Effects Of Altitude On The Human Body

Effects of Altitude on the Human Body by Rick Newman

While the effects of altitude on the human body are better understood now than even a few short years ago, much is still unknown. Doing research on altitude issues is difficult; there are no easy methods of controlling experiments in order to gather reliable data, and exposure to high altitude usually also includes exposure to cold, heat, exercise, and dehydration. Further confusing the issue is that each individual may respond differently than his companions and differently than he did in the past. Still, some effects are well documented.

Hypoxia

As you climb higher, there is (effectively) less oxygen in the air to breathe. As your blood oxygen levels decrease, your body will signal the brain to increase ventilation, or your breathing rate. This is called the hypoxic ventilator response (HVR). This increases oxygen levels (which is good) but also causes too much carbon dioxide to be exhaled (which is bad). Hypoxia (a deficiency in the amount of oxygen reaching body tissues) creates a conflict in the body. Either oxygen levels are too low (due to hypoventilation), or carbon dioxide levels are too low (due to hyperventilation). Since the low oxygen will win this battle, carbon dioxide levels will be low, increasing blood pH and disrupting normal body function. Normally, this would be corrected quickly, but at altitude this process is slow and normal pH may not be Hypoxic conditions from reached for several weeks. http://www.diffusionpharma.com/?page_id=15

Acclimatization

Up to 25,000’ (above which they call the “death zone”), the human body will adapt to altitude. This process is acclimatization. One of the first changes is an increase in the heart rate (which returns to normal after a few days at altitude). Ventilation (both the rate and depth of breathing) will also increase, and continue to increase slowly for about a week before leveling off. Within a couple of hours at altitude, the body will begin to produce more hemoglobin, the oxygen carrying red blood cells. Red blood cells take about a week to form and mature. How do you know when you are acclimatized? Normal sleep, a normal appetite, and a normal heart rate have all been used as signs that acclimatization is adequate.

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AMS, HAPE, and HACE

There are three major illnesses caused directly by altitude: acute mountain sickness (AMS), high-altitude pulmonary edema (HAPE), and high-altitude cerebral edema (HACE). The primary symptoms of altitude illness are loss of appetite/nausea, light headedness, poor sleep, headache, mental abnormalities, lack of coordination, excessive fatigue, and excessive shortness of breath. Most people will experience some AMS while on the mountain, until they acclimate to the altitude. HAPE is excess fluid in the lungs. This fluid leaks from the capillaries, enters the intercellular spaces, and fills the alveoli (air sacs). The lungs lose their ability to serve as the interface between the atmosphere and the blood. HACE is a life threatening illness that requires immediate medical treatment. It is the result of swelling of brain tissue from fluid leakage and almost always begins as AMS. Descent to lower altitude, proper hydration, and certain drugs are the treatments for altitude illnesses.

HAPE Study - see http://www.altitude.org/HAPEposter1.j

The effects of altitude on the body are a challenge for any climber or trekker. Proper training, preparation, and experience can mitigate the negative impacts, but each person can still expect a unique experience on each trip to altitude.

Source: The Altitude Experience, Mike Farris/2008 see thealtitudeexperience.com/blog/

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