A person living at low altitude needs time to adjust to the low oxygen pressure at high altitude. Breathing is deeper during the first days at high altitude. This improves the oxygen supply to the organs, but also causes shortness of breath during exertion. Ascending too quickly means that there is not enough time to acclimatise and this can cause altitude sickness to develop within several hours to two days.
People differ in their susceptibility to altitude sickness and this is not related to their physical fitness. Young people are generally more susceptible to altitude sickness than older people.
Mild altitude sickness usually goes away within several days, provided you do not go to a higher altitude. However, severe altitude sickness with cerebral or pulmonary oedema (fluid accumulation in the brain or lungs) can rapidly result in death.
Symptoms of mild altitude sickness include:
- nausea or vomiting
- weakness or abnormal fatigue
Symptoms of severe altitude sickness include:
- very severe headache, which no longer responds to painkillers
- increased vomiting
- coordination disorders (being unable to walk in a straight line)
- behavioural changes
- confusion or disorientation
- increased coughing
- shortness of breath that does not disappear after resting
- tight sensation across the chest (being unable to lie flat)
People who are susceptible can develop altitude sickness from 2000 metres, but severe symptoms occur primarily with overnight stays above 3000 metres.
If you have any health issues, first discuss with your physician whether it is wise to visit high altitude areas.
- Spend at least two nights at moderate altitude first (2000 to 2500 metres). Also try this if you are flying directly to a high altitude airport.
- Above 3000 metres, never sleep more than 500 metres higher than the previous night or spend two nights at the same altitude if this cannot be avoided.
- Consider climbing to a higher altitude during the day, “climb high, sleep low”. Do not do this if you already have symptoms of altitude sickness.
- Spend several nights at moderate altitude (2000 to 3000 metres) in the weeks before departure. Sleeping in a hypobaric hypoxia tent for at least seven consecutive nights just prior to departure can also increase acclimatisation, but training in a hypobaric environment does not help.
- You can take preventive acetazolamide if you have insufficient time to acclimatise, or if you have suffered from altitude sickness in the past at a similar altitude.
Adjust your behaviour
- Do not use sleeping pills or alcohol during the first days at high altitude. Do not exert yourself strenuously during the first days at high altitude.
- Drink sufficient water to prevent dehydration. Your urine must remain light-coloured.
- Make sure you have a flexible schedule so that you can rest for a few days in case of problems.
- Measuring the arterial oxygen saturation (SpO2) has only very limited value. It is much more useful to respond quickly and adequately to the first symptoms of altitude sickness.
Acetazolamide - above 3000 metres
Take acetazolamide (Diamox®) with you if you are going to be staying above 3000 metres. Acetozolamide facilitates acclimatisation.
You can take it to prevent or treat altitude sickness.
- Take half of a 250 mg tablet, twice a day (early in the morning and - for example - at around 16:00, so that the diuretic effect has reduced by nighttime).
- Start on the day before you ascend to 3000 metres or higher and continue for two days after reaching the maximum altitude. You can stop taking this medication if you descend before this time.
- Tingling sensations and abnormal taste sensations are common but harmless side effects. They will disappear when you stop taking the medication. As acetazolamide is a mild diuretic, you may notice a need to urinate larger volumes or more frequently.
See also the general tips for a stay at high altitude.