Acute mountain sickness

Travel brochures offer dreams of pristine, idyllic settings: an azure-blue lake rimmed with tall pine trees accented by a backdrop of jagged, snowcapped summits; mountain trekkers, campers and adventurers seated at an inviting picnic spread, or a fisherman displaying a striking rainbow trout ready for the frying pan that will satisfy the palates of avid and amateur outdoorsman.

Images such as these fill travelers' minds as they plan trips to spectacular and stunning mountain destinations. Whether traveling to the Rocky Mountains, Kilimanjaro or Mount Everest, the challenge of overcoming the physical hurdles is an enticement to push the edge of the envelope of human limits.

Familiar challenges that face mountain climbers include negotiating treacherously slippery paths; hours of uphill walking; rock slides reminiscent of tumultuous snow avalanches; dubious hygiene; enduring relentless and unremitting windstorms, and having to haul a pack around.

Regardless of whether traveling to a domestic or international mountain climbing destination, climbers are susceptible to a serious and potentially life-threatening condition known as Acute Mountain Sickness: Anyone who goes to a high altitude could experience AMS, which is primarily related to rate of ascent.

There has been no way to predict who is likely to get sick at high altitudes. Anyone can get AMS, regardless of one's age, gender, physical fitness or previous altitude experience.

About 75% of individuals who ascend to levels over 10,000 feet will experience mild symptoms. These consist of headache, dizziness, fatigue, shortness of breath, loss of appetite, nausea, disturbed sleep and a general feeling of malaise. The symptoms usually start 12 to 24 hours after arrival at altitude and begin to decrease in severity by the third day.

Mild symptoms

Mild AMS does not interfere with normal activity, and symptoms generally subside within two to four days as the body acclimates. Moderate AMS includes severe headache that is not relieved by medication; nausea and vomiting; increasing weakness and fatigue; shortness of breath, and decreased coordination.

Normal activity is difficult, although the individuals still may be able to walk on their own. At this stage, only advanced medications or descent can reverse the problem.

Severe AMS presents as an increase in the severity of the previously mentioned symptoms, including shortness of breath, which occurs at rest; inability to walk; decreasing mental status, and fluid buildup in the lungs. Severe AMS requires immediate descent to lower altitudes of 2,000 to 4,000 feet.

The concept behind altitude sickness is lack of oxygen at high altitudes (over 10,000 feet), which affects most people to some extent. This occurs because less oxygen reaches the muscles and the brain at high altitude, requiring the heart and lungs to compensate by working harder.

Interestingly enough, physicians don't generally worry much about elevations below about 8,000 feet since altitude illness rarely occurs lower than this.

Acclimation is the process of the body's adjusting to the decreasing availability of oxygen. It is a slow process, taking place over a period of days. Certain normal physiological changes occur in every person who goes to a high altitude.

These changes include hyperventilation (rapid breathing), shortness of breath during exertion, increased urination, changed breathing pattern at night, awakening frequently at night and bizarre dreams.

Experienced climbers invest time in training for their trek to prepare for the physical challenges and doldrums. The better cardiovascular shape you are in previous to your trip, the better you'll be able to withstand exertion at elevation.

Increase exercise

Run, hike with a pack or merely climb stairs, starting at least a month before you embark on your high-altitude adventure. Being in good shape will do nothing to protect you from altitude illness, but you do want to increase your respiratory rate, such as the ability to hyperventilate, in order to more quickly acclimate to altitude.

Gradual ascent to elevation is the best method to avoid altitude sickness. Your best tactic is to embark on day trips to altitude before your big trip. If possible, go to your local ski area or the highest elevation in your locality. Hike around, have a picnic and camp overnight, if possible.

If you are planning on hiking or climbing in a mountainous area (Colorado, Tanzania, Peru, Tibet, Bolivia, Alaska, etc.), try to arrive at your destination several days in advance. Your body needs time to acclimate. Sleeping, walking around and even shopping at altitude will improve your ability to deal with conditions even higher up.

Mountain climbers who have had previous symptoms of altitude sickness might consider contacting a physician before their next trip. Certain medications (like Diamox [acetazolamide], a prescription drug) have proven effective in decreasing altitude illness, especially when used in conjunction with graded ascent.

Diamox works by increasing respiratory rate. It is also a diuretic, so you need to drink plenty of fluids when taking it.

Respiratory depression (the slowing down of breathing) can be caused by various medications and may be a problem at high altitude. Alcohol, sleeping pills and narcotic pain medication each can cause this and should never be used by someone who has symptoms of altitude illness.

At high altitude, a good rule of thumb is to sleep no more than 1,000 feet higher each night above 10,000 feet. Your best strategy is to train high and sleep low. This means setting up a low base camp, taking a hike to elevation and then returning to base camp to sleep.

Dehydration can increase the risk of developing altitude illness. During all hiking and trekking, you should be monitoring your water intake by your output. If you are not urinating regularly or your urine is dark yellow, you need to drink more liquid.

Dr. Larry G. Baratta is chief medical officer of Passport Health (www.passporthealthusa.com), with clinics nationwide. Reach him by email at travelvaccines1@aol.com.

Next month in this column: Dr. Alan M. Spira discusses "bird flu."

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