Your lungs while climbing Everest

If you ascend without proper acclimatization, at around 9,000 feet, your lungs may begin to swell because the blood vessels constrict. Symptoms include a persistent cough and labored breathing.

If the swelling in your lungs worsens, high-altitude pulmonary edema (HAPE) can occur. Symptoms are a bluish discoloration of the skin, rapid breathing, and fever. The most effective treatment is to descend immediately.