High Altitude Pulmonary Edema; True is

The High Altitude Pulmonary Edema (HAPE) is due to raised pulmonary capillary pressure and high  permeability of pulmonary capillary. This leads to leakage of proteins and white blood cells. High-altitude pulmonary edema is a patchy edema of the lungs that is related to the marked pulmonary ​hypertension that develops at high altitude. It has been argued that it occurs because not all pulmonary arteries have enough smooth muscle to constrict in response to hypoxia, and in the capillaries supplied by those arteries, the general rise in pulmonary arterial pressure causes a capillary pressure increase that disrupts their walls (stress failure). ​ In high-altitude pulmonary edema, prompt treatment with O2  is essential-and, if available, use of a hyperbaric chamber. Portable hyperbaric chambers are now available in a number of mountain areas. Nifedipine, ​a Ca2+  channel blocker that lowers pulmonary artery pressure, can also be useful. Reference: Ganong’s Review of Medical Physiology 25 Ed page no 649​