The Effects of Altitude on the Brain (Altitude Sickness on Mt Everest)

What is altitude sickness?
Altitude sickness is the term for medical conditions that can happen when you move to a higher altitude too quickly. The higher up you go, the thinner the atmosphere gets. That means breathing in the same amount of air gets you less oxygen than at a lower altitude. Altitude sickness happens when your body has trouble adjusting to the difference in how much oxygen you’re getting with each breath.
Types of this condition
Altitude sickness can refer to three distinct conditions:
Acute mountain sickness (AMS). This is the mildest and most common form of altitude sickness.
High altitude pulmonary edema (HAPE). This is when altitude sickness affects your lungs, causing them to fill with fluid. It’s a medical emergency that needs immediate medical attention. While not the most severe form, it can cause death faster than other forms of altitude sickness.
High altitude cerebral edema (HACE). This is the most severe form. It happens when altitude sickness causes your brain to swell. It’s a very dangerous condition that needs emergency care.
How common is altitude sickness?
Altitude sickness is common among people who aren’t acclimated, meaning they’re not used to breathing at high altitudes. AMS is rare below 8,000 feet (2,438 meters) above sea level. Almost everyone who ascends quickly to 11,000 feet (3,352 meters) will develop AMS.
Symptoms and Causes
What are the symptoms of altitude sickness?
Altitude sickness can cause many symptoms, and these can vary depending on the severity. The symptoms of acute mountain sickness usually appear within the first day or so of reaching a high altitude. More severe forms like HAPE or HACE take longer to appear, usually between two and five days.
The symptoms of AMS include:
Headache (this is the most common symptom).
Nausea and vomiting.
Loss of appetite.
Fatigue, even when resting.
Malaise (a noticeable “unwell” feeling).
Trouble sleeping.
Dizziness or lightheadedness.
Vision changes (while rare, these usually indicate more severe altitude sickness, and are due to blood vessel ruptures in your retinas).
What causes altitude sickness?
Given time, your body can usually adapt to altitude-related changes that affect how much oxygen you get with each breath. Without enough time to adapt, altitude sickness is the result.
What are the risk factors for altitude sickness?
The risk factors for altitude sickness often relate to the altitude itself or how you get there.
Higher altitudes: The higher you go, the greater your risk for altitude sickness.
Speed of ascent: Getting to a higher altitude quickly increases your risk of developing altitude sickness. People who fly to high altitudes rather than walk, hike or drive are much more likely to develop it. Above 8,000 feet, you should ascend no more than 1,640 feet (500 meters) per day.
Alcohol and drug (medical and nonmedical) use. Drinking alcohol or using certain medications, especially sedatives (either medical or nonmedical), can greatly increase the chances of developing altitude sickness.
History of altitude sickness. Having any form of altitude sickness, especially the more severe forms like HAPE or HACE, increases your risk of having it in the future.
A common misconception is that your physical health is a risk factor for developing altitude sickness. It isn’t, but altitude sickness can make symptoms of some existing conditions worse. Examples include anemia and chronic obstructive pulmonary disease (COPD).
How is altitude sickness treated, and is there a cure?
There’s only one way to “cure” altitude sickness outright: descend to a lower altitude.
Several treatments can help altitude sickness when it’s not as severe. Some of these are also helpful when an immediate descent isn’t possible. Treatment approaches include:
Stop and acclimate. Stopping and resting is a good idea at the first signs of altitude sickness.
Descend. If symptoms are more severe (such as additional dizziness, fatigue or nausea) or get worse, descending is a top priority. Most experts recommend descending until the symptoms get better. This usually involves a decrease of at least 984 feet (300 meters) and as much as 3,281 feet (1,000 meters).
Supplemental oxygen. Breathing higher concentrations of oxygen can help offset some of the symptoms of altitude sickness.
Medications. Certain medications, especially acetazolamide, dexamethasone or nifedipine, can treat altitude sickness and delay more severe symptoms or complications. Dexamethasone and nifedipine are generally reserved for moderate or worse altitude sickness.
Hyperbaric therapy. This is similar to treating a scuba diver with decompression sickness (better known as “the bends”). At high altitudes, hyperbaric therapy is possible with portable hyperbaric bags (sometimes known as “Gamow bags” after their inventor, Igor Gamow). These can delay the worsening of symptoms until it’s possible to evacuate a person to a lower altitude.