Acute Mountain Sickness (AMS)
Acute Mountain Sickness or AMS is the symptoms suffered by individuals who climb or travel (ascend) to more than 1500 (4900 feet) to 2500 metres and higher altitude, particularly if they ascend too quickly.
AMS is actually a constellation of different conditions that occur when the body doesn’t have enough time to adapt to the lower air pressure and lower oxygen level at high altitudes, explains Dr. Clayton Cowl, chair of the division of preventive, occupational and aerospace medicine at the Mayo Clinic.
The breathing rate increases and that pushes blood oxygen levels to abnormal levels — forcing the body to function with less oxygen than usual. He said it can affect various systems in the body including the lungs, the kidneys and the brain.
Also called mountain illness, common early symptoms are headache, nausea, dizziness and shortness of breath. A mild case might be relieved with over-the-counter drugs such as ibuprofen. More intense symptoms can be serious or life-threatening.
If symptoms become severe — including shortness of breath even when resting, discolored skin, coughing and mental confusion — medical attention is needed.
Cowl said buildup of fluid could occur in the lungs and the brain and put someone at risk for death.
For most people, it causes mild symptoms that improve with rest and time spent at altitude. However, in some people, it can lead to serious symptoms which can become life-threatening, particularly if they are not recognised and the person does not move down (descend) to a lower altitude. The most important treatment if you develop symptoms of altitude sickness is to stop your ascent and rest. If your symptoms are severe, do not improve, or they are getting worse, you need to descend to a lower altitude. There are various preventative measures, the most important being slow ascent so that your body can adapt to conditions at the right pace (acclimatise).
Theory of Acute Mountain Sickness
The percentage of oxygen in the atmosphere at sea level is about 21%. As altitude increases, the percentage remains the same but the number of oxygen molecules per breath is reduced. 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. Altitude sickness, known as AMS, is caused by the failure of the body to adapt quickly enough to the reduced oxygen at increased altitudes. Altitude sickness can occur in some people as low as 8,000 feet, but serious symptoms do not usually occur until over 12,000 feet.
Mountain medicine recognizes three altitude 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.
At over 10,000 feet (3,000 m), more than 75% of climbers will experience at least some form of mild AMS.
There are four factors related to AMS:
- High Altitude
- Fast Rate of Ascent
- High Degree of Extertion
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
Again, AMS is very common at high altitude. It is difficult to determine who may be affected by altitude sickness since there are no specific factors such as age, sex, or physical condition that correlate with susceptibility. Many people will experience mild AMS during the acclimatization process. The symptoms usually start 12 to 24 hours after arrival at altitude and will normally disappear within 48 hours. The symptoms of Mild AMS include:
- Nausea & Dizziness
- Loss of appetite
- 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. As long as 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 a significant improvement. The person should remain at lower altitude until all the symptoms have subsided. At this point, the person has become acclimatized to that altitude and can begin ascending again.
Continuing on to higher altitude while experiencing moderate AMS can lead to death.
Severe AMS results in an increase in the severity of the aforementioned 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 of these 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 build up 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. Symptoms of HACE include:
- Loss of co-ordination
- Decreasing levels of consciousness
- Loss of memory
- Hallucinations & Psychotic behavior
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.
Treatments for HAPE include:
●Descend or seek medical care at the first sign of HAPE.
●Supplemental oxygen; this is the most effective treatment and should be started as soon as possible. It should be continued until symptoms resolve. Oxygen may be life-saving if descent is not possible.
●Hyperbaric treatment may be used as an alternative to descent, if it is available. You can use oxygen inside a hyperbaric chamber.
●Nifedipine or other medicines may be helpful if oxygen is not available and descent is not possible.
●Stay warm and avoid cold temperatures.
●Rest; this includes not carrying a pack while descending.
The following are recommended to achieving acclimatization:
- Pre-acclimatize prior to your trip by using proper training.
- Ascend Slowly. Your guides will tell you, “Pole, pole” (slowly, slowly) throughout your climb. Because it takes time to acclimatize, your ascension should be slow. Taking rest days will help. Taking a day increases your chances of getting to the top by up to 30% and increases your chances of actually getting some enjoyment out of the experience by much more than that.
- Do not overexert yourself. Mild exercise may help altitude acclimatization, but strenuous activity may promote HAPE.
- Take slow deliberate deep breaths.
