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How the body adapts to altitude
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A lot of people think mountain air has less oxygen in it. It does not: the proportion of oxygen in the air is the same up there as it is at sea level. What changes is atmospheric pressure, the force pushing that air into your lungs. Picture the same faucet opened exactly the same amount, but with very little pressure in the pipe: the same water comes out, it just arrives with less push.
Because it arrives with less push, less oxygen crosses into the blood. The body picks this up at the carotid body, a sensor in the neck that is the main gauge of the oxygen in your blood, and that sensor makes you breathe faster.
People whose families have lived up high for generations do not all adapt the same way. Tibetans do it with a blunted response in the production of red blood cells, while Andeans rely on maintaining a higher level of hemoglobin, the protein that carries oxygen inside the red blood cell.
And there is an altitude where this tends to start: in most people hypoxemia, meaning low oxygen in the blood, shows up between two thousand and three thousand meters.
In brief
At altitude the air holds the same proportion of oxygen; what drops is the atmospheric pressure driving it.
The same air, but reaching the lung with less force.
That drop pulls down arterial oxygen pressure, and the carotid body, the main sensor, responds by raising the respiratory rate.
High-altitude populations adapt differently: Tibetans with a blunted erythropoietic response, Andeans with more hemoglobin.
Hypoxemia usually begins between 2,000 and 3,000 meters.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingHigh-Altitude Oxygenation, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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