How much do you know about plateau health? - Understanding the plateau and altitude sickness

Author: Wan Yaqi Qinghai Provincial People's Hospital

Reviewer: Qi Yujuan, Chief Physician, Qinghai Provincial People's Hospital

With its clear blue sky, clear water and pure land, the Qinghai-Tibet Plateau has become a "poetry and distant place" that many people yearn for due to its unique geographical and climatic features. However, the possible altitude sickness often makes people hesitant and discouraged.

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How can you avoid the fate of stopping your trip to the plateau due to the "high altitude" or "turning back" due to the "reverse"? These knowledge about the plateau and altitude sickness may "save" your trip from being aborted.

1. What is a “plateau”?

The definition of "plateau" has always been controversial. Geography describes it this way: "Any highland with an altitude of more than 500 meters, a gentle top, small undulations, and a relatively large area is called a plateau." In medicine, a plateau refers to an area with an altitude of more than 3,000 meters that can cause obvious plateau environment-related body reactions such as headaches, dizziness, and sleep disorders. Obviously, medicine uses 3,000 meters as the boundary of a plateau.

Some international scholars have divided altitude into five levels based on the physiological responses of the human body when exposed to a plateau environment: low altitude, medium altitude, high altitude, ultra-high altitude, and extremely high altitude [1].

(1) Low altitude: The altitude is 500 to 1500 meters. When the human body is exposed to a low altitude environment, there is basically no physiological change.

(2) Medium altitude: The altitude is 1500-2500 meters. When a person enters a medium altitude area, there are generally no symptoms or mild symptoms, such as only a slight increase in breathing and heart rate, a slight decrease in exercise capacity, and basically normal pulmonary gas exchange.

(3) High altitude: The altitude is 2500-4500 meters. Most people will experience varying degrees of hypoxia when entering this altitude area, such as increased breathing and heart rate, headache, loss of appetite, poor sleep, arterial oxygen saturation below 90%, and even acute mountain sickness.

(4) Ultra-high altitude: The altitude is 4500-5500 meters. When entering ultra-high altitude areas, the body's hypoxia symptoms will be further aggravated, arterial oxygen saturation is usually less than 60%, and severe hypoxemia will occur during exercise and sleep at night. Adults should adopt a step-by-step or staged adaptation method when in this altitude area, otherwise they are prone to severe acute altitude sickness such as high-altitude pulmonary edema and high-altitude cerebral edema.

(5) Extremely high altitude: Altitude > 5,500 meters. When entering this altitude area, the body's physiological functions will be progressively disturbed, the body's internal environment self-regulation function will be lost, and extremely severe altitude sickness, significant hypoxemia and hypocapnia will occur. Arterial oxygen saturation is often below 50%, and additional oxygen supply is required to maintain the body's normal physiological functions.

2. What is altitude sickness?

Altitude sickness refers to a series of uncomfortable symptoms that occur after reaching a certain altitude (usually above 2,500 meters) because the body cannot adapt well to the environmental changes due to dry and cold air, strong ultraviolet rays, and the low pressure and low oxygen environment of the plateau.

There are certain individual differences in altitude sickness, and there is no clear diagnostic standard. The manifestations, severity, and symptoms of each person are not completely consistent. The higher the altitude at which you enter the environment, the greater the possibility of altitude sickness, and the more severe the clinical symptoms may be. Some studies [2] have found that the occurrence of altitude sickness varies with seasons and ages, with winter being higher than summer and young people being higher than the elderly. Another study [3] found that the incidence of altitude sickness is positively correlated with the body mass index of men, but not with the body mass index of women. In other words, obese men are more likely to experience altitude sickness, which may be related to hormone levels and oxygen consumption.

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Altitude sickness can affect the whole body system. The main symptoms include headache, dizziness, insomnia, fatigue, blurred vision, tinnitus, and even nausea, vomiting, chest tightness, dyspnea, palpitations, edema, etc. The most common manifestation is headache. It is important to remind people with hypertension, intracranial aneurysms, and risk factors for cerebrovascular disease (such as smoking, diabetes, hyperlipidemia, family history of cerebrovascular disease, etc.) who suddenly have severe headaches in plateau areas. The possibility of acute cerebrovascular disease, such as cerebral hemorrhage and cerebral infarction, cannot be completely ruled out. It is recommended to seek medical attention as soon as possible.

If you experience altitude sickness during your trip, don't panic. Once altitude sickness occurs, the first thing to do is to actively breathe oxygen and lower the altitude of the environment as soon as possible. In simple terms, it means "going lower." However, it should be noted that a small number of people still suffer from severe acute mountain sickness, such as high-altitude pulmonary edema and high-altitude encephalopathy, which endanger their lives and health. Therefore, before starting a plateau journey, you must fully assess your physical condition and be fully prepared before setting off.

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References

[1]Luks AM, Swenson ER, Bartsch P. Acute high-altitude sickness[J]. European Respiratory Review An Official Journal of the European Respiratory Society, 2017, 26(143):160096.

[2]Liu JC, Yu FF, Song H. Application of SARIMA model in forecasting and analyzing inpatient cases of acute mountain sickness[J]. BMC Public Health, 2023, 23(1):56.

[3]Carlo Vignati, Massimo Mapelli, Benedetta Nusca, et al. A Breathtaking Lift: Sex and Body Mass Index Differences in Cardiopulmonary Response in a Large Cohort of Unselected Subjects with Acute Exposure to High Altitude[J]. High Alt Med Biol, 2021, 22(4): 379-385.