- Climb high, sleep low. Climb to a higher altitude during the day, then sleep at a lower altitude at night. Most routes comply with this principle and additional acclimatization hikes can be incorporated into your itinerary.
- Eat enough food and drink enough water while on your climb. It is recommended that you drink from four to five liters of fluid per day. Also, eat a high calorie diet while at altitude, even if your appetite is diminished.
- Avoid tobacco, alcohol and other depressant drugs including, barbiturates, tranquillizers, sleeping pills and opiates. These further decrease the respiratory drive during sleep resulting in a worsening of altitude sickness.
- If you begin to show symptoms of moderate altitude sickness, don’t go higher until symptoms decrease. If symptoms increase, descend.
If you suffer any possible symptoms of AMS on the trail, please report this to your guide immediately. Don’t try to hide it or tough it out. It can happen to anyone. If you act carelessly and don’t report symptoms, it can result in emergency evacuation or even death in severe cases.
A pulse oximeter to measure the oxygen level in your blood and your pulse rate in the morning and evening. The oximeter is placed on a climber’s fingertip. The oximeter uses two beams of light that shine into small blood vessels and capillaries in your finger. The sensor reflects the amount of oxygen in the blood.
Oxygen saturation is a measurement of how much oxygen your blood is carrying as a percentage of the maximum it could carry. Normal blood oxygen levels at sea level are 95-100%.
As altitude increases, oxygen saturations decrease. Proper acclimatization generally brings oxygen saturations higher, which is why these figures typically rise when oxygen saturations are tested after resting overnight. On Kilimanjaro, oxygen saturations percentages are regularly in the 80’s. However, if oxygen saturation is ever less than 80%, the climber needs to be monitored very closely.
Bottled oxygen can be used as a precaution and additional safety measure. The oxygen cannister is for use only in emergency situations. The most immediate treatment for moderate and serious altitude sickness is descent. Therefore, oxygen is used strictly to treat a stricken climber, when necessary, in conjunction with descent, to treat those with moderate and severe altitude sickness.We are aware that some operators market the use of supplementary personal oxygen systems . To administer oxygen as a means to eliminate the symptoms of AMS without descending and proper medical treatment is dangerous because it is a temporary treatment of altitude sickness. Upon the cessation of the use of oxygen, the climber will be at an even higher altitude without proper acclimatization.
The Gamow Bag is portable hyperbaric chamber used to treat AMS. The inflatable bag simulates descent to lower altitude. The patient is placed inside the bag and it is inflated with air to increase the concentration of oxygen. A Gamow bag weighs about 12 lbs. Inflated, the bag is about 7 feet long and 2 feet in diameter.
At 9,800 feet (3,000 m), the Gamow Bag can simulate a descent of 4,800 feet (1,500 m). After two hours in the bag, the person’s body chemistry will have “reset” to the lower altitude. This acclimatization lasts for up to 12 hours outside of the bag which should be enough time to get them down to a lower altitude and allow for further acclimatization.
Diamox (generic name acetazolamide) is an F.D.A. approved drug for the prevention and treatment of AMS. The medication acidifies the blood, which causes an increase in respiration, thus accelerating acclimatization. Diamox does not disguise symptoms of altitude sickness, it prevents it. Studies have shown that Diamox at a dose of 250 mg every eight to twelve hours before and during rapid ascent to altitude results in fewer and/or less severe symptoms of acute mountain sickness (AMS). The medicine should be continued until you are below the altitude where symptoms became bothersome. Side effects of acetazolamide include tingling or numbness in the fingers, toes and face, taste alterations, excessive urination; and rarely, blurring of vision. These go away when the medicine is stopped. It is a personal choice of the climber whether or not to take Diamox as a preventative measure against AMS.
Please note that Diamox is simply a preventative drug and does not cure altitude sickness or prevent it entirely, it simply can help. If altitude sickness symptoms appear then descending is the only cure. Diamox should never be taken to continue upwards with AMS symptoms.
Remember, Diamox is a prescriptive medicine and you will need to consult your doctor if you are thinking of taking it. The drug is not suitable for people with liver or kidney issues and should not be taken by pregnant woman.
Ibuprofen can be used to relieve altitude induced headaches.
References:- http://dxline.info/diseases/altitudemountain-sickness http://www.ultimatekilimanjaro.com/acclimatization.htm http://www.cbsnews.com/news/mount-everest-altitude-sickness-turns-deadly/