Adventures in India

There are inherent risks in traveling at high altitude. The information provided here is designed for educational use o­nly and is not a substitute for specific training or experience.

Princeton University and the author assume no liability for any individual’s use of or reliance upon any material contained or referenced herein. This paper is prepared to provide basic information about altitude illnesses for the lay person. Medical research o­n high altitude illnesses is always expanding our knowledge of the causes and treatment. When going to altitude it is your responsibility to learn the latest information. The material contained in this article may not be the most current.

High altitude - we all enjoy that tremendous view from a high summit, but there are risks in going to high altitude, and it’s important to understand these risks. Here is a classic scenario for developing a high altitude illness.

You fly from New York City to a Denver at 5,000 feet (1,525 meters). That afternoon you rent a car and drive up to the trailhead at 8,000 feet (2,438 meters). You hike up to your first camp at 9,000 feet (2,745meters). The next day you hike up to 10,500 feet (3,048 meters). You begin to have a severe headache and feel nauseous and weak. If your condition worsens, you may begin to have difficulty hiking. Scenarios like this are not uncommon, so it’s essential that you understand the physiological effects of high altitude.

What is high altitude?

Altitude is defined o­n the following scale High (8,000 - 12,000 feet [2,438 - 3,658 meters]), Very High (12,000 - 18,000 feet [3,658 - 5,487 meters]), and Extremely High (18,000+ feet [5,500+ meters]).

Since few people have been to such altitudes, it is hard to know who may be affected. There are no specific factors such as age, sex, or physical condition that correlate with susceptibility to altitude sickness. Some people get it and some people don’t, and some people are more susceptible than others.

Most people can go up to 8,000 feet (2,438 meters) with minimal effect.

If you haven’t been to high altitude before, it’s important to be cautious. If you have been at that altitude before with no problem, you can probably return to that altitude without problems as long as you are properly acclimatized.

What Causes Altitude Illnesses

The concentration of oxygen at sea level is about 21% and the barometric pressure averages 760 mmHg. As altitude increases, the concentration remains the same but the number of oxygen molecules per breath is reduced.

At 12,000 feet (3,658 meters) the barometric pressure is o­nly 483 mmHg, so there are roughly 40% fewer oxygen molecules per breath. In order to properly oxygenate the body, your breathing rate (even while at rest) has to increase. This extra ventilation increases the oxygen content in the blood, but not to sea level concentrations.

Since the amount of oxygen required for activity is the same, the body must adjust to having less oxygen. In addition, for reasons not entirely understood, high altitude and lower air pressure causes fluid to leak from the capillaries which can cause fluid build-up in both the lungs and the brain. Continuing to higher altitudes without proper acclimatization can lead to potentially serious, even life-threatening illnesses.

Acclimatization

The major cause of altitude illnesses is going too high too fast. Given time, your body can adapt to the decrease in oxygen molecules at a specific altitude. This process is known as acclimatization and generally takes 1-3 days at that altitude.

For example, if you hike to 10,000 feet (3,048 meters), and spend several days at that altitude, your body acclimatizes to 10,000 feet (3,048 meters). If you climb to 12,000 feet (3,658 meters), your body has to acclimatize o­nce again. A number of changes take place in the body to allow it to operate with decreased oxygen.

• The depth of respiration increases.
• Pressure in pulmonary arteries is increased, “forcing” blood into portions of the lung which are normally not used during sea level breathing.
• The body produces more red blood cells to carry oxygen,
• The body produces more of a particular enzyme that facilitates the release of oxygen from hemoglobin to the body tissues.