Altitude sickness is when the body fails to acclimatise resulting in insufficient oxygen (hypoxia). This can be due to climbing to high altitude too quickly or genetic susceptibility. Breathing becomes difficult as you aren’t able to take on enough oxygen.
Risk Category: Low
- People with no prior history of altitude illness and ascending to less than 9,000 ft (2,750 m)
- People taking ≥2 days to arrive at 8,200–9,800 ft (2,500–3,000 m), with subsequent increases in sleeping elevation less than 1,600 ft (500 m) per day, and an extra day for acclimatization every 3,300 ft (1,000 m)
- Prophylaxis Recommendations: Acetazolamide prophylaxis generally not indicated
Risk Category: Moderate
- People with prior history of AMS and ascending to 8,200–9,200 ft (2,500–2,800 m) or higher in 1 day
- No history of AMS and ascending to more than 9,200 ft (2,800 m) in 1 day
- All people ascending more than 1,600 ft (500 m) per day (increase in sleeping elevation) at altitudes above 9,900 ft (3,000 m), but with an extra day for acclimatization every 3,300 ft (1,000 m)
- Prophylaxis Recommendations: Acetazolamide prophylaxis would be beneficial and should be considered
Risk Category: High
- History of AMS and ascending to more than 9,200 ft (2,800 m) in 1 day
- All people with a prior history of HAPE or HACE
- All people ascending to more than 11,400 ft (3,500 m) in 1 day
- All people ascending more than 1,600 ft (500 m) per day (increase in sleeping elevation) above 9,800 ft (3,000 m), without extra days for acclimitisation.
- Very rapid ascents (such as less than 7-day ascents of Mount Kilimanjaro)
- Prophylaxis Recommendations: Acetazolamide prophylaxis strongly recommended
Abbreviations: AMS, acute mountain sickness; HACE, high-altitude cerebral edema; HAPE, high-altitude pulmonary edema.
High-Altitude Travel & Altitude Sickness - Peter H. Hackett, David R. Shlim – Centers for Disease Control & Prevention
Signs and Symptoms
Altitude sickness is divided in to 3 types:
- Acute Mountain Sickness (AMS): Is the most common form of altitude sickness. Symptoms are like a hangover headache, dizziness, tiredness, weakness, nausea and occasional vomiting. AMS generally resolves with 12–48 hours of acclimatisation.
- High Altitude Cerebral Edema (oedema) (HACE): Is a severe progression of AMS which can occur by itself or in conjunction with AMS and HAPE. Symptoms usually come within 12-24 hours of reaching a higher altitude. The symptoms are more severe than those with AMS but may also develop loss of coordination, difficulty walking, drowsiness, confusion, shortness of breath at rest and a cough. Someone with HACE needs immediate decent and oxygen if available.
- High AltitudePulmonary Edema (oedema) (HAPE): Is a build-up of fluid in the lungs and can occur in conjunction with AMS and HACE. Symptoms begin with shortness of breath on exertion progressing eventually to shortness of breath at rest with tightness in the chest. There may be a blue tinge to the skin (cyanosis) and a persistent cough bringing up pink/white frothy sputum. Treatment for HAPE is immediate decent and oxygen if available. Nifedipine helps to reduce the chest tightness and help breathing.
Prevention of Altitude Sickness
- Ascend gradually
- Avoid going directly from low altitude to more than 9000 feet in 1 day
- Once over 9000 feet don’t ascend more than 1600 feet per day and plan an extra day for every 3300 feet.
- Avoid alcohol for the first 48 hours
- Only mild exercise for the first 48 hours
- Acetazolamide (Diamox) can also help to prevent Altitude Sickness.
Altitude sickness drugs:
- Acetazolamide (Diamox) 125mg twice daily
Commence 2-3 days before ascent and discontinue 2-3 days after reaching highest sleeping altitude or once decent has begun.