Altitude sickness is a condition of oxygen deficiency

Climbing high mountains (generally defined as an altitude of over 2500 meters) is a desire for many people, but besides being affected by weather, physical strength, and other factors, mountain sickness is another dangerous factor.

We know that the air pressure at sea level is 760mmHg and the oxygen concentration is 21%. The higher the altitude, the lower the air pressure, but its oxygen concentration (percentage) remains unchanged. For example, at an altitude of 5500 meters and a pressure of 379mmHg, although the oxygen concentration is still 21%, the amount of oxygen contained in it is only 46% of that at sea level. In this way, the oxygen concentration in the blood also decreases, and in severe cases, it can become tissue hypoxia.

    最常见的高山症症状是：头痛、恶心、呕吐、疲倦、虚弱、眩晕及无法入睡。这些症状，有时和感冒症状有些类似，不少人在登高山，有了高山症，却 以为自己是感冒或者水土不服，但其实是得了急性高山症。

所以说，高山症就是典型的缺氧造成的症状。

    一部分人的这些症状一两天后会减轻，但也有一部分人因劳累、受寒和上呼吸道感染等原因，症状可能逐渐加重，发展成为高原肺水肿或高原脑水肿。人们常常提倡用吸氧来缓解不适。