Written August 2021
Altitude sickness, or Acute Mountain Sickness (AMS), is no joke. It’s especially not a joke if it progresses to High Altitude Pulmonary Edema (HAPE) or a High Altitude Cerebral Edema (HACE). AMS is common and unpleasant. HAPE and HACE are uncommon and life threatening.
Back in 2011, I thought it would be cute and fun to head to Ecuador to climb Mount Cotopaxi, which is Ecuador’s second highest peak and an active stratovolcano standing 5,897 meters (19,347 feet) above sea level. My friend, Jacquie, was studying Ecuador’s Amazon, so we though it’d be really hardcore and awesome to do a few days in the Amazon, then a night in Quito (elevation 9,350 feet) before attempting a guided summit of Cotopaxi. Mind you, neither of us had any mountaineering experience at this point. I showed up to meet our guide wearing a Jansport backpack and had never seen an ice axe in person before (though the pictures looked SO COOL). With minimal time to adjust to high altitudes, our summit attempt was not limited by our skills and experience (which could have easily been a limiting factor hah), but our unpreparedness. We spent only two days in Quito and didn’t give ourselves time to adjust to higher altitude. Spoiler alert: both Jacquie and I got altitude sickness.
I write this as a reminder to consider altitude when planning hikes/expeditions/outdoor adventures. I now have a few years of experience traveling to higher altitudes without negative affects, but am more aware of the signs to pay attention to. I certainly have NOLS (National Outdoor Leadership School) to thank for this knowledge I gained during my Wilderness First Responder courses (10/10 recommend; more in my posts here!).
Let’s talk about altitude sickness!
Defining High Altitude
- High altitude: 8,000-14,000 feet (2,400-4,200 meters)
- Very high altitude: 14,000-18,000 feet (4,200-5,400 meters)
- Extreme altitude: Above 18,000 feet (5,400 meters)
Basically, altitude can be split into the above categories. It’s important to note that every body feels the affect of altitude at different elevations. This varies between people, but also varies in experiences. Personally, I felt the altitude effects at Cotopaxi’s basecamp (elevation=15,760 feet), but have not since experienced similar Acute Mountain Sickness. In Washington State, I spent about 45 minutes at the summit of Mount Adams (12,280 feet) without any negative side effects.
A Personal Note
Before we dive into sciencey, nerdy fun… let me share my abbreviated story!
When traveling to Mount Cotopaxi in Ecuador, I was unaware of mountain safety and mountaineering techniques. My friend and I had a guide for our trip, but I am not sure our skillset would have allowed us to reach the summit of Cotopaxi. With donning crampons and holding ice axes for the first time, our training in mountaineering safety was limited to a crash course in the snow at our basecamp. At the 15,760-foot base camp, I began feeling the affects of altitude. While we were
playing in the snow *cough* learning really important mountain safety skills, I started getting a headache. Soon after, I was going to the bathroom with the runs (ew gross, sorry for the details). Around 5pm, we sat to eat some food and I could barely eat. I decided I was just nervous about the climb and would be able to eat when we awoke. All of us settled down to sleep around 6pm, as we were waking at midnight (12am) to prepare for our climb. I didn’t sleep at ALL. I kept going to the bathroom to vomit. I was sweating. My head was pounding.
We woke up at midnight to eat. I could barely eat the Cheerios. Everyone else had all this energy. I felt like I was crumbling. We decided to start climbing anyways. I could do this, right? As we began climbing with the light of our headlamps, I was traveling behind my guide. I kept seeing his feet swaying right… left… was he even stepping? Was I even moving? My whole world was dizzy, blurry. I kept falling to the right, uphill. A few times, my guide and friend picked me up. “Be more careful, Kristen.” My head was throbbing more… and more. I could barely focus. “This isn’t safe,” our guide exclaimed (no duh), “We have to rope up.” We roped up, the three of us. Too early. We weren’t even close to the crevasses.
Things didn’t get better. In fact, they only got worse. I was dry heaving (nothing to vomit), my head was pounding, and I couldn’t focus at all. It was not safe. We had to descend. Once we returned to base camp, I was able to sleep. My friend didn’t feel any affect of the altitude for another few hours, then she ended up also getting severely sick (ending up in a hospital in Ecuador). I can’t even explain how good sea level felt after this experience.
I thought to myself, “I guess we could have spent more time at altitude.” Yes, Kristen. Yes you could have. I felt like a failure, but really, I felt like I had a lot to learn.
