Longing to stand on the peak of a high mountain, looking down at the magnificent sea of clouds and rolling ridges, but feeling inexplicably nervous at the mere mention of “altitude sickness”?
What is High-Altitude Illness? Is it Related to Physical Fitness?
Many people believe that having good physical fitness and regular exercise habits prevents altitude sickness.
Altitude sickness has absolutely nothing to do with your physical fitness.
A marathon runner is not necessarily better at adapting to high altitudes than an average person, because the cause of altitude sickness is thin air and decreased oxygen partial pressure, unrelated to muscle endurance.
When we climb to altitudes above 2,500 meters, atmospheric pressure drops, causing oxygen molecules in the air to become sparse.
Taking 3,000 meters above sea level as an example, the oxygen content at the peak is only about 70% of that at sea level.
If the speed of ascent is too fast, the cardiopulmonary function and blood system fail to adapt to this sudden hypoxia, and the organs in the body will begin to protest.
This is High-Altitude Illness (or Altitude Sickness).
Three Classifications of Altitude Sickness
Based on severity and the affected organs, high-altitude illness is classified into three types:
| Type | English | Core Symptoms | Danger Level |
|---|---|---|---|
| Acute Mountain Sickness (AMS) | Acute Mountain Sickness | Headache, accompanied by nausea, dizziness, insomnia, weakness | Most common, resolves on its own for most people |
| High-Altitude Cerebral Edema (HACE) | High-Altitude Cerebral Edema | Unsteady gait (ataxia), confusion, lethargy, coma | Extremely dangerous, can be fatal within 24 hours |
| High-Altitude Pulmonary Edema (HAPE) | High-Altitude Pulmonary Edema | Shortness of breath even at rest, dry cough, pink frothy sputum | Highest mortality rate, requires immediate treatment |
Acute Mountain Sickness (AMS) is the most common type, usually appearing within 1 to 12 hours after arriving at high altitude, experienced by about 25% to 50% of travelers.
For most people, symptoms relieve within 2 to 3 days after the body adapts, but if it continues to worsen, it may progress to fatal cerebral edema (HACE) or pulmonary edema (HAPE).
Is a Headache Just a Cold? Never Think This Way in the Mountains
Early symptoms of altitude sickness are very similar to many common illnesses:
| Common Misjudgment | Real Symptoms of Altitude Sickness |
|---|---|
| Thought to be a cold | Headache, general fatigue, nausea |
| Thought to be a hangover | Throbbing headache, insomnia, loss of appetite |
| Thought to be motion sickness | Dizziness, vomiting |
| Thought to be exhaustion | Weakness, decreased athletic performance |
In the mountains, any headache must be treated as altitude sickness first, unless proven to be caused by other reasons.
Many mountaineering accidents are actually related to altitude sickness. Because high-altitude cerebral edema causes unsteady gait leading to falls off cliffs, and the weakness of acute mountain sickness makes people move slowly, failing to reach camp in time and causing hypothermia.
Never ignore symptoms just because you think it is “just a mild cold,” missing the best timing for descent.
Who is Prone to Altitude Sickness? Who are the High-Risk Groups?
The primary risk factors for altitude sickness are related to genetics and ascent speed:
| Risk Factor | Explanation |
|---|---|
| Rapid ascent | The primary risk factor, ascending to altitudes above 2,800 meters within one day |
| History of altitude sickness | People who have experienced it before have a higher chance of recurrence |
| Individual genetic makeup | Natural adaptation speed to hypoxic environments varies from person to person |
| Unresolved cold/respiratory infection | Going uphill with airway inflammation can cause altitude sickness to worsen directly into pulmonary edema |
| Staying up late or extreme fatigue | Autonomic nervous system dysfunction reduces the body’s ability to regulate hypoxia |
The following groups are not recommended to travel to areas above 2,500 meters:
- Patients with unstable
angina - Patients with
pulmonary hypertension - Patients with severe
chronic obstructive pulmonary disease (COPD) - Patients with
sickle cell disease
Having no issues last time does not mean you will be fine this time.
