Altitude Sickness

Have you ever taken a day trip up the mountains only to feel woozy, nauseated, and out of breath? That’s called altitude sickness my friends, and it’s a real problem for both beginner mountaineers and experienced climbers alike.

If you’re planning a camping trip or a hike up your local peak, then you’ll need to know all about Acute Mountain Sickness (aka altitude sickness), its symptoms, and how to prevent and treat it effectively so that you can enjoy the mountains without feeling hungover.

What is Altitude Sickness, How is it Caused, and What are its Symptoms?

It goes without saying that every cell in the human body requires oxygen to function properly. Under normal circumstances, a healthy individual’s blood will contain a Partial Pressure of Oxygen level of 95-100%. Partial Pressure of Oxygen, or PO2, stands for the amount of dissolved oxygen in the blood. When levels drop between 94-90%, you will start to feel the first signs of altitude sickness.

Altitude sickness is like feeling hungover. You might have a headache, feel thirsty, feel a bit nauseated, and have a lack of energy due to low PO2 levels in your blood. Low oxygen levels at high altitudes cause your body to produce more hemoglobin (the protein responsible for carrying oxygen) in order to help the body acclimatize. When this happens too quickly, like when climbing a high mountain in a short amount of time, your blood ends up getting thicker and stickier as more and more hemoglobin is produced. This thick blood makes it harder for your heart to deliver oxygen-rich blood to your cells.

As you ascend into higher altitudes, oxygen becomes less and less available as the air becomes thinner. In addition to producing more hemoglobin, the body tries to adapt to these changes by raising blood pressure, elevating heart rate, and increasing heavy breathing in order to up the oxygen levels in your blood.

However, the higher up in elevation you go, the higher the demands become on your body to get that oxygen. At sea level, the air contains 20.9% oxygen. If you’re climbing a peak like Mt. Kilimanjaro  which resides at about 14,000 feet, the amount of effective oxygen in the air is only 11.9%. That’s practically HALF the amount of oxygen your body is used to getting!

When it becomes too difficult for the body to keep up with the oxygen levels your cells need, that’s when altitude sickness begins to occur.

High altitude is considered anything over 5000 feet (1500 meters) above sea level. Altitude sickness can occur anywhere from 8000 feet (2500 meters) and higher due to rapid ascent and decreased oxygen availability.

Symptoms can progressively get worse as you climb higher if you don’t descend to lower elevation or treat symptoms once they begin.

Symptoms of Altitude Sickness

Altitude sickness does not affect everyone. In fact, it only affects about 20% of people who reach elevations of 10,000-14,000 feet. Anything above that, and the percent of those affected can rise to 50% or more.

For those who ascend too fast in a short amount of time (generally 1,500 feet or more in 24 hours) and are dehydrated, out of shape, or suffer from breathing conditions like asthma, you will be more at risk of developing altitude sickness.

However, keep in mind that even the most athletic and most experienced mountaineers are susceptible to altitude sickness, it really just depends on how well your body is acclimating to the change in elevation

So, what are the symptoms of altitude sickness?

• Breathlessness (keep in mind that breathlessness while at rest is definitelyconsidered a sign of AMS)
• Clumsiness
• Confusion
• Dizziness
• Fever
• Headache
• Heart palpitations
• Impaired thinking and concentration
• Insomnia
• Lethargy
• Loss of appetite
• Nausea
• Stumbling
• Swelling of the extremities
• Vomiting

At around 8,000 feet, symptoms of altitude sickness can start within the first 2-12 hours but can dissipate within a day or two as your body acclimatizes to the altitude.

Symptoms are generally worse at night as your body naturally uses less oxygen while asleep. In fact, it’s recommended that you sleep at lower elevations for this reason especially if you are already showing signs of altitude sickness. For example, if you climb to 10,000 feet, you should sleep at 8,500 feet in order to prevent or alleviate any symptoms

The most prominent symptoms of mild altitude sickness include headache, breathlessness, lack of appetite, and trouble sleeping. These are the early signs that you need to up your water intake and allow yourself to take it easy. There is no reason to rush up a mountain if your body is telling you to slow down!

