MAY / JUNE 2005

AROUND HARVARD

This article originally appeared in the March 2005 Harvard Men’s Health Watch and is provided courtesy of Harvard Health Publications.

Into thin air: Medical problems at new heights

It used to be a problem for the very few, the hardy adventurers who trek or climb at breathtaking heights. But high places continue to beckon, and as travel becomes easier and less expensive, more and more men are responding with their ascent. If you maintain a low profile, you don’t have to worry about altitude sickness, but if your travel plans are uplifting, you should know how to handle new heights.

The problems
Although a low oxygen level is the most obvious and important cause of altitude sickness, several factors actually combine to trigger problems:

Oxygen. Oxygen levels are highest at sea level, but they fall steadily at increasing altitudes. Most men won’t notice any effect until about 5,000 feet; even at one mile above sea level, breathing is comfortable at rest but becomes labored with exertion. And the higher you go, the harder your lungs have to work to take in the oxygen you need.

Barometric pressure. When the forecaster predicts low pressure at home, you expect dull, heavy air. But as men ascend to high altitude, low pressure means less efficient oxygen uptake.

Falling temperatures. At home, it’s easier to exercise when it’s cool. But at heights, cool temperatures mean that your body will have to divert some of its oxygen simply to keep you warm. On average, ambient temperature falls about 4¾F for each 1,000 feet of elevation.

Ultraviolet (UV) radiation. Thin air lets in more UV radiation, resulting in a higher risk of snow blindness and sunburn.

Dehydration. Mountain air is dry, and breathing is fast at heights. The result: Lots of fluid is lost from the lungs.

Healthy bodies can adapt to the challenges of high altitude remarkably well. Breathing becomes faster and deeper to take in more oxygen, the heart beats faster and pumps harder to propel more oxygen to the tissues, and the sympathetic nervous system pours out more adrenaline to meet the stress. During weeks and months of high-altitude living, the bone marrow produces more oxygen-carrying red blood cells, and the circulatory overactivity settles down. But until acclimatization occurs, the stresses of altitude can tax the heart and lungs, particularly if they’re not entirely healthy to begin with.

How high is high?
A mile seems like quite a height, but in medical terms, altitude-related problems don’t usually begin until you’ve gone beyond 5,000 feet above sea level. Heights from 5,000 to 8,000 feet are considered moderate; high altitude extends from 8,000 to 14,000 feet, very high altitudes from 14,000 to 18,000 feet, and extreme altitude beyond that.

To give you some perspective, commercial airplanes maintain a cabin pressure of about 6,400 feet above sea level. It’s enough to make your ears pop and to increase fluid losses and cause dehydration on long flights, but not enough to make you sick. That’s why air travel is safe unless you have severe heart or lung disease.

By 8,000 feet, though, things can get dicey. That’s the altitude of many western ski resorts and some of the most beautiful spots in our national parks. Most sightseers will feel fine at 8,000 feet, but the stress of skiing or hiking can trigger problems, especially in older people. Since more than 35 million Americans visit these high altitudes each year and 5 million of them are over 60, it’s a potential concern.

A study of 20 Army veterans who had a reunion in Vail, Colorado, illustrates the problem. Their average age was 68, and about a third had coronary artery disease. Nearly half the men experienced symptoms of acute mountain sickness during their first three days at Vail, but all the symptoms resolved within five days. Physical work capacity declined by 12% at first, but it returned to normal after several days. Of concern, however, were the three people who had normal exercise stress tests at sea level but developed abnormalities when their tests were repeated at Vail. In addition, one veteran with a history of heart disease and bypass surgery suffered a heart attack after exercising during the reunion.

For most people, a moderate altitude of 8,000 feet is safe, but many have temporary symptoms, and a few develop serious problems. Above 8,000 feet, the risks rise. Still, healthy men in search of a challenge can ascend higher, but to avoid problems they should take special precautions. And these same preventative measures can help everyone who travels above 7,000–8,000 feet.

Altitude sickness
There are three well-defined forms of high-altitude illness:

Acute mountain sickness (AMS) is the most common but least serious syndrome. The earliest medical description of AMS dates to 36 B.C., when a Chinese official noted that as people travel through the Himalayas, “a man’s face turns pale, his head aches, and he begins to vomit.” AMS usually begins within the first 6–24 hours at altitude, but it can be delayed by several days. Headache is the most common complaint; that’s why the ancient Chinese named one peak Great Headache Mountain and another Little Headache Mountain. Other symptoms may include shortness of breath, dizziness, loss of appetite, nausea, insomnia, weakness and lethargy, and flu-like symptoms.

