(Acute Mountain Sickness ~ AMS)
It is most unusual to feel 100% healthy at altitudes of more than 3,000 metres (9,800 feet). You should expect these symptoms:
- Sudden, temporary shortness of breath
- Periodic breathing that wakes you up
- Breathing frequently; feeling the need to take frequent rest breaks while trekking
- Sleeping more than normal, often 10 hours or more
- Loss of appetite
- Vivid dreams from 2,500 to 3,500 metres (8,200 feet to 11,500 feet)
- Runny nose (and that's putting it mildly!)
- Frequent urination: While trekking at altitude, most people urinate at least once during the night. Many trekkers urinate more than once during the night, and very frequently during the day as well.
If you have one or more of the above symptoms, there is nothing to worry about and you can continue your ascent.
Mild Symptoms of Altitude Sickness
However, you only need to get one of the symptoms listed below (not all of them) to diagnose altitude sickness.
- Headaches are a very common symptom of mild altitude sickness. If you develop a headache at altitudes above 2,500 metres or 12,000 feet, assume that it is a symptom of altitude sickness / acute mountain sickness (AMS). Altitude headaches are usually felt most at the top of the head, and is usually a throbbing headache. It may begin in the evening and get worse at night. Sometimes it may improve temporarily if you raise your head and shoulders at night. Symptomatic treatment includes spirin (dispirin), paracetamol, ibuprofen (Nurofen, Brufen) or acetamenophen (tylenol). Do not take sleeping tablets. Diamox may give more lasting relief.
- Nausea, with or without vomiting: Nausea may be the only symptom, but more often nausea presents along with a severe headache. If you develop nausea during the evening or night, but feel better in the morning, take a whole day's rest. If it persists, consider descending to a lower altitude. If it becomes more severe the next morning, descent is recommended.
- Vomiting tends to be urgent and projectile.
- Mild dizziness: You may feel slightly dizzy. If this happens when you are walking, stop and take rest, preferably in the shade, and drink as much water as you can. Make your way to the closest guest house or tea house and rest for the remainder of that day.
- Lack of appetite
- Malaise: General feeling of ill health
- Cough: You may develop a dry cough, which can be painful.
Mild Symptoms: Course of Action
Never go higher with mild symptoms. Any symptom except diarrhoea or a mild sore throat can be caused by altitude sickness. In fact, assume that it is altitude sickness unless you can demonstrably prove otherwise. The human body needs time to acclamatize and adapt to altitude, so give your body the time it needs to adjust to changing altitude.
Don't try to convince yourself that "all will be well" and continue your ascent in the face of mild symptoms. Experienced mountaineers will tell you that it's is a recipe for disaster.
Drink plenty of water from the very outset. Don't wait for mild symptoms to develop before you hydrate your body. Drink a minimum of 3 litres a day. 4 to 5 litres is not only recommended, this high volume of water will give your body the best chance at acclamatisation.
Don't focus on the social inconvenience of having to urinate frequently during the day - drinking enough water will make your tour or trek more enjoyable (without the annoyance of mild symptoms or the spectre of severe altitude sickness). It would not be dramatic to say that adequate hydration at altitude may very well save your life!
If mild symptoms do not subside in a day or so despite adequate rest and hydration, or if symptoms get worse, the only recourse is to descend to a lower altitude. Descending by even 100 to 300 metres (325 to 100 feet) can make a big difference. Another rule of thumb is to descend the altitude where you last felt well.
It is important to note that there is usually a lag time between your arrival at high altitude and the onset of symptoms. In other words, symptoms may not develop immediately - they may take a day or so. It is common to feel fine for the first day and night, and then experience symptoms on the second night at the same altitude.
- Mild symptoms worsening rapidly
- Severe vomiting that is persistent
- A severe headache that persists
- A cough that is severe and persistent
- Lack of co-ordination (ataxia). The person may not be able to walk in a straight line, and may look drunk (though they are not)
- Loss of conciousness
- Bluish discolouration of the lips or even the whole face
- A high resting heart rate of over 120 beats per minute
- Lethargy and drowsiness
- Crepitus / hearing the sound of fluid accumulating in the lungs
- Severe breathing difficulties
- Breathlessness at rest
- Coughing blood, pink sputum, or quantities of clear fluids
High Altitude Cerebral Oedema (HACE)- this is a build-up of fluid around the brain. It causes the first 4 symptoms of the mild, and the severe symptom lists.
High Altitude Pulmonary Oedema (HAPE) - this is an accumulation of fluid in the lungs, and since you are not a fish, this is serious. It is responsible for all the other mild and serious symptoms.
Severe Symptoms: Course of Action
If symptoms are severe - one or more of any of the symptoms listed above - immediate and rapid descent is the only possible course of action.
It is important to note that a person with severe symptoms may not be able to think straight, and may insist that they are feeling fine. That may not be the case at all, so disregard what the person says and evaluate their symptoms objectively. Take them down immediately to as low an altitude as possible. Time is of the essence, and may save their life. They must see a doctor as soon as possible. In the meanwhile, if a Gamow bag is available, use it!
Slow Healing: Cuts heal slowly at altitude. Infections also resolve slowly, wound healing is also slow. If you develop a moderate to sever infection of any kind, you must descend.
Swelling: Your face, hands, feet and even abdomen can swell up at altitude. Remove any rings you may be wearing if you experience this symptom. Women are more susceptible than men. Unless you have severe swelling, there is no need to worry and it is OK to continue your ascent.
Periodic Breathing: Although studies have found no direct link between periodic breathing and altitude sickness, it is nevertheless common to find altitude affecting the body's ability to breathe normally. This usually happens while you sleep, or while you are at rest. Breathing automatically becomes shallower, and you breathe less and less until you need some deep breaths to recover. This shallow breathing followed by deep breathing becomes a cycle. Many people are not aware of this, as they are sleeping. But almost all trekkers experience it above 5,000 metres (16,000 feet).
Links to external websites:
- A Non-Physician Altitude Tutorial from the International Society for Mountain Medicine
- Altitude Sickness on Wikipedia
- How to use a hyperbaric chamber: Gamow bag, CERTEC and PAC
PLEASE NOTE: The above information has been provided on this website as a brief overview, from a lay person's perspective, for your convenience. We do not claim to be medical professionals or health care workers in any capacity. We do not guarantee the accuracy or medical efficacy of any of the information, symptoms or treatment protocols mentioned on this website. Please consult your physician for accurate information, prevention and treatment of altitude sickness.