Why Altitude Can Make You Sick & What to Do About It

Every breath you take isn't the same. Board a plane in New York and step off hours later in Aspen, or Chamonix or Lhasa, and, chances are, the plane food isn't what's turning your stomach. It's the change in altitude.

Altitude sickness can be the Achilles' heel of adventure travelers because there is no way to prepare for it before you go and no quick remedy to overcome it once you've arrived. It can choose its victims with amazing unpredictability, sometimes leaving the fittest gasping for breath while allowing the weakest and flabbiest to breathe freely. Age, gender and ethnicity also seem to make no difference as to who is affected.

"The only surefire way to minimize the effects of altitude change is to acclimatize," says Dr. Ronald G. Crystal, chair of genetic medicine at Weill Cornell Medical College, and chief of pulmonary and critical care medicine at NewYork-Presbyterian Hospital/Weill Cornell Medical Center. An experienced mountaineer and ice climber, Dr. Crystal has personally experienced the effects of altitude sickness. "Travel to a high-altitude location slowly, or give yourself a few days to adjust, once there. But nowadays this doesn't always happen. People have limited time. They fly into 8,000 feet and take a chairlift the next day to 10,000."

Interestingly, the cause of altitude sickness isn't the percentage of oxygen in the air, which remains at about 21 percent worldwide. The difference is how closely oxygen molecules are squeezed together by barometric pressure. Descend toward sea level and barometric pressure increases; ascend upward and the reverse happens. This is why a breath in Seattle feels more satisfying than one in, say, Machu Picchu.

"Stay below 15,000 feet and altitude sickness can be troublesome, but generally not life-threatening," says Dr. Crystal. People may experience nausea, headache, fatigue and shortness of breath, but within a few days, their bodies usually acclimatize and symptoms subside. Keeping hydrated and staying away from alcohol and barbiturates, such as sleeping pills and tranquilizers, will help speed the process toward acclimatization.

However, above 15,000 feet, the consequences of altitude sickness are more serious and can even be fatal. The primary danger is that the thin air will allow fluid to seep from capillaries and result in either High Altitude Pulmonary Edema (H.A.P.E.) or High Altitude Cerebral Edema (H.A.C.E.). With H.A.P.E., fluid leaks into the sacs of the lungs, making breathing difficult. A person can literally suffocate from within. With H.A.C.E., fluid leaks into the brain; the brain swells and is pushed against the skull.

Both conditions are extremely serious, and anyone with symptoms needs to get down to a lower altitude immediately. Those with H.A.P.E. have difficulty breathing; often cough up blood; and can make a crackling sound when they breathe. Those with H.A.C.E. are likely to lose coordination; have vision problems; or become irrational.

There are medicines that can help with both mild and severe altitude sickness, but the only certain remedy is to move to a lower altitude. For medication, Acetazolamide (Diamox) can help relieve the symptoms of mild altitude sickness. The drug encourages the kidneys to excrete bicarbonate, the base of carbon dioxide, which makes the blood more acidic and signals the lungs to breathe more frequently. Acetazolamide has some side effects, though: mainly, frequent urination; tingling in fingers and toes; and giving an unpleasant taste to carbonated beverages.

For more severe altitude sickness, physicians recommend Dexamethasone and Nifedipine. Dexamethasone is used to treat H.A.C.E. by reducing brain swelling and bringing down pressure within the skull. The other drug, Nifedipine, can lower pressure in the pulmonary artery and is therefore used to treat H.A.P.E. Reducing pressure in the pulmonary artery reduces the risk that fluid will seep out through capillaries and flood the lungs.

"One last thing," says Dr. Crystal, whose mood has now turned from scientific to humorous. "In the movie 'Vertical Limit' where the climber with H.A.P.E. takes a syringe of medication and plunges it into his heart. You don't want to do that."

http://www.med.cornell.edu/ science/2006/04_06/ 04_06-5.shtml

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