Trekkers in Nepal must understand the risks of acute mountain sickness (AMS), which can occur at high altitudes where there is less oxygen available. AMS can begin at sleeping altitudes over 2,500m (8,000ft), but is more likely to occur at altitudes over 3,000m (10,000ft), especially when ascending rapidly. Day hikes to high altitudes are less likely to result in AMS as there is less stress put on the body.
AMS varies from person to person and is not dependent on age or a person’s degree of physical fitness. The only predictor of AMS is how you reacted on a previous trip to high altitude – if there were previous problems at high altitude then these are likely to return the next time.
Altitude sickness symptoms may be mild and include headache, fatigue, lack of appetite, nausea, insomnia, dizziness, and general malaise. A small number of people can develop more severe symptoms of High Altitude Pulmonary Edema (HAPE) or High Altitude Cerebral Edema (HACE).
Symptoms of HAPE include a dry cough and shortness of breath at rest, when “it becomes impossible to finish a sentence without gasping for breath.” In addition to AMS symptoms, HACE causes profound lethargy, drowsiness, confusion, slurring of speech, and difficulty walking in a straight line.
If symptoms of HACE or HAPE appear, a person requires immediate descent and medical attention. Both HACE and HAPE can be fatal if a person does not descend to a lower altitude.
Keep in mind the following tips about altitude sickness prevention to help you prepare for a successful trek:
- Ascend slowly
- Climb high, sleep low
- Consider altitude sickness medications
- Stay hydrated!