AMS-Kilimanjaro

Acute Mountain Sickness (AMS) on Kilimanjaro

If you are climbing Kilimanjaro, you should be aware of a condition called Acute Mountain Sickness, or AMS.

AMS occurs when the human body reacts negatively at high altitude due to a lack of oxygen. High altitude is defined as an altitude greater than 4,900 feet. At both sea level and high elevation, the oxygen percentage does not change – it comprises approximately 21 percent of the air.

However, at high altitude the air pressure is lower and thus there are less gases overall. The number of oxygen molecules decreases. Altitude sickness can occur in some people as low as 8,000 feet, but serious symptoms do not usually occur until they are over 12,000 feet. At 12,000 feet (3,600 m) there are roughly 40% fewer oxygen molecules per breath so the body must adjust to having less oxygen.

On the summit of Kilimanjaro, there is only about half the oxygen found at sea level.

High Altitude Categories

• Mountain medicine recognizes three categories:
• High altitude: 4,900 to 11,500 ft (1,500 to 3,500 m)
• Very high altitude: 11,500 to 18,000 ft (3,500 to 5,500 m)
• Extreme altitude: 18,000 ft and above (5,500 m and above)

In the first category, high altitude, AMS and decreased performance is common. In the second category, very high altitude, AMS and decreased performance are expected. And in extreme altitude, humans can function only for short periods of time, with acclimatization.

Mount Kilimanjaro’s summit stands at 19,340 feet – in extreme altitude.

What Causes Acute Mountain Sickness?

AMS is caused by the failure of the body to adapt quickly enough to the reduced oxygen at increased altitudes.

A shortage of oxygen leads to a physiological response by our bodies. We compensate by breathing faster and deeper. We produce more red blood cells which carry oxygen around the body. The process continues as we adjust to the atmospheric conditions – a process known as acclimatization.

There are four factors related to AMS:

• High Altitude
• Fast Rate of Ascent
• High Degree of Exertion
• Dehydration

The main cause of altitude sickness is going too high (altitude) too quickly (rate of ascent). Given enough time, your body will adapt to the decrease in oxygen at a specific altitude. This process is known as acclimatization and generally takes one to three days at any given altitude.

Several changes take place in the body which enable it to cope with decreased oxygen:

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

When our bodies struggle to adjust to the elevation, we develop symptoms of AMS. 

Some early symptoms include a headache, nausea, shortness of breath and a general feeling of malaise. AMS is typically the result of ascending too quickly, which is why it is preferable to take slower routes to the top and to walk at a deliberately slow pace.

Who is at Risk for Acute Mountain Sickness?

AMS is common, yet unpredictable.

It is hard to know who will or will not be stricken with AMS until they are at high altitude. There are no specific factors such as age or gender that correlate with susceptibility. Interestingly, a good level of physical fitness does not appear to have much of a correlation with the ability to acclimatize better. Genetics seems to play a main role.

Your risk of experiencing acute mountain sickness is greater if the following factors apply:

• live by or near the sea/unaccustomed to high altitudes
• gain elevation quickly at high altitudes
• exert yourself physically at high altitudes
• have a low red blood cell count due to anemia
• have heart or lung disease
• take medications like sleeping pills, narcotic pain relievers, or tranquilizers that can lower your breathing rate
• have had past bouts of AMS

How Do You Treat Acute Mountain Sickness on Kilimanjaro:

Many people will experience mild AMS while climbing Kilimanjaro during the acclimatization process.

At over 10,000 feet (3,000 m), more than 75% of climbers will experience at least some form of mild AMS. The symptoms usually start 12 to 24 hours after arrival at altitude and will normally disappear within 48 hours. When the symptoms are gone, you have acclimatized to the current elevation.

In general, any illness at altitude should be presumed to be AMS.

On the mountain, our professional guides will monitor you throughout the climb. We implement daily health checks to make sure our clients can climb as safely as possible, though risks always remain as AMS can develop and worsen quickly.

Treatment for acute mountain sickness varies depending on its severity. The most effective treatment is to simply descend to a lower altitude. However, this usually means abandoning the climb and getting off the mountain. You may be administered bottled oxygen as well. Our teams carry emergency oxygen and a portable stretcher on every trip in case a rescue is necessary. Hospitalization is required for serious cases of AMS.

What are the Symptoms of AMS?

The symptoms of Mild AMS include:

• Headache
• Nausea & Dizziness
• Loss of appetite
• Fatigue
• Shortness of breath
• Disturbed sleep
• General feeling of malaise

Symptoms tend to be worse at night and when respiratory drive is decreased. Mild AMS does not interfere with normal activity and symptoms generally subside as the body acclimatizes. If symptoms are mild, and only a nuisance, ascent can continue at a moderate rate.

While hiking, it is essential that you communicate any symptoms of illness immediately to others on your trip.

The signs and symptoms of Moderate AMS include:

• Severe headache that is not relieved by medication
• Nausea and vomiting, increasing weakness and fatigue
• Shortness of breath
• Decreased coordination (ataxia)

Normal activity is difficult, although the person may still be able to walk on their own. At this stage, only advanced medications or descent can reverse the problem. It is important to get the person to descend before the ataxia reaches the point where they cannot walk on their own (which would necessitate a stretcher evacuation). Descending only 1,000 feet (300 m) will result in some improvement, and 24 hours at the lower altitude will result in significant improvement.

Continuing to higher altitude while experiencing moderate AMS can lead to death.

Severe AMS results in an increase in the severity of the symptoms including:

• Shortness of breath at rest
• Inability to walk
• Decreasing mental status
• Fluid build-up in the lungs

Severe AMS requires immediate descent of around 2,000 feet (600 m) to a lower altitude. There are two serious conditions associated with severe altitude sickness: High Altitude Cerebral Edema (HACE) and High-Altitude Pulmonary Edema (HAPE).

Both happen less frequently, especially to those who are properly acclimatized. But, when they do occur, it is usually in people going too high too fast or going very high and staying there. In both cases the lack of oxygen results in leakage of fluid through the capillary walls into either the lungs or the brain.

High Altitude Pulmonary Edema (HAPE)

HAPE results from fluid buildup in the lungs. This fluid prevents effective oxygen exchange. As the condition becomes more severe, the level of oxygen in the bloodstream decreases, which leads to cyanosis, impaired cerebral function, and death.

Symptoms of HAPE include:

• Shortness of breath at rest
• Tightness in the chest
• Persistent cough bringing up white, watery, or frothy fluid
• Marked fatigue and weakness
• A feeling of impending suffocation at night
• Confusion, and irrational behavior

Confusion and irrational behavior are signs that insufficient oxygen is reaching the brain. In cases of HAPE, immediate descent of around 2,000 feet (600 m) is a necessary life-saving measure. Anyone suffering from HAPE must be evacuated to a medical facility for proper follow-up treatment.

High Altitude Cerebral Edema (HACE)

HACE is the result of the swelling of brain tissue from fluid leakage. Cerebral edema can restrict the supply of blood and oxygen to the brain.

Symptoms of HACE include:

• Headache
• Weaknesses
• Disorientation
• Loss of co-ordination
• Decreasing levels of consciousness
• Loss of memory
• Hallucinations & Psychotic behavior
• Coma

This condition is rapidly fatal unless the afflicted person experiences immediate descent. Anyone suffering from HACE must be evacuated to a medical facility for follow-up treatment.