Altitude Sickness: Causes, Symptoms, Prevention and Treatment

~Introduction

Altitude sickness, also known as acute mountain sickness (AMS), is a health condition that occurs when individuals ascend to high altitudes too quickly, where oxygen levels are significantly lower than at sea level. It primarily affects people traveling or climbing to altitudes above 2,500 meters (8,000 feet). The body struggles to adapt to the reduced air pressure and oxygen availability, leading to a range of symptoms from mild discomfort to life-threatening complications.

With the growing popularity of adventure tourism, trekking, mountaineering, and high-altitude expeditions, altitude sickness has become a concern not only for mountaineers but also for tourists visiting high-altitude destinations like the Himalayas, Andes, Alps, and Rocky Mountains. Understanding its causes, symptoms, risk factors, prevention, and treatment is essential for safe travel and survival in high-altitude environments.

~Understanding Altitude and Oxygen Levels

The air we breathe contains about 21% oxygen, regardless of altitude. However, as we climb higher, the atmospheric pressure decreases, making oxygen molecules less available to our bodies. This condition is called hypobaric hypoxia.

At sea level, the atmospheric pressure is around 760 mmHg.
At 3,000 meters (10,000 feet), the pressure drops to about 523 mmHg, reducing oxygen availability by almost one-third.
At extreme altitudes (above 8,000 meters or 26,000 feet, often called the “death zone”), the oxygen is so scarce that survival without supplemental oxygen becomes nearly impossible.

The body needs time to adjust to these changes. When ascent is too rapid, adaptation fails, and altitude sickness develops.

~Types of Altitude Sickness

Altitude sickness is broadly categorized into three main types:

1. Acute Mountain Sickness (AMS)

This is the most common and mildest form of altitude sickness. Symptoms resemble those of a hangover and usually appear within 6 to 12 hours of arrival at high altitude.

Symptoms include:

Headache
Dizziness
Fatigue
Shortness of breath
Loss of appetite
Nausea and vomiting
Sleep disturbances

While not usually life-threatening, AMS can progress to more severe forms if ignored.

2. High-Altitude Cerebral Edema (HACE)

HACE is a severe, potentially fatal condition caused by swelling of the brain due to fluid leakage. It usually occurs in individuals who continue ascending despite having AMS symptoms.

Symptoms include:

Severe headache
Confusion or disorientation
Loss of coordination (ataxia)
Hallucinations
Coma in advanced stages

Without immediate descent and medical intervention, HACE can be fatal.

3. High-Altitude Pulmonary Edema (HAPE)

HAPE is another life-threatening condition where fluid accumulates in the lungs, making breathing extremely difficult. It can occur independently or along with AMS/HACE.

Symptoms include:

Severe shortness of breath, even at rest
Persistent cough producing frothy or pink sputum
Rapid heartbeat
Chest tightness
Cyanosis (bluish discoloration of lips and skin)

HAPE is a medical emergency and requires immediate descent and oxygen therapy.

~Causes of Altitude Sickness

The primary cause of altitude sickness is the body’s inability to adapt quickly to reduced oxygen levels. Several factors contribute to its development:

Rapid Ascent – Climbing too fast without allowing time for acclimatization is the biggest risk factor.
Altitude Reached – The higher the altitude, the greater the risk.
Physical Exertion – Overexertion increases oxygen demand, worsening symptoms.
Individual Susceptibility – Some people are genetically more vulnerable.
Dehydration – Dry air and increased urination at high altitudes contribute to dehydration, worsening symptoms.
Pre-existing Conditions – People with lung or heart diseases may be at higher risk.

~Risk Factors

Not everyone exposed to high altitude develops altitude sickness. However, certain groups are more at risk:

People ascending above 2,500 meters rapidly
Those with a previous history of altitude sickness
Young, physically fit individuals who may push themselves harder
Climbers not allowing rest days for acclimatization
Tourists traveling by airplane directly to high-altitude destinations (e.g., flying into Lhasa, Tibet, or La Paz, Bolivia)

~Symptoms and Clinical Features

Symptoms usually appear within 6–24 hours of arrival at high altitude and can worsen at night.

