What are the best strategies for preventing altitude sickness?

Best Strategies for Preventing Altitude Sickness

The most effective strategy for preventing altitude sickness is slow ascent, with a recommended rate of 300-600 meters per day above 2500 meters, combined with rest days for every 600-1200 meters gained. 1

Understanding Altitude Sickness

Altitude sickness occurs due to hypobaric hypoxia at elevations typically above 2500 meters (8200 feet). It encompasses:

• Acute Mountain Sickness (AMS): Headache, nausea, fatigue, dizziness, poor sleep
• High Altitude Pulmonary Edema (HAPE): More serious condition with pulmonary symptoms
• High Altitude Cerebral Edema (HACE): Life-threatening cerebral manifestation

Prevention Algorithm

Step 1: Acclimatization Strategies (First-Line Prevention)

• Gradual ascent: 300-600 meters/day above 2500 meters 1, 2
• Rest days: Include one rest day for every 600-1200 meters gained 1
• Pre-acclimatization: If possible, spend time at intermediate altitudes before major ascent 1
• Avoid overexertion: Particularly during the first days at altitude 1
• Stay hydrated: Maintain adequate fluid intake and avoid alcohol 1

Step 2: Pharmacologic Prevention (Based on Risk Assessment)

For individuals with history of AMS or rapid unavoidable ascent:

• Acetazolamide: 250 mg twice daily or 500 mg slow-release once daily, starting 1 day before ascent and continuing for 2-3 days at altitude 1, 3

For individuals with history of HAPE:

• Nifedipine: 20 mg extended-release three times daily, starting one day before ascent 1, 2
• Begin with ascent and continue for 3-4 days after arrival at terminal altitude 1

Alternative medications:

• Dexamethasone: 4 mg four times daily (for short-term prevention only, maximum 2-3 days) 4, 3
• PDE5 inhibitors (sildenafil, tadalafil): May reduce HAPE incidence but use with caution due to potential side effects 1

Risk Assessment for Pharmacologic Prevention

Consider prophylactic medication if:

• Previous history of altitude illness
• Rapid ascent above 2500 meters is unavoidable
• Ascending to sleeping altitude above 3000 meters in one day
• Underlying cardiopulmonary conditions

Special Considerations

For Patients with Cardiopulmonary Disease

• Patients with heart failure should be assessed based on their functional capacity at sea level 1
• Travel to intermediate altitudes (~2000m) is generally safe for patients with heart failure who have good exercise tolerance 1
• Patients with severe COPD should be assessed before traveling to high altitude destinations 1

For Women

• Women may experience different physiological responses to altitude:
  • Higher hypoxic ventilatory response during luteal phase of menstrual cycle 1
  • Less shift toward carbohydrate metabolism at altitude 1
  • Consider timing of altitude exposure relative to menstrual cycle phase 1

Common Pitfalls to Avoid

• Underestimating altitude: Even moderate altitudes (2000-2500m) can cause symptoms in susceptible individuals
• Ascending too quickly: The most common mistake leading to altitude sickness
• Ignoring early symptoms: Continuing ascent despite early AMS symptoms can lead to more severe illness
• Overreliance on medications: Drugs should supplement, not replace, proper acclimatization
• Overexertion: Strenuous activity before acclimatization increases risk
• Dehydration: Low humidity at altitude increases fluid requirements

By following these preventive strategies, most travelers can significantly reduce their risk of developing altitude sickness and enjoy their high-altitude experience safely.