The majestic Potala Palace, the mysterious Four Girls Mountain, and the towering Mount Everest are dream destinations for every mountain enthusiast. While enjoying the breathtaking scenery and pushing personal limits, altitude sickness often accompanies every climb. Statistics show that a significant proportion of mountaineering accidents are caused by altitude sickness.
With the opening of the Qinghai-Tibet Railway, more and more people can easily reach high-altitude areas, and consequently, more will experience the discomfort of altitude sickness. We should neither fear altitude sickness nor underestimate its dangers. It is hoped that this article will help you develop a correct understanding of it.
Altitude sickness, also known as high-altitude illness, refers to a series of maladaptation symptoms caused when an unacclimatized person rapidly ascends to altitudes above 3,000 meters. Due to the reduced oxygen partial pressure in the atmosphere, the body’s tolerance to low-oxygen environments decreases, making it difficult to adapt and leading to oxygen deficiency. Of course, apart from the factor of high-altitude hypoxia, harsh weather conditions such as wind, rain, snow, cold, and intense ultraviolet radiation can also exacerbate maladaptation and trigger various types of high-altitude maladjustment syndromes.
After a period of acclimatization, the body can undergo a series of adaptive changes—for example, increasing ventilation to help tissues utilize oxygen to near-normal levels; accelerating heart rate and enhancing cardiac pumping capacity to increase blood output per minute and improve hypoxia; and increasing red blood cells and hemoglobin to boost oxygen-carrying capacity and ensure the body’s oxygen supply. However, some individuals are more sensitive to low oxygen partial pressure in the air and have poorer adaptability, resulting in a range of symptoms and functional metabolic changes known as high-altitude maladjustment syndrome, also called acute altitude sickness. Internationally, it is categorized into acute altitude sickness, high-altitude pulmonary edema, high-altitude cerebral edema, high-altitude retinal hemorrhage, and chronic mountain sickness, while China classifies it into acute and chronic high-altitude illnesses. For individuals, the onset is often mixed and hard to distinguish, and during the entire progression, one type of symptom may be more prominent at a certain stage.
Symptoms of Altitude Sickness and Self-Assessment
Some people visiting high altitudes for the first time may experience symptoms such as headache, dizziness, blurred vision, tinnitus, general fatigue, difficulty walking, and trouble sleeping within 24 hours at altitudes of 3,000 meters. In severe cases, symptoms include abdominal bloating, loss of appetite, nausea, vomiting, palpitations, shortness of breath, chest tightness, cyanosis of the face and lips, or facial swelling. When these symptoms occur, staying at the same altitude and resting for 3–5 days, or immediately descending several hundred meters, will usually lead to recovery.
Reports indicate that the incidence of altitude sickness is 37%–51% below 3,500 meters and reaches 50% between 3,600 and 5,000 meters. This shows that the higher the altitude, the greater the incidence of altitude sickness.
Severe altitude sickness can be quite harmful to the human body. Therefore, after entering a high-altitude area, if you experience any of the following symptoms, you should consider that altitude sickness has occurred:
1. Severe headache, palpitations, shortness of breath, chest tightness, loss of appetite, nausea, vomiting, and cyanosis of the lips and fingernails.
2. Confusion and a sudden decline in cognitive ability. This is mainly manifested as difficulty in calculations. Record the time it takes to complete a simple addition problem before entering a high-altitude area, then repeat the same calculation when symptoms appear. If it takes longer than before, it indicates that altitude sickness has occurred.
3. Hallucinations and a sensation of warmth, often walking aimlessly behind others.
Preventive Measures and Medications to Alleviate Symptoms
Before entering a high-altitude area, undergo a thorough medical examination. People with severe anemia, hypertension, or obvious heart, liver, lung, or kidney diseases should avoid high altitudes. Obese individuals, due to their higher oxygen consumption, generally have a greater chance of developing high-altitude illness compared to thinner individuals.
When first entering a high-altitude area, reduce physical activity to protect your heart. Therefore, strictly control the speed of ascent; generally, it is not advisable to ascend more than 1,000 meters in a single day during climbing activities.
From two days before entering a high-altitude area until three days after arrival, taking certain preventive medications orally can help alleviate symptoms of altitude sickness:
Acetazolamide 0.25g, twice daily. Acetazolamide itself has a diuretic effect and is mainly used for cardiac edema, cerebral edema, and peptic ulcers. When taken preventively, it can reduce symptoms of altitude sickness. Side effects of acetazolamide include renal colic, kidney stones, sulfonamide crystaluria, nephrotic syndrome, and agranulocytosis (sulfonamide allergy). Long-term use can lead to low potassium levels in the blood, so potassium supplementation (such as eating oranges or bananas) is needed. It should not be taken by those with hepatic coma or impaired kidney function.
Rhodiola rosea is a medication many people hope will prevent altitude sickness. Its functions include clearing heat and detoxifying, drying dampness, and treating lung heat, pulse heat, epidemic fevers, and limb swelling. In recent years, rhodiola glycosides have been isolated from rhodiola in China, and experiments have shown they have cardiotonic, sedative, blood-pressure-raising, and anti-fatigue effects. Rhodiola extract is used for anti-fatigue purposes, increasing stamina, and aiding recovery from weakness. However, whether it can actually prevent or treat altitude sickness has not been scientifically confirmed by the author.
Depending on the level of hypoxia, dexamethasone 0.75–6mg can be additionally taken, divided into 2–4 doses per day. The primary role of this drug in alleviating hypoxia-related altitude sickness is to increase the content of red blood cells and hemoglobin to enhance oxygen-carrying capacity. Dexamethasone is a glucocorticoid medication, and its indications must be strictly controlled. Misuse of this drug can reduce its effectiveness when it is truly needed for rescue. High doses can cause obesity, increased intraocular pressure, hypertension, and peptic ulcers, bleeding, or even perforation. Especially for those with viral infections, taking glucocorticoid medications can spread and worsen the viral infection.