Mild to Moderate AMS Symptoms:

Headache (most common)
Nausea, vomiting
Fatigue and weakness
Dizziness or lightheadedness
Loss of appetite
Difficulty sleeping

Severe AMS / HACE Symptoms:

Severe headache unrelieved by medication
Confusion, memory loss, poor judgment
Ataxia (clumsy walking, inability to balance)
Altered consciousness, stupor, or coma

HAPE Symptoms:

Shortness of breath at rest
Inability to walk uphill due to breathlessness
Cough with frothy sputum
Crackling sounds in lungs when breathing
Severe fatigue and weakness

~Diagnosis

Altitude sickness is primarily diagnosed based on history and symptoms, since specialized equipment may not be available in remote areas. However, some useful diagnostic tools include:

Pulse Oximetry: Measures blood oxygen levels (low levels indicate hypoxia).
Chest X-ray: Helps detect pulmonary edema in HAPE.
Neurological Examination: Assesses balance and mental function for HACE.

~Prevention of Altitude Sickness

Prevention is the best approach to avoid altitude sickness. Some well-established strategies include:

1. Gradual Ascent

Do not ascend more than 300–500 meters (1,000–1,600 feet) per day above 2,500 meters.
Rest for a day after every 1,000 meters of ascent.

2. Acclimatization

Spend a few days at intermediate altitudes before going higher.
Engage in light physical activity during acclimatization.

3. Stay Hydrated

Drink enough fluids but avoid excessive alcohol and caffeine, as they cause dehydration.

4. Balanced Diet

Eat a high-carbohydrate diet, which provides quick energy and reduces oxygen demand during metabolism.

5. Avoid Overexertion

Climb slowly and avoid strenuous exercise in the first 24–48 hours.

6. Medications for Prevention

Acetazolamide (Diamox): Helps speed acclimatization by stimulating breathing.
Dexamethasone: Steroid used in high-risk cases.
Nifedipine: Prevents HAPE in individuals prone to it.

7. Supplemental Oxygen

Oxygen cylinders or portable hyperbaric chambers can be life-saving in emergencies.

~Treatment of Altitude Sickness

The gold standard treatment is immediate descent to a lower altitude. Other supportive measures include:

1. For AMS

Rest and avoid further ascent.
Acetazolamide for symptom relief.
Pain relievers (ibuprofen or paracetamol) for headache.
Antiemetics for nausea and vomiting.

2. For HACE

Immediate descent of at least 500–1,000 meters.
Oxygen therapy.
Dexamethasone to reduce brain swelling.
Portable hyperbaric chamber if descent is not possible.

3. For HAPE

Immediate descent.
Oxygen therapy or portable hyperbaric chamber.
Nifedipine to lower pulmonary artery pressure.
Rest and avoid physical exertion.

~Complications of Untreated Altitude Sickness

If ignored, altitude sickness can lead to:

Permanent brain damage due to cerebral edema
Pulmonary failure due to fluid accumulation in lungs
Death in severe cases of HACE and HAPE

~Famous Cases and Real-Life Relevance

Altitude sickness has claimed the lives of many trekkers and climbers, including on Mount Everest, K2, and other peaks. Even professional climbers are not immune. In recent years, an increasing number of tourists flying directly to high-altitude cities like La Paz (3,640 m) or Lhasa (3,650 m) have also reported AMS symptoms. This highlights the universal nature of the condition.

~Research and Advances

Modern research focuses on:

Genetics of hypoxia tolerance: Why some people adapt better than others.
Pharmaceutical interventions: Developing better drugs to prevent or treat AMS.
Portable medical devices: Improved oxygen delivery systems and lightweight hyperbaric chambers.

~Conclusion

Altitude sickness is a significant medical challenge for climbers, trekkers, and travelers to high-altitude regions. While mild cases of AMS are common and usually resolve with rest and acclimatization, severe forms like HACE and HAPE can be fatal without prompt intervention. The best defense against altitude sickness remains gradual ascent, proper acclimatization, hydration, and awareness of early symptoms.

With proper education, preparation, and timely action, the risks of altitude sickness can be minimized, allowing adventurers to safely explore the breathtaking beauty of the world’s high mountains.

Health Lines

Friday, August 22, 2025