For those of you who have had the opportunity to experience it for yourself, how many times have you been short of breath as you climbed a mountain? That… "I'm short of breath." Popularly called as, altitude sickness or soroche. It is that physical discomfort that can manifest itself with a headache, weakness or even nausea. It is often popularly attributed to missing oxygen as we go up.
Well no, neither is it missing nor is it excess The oxygen remains the same, there is always 21% whether we go down or up.. But ... climbers and mountaineers who climb great peaks like Everest ... Don't carry oxygen bottles? Yes it is. At this point, you may have a headache. The key factor is not oxygen but, the amount of air we have on top. Atmospheric pressure.
How does atmospheric pressure influence lack of air?
As there is less pressure, causes our lungs to need to make a greater effort to absorb air through the trachea. And with it, oxygen.
As a good example, we can take The Everest. With its almost 9.000 meters high, its atmospheric pressure at the top is 0,33 compared to 1 at sea level. With that pressure, it is the air that barely enters the lungs, and it takes a very great overexertion to be absorbed. The alveoli can barely take in oxygen to carry it into the bloodstream. It is precisely there, where this lack, causes all physical ailments. In the most serious cases, pulmonary edema and even myocardial infarctions.
It's hard to imagine right? Air is still air and may not be too light. Another analogy. Imagine the wheel of a bicycle filled with air. You have to "swell it up a lot", put it more pressure, that is, more air. With so much air pressure, will there be more oxygen, right, in that volume? Also, if we open our mouths (don't try it!) Into a hole, it would go in alone without almost sniffing it.
When you find yourself in those situations, you know. It's not that oxygen is lacking and stay lower, is that you cannot absorb more.