What is high altitude pulmonary edema (HAPE)? Cardiology Basics

What is high altitude pulmonary edema (HAPE)? Cardiology Basics

High altitude pulmonary edema is pulmonary edema which occurs on rapid ascent to high altitudes. It is a potentially life threatening condition and is a severe form of mountain sickness. Severe breathlessness with fall of oxygen level in the blood occurs in this condition. Cyanosis may be noted. The best way to prevent it is to ascend gradually, taking a few days to climb to 3000 meters. After that climb only very slowly, only about 300 to 500 meters a day. The risk is more if your usual residence is near sea level so that you are not acclimatized to high altitude at all. Previous episode increases your risk of a recurrence. Pre-existing cardiopulmonary disease may also enhance the risk.

High altitude pulmonary edema is characterized by inhomogeneous pulmonary vasoconstriction in response to reduced oxygen concentration in the inhaled air at high altitude. It may be noted that oxygen is one of the most potent pulmonary vasodilators, which is used therapeutically in the management of chronic pulmonary hypertension by way of nocturnal oxygen therapy. In high altitude pulmonary edema, the inhomogeneous pulmonary vasoconstriction leads to elevated pulmonary capillary pressure and leakage of fluid into the alveoli. This is in fact a form of non cardiogenic pulmonary edema. Oxygen therapy and descend to lower altitudes are the logical answer for the treatment of high altitude pulmonary edema.

Defective alveolar fluid clearance may be an important component in the pathogenesis of high altitude pulmonary edema. Ultrasound lung comets have been detected as evidence of subclinical high altitude pulmonary edema in recreational climbers rather frequently.

If you are planning to travel above 3000 meters, carry enough oxygen to last for several days. Drugs like sildenafil, tadalafil and nifedipine have been used as pulmonary vasodilators in the management of high altitude pulmonary edema. Dexamethasone is also considered useful in high altitude pulmonary edema.

Portable hyperbaric chamber has also been used in the immediate management of high altitude pulmonary edema. They allow hikers to simulate conditions at lower altitude without actually climbing down. They are useful if bad weather or some other factors prevent a quick descent to a lower altitude. A portable hyperbaric chamber can be operated by a foot pump and can simulate a descent of about 1500 meters within a few minutes by increasing the pressure within the bag. Portable hyperbaric chambers are inflatable bags and weigh about 6.5 Kg. When expanded they are cylindrical in shape and large enough to accommodate a person. The foot pump has to be operated continuously while the person is in the bag to supply fresh oxygen and to flush out carbon dioxide.