Respiratory Considerations at High Altitude

Patient Assessment and Risk Factors

Patients with COPD or sleep apnea should undergo respiratory function assessment if clinically indicated, as recommended by the European Respiratory Society 1
Patients with certain medical conditions, such as coronary artery disease, should consult their physician before high altitude travel, as acetazolamide may reduce the risk of subendocardial ischemia at high altitude, as stated by the European Society of Cardiology 2
Women may have a higher risk of acute mountain sickness, and pre-acclimatization and slow ascent are particularly important, with consideration of iron supplementation before altitude exposure due to higher risk of iron deficiency, as recommended by the European Society of Cardiology 3
Well-controlled hypertensive patients may reach high altitudes (>4000m) with adequate therapy, while uncontrolled/severe hypertensive patients should avoid high altitude exposure, as recommended by the European Society of Cardiology 2

Gradual ascent, not exceeding 300-600 m/day above 2500 m, can help prevent high-altitude pulmonary edema (HAPE) and AMS, as recommended by the European Heart Journal and Wilderness Medical Society 2, 4
Proper acclimatization, including gradual ascent, rest days, adequate hydration, and avoiding overexertion, is essential to prevent altitude sickness, with a rest day included for every 600-1200 m gained 2, 4
Acetazolamide, a carbonic anhydrase inhibitor, can increase ventilation, improve oxygenation, reduce the risk of AMS symptoms, and lower blood pressure at high altitude, as recommended by the European Society of Cardiology 2
The recommended dosage for altitude sickness prevention is 125-250 mg twice daily starting 24 hours before ascent, as suggested by the European Heart Journal and European Society of Cardiology 2, 3, 5
Higher doses (500-750 mg/day) may be more effective for rapid ascents over 3,500m, although the specific guideline society is not mentioned in this context, it is generally recommended for prevention of AMS 2

Acetazolamide is contraindicated in patients with kidney stones, aplastic anemia, sickle cell disease, sulfa allergy, severe hepatic disease, severe renal disease, adrenocortical insufficiency, and hyperchloremic acidosis, as stated by the European Respiratory Society and other guidelines 6, 2
Common side effects of acetazolamide include paresthesias, vertigo, alteration of taste, and allergic dermatitis/conjunctivitis, as reported by the European Respiratory Society 5
Serious side effects include kidney stones, metabolic acidosis, blood dyscrasias, Stevens-Johnson syndrome, serum electrolyte imbalances, lethargy, and suppression of appetite, as stated by the European Respiratory Society and other guidelines 6, 5

Immediate descent is the primary treatment for severe altitude illness, and supplemental oxygen should be used to maintain saturation >90% if available, acetazolamide can also be used for treatment of mild AMS (250mg twice daily), as suggested by the European Society of Cardiology 2
Patients taking acetazolamide should limit caffeine intake due to potential interactions that could worsen side effects and impact treatment efficacy, as recommended by clinical guidelines for patients with headache disorders such as idiopathic intracranial hypertension (IIH) and the European Society of Cardiology for heart failure management 7, 2
Monitor serum electrolytes, renal function, acid-base status, and clinical response when using acetazolamide, and avoid combining acetazolamide with other diuretics due to increased risk of dehydration and electrolyte imbalances, as recommended by the European Respiratory Society and other guidelines 5, 2, 3