You live, you learn.
Oxygen Levels at Altitude
At higher altitudes, the barometric pressure in the atmosphere decreases. This means a decrease of pressure in our lung’s alveoli, which bring oxygen into the blood via a pressure differential between the alveoli (higher pressure) and blood (lower pressure). Side note: pressure and concentrations like to move from high to low, so oxygen moves from alveoli to the blood… or from high to low pressure.
Many other things affect the barometric pressure, such as distance from the equator and the season (summer vs. winter). The take home message is: there’s less oxygen at higher altitudes. Science is fun!
Adapting to Altitude
Our body is super awesome. It can adapt to any (most) stresses put on it. So, it’s really good at learning how to be at altitude. We just have to give it the time for acclimatization.
Keeping in mind every body is different, we typically experience the below at higher altitudes:
- Increased respiratory rate (early on, within a few hours of increasing altitude) to deliver more oxygen to the alveoli.
- Increased heart rate (the heart pounding is palpable!), which allows our heart to meet the demand for oxygen in our cells.
- Fluid shifts where our body will constrict the small blood vessels in our lungs (capillaries) to increase blood pressure and increase resistance to flow. Sometimes… this pressure can increase a whole lot and this causes fluid to leak from the capillaries into the lungs (can cause… PULMONARY EDEMA!).
After 3 to 5 days (or more) at altitude, our body undergoes further changes. This is where the altitude training effect can have its advantage for athletes:
- Increased red blood cell production after ~3 to 5 days at altitude to increase the blood’s oxygen carrying capacity.
- Increased 2, 3-DPG Production, which helps with oxygen combining with red blood cells.
- Increased number of capillaries, which helps to diffuse the oxygen between alveoli and the blood.
If we don’t allow our bodies enough time to acclimate to altitude, we can get uncomfortable and/or serious sickness. All the below are considered altitude illness, but range in severity:
Acute Mountain Sickness (AMS) is the most common type of altitude sickness. Signs/symptoms can start 6-36 hours after arrival at an altitude to which we are not acclimated. The main symptom is a headache and can also include malaise, loss of appetite, nausea, vomiting, and disturbed sleep. For this, you can definitely take pain medication for headaches, BUT sedatives should be avoided!
High Altitude Pulmonary Edema (HAPE) is when fluid accumulates in the lungs at altitude and is LIFE threatening. It causes the most deaths from altitude illness. Signs/symptoms to watch out for: Shortness of breath with exertion, which progresses to SHORTNESS OF BREATH AT REST, fatigue, dry cough, the sound of fluid in the lungs.
High Altitude Cerebral Edema (HACE) is accompanied by swelling of the brain and usually occurs over 12,000 feet (3,600 meters). Classic (and scary!) signs of HACE are change in mental status, ataxia, and severe lassitude. This can be observed as decreased coordination, difficulty with walking, or unresponsiveness. These individuals can benefit from oxygen and NEED to descend quickly.
Factors Affecting the Incidence and Severity of Altitude Illness
- Rate of ascent: faster increase in altitude=increased risk of altitude illness.
- Altitude you sleep at: higher altitude for sleeping=higher risk. General rule is “climb high, sleep low” when adjusting.
- Length of exposure: longer stay=higher risk.
- Individual physiology: some people are just made differently and experience different affects at altitude!
- Ego, peer pressure, and schedules: be aware of falling into the pressure to move forward without acclimatizing. Stop ascending until you adjust. Your friends will forgive you later, but your body will thank you NOW!
Treatment of Altitude Illness
- STOP ascent if/when symptoms develop.
- DESCEND if there’s no change in symptoms or they get worse. Go down to altitude you feel good at.
- DESCEND IMMEDIATELY if you have shortness of breath at rest, loss of coordination, or altered metal status.
- DO NOT LEAVE PEOPLE WITH ALTITUDE ILLNESS ALONE!!! In fact, don’t leave ANYONE in the mountains alone.
- Take time for acclimatization to prevent altitude sickness.
- Descend, descend, descend for ANY altitude sickness. The rate at which you descend is the only difference, depending on severity of symptoms.
- Climb high, sleep low.
- Stay hydrated!
- Do not ignore signs and symptoms. Acute Mountain Sickness is not life threatening, but High Altitude Cerebral Edema (HACE) and High Altitude Pulmonary Edema (HAPE) are life-threatening and should be treated as medical emergencies.