In order to function at altitudes higher than a few thousand feet above sea level, the human body must make several adjustments to compensate for the reduced availability of oxygen, especially when exertion takes place. People who begin strenuous exercise in the mountains without first becoming acclimatized may become very uncomfortable or in some cases seriously ill. Some individuals have difficulty even without exerting themselves.
Acute mountain sickness can begin a few hours or days after arrival at altitudes over 6,500 feet. Headache, loss of appetite, nausea, and fatigue are its primary symptoms. Irregular breathing patterns during sleep may cause frequent awakening, but with time sleep patterns return to normal. More severe cases are evidenced by changes in consciousness, cyanosis (a bluish discoloration of the skin, area beneath the nails, and lips), and a staggering gait.
Rapid ascent to higher altitudes (usually over 8,000 feet) followed by heavy exertion can lead to a serious disorder in which fluid leaks from small blood vessels into the air sacs of the lungs. Shortness of breath, cough, rapid heart rate, and fatigue develop over one to three days, and a characteristic gurgling sound may be heard if one listens to the chest. If untreated, this condition, known as pulmonary edema, can progress to cyanosis, changes in consciousness, coma, collapse of the cardiopulmonary (heart and lung) system, and even death. Mild mountain sickness will usually improve with rest, increased fluids, and mild pain relievers for headache. A physician might prescribe the drug acetazolamide (Diamox) to help reduce symptoms. People who are more severely ill must be escorted or carried to a lower altitude as soon as possible. Improvement begins after the victim descends a thousand feet or more and receives oxygen by mask. Never let the victim descend alone. A thorough evaluation by a physician is mandatory before returning to a high altitude.
The most effective measure to prevent altitude-related illness is to allow enough time – two to four days, if necessary – for a child to become accustomed to the reduced oxygen concentration before beginning strenuous activities at a higher altitude. Increasing fluid intake will help, as will a high-carbohydrate diet. Teenagers or adults who have experienced acute mountain sickness (or worse) in the past may benefit from taking acetazolamide (Diamox) on the day of ascent and for two days after arrival. Teenagers involved in rock climbing or other mountain activities should be warned not to ignore symptoms because of peer pressure or a misguided desire to tough bout when they feel sick. Assume any illness at high altitude to be mountain sickness or one of its more serious variations until proven otherwise, and treat it accordingly.