High-altitude pulmonary edema (HAPE) is a serious illness that can be fatal. Uncommon at 8,000 feet, HAPE can affect up to 15% of previously healthy people at 14,000 feet. Symptoms of cough, shortness of breath, extreme fatigue, chest tightness, and mild mental dullness or confusion begin two to four days after reaching altitude.

High-altitude cerebral edema (HACE) is the most critical form of altitude sickness. It occurs when fluid and pressure build up in the brain; most victims also have fluid in their lungs. Confusion rapidly gives way to bizarre behavior, incoordination, and hallucinations. Without treatment, HACE progresses to coma and death.

Other conditions can occur at moderate and high altitudes. Leg swelling is common but usually mild and temporary; less often, blood clots can develop, particularly in people who become dehydrated and suffer injuries that limit walking. Dehydration also increases the risk of retinal hemorrhages, bleeding into the back of the eye. Ultraviolet keratitis (snow blindness) results from excessive sun exposure that burns the cornea, the membrane covering the eye’s lens. It causes burning pain, tearing, redness, and swelling of the eyes; fortunately, the damage is temporary.

Prevention
A few simple precautions can prevent nearly all problems, at least at moderate altitude:

  Be sure you are in good shape before you travel. If you have significant medical problems, check with your doctor before you go; even with his approval, be sure to go slowly and listen to your body for warning symptoms. Travel is usually safe for men with mild to moderate heart or lung disease and for most with well-controlled high blood pressure or diabetes, but high altitudes are very dangerous for people with sickle cell anemia.

  Ascend gradually. You can fly to Denver or Mexico City in one hop, but if you’re going higher, a few days of acclimation are worth your time. Above 8,000 feet, don’t go up more than 1,000 feet a day.

  Travel high, sleep low. For example, if you ski at 9,000 feet, you’ll do best if your lodge is 1,000–1,500 feet lower. If you’re hiking, ascend in stages, and sleep at altitudes below your daily peak.

  Limit your exercise during your first days at altitude — and take it easy throughout your trip if you have medical problems or you feel sick in any way.

  Drink plenty of fluids. Dehydration is sneaky at altitude, because you will lose lots of water through your lungs even if you don’t perspire. Drink enough to keep your urine clear and copious.
Avoid alcohol or minimize your consumption, particularly for the first 48 hours at altitude. Avoid sedatives.

  Dress warmly.

  Wear sunglasses.

  Be alert for symptoms. You can manage mild mountain sickness yourself (see “Treatment” below), but you’ll need help for anything more serious. Don’t ignore symptoms; instead, return to a lower elevation and get help.

  Consider medication. Acetazolamide (Diamox) is a prescription drug that can facilitate acclimatization and lessen the risk of mountain sickness; it is a mild diuretic that stimulates breathing by causing the kidneys to secrete bicarbonate and sodium in the urine. The usual dose is 250 mg two or three times a day, starting one day before the trip and continuing for two to four days at peak altitude. People who are allergic to sulfa drugs may develop allergic reactions. Acetazolamide speeds acclimatization, but many experts think a slow ascent is safer and wiser. Other medications that can prevent mountain sickness include the calcium-channel blocker nifedipine and the steroid dexamethasone, but they may have more side effects than acetazolamide.

As an alternative, some people have considered herbal therapy with Ginkgo biloba. Two early studies reported that doses of 80–120 mg twice a day can reduce the risk of acute mountain sickness, but an excellent 2004 study found no benefit.

Treatment
Mild mountain sickness will resolve on its own within a few days. Rest, hydration, and aspirin will help speed things along. Inhaling oxygen can also reduce symptoms. Acetazolamide, the same medication that can help prevent AMS, is also beneficial. But if symptoms are severe, descent is necessary.

High-altitude pulmonary and cerebral edema are medical emergencies. Oxygen therapy, descent, and expert medical attention are mandatory. Useful medications include acetazolamide, nifedipine, and dexamethasone.

Up and down
Although our world is getting smaller, it’s certainly not getting flatter. The beauties of nature, opportunities to ski and hike, and meetings and festivals in mountain resorts are all calling men to high places. If you are among the millions who enjoy them, get the lowdown on altitude and health before you start your trip; a little low-altitude planning will keep your journey flying high.

Copyright 2006 Harvard Medical International