Mountain sickness

Disease Description (Causes and Symptoms)

• Causes and pathophysiology: As altitude increases, atmospheric pressure and the partial pressure of inhaled oxygen decrease, causing systemic hypoxia. Compensatory and maladaptive responses—including increased respiratory rate, changes in fluid distribution, and reduced oxygen transport in the blood—then develop, resulting in acute mountain sickness symptoms. It can generally occur at altitudes of 2,400 m or higher.
• Main symptoms: Headache (the primary symptom), sleep disturbance, loss of appetite, fatigue and weakness, nausea and vomiting, dizziness, peripheral edema, shortness of breath (dyspnea), and altered mental status (confusion and lethargy). Decreased urine output and unsteady gait (staggering) may also occur.
• Risk of progression to severe disease: In approximately 5–10% of cases, it may progress to high-altitude pulmonary edema (HAPE) or high-altitude cerebral edema (HACE), which can be life-threatening if treatment is delayed.

Treatment Methods

• Basic principles
  • Immediately descend to a lower altitude (descent is the most effective measure and should be prioritized).
  • Rest and stabilization. Do not ascend further.
• Oxygen therapy
  • Administer supplemental oxygen when possible (for example, inhaled oxygen at 2–3 L/min is recommended, with an increase depending on symptoms and oxygen saturation).
• Medication treatment
  • Prevention and treatment of mild cases: Acetazolamide — the usual preventive dose is 125–250 mg every 12 hours (as directed by a physician). The treatment dose depends on the symptoms and the physician’s judgment.
  • In severe cases or when cerebral edema is suspected: Dexamethasone 4 mg orally or intravenously, followed by administration every 6–8 hours (by physician prescription).
  • When pulmonary edema is suspected: Oxygen, descent, and, if necessary, diuretics and vasodilators (for example, nifedipine extended-release preparations may be used) — medication selection and dosage should be determined by a specialist.
  • A portable pressurized chamber (Gamow bag) can create an artificially lower altitude and may help as emergency treatment.
• Lifestyle management (self-care)
  • Ascend slowly (general recommendation: above 3,000 m, limit the ascent to 300–500 m per day and allow acclimatization days).
  • Drink sufficient fluids (to prevent dehydration); avoid excessive alcohol consumption and smoking.
  • Keep luggage light and avoid strenuous activity.
  • If symptoms develop, stop ascending immediately; if symptoms worsen, descend.
• In an emergency
  • Severe shortness of breath (even at rest), coughing with pink frothy sputum, severe confusion, or ataxia (staggering while walking or difficulty communicating) require immediate descent and emergency treatment.
• Risk of complications
  • If treatment is delayed, HAPE (pulmonary edema) or HACE (cerebral edema) may develop. These are emergencies requiring medical personnel, descent, oxygen, steroids, and specialized treatment.

Checklist Before an Outpatient Visit (Items to Prepare, Records · Example Questions)

• Items/materials to prepare or submit
  • List of currently used medications (including prescription and nonprescription medications)
  • History of previous mountain sickness and other cardiopulmonary diseases (heart disease and chronic respiratory disease)
  • Recent test results (electrocardiogram, chest imaging, oxygen saturation measurements, etc.; copies if available)
  • Timing and course of recent symptoms (symptom diary: onset, whether symptoms worsened or improved, and activity level)
  • Travel and climbing plans (target altitude, rate of ascent, altitude of accommodations, and whether companions will be present)
• Checklist before the visit
  • Photos or videos of symptoms (such as shortness of breath or unclear speech)
  • Records of measurements from a portable oxygen saturation monitor (pulse oximeter), if available
  • Amount of exercise at each altitude (for example, how much altitude was gained in one day)

Examples of General Questions to Ask the Doctor

• What are the expected effects and side effects of this medication (for example, acetazolamide or dexamethasone)?
• When should I go to the emergency room if my symptoms do not improve or worsen?
• If I have another climbing or travel plan, what preventive measures should I take?
• I have an underlying heart or respiratory condition. Are there any additional precautions I should take?

Examples of Condition-Specific Questions

• I have had mountain sickness before. Is it appropriate to take acetazolamide preventively before my next climb? When should I start taking it, and what should the dosage be?
• I currently have mild symptoms but am in a situation where it is difficult to descend immediately. When and how should the use of oxygen or a pressurized chamber (portable hyperbaric bag) be decided?

(Note: The information above is general medical information. Recommended treatment and dosage may vary depending on an individual’s condition, so follow the instructions of the responsible medical professional for actual prescriptions and emergency treatment.)