Why is there less oxygen at the summits?

In reality, it is not that there is less oxygen. The percentage of this gas in the air remains constant throughout the atmosphere: regardless of the level.

In reality, it is not that there is less oxygen. The percentage of this gas in the air remains constant throughout the atmosphere: whether at sea level or on the tops of mountains, it is always 21%.

What happens is that the higher we ascend, the less air mass we have above our head and, therefore, less pressure, which is the force that the lungs need to be able to absorb that air – and with it, oxygen – through of the trachea.

At the summit of Everest, located 8,848 meters above sea level, the pressure is 0.33 atmospheres, two-thirds less than on the coast, where the atmospheric pressure is 1 atmosphere.

Under these conditions, air barely enters the lungs, and the alveoli do not receive the oxygen they need to incorporate it into the bloodstream and supply it to the muscles and other organs of the body. This deficiency is what produces the famous soroche or altitude sickness, which from 2,500-3,000 meters of altitude translates for many people into extreme fatigue, headache, dizziness, slow digestion, nausea, tachycardia and, in more serious cases, pulmonary edema and even myocardial infarction.

For this reason, most mountaineers who climb eight thousand use supplemental oxygen bottles. Furthermore, before attacking the summit they spend a few weeks of acclimatization between 3,000 and 6,000 meters. In this way, the body increases the production of hemoglobin, the protein that transports oxygen from the lungs to the tissues through red blood cells.