch for symptoms to improve or worsen.  If the symptoms don't improve, try returning to a lower elevation.  The best thing about acute mountain sickness in the wilderness is that you have easy access to definitive care: turn around and go down. I have seen incredible improvements in AMS patients by descending just a thousand feet in elevation.  If symptoms worsen and you suspect HAPE or HACE, descend immediately and consider activating EMS or calling for rescue. 

Altitude illness is a fascinating and complicated subject.  To learn more about AMS, HACE, HAPE, and other altitude-related illnesses, consider taking a wilderness medicine class with CPR Seattle.  Wilderness First Aid is a 16-hour class that will prepare you to recognize and treat life-threatening conditions when outside the easy reach of urban ambulance services.  Wilderness First Responder is a comprehensive curriculum covering those basics as well as more advanced patient assessment and treatment for higher risk activities, extended wilderness trips, and expeditions.  Stay safe out there!


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Published on February 20, 2024