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Why Do We Feel So Funny at High Altitudes?

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There are few things as breathtaking as a hike through the mountains. Sure, the scenery’s gorgeous, but what really makes us gasp for air is the dramatic change in altitude we experience. Even if you’ve never traversed through the Alps, you’ve probably visited a ski town, gone to a tall building’s top floor, or driven through higher terrains. Most of us have been in a high altitude situation and felt its effects—breathlessness, dizziness, and sometimes even headaches. But what makes our bodies react so strongly to high altitudes and perhaps more importantly, when is it a cause for alarm? 

The Air Outside Affects Our Insides
Because we get so short of breath when ascending to higher altitudes, it seems like oxygen’s in shorter supply up there, but that’s not the case. At sea level, the air is condensed due to the atmospheric air pressing down from above. Higher in the atmosphere (like at the tops of mountains), the air isn’t as compressed and oxygen molecules can spread out more. So although the percentage of oxygen in the air remains consistent, increased space between them makes it harder for us to breathe. 

To compensate for the lack of oxygen, our bodies go through acclimatization (also known as acclimation), a series of changes to help us physically adapt to different environments. Once exposed to high altitudes—generally anything 6,500 to 8,000 feet or more above sea level—we automatically start breathing more rapidly and deeply to compensate for the oxygen loss. Our hearts work harder and send blood more quickly to the rest of our bodies. Without acclimatization, we’d experience even more severe high altitude effects. 

Some Discomfort Is Expected …
Even with the body’s adaptive plan, functioning at high altitudes is tough. People have different reactions depending how high they go above sea level; some can’t handle anything above 5,000 feet. And some features of acclimatization actually have negative consequences. For example, the amount of hemoglobin, a protein that transports oxygen, in our blood increases at high altitudes. That means more oxygen can move throughout the body, but hemoglobin also thickens the blood, making it that much harder for the heart to pump it efficiently. 

Side effects like loss of appetite, hyperventilation, increased heart rate, and some swelling in the extremities is considered normal in high altitude situations. People seem to cough more at high altitudes, though scientists aren’t quite sure why. Many sleep poorly due to periodic breathing—switching between deep and light breathing (and sometimes taking an unconscious pause) as a result of lowered carbon dioxide levels in the body and difficulty breathing in general. Plus, our deep sleep stages are significantly shortened at high altitudes, leaving us tired and groggy come morning. 

… But Recognize When It’s Too Much
While some coughing and sleep deprivation are considered “normal” conditions of high altitude situations, some symptoms indicate real sickness that shouldn’t be ignored. Feeling a little ill is common, but depending on the body’s reaction, the altitude, and how quickly that height was reached, that under the weather feeling could turn into one of three illnesses. 

Acute Mountain Sickness
This is the most common high altitude illness and the least dangerous of the three. Its symptoms mirror that of an extremely wicked hangover—upset stomach/vomiting, a bad headache, exhaustion, and some dizziness. 

High Altitude Cerebral Edema
HACE is a more extreme form of acute mountain sickness, except that the terrible headache and dizziness turns into a coma and potentially death. Those with HACE are incoherent and can’t walk steadily. According to, nearly 1 percent of people who go 10,000 feet or more will get HACE

High Altitude Pulmonary Edema
This means that the lungs contain a dangerous amount of fluid that’s blocking oxygen from entering. It can come forty-eight to seventy-two hours after being 8,000 feet or more above sea level. Sufferers start with a cough (sometimes even coughing up fluid), get short of breath without exertion, and have an elevated heart rate. 

Know Before You Go
Why some people are more susceptible to these illnesses isn’t known, but the rate of ascension and height of altitude play a part. The faster you go up into the atmosphere, the more likely you are to get sick. However, there’s one surefire way to get over it—go toward lower altitudes immediately. 

None of this means we should avoid all high altitude expeditions; we’d miss out on some pretty spectacular experiences that way. We just need to differentiate between what’s normal and what’s not when it comes to its effects. If you feel the side effects too much, consider that your body’s warning to take it easy and take the ascent slowly and steadily. You might be in a hurry to reach the peak or push yourself toward the end of the hike, but no view is so amazing it’s worth risking your life over.


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