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High Altitude Illness

Traveling to high altitudes exposes people to increasingly rarefied air and progressively decreasing amounts of oxygen, resulting in declining levels of oxygen in the blood, which can lead to impaired physical and mental performance.Traveling to high altitudes exposes people to increasingly rarefied air and progressively decreasing amounts of oxygen, resulting in declining levels of oxygen in the blood, which can lead to impaired physical and mental performance. Responses to high altitudes vary, but most people can function normally at heights up to 8,000 feet (2,438 meters) above sea level. At altitudes greater than that, the oxygen deficit can begin to cause a condition known as acute mountain sickness (AMS). At elevations higher than 10,000 feet (3,048 meters), 75 percent of people will experience at least mild AMS symptoms.The onset of AMS symptoms varies according to the altitude, the rate of ascent and the individual's susceptibility to the disease. A slow ascent may allow the body to acclimate by establishing a more rapid spontaneous breathing rate to make up for the decreased oxygen in the atmosphere. Symptoms usually start 12 to 24 hours after arrival at altitude and begin to decrease in severity around the third day at a given elevation.

AMS causes travelers to feel generally unwell. They may also experience a loss of appetite, headaches, lightheadedness, fatigue, breathlessness, rapid heartbeat, nausea or difficulty sleeping. Symptoms tend to be worse at night. Mild AMS does not interfere with normal activities, and symptoms generally subside within two to four days as the body acclimates.

Severe HAI manifests as serious conditions known as high-altitude pulmonary edema (HAPE) or high-altitude cerebral edema (HACE), caused by the accumulation of excess fluid in the lungs or brain. Symptoms of HAPE and HACE include a gray or pale complexion, a blue tinge to the skin (cyanosis), chest tightness or congestion, cough, coughing up blood, difficulty walking, shortness of breath when at rest, withdrawal from social interaction, confusion or decreased consciousness. These conditions can be fatal if not treated or if the victim is not returned to a lower altitude.

Responding promptly to signs or symptoms of AMS is essential. Immediately call the nearest emergency medical services (EMS) if you or someone traveling with you experiences any of the following symptoms that could be HACE or HAPE:

  • severe breathing problems
  • altered level of alertness
  • coughing up blood
  • If you cannot count on EMS aid, move the affected individual to a lower altitude as quickly and as safely as possible, and administer oxygen if it is available. Keep victims warm, and be sure they stay well hydrated if they are conscious.

To avoid high altitude illness, it is important to ascend slowly enough to allow time for your body to acclimate. Some people also find it beneficial to take prophylactic medication to help with the acclimatization process or to prevent some ill effects. If you plan to travel to a high-altitude location, visit your doctor or a travel clinic before your trip to evaluate your risk of HAI and to obtain prophylactic medication that may prevent or alleviate AMS.

Anybody can be affected by AMS. Individuals who meet the following conditions are at a higher risk:

  • You live at or near sea level and travel to a high altitude.
  • You have had AMS before.
  • You have preexisting medical conditions.
  • You ascend quickly to a high elevation.
  • Consult your doctor before traveling to a high-altitude location if you have a heart, lung or blood disorder. You may need to travel with supplemental oxygen.

The following strategies can help prevent or moderate AMS:

  • Ascend slowly above 8,000 feet.
  • If you travel to high altitudes, choose a slow transportation method or walk.
  • If you get there by flying, do not overexert yourself or travel still higher for the first 24 hours.
  • If you travel above 10,000 feet (3,048 meters), increase your altitude by no more than 1,000 feet (305 meters) per day.-After every 3,000 feet (914 meters) of elevation gained, take a rest day.
  • After daily excursions, return to a lower altitude for the night, if possible.
  • Do not go higher if you experience any AMS symptoms; wait for the symptoms to decrease before ascending.
  • If your symptoms worsen, go to a lower altitude.
  • Stay properly hydrated. Drink at least three to four quarts of fluids per day, and be sure to quench your thirst. Make sure to urinate regularly.
  • Engaging in light activity during the day is better than sleeping, because respiration decreases during sleep, exacerbating AMS symptoms.
  • Avoid tobacco, alcohol and depressant drugs (such as barbiturates, tranquilizers and sleeping pills), all of which worsen AMS symptoms.
  • Eat a high-carbohydrate diet while at altitude, but do not overeat.
  • Boating or diving are not recommended.HAI can affect those engaging in mountain climbing, mountaineering, rock climbing and hiking at higher elevations. Often these locations make medical evacuation difficult and delayed. Moving the victim to lower elevations becomes a priority for those who are accompanying the victim.


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