Altitude Sickness

In this column we will look at altitude sickness and associated conditions caused by increased elevation. As all of you are aware, as altitude increases oxygen levels decrease. This is because at increased altitudes barometric pressure decreases. From high school physics remember that the amount of gas dissolved in solution is a function of pressure. At higher elevations there is less barometric pressure and so less oxygen is dissolved in the air you breath. In Denver which is about 1 mile high there is 17% less oxygen in the air than at sea level. At 8000 feet the amount of available oxygen is 25% less than at sea level. All of the various types of altitude illnesses are basically caused by a lack of oxygen and your body's response to this stress.

Bowsite Founder Pat Lefemine took this goat in Colorado's Needle Mts. at 13,500 feet. While the affects of altitude sickness hit people in different ways, during this hunt Pat was unable to sleep for four days and became lethargic and in a state of intoxication. So much so that he left the horns and cape behind thinking the goat was 'too small' he later climbed back up to get them.  Goat at 13,800

Your body is an amazingly adaptable machine and will make the necessary adjustments it needs as you ascend to higher altitude. As you increase elevation your body's initial response is to breath faster. This works well to keep your oxygen level up initially but your body must make other adjustments because of the increased breathing rate. To keep your body in chemical balance your kidneys produce more urine. Over 4-7 days your body will adapt to the altitude by adjusting your breathing rate and kidney function. Over many days your body will increase the amount of red cells in your blood in an effort to carry more oxygen to your system. This does not occur soon enough to help you on a 10 day hunt for mountain goats in Colorado and plays no role in initial acclimation to altitude. All forms of mountain sickness can be prevented by gradual ascent. If you give your body time to make the necessary adjustments you will have no problems. A night spent in Denver before heading into elk camp at 7500 feet can prevent a lot of problems. If more time is available 2-3 days of gradually increasing your elevation will prevent mountain sickness. On the other hand if you are on a tight schedule as most of us are and quickly travel to base camp at 8000 feet you are much more likely to have problems. In fact, about 25% of unacclimated people will develop some symptoms of altitude sickness at 6000 feet. As elevation increases so does the risk of illness. Physical conditioning unfortunately does not prevent altitude sickness and it is very difficult to predict who will develop symptoms. If you have experienced mountain sickness before you are at increased risk. The altitude that you are sleeping at clearly plays a role. When you sleep your respiratory rate naturally decreases exacerbating the effects of low oxygen. Whenever possible sleep low and hunt high. As noted earlier a night spent at 5000 feet can really help your system adjust.

We will now look at the various physical illnesses that are caused by the low oxygen level. The most common and typically least severe is Acute Mountain Sickness (AMS). The vast majority of people who suffer from AMS are unacclimated and rapidly ascend to an altitude greater than 6000 feet. Symptoms include headache, sleepiness, irritability and shortness of breath. These early symptoms can easily be mistaken for the flu or other benign illnesses. It is important to recognize these early symptoms and act appropriately to prevent more serious effects. In more severe cases the victim will begin vomiting and become very lethargic. The patient may develop swelling of the face and extremities. As with all altitude sickness this is due to decreased oxygen levels in your body. Researchers believe that AMS is caused by mild swelling of your brain due to the hypoxia. The low oxygen level causes the blood vessels in your brain to become leaky and as fluid leaks out of the damaged vessels, swelling occurs. Treatment in mild cases is simply descent to a lower altitude. Oxygen therapy also helps symptoms but is often not available. Medical therapy is typically steroids once symptoms have begun. Steroids decrease brain swelling and stabilize the leaky blood vessels. Acetazolamide(Diamox) is a medication that is used to help prevent AMS. It is a diuretic medication meaning that it makes you urinate a lot. Researchers found that Diamox causes the same effects on your body that increasing altitude causes. It tricks your body into adjusting for high altitude even when you are in Florida. It is like altitude in a bottle. It has been well proven to prevent AMS with minimal side effects. It has not been well studied for use after symptoms begin but most authorities believe that it is helpful.

The other illnesses that are caused by high altitude are basically more serious variants of AMS. If AMS is unrecognized or untreated, more severe symptoms will occur. If a patient with AMS continues to ascend or not appropriately descend the brain swelling can worsen and the patient can become markedly confused, uncoordinated and eventually will slip into a coma. An associated condition can effect the victims lungs. Low oxygen levels can also damage blood vessels in the lungs and cause them to leak fluid. Your lung tissue fills up with fluid and paradoxically worsens your body's low oxygen level. This is the most serious complication of AMS because it is quickly fatal. These more serious complications are easily prevented by recognizing the early symptoms of AMS and descending to a lower altitude. Most authorities recommend a drop of about 1000-2000 feet or until symptoms resolve. Typically, 1-2 nights at the lower elevation will allow your body to adjust and then you can gradually move to higher elevation.

In conclusion, gradual ascent is the most important measure that one can do to prevent altitude sickness. If you are on a tight schedule and will be moving quickly to an altitude greater than 6000 feet, acetazolamide is probably a reasonable way to go. Your physician can prescribe this for you before you leave on your trip. You generally need to take it for about 2 days prior to your trip to prevent altitude sickness. Always sleep at the lowest altitude that is practical. Most importantly, if you or someone in your party develops flu like symptoms including cough, severe sleepiness or severe headache, quickly proceed to lower elevation. Symptoms can worsen rapidly and lead to a much more serious situation.

For more detailed information on Altitude sickness including life threatening conditions such as High Altitude Pulmonary Edema (HAPE) please visit the Altitude Info Center Online


Next month: Wound Management