High Altitude Medicine

Classification of Altitudes

The European Society of Cardiology considers high altitude to be elevations above 2,500 meters, where significant physiological acclimatization processes begin in the cardiopulmonary and circulatory systems 1, 2
The European Heart Journal defines very high altitude as above 4,000 meters, where well-controlled patients with mild hypertension can reach with adequate medical therapy 3, 4
The European Heart Journal also defines extreme altitude as above 5,000 meters, where the underlying mechanisms of increased blood pressure are complex and certain medications may lose efficacy 3, 5

The American College of Cardiology notes that high altitude exposure triggers important physiological changes due to a gradual decrease in barometric pressure 1
The American College of Cardiology also notes that high altitude exposure leads to a reduction in the partial pressure of oxygen in the inspired air 1
The American College of Cardiology states that hypobaric hypoxia causes an increase in respiratory rate and tidal volume 1
The American College of Cardiology notes that hypobaric hypoxia also causes respiratory alkalosis and hypoxic diuresis 1
The American College of Cardiology states that high altitude exposure leads to pulmonary vasoconstriction and pulmonary hypertension 1, 6
The American College of Cardiology notes that high altitude exposure activates the sympathetic nervous system, increasing heart rate and stroke volume 1

The American College of Cardiology recommends that patients with heart failure class NYHA I-II can travel to high altitude if they are stable 2
The American College of Cardiology recommends that patients with heart failure class NYHA III can travel to high altitude if they are stable, but should consider oxygen during flights 2
The American College of Cardiology advises against travel to high altitude for patients with heart failure class NYHA IV 2
The European Heart Journal notes that patients with well-controlled mild hypertension can reach very high altitudes (>4,000 m) with adequate therapy 3, 4
The European Heart Journal recommends that patients with moderate to severe hypertension should check blood pressure values before and during their stay at high altitude 3, 5
The European Heart Journal advises against exposure to high altitude for patients with uncontrolled or severe hypertension 3
The American College of Chest Physicians recommends that patients with pulmonary arterial hypertension should avoid exposure to altitudes above 1,829 meters (6,000 feet) 6, 8
The American College of Chest Physicians advises the use of supplemental oxygen to maintain saturations >91% for patients with pulmonary arterial hypertension 6, 8

The Journal of Travel Medicine notes that retinopathy of altitude can occur at altitudes above 4,900 meters 7