A patient asks: How does altitude above sea level affect the heart and blood pressure, and how high should we go?
The doctor answers: These are good questions, ones frequently neglected in decisions about traveling, buying a second home, etc. Altitude above sea level affects the heart, brain and other organs primarily through the mechanism of oxygen deprivation.
As a cardiologist, I focus on the heart, which is a working muscle — but unlike other muscles in the body, it’s working 24 hours a day. If you exercise other muscles, and get fatigued, your brain gets the signal and you sit down and rest. Your heart can’t do that, so when oxygen deprived, it is vulnerable to problems like rhythm abnormalities.
The oxygen content of air decreases with altitude above sea level, but most people tolerate this reasonably well until about 8,000 feet. Airplane cabins are pressurized to keep the cabin altitude below 8,000 feet, and this generally avoids significant hypoxia (low oxygen) and altitude sickness. Federal Aviation Administration regulations mandate the cabin altitude not exceed this at the maximum operating altitude under normal operating conditions.
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People have different susceptibilities to altitude sickness. For some otherwise healthy people, acute altitude sickness can begin to appear at around 6,500 feet elevation above sea level, such as at many mountain ski resorts (Tahoe, Sun Valley).
Alcohol increases the development of altitude sickness. Exertion aggravates the symptoms.
More people will have symptoms of altitude sickness at altitudes of 9,000 feet and higher, commonly encountered at ski resorts in Colorado. Symptoms of altitude sickness often manifest themselves six to 10 hours after ascent and generally subside in one to two days. But they occasionally develop into the more serious conditions. Symptoms include headache, fatigue, stomach illness, dizziness and sleep disturbance.
Exertion aggravates the symptoms. Alcohol increases the development of altitude sickness.
At altitudes of 12,000 feet (Cuzco, Peru, and Lhasa, Tibet) or higher, altitude sickness is common. Susceptible individuals can develop more serious manifestations such as HAPE (high-altitude pulmonary edema, where the lungs fill up with fluid), and HACE (high-altitude cerebral edema, swelling of the brain), both of which can be fatal.
People going for sustained trips to altitudes of 9,000 feet or higher may want to consider taking a medicine called Diamox (acetazolamide) starting 24 to 48 hours before ascent, and continue for 48 hours after arrival at peak altitude. This will often prevent or greatly ameliorate the symptoms of high-altitude sickness.
My wife and I recently took Diamox before a trip to Machu Picchu, an Incan citadel high on the summit of the Andes Mountains in Peru. We walked from the bottom to the top — about 8,000 feet — with no problems.
I have patient in his 50 who had suffered a heart attack, but is now on proper treatment. With the proper medication and preparation, he was able to reach the summit of Mount Kilimanjaro, the highest mountain in Africa, without oxygen tanks.
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If you take good care of yourself — regularly exercise, maintain a healthy weight, avoid excessive alcohol, and eat a sensible diet, with plenty of fruit and vegetables — get checked before a trip to high altitude and make any adjustments in medication, you should be fine.
Be prepared. So just like when you go into an auditorium, you know where the exits are — you should have an exit strategy for trips to high altitude. Even a descent of 2,000-3,000 feet can make a big difference. However, you should know that for severe symptoms there is no substitute for prompt return to sea level.