If you experience nausea, lethargy, vomiting, or worse, it’s really important that you descend to a lower elevation as soon as possible until symptoms improve or seek medical attention. The only way to cure altitude sickness is to get to where there is more oxygen.

The Golden Rules

1. If you feel unwell, you have altitude sickness until proven otherwise
2. Do not ascend further if you have symptoms of altitude sickness
3. If your symptoms are getting worse, descend immediately
4. If you climb high, sleep low
5. STAY HYDRATED to keep your blood from becoming too viscous

Types of Altitude Sickness

In case you didn’t think regular ol’ altitude sickness wasn’t bad enough, there are actually different types of altitude sickness.

Acute Mountain Sickness (AMS)

Acute mountain sickness, or AMS, is the mildest form of altitude sickness that can often afflict hikers, high-altitude skiers, and tourists visiting popular high elevation destinations like Mt. Kilimanjaro 

The symptoms for AMS are akin to a bad hangover – headache, insomnia, dizziness, fatigue, and loss of appetite.

This is the most common form of altitude sickness, and can be easily overcome by upping your hydration levels and taking it easy.

High-Altitude Cerebral Edema (HACE)

On rare occasions, AMS may develop into high-altitude cerebral edema where the brain swells with fluid, resulting in severe impairment. If the swelling goes untreated, it will cause death by brain herniation within 48 hours.

It goes without saying that HACE is considered to be an extreme form of altitude sickness due to low oxygen levels affecting the brain and the ability to think clearly. In fact, people who develop HACE may not even realize that something is “off” about their behavior which is why it’s so important to hike in groups so you can buddy up and keep an eye on one another.

It is estimated that one percent of people who ascend to 13,000 feet (4,000 meters) or more may develop HACE.

The initial symptoms of HACE commonly include confusion and an altered mental state, rapid heartbeat, and possible loss of consciousness. Those who suffer from this form of AMS will attempt to cease all physical movement and will often have trouble sitting up. Early recognition is key because as HACE progresses, the sufferer becomes unable to descend without assistance.

The most common symptoms of HACE include:

• Changes in normal behavior
• Coma (in advanced cases)
• Confusion
• Exhaustion
• Extreme fatigue
• Visual hallucinations
• Walking with a stagger
• Worsening headache that does not respond to OTC medications
• Vomiting

One of the best ways to prevent HACE is to keep yourself from ascending more than 3,300 feet a day too quickly at high elevations.

Those suffering from HACE should be brought to lower elevation as soon as possible for medical attention and provided supplemental oxygen.

High-Altitude Pulmonary Edema (HAPE)

HAPE is another severe form of altitude sickness where fluid accumulates in the lungs either in the lung tissue itself or in the spaces used for gas exchange in otherwise healthy individuals at altitudes above 8,200 feet. This means that the lungs are less able to exchange oxygen and carbon dioxide properly and the sufferer cannot get enough oxygen to function properly. It is the leading cause of death related to high altitude exposure.

While still a rare occurrence, it’s important to recognize symptoms of HAPE.

These symptoms include (typically a combination of at least two):

• Blue skin color (lips and fingernails)
• Chest tightness
• Collapse
• Coma (in advanced cases)
• Confusion
• Congestion
• Cough
• Difficulty breathing at rest
• Difficulty walking or inability to keep up with others
• Fever of 101 degrees or higher
• Profuse perspiration
• Rapid heart rate
• Rapid shallow breathing
• Weakness and decreased physical performance
• Wheezing, crackling, or gurgling noises while breathing in at least one lung field (listen with your ear pressed against the sufferer’s chest)

Men and those with sleep apnea are more susceptible to developing HAPE. It is also important to note that HAPE can develop without the traditional signs of altitude sickness.

Using an oximeter to track your arterial oxygen levels is a great way to keep track of your blood oxygen percentage. Typically, an arterial saturation of 90% or more will begin to lessen severity and symptoms.

If you suspect HAPE, it’s important to descend as soon as possible and administer oxygen treatment.