Altitude adaptability is not always the same for every individual, and colds or staying up late can reduce your adaptability to zero.
How to Prevent Altitude Sickness? The "2500+300 Rule" and "Climb High, Sleep Low"
Prevention is key. Slowly ascend to allow the body to adapt.
Core Speed Guide
| Rule | Explanation |
|---|---|
| First Night Altitude Control | On the first day of entering high altitude, keep the overnight altitude below 2,500 to 2,800 meters as much as possible |
| Daily Sleep Altitude Control | Above 3,000 meters, the net increase in sleeping altitude per night should not exceed 300 to 500 meters |
| Forced Rest Every 3 Days | After the sleeping altitude has risen continuously for 1,000 meters, stay one more night at the same altitude to adapt |
Climb High, Sleep Low
During the day, you can climb higher to stimulate the body’s response mechanisms, but at night you should descend to a lower altitude to sleep, allowing the body to recover in an environment with higher oxygen content.
The golden rule of mountaineering: "Climb high, sleep low."
Pre-trip Preparation Checklist
| Preparation Item | Explanation |
|---|---|
| Travel Medicine Clinic | Consult a physician before departure to evaluate the need for preventive medication (such as Acetazolamide) |
| Acclimatization in Advance | Stay in areas above 2,750 meters for 2 or more days within 30 days prior to departure |
| Layering Clothing System | Moisture-wicking base layer, warm middle layer, and windproof/waterproof outer layer |
| High-Carb Diet | Carbohydrates consume less oxygen than fats; replenish sugars anytime during the hike |
| No Alcohol and Smoking | Alcohol and sedatives suppress the respiratory center, worsening hypoxia |
General Precautions at High Altitudes
At high altitudes, besides controlling the speed of ascent, daily behaviors also need adjustment:
| Behavioral Control | Explanation |
|---|---|
| Reduce Strenuous Activities | Strenuous exercise accelerates blood oxygen consumption; slow down your pace and stabilize your breathing |
| Keep the Body Warm | Low temperatures increase pulmonary arterial pressure; use the layering system to dress up when cold and de-layer when warm |
| High-Carb Diet | Carbohydrates consume less oxygen than fats; replenish sugars anytime during the hike |
| Avoid Gas-Producing Foods | Foods like beans and carbonated drinks expand and bloat in the gastrointestinal tract under low air pressure, causing discomfort, which affects breathing and appetite |
| Actively Replenish Water | High-altitude air is dry, and rapid breathing causes significant water loss; replenish water in small amounts and multiple times |
| Monitor Yourself and Teammates | Physical conditions can change at any time in high altitudes; do not push yourself, and rest or descend immediately if you feel unwell |
What to Do When Altitude Sickness Occurs? "Descend, Descend, and Descend"
Lowering altitude is the most effective and only way to treat altitude sickness.
| Severity | Symptoms | Treatment |
|---|---|---|
| Mild | Headache, nausea | Stop ascending, rest and observe at the same altitude; take pain relievers to alleviate |
| Moderate | Vomiting, worsening headache | If no improvement after resting for 24 hours, descend immediately |
| Severe | Ataxia (unsteady gait), rest dyspnea | Descend immediately by at least 500 to 1,000 meters, while administering oxygen |
Medications, oxygen cylinders, and Portable Altitude Chambers (PAC) are only "time-buying" tools to keep the patient stable until they can safely descend.
Never continue to push uphill just because symptoms are temporarily relieved after taking medication or inhaling oxygen.
When there is an issue with your body at high altitude, you must remember the "3D" formula:
Down, Down and Down (Descend, descend, and descend).
Never leave a person with altitude sickness alone; they must be accompanied by at least one teammate who is familiar with the route and possesses basic medical knowledge to descend.
The mountains will always be there.
Be fully prepared, do not rush, listen to your body, and everyone can safely enjoy the beauty of high altitudes.