In its mildest of forms, AMS might produce the following symptoms, which can typically occur a few hours after reaching altitude:
- A loss of appetite
- Difficulty sleeping
- Tiredness (fatigue)
- Shortness of breath
It is common for symptoms to begin to show between 12 and 24 hours after the climber reaches high altitude. As the body adjusts to the thinner air at high altitude, normally after a day or two, improvement can be expected.
Remember the golden rule, namely, to tell your mountain guides if you experience any of the above symptoms. Further continued acclimatization should see these symptoms reduce and there should be no need to stop the ascent, as long as you take it slowly.
Of course, the AMS might become worse and the following symptoms can indicate the onset of moderate AMS :
- Nausea and vomiting
- Increased severity of headache
- Ataxia, which in layman’s terms means that co-ordination of movement becomes difficult
- A tightening in your chest
Once these symptoms occur, the only option on the mountain is to descend, if advanced medication is not available. (Note that ataxia can result in the sufferer becoming incapable of walking unaided, so prompt reaction is required to avoid an evacuation by stretcher). A descent of around 300 metres in altitude is usually sufficient to allow the climber some recovery; a day of extra acclimatization at the lower altitude will produce a substantial recovery.
Descent at this stage is essential, as continuing to climb will lead to the AMS becoming severe. Severe AMS can be fatal. Two potentially fatal conditions are associated with this severe stage, HAPE and HACE. In both cases the lack of oxygen results in leakage of fluid through the capillary walls into either the lungs or the brain.
A sufferer of severe AMS like HAPE and HACE will demonstrate the above symptoms plus:
- An inability to walk unaided
- Difficulty in breathing, even when trying to rest
- Fluid entering into the lungs
- A reduction of mental ability
- A cough that produces a white or pink frothy substance
An immediate descent of the mountain is required, if this severe stage is reached. And the descent has to be further, down by 600 metres at least.