Altitude Sickness: Prevention, Recognition, and Emergency Treatment

Altitude sickness doesn't care how fit you are. Olympic athletes have been evacuated from high-altitude peaks for acute mountain sickness. What determines your susceptibility is largely genetic—your body's speed of acclimatization to lower oxygen levels—and it varies enormously from person to person, and even from trip to trip for the same person.

Understanding the spectrum from mild to life-threatening is what lets you make smart decisions in the backcountry.

The Acclimatization Process

As elevation increases, barometric pressure drops, and each breath of air contains fewer oxygen molecules. Your body compensates by:

• Breathing faster (the first response)
• Increasing heart rate
• Producing more red blood cells over days to weeks

This process takes time. Going from sea level to 12,000 feet in one day overwhelms the system's ability to adapt.

Acute Mountain Sickness (AMS)

The most common form. Typically begins 6–12 hours after reaching elevation above 8,000 feet.

Symptoms: Headache (the defining symptom), fatigue, loss of appetite, nausea, dizziness, and difficulty sleeping.

"The Lake Louise Score": A standardized AMS assessment tool. Score 3 or higher suggests AMS:

• Headache: 0 (none) to 3 (severe, incapacitating) — must be present for AMS diagnosis
• GI symptoms: 0 (none) to 3 (vomiting)
• Fatigue: 0 (none) to 3 (severe)
• Dizziness: 0 (none) to 3 (severe)
• Sleep quality: 0 (well) to 3 (unable to sleep)

Management: Rest at current altitude for 24 hours. Hydrate well. Ibuprofen (600–800mg) for headache. Do NOT ascend further until symptoms resolve. If symptoms worsen or don't improve within 24 hours: descend.

The Life-Threatening Spectrum

High Altitude Cerebral Edema (HACE)

Fluid accumulates in the brain. A progression of severe AMS.

Warning signs (any of these = immediate descent):

• Confusion, altered consciousness, unusual behavior
• Loss of coordination: "the ataxia test"—walk heel-to-toe in a straight line. Inability to do this at altitude is a red flag.
• Severe headache unresponsive to ibuprofen
• Lethargy progressing toward unconsciousness

Action: Descend immediately. 1,000–2,000 feet of descent often produces dramatic improvement. If descent isn't immediately possible: supplemental oxygen if available; dexamethasone (Decadron) 8mg initial dose if carried.

High Altitude Pulmonary Edema (HAPE)

Fluid accumulates in the lungs. The leading cause of altitude-related death.

Warning signs:

• Dry cough that progresses to a productive pink or frothy cough
• Shortness of breath at rest (not just on exertion)
• Crackling sounds in the lungs when breathing
• Decreased exercise tolerance developing rapidly

Action: Descend immediately. This is a life-threatening emergency. 1,000–2,000 feet of descent is often lifesaving. Supplemental oxygen and nifedipine (10mg immediate-release, then 30mg extended-release) if available. Evacuate.

Prevention: The Acclimatization Rules

"Climb high, sleep low": You can go higher during the day, but sleep at the lowest elevation you visit. Your body acclimatizes best during sleep.

Rate of ascent: Above 8,000 feet, limit your sleeping altitude gain to 1,000–1,500 feet per day. Take a rest day every 3rd day of ascent.

Hydration: Drink more than you think you need. Aim for pale yellow urine. Dehydration worsens AMS.

Avoid alcohol and sedatives for the first 48 hours at altitude. Both suppress breathing and impair acclimatization.

Acetazolamide (Diamox): A prescription medication that accelerates acclimatization by stimulating breathing. 125–250mg twice daily, starting 24 hours before ascent. Requires a prescription—discuss with your physician. Common side effect: tingling in hands and feet.

HAVEN at Altitude

HAVEN's Adventure mode AI can guide you through altitude assessment and management without signal. Ask it:

• "My hiking partner has a headache and nausea at 11,000 feet. What should I check?"
• "How do I do the coordination test for HACE?"
• "We're at 13,500 feet and my partner's cough is getting worse. What are the HAPE warning signs?"
• "What's the decision framework: push to camp or descend now?"

The wilderness medicine library in Sanctuary includes detailed altitude illness management protocols with differential diagnosis guidance. Download your region and activate Adventure mode before you leave the trailhead—HAVEN works without a single bar of signal.