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Mountain Sickness.
--Frank Gillingham, MD
Modern travel has made it easy to reach high altitude destinations such as the Peruvian Andes, Lhasa (Tibet), or even the ski resorts of Colorado, without doing any actual mountain climbing. If you're planning such a trip, be sure to familiarize yourself with the health effects of altitude.
Background
First, some basics. Because of the effect of gravity on the atmosphere, air pressure falls as you ascend above sea level. Though the percentage of oxygen in air remains about the same (21%), the air is 'thinner.' The result is a decline in the absolute amount of oxygen available, which results in a decline in the amount of oxygen available to your tissues. Without sufficient oxygen, your tissues can't convert nutrients into energy.
At sufficiently high altitudes (above 8000 ft., typically), symptoms can occur in anyone. Oddly enough, physical conditioning does not seem to protect against Mountain Sickness. In fact, it often strikes younger, more fit members of climbing expeditions and is less common in those over 50. Tolerance to high altitude varies tremendously between individuals, and can vary from trip to trip for the same individual. Cold weather seems to worsen the effects of altitude.
Anyone with chronic medical conditions or a history of lung or heart problems should discuss travel to a high altitude destination with a physician well in advance of travel. Individuals who suffer from the following chronic medical conditions should never travel to high altitude destinations:
- Chronic Obstructive Lung Disease (including Emphysema and Chronic Bronchitis)
- Congestive Heart Failure
- Sickle Cell Anemia and other hemoglobinopathies
- Pulmonary Hypertension
Those who suffer from asthma or coronary artery disease are also at increased risk, and should be certain to have a thorough evaluation by a physician prior to travel.
Everyone who visits a high altitude destination will breathe more frequently and experience increased heart rate and pulse. Dryness of the skin and mucous membranes occurs, as does minor headache. These are normal mechanisms of high altitude adaptation.
Acute Mountain Sickness
Acute Mountain Sickness (AMS) is more common in those who have ascended too rapidly above 2,400 meters (8,000) feet. Typical symptoms include:
- Extreme increase in breathing frequency, with shortness of breath and/or cough
- Very rapid heart rate with palpitations, chest discomfort or a perception of pulses in the neck and head
- Headache
- Nausea and/or vomiting
- Fatigue and sleeplessness
The symptoms typically develop within 36 hours at altitude.
The most severe forms of AMS are "High Altitude Cerebral Edema" (HACE), which is result of swelling of the brain from fluid leakage, and "High Altitude Pulmonary Edema" (HAPE) which results from fluid build-up in the lungs. Trekkers suffering from HACE are unable to walk a straight line, become disoriented, and can lapse into a coma if not given proper medical treatment. Signs of HAPE that can be detected by medical personnel or laboratory testing include widespread wet noises (crackles) in lungs, and extremely low oxygen levels. Left untreated, HAPE can lead to death in the most severe cases.
Prevention
Proper acclimatization, the process of allowing the body time to adapt to the decrease in oxygen molecules, may help prevent AMS. Gradual ascent is crucial.
- Start your journey below 10,000 feet and increase altitude by a maximum of 1,000 feet per day.
- Take a rest day every 3,000 feet attained.
- "Climb High and Sleep Low". Trek more than 1,000 feet per day, as long as you return to sleep at a lower altitude.
- Work on your physical conditioning before your trip.
- Follow all the normal safe-travel tips. As bad as food poisoning is at sea-level, it is much worse at 8000 feet.
- Acetazalomide (US Brand name Diamox) is a diuretic which is frequently prescribed for the prevention of AMS. Therapy must be started prior to ascent, and patients should avoid consuming alcoholic beverages while taking Diamox (also of note: Diamox makes carbonated beverages taste strange). People who are allergic to sulfa drugs should NOT take Diamox. A trial course is recommended before traveling to remote locations where treatment for an allergic reaction may be difficult.
- Some climbers, particularly those who ascend rapidly, favor a powerful steroid medication called Decadron, rather than Diamox. In one study of climbers on Mt. Rainier, Decadron did prove more effective. However, because Decadron can have serious side effects, travel medicine physicians typically reserve it for individuals who are allergic to sulfa and/or for those who perform rapid ascents, such as mountain rescue personnel.
Treatment of AMS
- Mild symptoms of AMS can be treated with rest at a stable altitude and acetaminophen or other analgesic.
- If symptoms consist of more than mild headache and nausea, and persist more than 24 hours, seek medical attention. If possible locate a physician who is experienced in high altitude medicine.
- Descent to a lower altitude is crucial. Never ascend if your symptoms are getting worse with rest at stable altitude.
- Treatment for HACE and HAPE victims includes descent to a lower altitude as rapidly and safely as possible, and oxygen therapy. Portable hyperbaric chambers are very effective in treating severe forms of altitude illness. Decadron and Diamox are also used for treatment.
Buddya Basnyat, M.B.B.S., a Participating Physician in Kathmandu, Nepal, wrote in the September 1999 issue of the Journal of Travel Medicine that despite an increase in trekkers entering the Himalayas in Nepal, the number of cases of severe AMS cases has not increased. Dr. Basnyat attributes the decease in the rate of AMS to the success of education campaigns by organizations such as the Himalayan Rescue Association, among others.
Special thanks to Carol Foley, Dr. Gustavo Zubieta-Calleja, Sr. (LaPaz, Bolivia, Dr. Buddya Basnyat (Kathmandu, Nepal) and Dr. Matthew Rusk (Philadelphia, PA, USA) for assistance in preparing this article.
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