Acute Mountain Sickness (AMS)

     Acute Mountain Sickness (AMS), often referred to as altitude sickness, is a fairly common and serious risk when trekking at high altitude in Nepal. AMS can develop at altitudes above 2000 meters (6500 ft), and the risk increases significantly as you ascend to higher altitudes.

     The early symptoms of AMS are headache, extreme fatigue, and loss of appetite/nausea. Some people also experience shortness of breath while resting. AMS is a result of the excessive accumulation of fluid in certain parts of the body, specifically the brain and lungs. When mild symptoms occur you must stop immediately at the current altitude until the symptoms have gone away. If symptoms persist after you have rested for a day or two, you must descend to a lower altitude (300 – 500m/1000-1700 ft lower)

     Worsening symptoms of AMS including increasing tiredness, severe headache, vomiting, and loss of coordination.  These are the symptoms of the more severe case of AMS call High Altitude Cerebral Edema (HACE). HACE can lead to unconsciousness and death within 12 hours if the symptoms are ignored. Increasing shortness of breath, coughing, and tiredness are signs of High Altitude Pulmonary Edema (HAPE), which can also be rapidly fatal if ignored.

     A person suffering from AMS may not be thinking clearly and may have to be forced to descend.  A person with AMS should not be allowed to descend alone. They should descend to an altitude where they feel their symptoms improve (usually after 300 – 500 meters of descent). Always follow your trek guide’s advice about how to deal with AMS symptoms.

     If you experience any AMS symptoms but are unsure whether it is AMS, always err on the side of caution and stop ascending and consider descending to lower altitude.

     Medications are not a good substitute for proper acclimatization in reducing the risk of AMS. Acclimatization requires a planned, slow ascent of not more than 300 – 500m (1000-1700 ft) per day. If you are acclimatizing properly you can also consider taking Diamox to prevent or alleviate AMS symptoms.

     You should not plan to trek to high altitude (over 3000 meters) if you have heart disease, difficulty breathing at sea level, or are pregnant. Children may be more susceptible to AMS, and because they may not be able to describe their symptoms should be watched very closely.

      Good physical conditioning does not prevent AMS, and persons who have not experienced AMS at high altitudes in the past may still develop symptoms on subsequent treks.

     Sleeping pills, sedatives and alcohol should not be used at high altitudes as they tend to decrease breathing and can lead to AMS. Drinking 3-4 liters of water or other fluids per day to avoid dehydration will help in the acclimatization process. It is also possible to use a Gamow bag to treat the effects of AMS. A Gamow bag, available at the Himalayan Rescue Association’s outposts in Periche (Everest) and Manang (Annapurna), simulates the air pressure of low altitude.

     While it is possible to employ helicopter rescue in case of serious AMS symptoms you should not rely on this, or wait for a helicopter if you experience AMS. Your first recourse should be to descend to lower altitude. However, because it may become necessary to call in a helicopter for evacuation, you should have an insurance policy in effect that covers this (very expensive) service. The helicopter service company requires a financial guarantee to implement a rescue so having this is essential if you are planning to trek at high altitudes, especially at or above 5000m/16,000 ft.

Key facts about AMS:

  • Anyone is susceptible to AMS, regardless of physical fitness or previous high altitude experience.
  • AMS can be deadly so act immediately at the first sign of any symptoms.
  • AMS can start to occur at altitudes as low as 2500 meters (8000 ft)

You can also read more about AMS at this professional site dedicated to the subject:

Altitude Comments

Of the main fears of trekking, especially in the Everest region, is the altitude and the problem of AMS (Acute Mountain Sickness).

The reason I was nervous about this is that there seems to be no pattern as to whom it affects. It does not depend upon the fitness of the trekker or on how many times that person has been to altitudes in the past. This seemingly random process worried me that it would prevent me from fulfilling my ambition of reaching Gokyo Ri and Everest Base Camp.

The best way to avoid the illness, or to reduce your chances of suffering from it, is to ascend gradually building in rest days to the schedule. One group I met was forced to descend after they ascended too quickly and had to abort their attempt for EBC. I was certainly glad that we had taken our ascent slowly and had an acclimitisation day in Namche.

The most common symptom of altitude sickness is a headache. In fact around 4000m it is almost universal to have one. Mine was a very dull and mild headache, not causing any concern for me as I knew to expect one. I would just pop some paracetamol and it cleared overnight. The headache is caused by the body pumping more blood to the head in order to give the brain the oxygen it is used to having at lower altitudes. Therefore deep breathing can help to alleviate it and this perhaps explains why my headache cleared overnight (compounded by the fact that my body became used to the altitude over time).

I also drank plenty of water. As you are exercising in sometimes cold conditions it can slip the mind not do drink. But not only will it help with any headache but it will defend you against the serious problem of dehydration. I aimed to drink at least 3-4 litres a day.

The only other mild symptom you may experience is a loss of appetite. Luckily I was not affected by this and found myself being called upon the finish the others meals – a role I delighted in.

You are rightly advised, if the symptoms progress into a more serious headache, dizziness and nausea, not to ascend any further; if the conditions becomes even more serious you should descend immediately and never alone. It can be a serious threat and so groups should always err on the side of caution. But for the most part it shouldn’t put your trek in jeopardy in any way.

Walking Technique

Though it may seem a little ridiculous to be talking about ‘How to Walk’ some of the tips I picked up from guides I used throughout my time.

Overall during the trek we were told to take a slow pace. Not only would you struggle taking a fast pace at the altitude, it’s thoroughly enjoyable to take in the majestic surroundings at a slower pace and really absorb the spectacular part of the world you find yourself in. I found that taking a slow pace and longer strides was a great technique for covering distance without expending too much energy. Lengthening my stride just a fraction allowed me to get into a good rhythm and take fewer steps. This I attempted to use throughout, particularly on level surfaces and slight inclines.

For steps I was advised to step up and down smoothly and gradually as opposed to sharply. Going up this would not result in a need for sudden bursts of strength and energy but more a constant pressure on the legs. Going down I kept my knees bent and ‘glided’ down rather than stepping down. This helped to keep my momentum under control and didn’t put too much impact on my knees, the most common problem when descending sharply.

My main issue was turning my ankles downhill. Luckily I had boots with good ankle-support but I found the loose rocks and stones going down were very easy to step on and turn the ankle on. So I soon became very careful of where I placed my foot on the downhill sections.

But the best piece of advice, and you’ll certainly hear it enough is: “Slowly, slowly”.