High-Altitude Acclimatization: The Science & Practice

The Physics of Altitude

At sea level, atmospheric pressure is 1013 mbar. At Everest Base Camp (5,364m), it's ~520 mbar — roughly half. Oxygen percentage stays 21%, but partial pressure drops proportionally. Your lungs rely on this pressure gradient to diffuse oxygen into blood.

Acute Mountain Sickness (AMS)

AMS is your body's response to hypoxia. Symptoms typically appear 6-24 hours after ascent:

• Headache (usually frontal, throbbing)
• Nausea / loss of appetite
• Dizziness / lightheadedness
• Fatigue / weakness
• Sleep disturbance

Diagnosis: Lake Louise Score ≥3 with headache + at least one other symptom.

Life-Threatening Complications

HAPE (High-Altitude Pulmonary Edema)

Fluid in lungs. Signs: breathlessness at rest, cough (pink frothy sputum), gurgling chest, extreme fatigue, cyanosis. Immediate descent mandatory.

HACE (High-Altitude Cerebral Edema)

Brain swelling. Signs: ataxia (wobbly gait), confusion, hallucinations, severe headache unresponsive to meds, decreased consciousness. Immediate descent mandatory.

Acclimatization Physiology

Your body adapts through:

1. Hyperventilation: Immediate. Blows off CO₂, raises blood pH (respiratory alkalosis).
2. Renal compensation: 24-48 hrs. Kidneys excrete bicarbonate, normalize pH.
3. Erythropoietin (EPO): Days-weeks. Increased red blood cell production.
4. Capillary density: Weeks-months. Improved tissue oxygen delivery.

Our Acclimatization Protocol

• Ascend slowly: Max 300-500m sleeping elevation gain per day above 3,000m.
• Climb high, sleep low: Day hikes 300-500m above sleeping altitude.
• Rest days: Every 3-4 days, or every 1,000m gained.
• Hydration: 3-4L/day. Monitor urine color.
• Carbohydrate-rich diet: Easier to metabolize at altitude.
• No alcohol/sedatives: Suppress respiratory drive.

Medications

Acetazolamide (Diamox): Carbonic anhydrase inhibitor. Stimulates ventilation, speeds renal compensation. Prophylactic: 125mg 2x/day starting 24h before ascent. Therapeutic: 250mg 2x/day. Sulfa allergy contraindication.

Dexamethasone: For HACE treatment only. 8mg stat, then 4mg 6-hourly. Not for prophylaxis.

Nifedipine: For HAPE treatment/prevention in susceptible individuals.

Red Flags — Immediate Descent

• AMS symptoms worsening despite rest
• Any HAPE/HACE signs
• O₂ saturation <75% at rest (context-dependent)
• Inability to walk heel-to-toe (ataxia test)

Winterfell Safety Standards

Every expedition carries: Pulse oximeter, Lake Louise scoring sheets, oxygen cylinder (2L), Dexamethasone, Nifedipine, portable hyperbaric chamber (Gamow bag) on trips >5,500m. Guides trained in wilderness medicine (WFR/WEMT). Satellite communication for evacuation coordination.