How Long Can Altitude Sickness Last?

AMS happens if the body is not able to adjust to the low air pressure and low oxygen at high altitudes. The low oxygen (hypoxia) levels in the air and blood cause the blood vessels of the brain to swell (dilate). The dilated blood vessels in the brain may cause headaches and swelling of the brain. The swelling puts pressure on the brain, squeezing it against the skull. 

Altitude sickness may rarely advance to a more severe form of the illness called high altitude cerebral edema (HACE). HACE occurs when brain swelling becomes severe manifesting as headache, confusion, lethargy, lack of coordination, irritability, vomiting, seizures, coma and eventually death if untreated.

Severe altitude sickness may cause the tiny blood vessels (capillaries) in the lungs to become swollen and leaky. This leads to an accumulation of fluid in the air sacs of the lungs. This condition is known as high altitude pulmonary edema or HAPE. HAPE severely decreases the exchange of oxygen in the lungs which may cause breathing difficulties and even death. If left untreated it may progress to severe breathlessness even at rest, a persistent cough sometimes with blood, chest tightness and severe weakness. Ultimately, it advances to confusion, unconsciousness and death.

The initial symptoms of altitude sickness are:

• Headache
• Nausea
• Feeling uneasy or sick
• Shortness of breath
• Tiredness or fatigue
• Dizziness

These initial symptoms, if left untreated, may progress to severe breathlessness, cough, vomiting, confusion and unconsciousness.

While staying hydrated is essential at high altitudes, drinking water over your requirement may not help you. Practically, you may only need an additional liter to a liter and a half of water at altitude. Too much water can harm you by diluting your body's sodium level (hyponatremia). This may lead to weakness, confusion, seizures and eventually coma. An easy way to assess hydration is to check your urine. If the urine is clear or pale yellow, it indicates adequate hydration. Dark urine suggests dehydration and the requirement for drinking more water.

You may prevent altitude sickness by:

• Moving slowly towards a higher altitude. This may help your body acclimatize or get adjusted to the decreasing air pressure and oxygen with altitude.
• Staying hydrated
• Taking adequate rest
• Avoiding strenuous workout for the first 24 hours
• Avoiding smoking and alcohol
• Avoiding alcohol or sleeping pills
• Taking preventive medications such as acetazolamide or nifedipine 
• Following the dictum “Climb high and sleep low,” meaning if you climb more than 1,000 feet in a day, come down to sleep at a lower altitude
• Include more than 70% carbohydrates in your diet.