When we visit high mountain regions we become susceptible to altitude sickness, known as Acute Mountain Sickness, or AMS. If you are planning a visit to anywhere over 2000m then it is worth understanding the causes, symptoms and possible outcomes of AMS your life could depend on it.

In its early stages AMS can be as innocuous as a head ache but if ignored it can lead to unconsciousness and death.  

When does it occur?
For the average person the threshold is 2500m to 3000m, but people have been known to suffer as low as 2000m. There doesn’t seem to be any way of telling who will suffer and who won’t. Being physically fit does not seem to be a guarantee of avoiding AMS, indeed it is normally the young and fit who suffer most but this is probably because they do not have the patience to acclimatise slowly.
Acclimatisation stops at around 5300m above sea level.

How can we avoid it?
Being at altitude is all about taking things slowly. Take a leaf out of the late, great Don Whillans and do the very minimum you can get away with whilst you acclimatise.
Being physically fit will definitely not be a disadvantage, it will also greatly aid your enjoyment once you are acclimatised so put some effort in before your trip. Aim for 3 sessions of hard exercise a week totalling 30 minutes or more. Swimming is ideal as it will give your cardiovascular system a good work out without stressing joints.

Drink plenty of water. As you acclimatise your body will need more water to adjust its fluid levels. You will also use more moisture than normal by breathing in dry mountain air and exerting yourself with reduced levels of oxygen in the air. Your urine should be clear and plentiful. The average adult male should be drinking 4 to 6 litres of water a day.

Keep your sleeping altitude as low as possible. The daily difference should not exceed 300 to 600 metres once you are over about 2500m, this will vary from person to person so keep an eye on each other for the symptoms detailed below. Always try a sleep lower than that days highest altitude.  

Change your diet. You will need a great deal more calories than normal when trekking at altitude but your body won’t deal well with fats and proteins. Carbohydrates are the way forward.  

Patients with heart or lung disease or high blood pressure should seek specialist medical advice before travelling above 4000m.

Diamox. This drug can be used to prevent AMS. It is used to reduce fluid retention (it makes you pee) and increases the amount of oxygen in the blood. It needs to be taken for several days before an ascent and for 3 days afetrwards and has several side effects. It can cause nausea, tingling in the fingers and make you generally feel unwell. More unusual side effects include flushing, rashes, thirst, drowsiness and excitement. It can be very useful for rescue teams who cannot afford to acclimatise properly but trekkers and climbers should consider the ethics of using drugs for sport.  

The Symptoms

Most people will feel a little unwell at altitude, it is perfectly normal and doesn’t mean you about to drop down dead! After a day or so at the same altitude then you should feel normal again, that’s acclimatisation.  

At altitude the fine tissues in your lungs and head that normally act as barriers start to leak. When you acclimatise slowly then this fluid, called oedema, is managed by your body and disposed of. If you don’t acclimatise slowly it builds up.  

If the oedema builds up in the head its called cerebral oedema, if its in the lungs its called pulmonary oedema. This happens to less than 2% of travellers at 4000 to 5000m, occasionally lower.  

High Altitude Pulmonary Oedema (HAPE)
Early symptoms: Headaches, a bad cough or chest infection causing breathlessness.  

If these are ignored HAPE may come on in minutes and can be recognised by breathlessness at rest and sometimes a bubbling sound in the chest and blood stained mucus. Patients are then dangerously ill and should be evacuated to a lower altitude as an emergency.   

High Altitude Cerebral Oedema (HACE)
Symptoms: Massive headaches, lack of balance and dizziness, patients become drowsy, irrational and confused over a period of hours and their walking becomes unsteady. Double vision may occur. Again patients are dangerously ill and should be sent to a lower altitude as an emergency.

Treatment

As mentioned above most people suffer some of the early symptoms of AMS.  If the symptoms get worse don’t go any higher. Wait 2 or 3 days for improvement. If there is none then descend at least 500m.  

In these early stages where a headache is common you can take headache tablets but they tend to just mask the symptoms. Oxygen by mask will also help the symptoms.  

It is worth re-emphasising that the acute symptoms of AMS ie HACE & HAPE are rare, this is because the early symptoms are strong enough not to be ignored. Your body is sending you this message for a reason – don’t ignore it!

 Anyone that suffers from the symptoms of HACE or HAPE should descend immediately and seek medical attention if possible. Often a descent of 500m is all that is required but the lower the better. The patient should not gain height again until medical attention has been sought.  

Conclusion

Build your trip programme around proper acclimatisation. I plan all of my courses that will involve altitude around the simple adage that gaining height slowly and descending rapidly if one is ill cannot be bettered. This sometimes means that we are more expensive than other operators but believe it’s worth spending a little extra on a longer trip so that you can acclimatise properly and enjoy the trip safely.  

The fitter you are before the trip, the more you will enjoy it and it can only help in acclimatisation.  

On the trip itself get used to monitoring how you feel and watching others for any changes in their personality that may be as a result of altitude sickness. Don’t be afraid to discuss any aches or pains that you may have.

 Have an emergency plan if someone needs to go down, who will accompany them, what will happen to the others? Go slowly. If you have a worsening headache, go down!