High altitude: What is altitude sickness and how to prevent it?

Are you planning to go to places that are at high altitudes like mountains, hill stations, plateaus, etc? It is fun to spend some free time at these places but the ascent to high altitude can lead to a series of adaptive changes in the body which is termed as ‘acclimatization’.

This happens as high altitude places have less oxygen in the atmosphere. So to maintain the amount of oxygen delivered to tissues, the body undergoes cardiovascular, respiratory, and hematologic changes that increase oxygen delivery to tissues and enhance oxygen uptake.

These changes include increased pulmonary ventilation and diffusing capacity of lungs, increased heart rate and cardiac output, increased red blood cell count, and increased mitochondria level inside cell. All these changes contribute to increased oxygen delivery even at low oxygen places.

If a person goes at high altitude places rapidly or if the body is unable to acclimatize properly, it can lead to altitude sickness or acute mountain sickness. Altitude sickness is simply a physical illness due to rapid exposure to a decreased amount of oxygen at high altitudes. However, it can lead to severe form: High Altitude Cerebral Edema (HACE) or High Altitude Pulmonary Edema (HAPE) which is a collection of fluid in the brain or lungs respectively that can hamper normal physiology of both organs and is life-threatening.

The symptoms of altitude sickness begin to appear above 2500 meters (8000 ft.) altitude within hours.

Symptoms

• Headache
• Dizziness or light-headedness
• Nausea and Vomiting
• Fatigue
• Loss of appetite
• Rapid breathing and shortness of breath
• Increased pulse rate

If you have a pre-existing medical condition such as heart failure, myocardial infarction, hypertension, diabetes, asthma or other pulmonary disorders, sickle cell disease, etc. consult your physician before you go to high altitude.

Prevention

Here are 6 different ways that you can do to prevent from suffering altitude sickness.

Ascend gradually

Acclimatization takes time around 2-4 days for letting your body to fully adjust to your surrounding environment. If you ascend too quickly, your acclimatization will be insufficient which can lead to altitude sickness.

According to research, it is recommended that at altitudes greater than 3000 meters, one should not spend subsequent nights 300 meters higher than the previous night. A rest day is necessary every 2-3 days. If you are suffering from altitude sickness, do not ascend until the symptoms are improved.

Sleep at low altitude

One of the main symptoms of altitude sickness is rapid breathing or hyperventilation. This occurs to collect more oxygen from the surroundings. However, rapid breathing can lead to increased carbon dioxide levels inside the blood which is converted to bicarbonate by carbonic anhydrase enzyme. This leads to respiratory alkalosis.

During sleep, the body undergoes shallow breathing. This also causes increased carbon dioxide in the blood that can cause alkalosis. Hence, sleeping in high altitudes can aggravate respiratory alkalosis and increase the risk of potential altitude sickness.

Therefore, if you are climbing above 300 meters, make sure to spend your night at lower altitudes. CLIMB HIGH, SLEEP LOW.

High Carbohydrate diet

High carbs diet is the logical source of foods to consume when traveling at high altitudes. In fact, 70% of the total calorie intake should be obtained from carbohydrates.

This is because carbohydrates give 15% more energy for the same amount of oxygen used in consumption of fats and proteins.

Staying Hydrated

Drinking water and staying hydrated is necessary to survive at high altitudes. In fact, a person should drink around 7-8 glasses of water every day.

As you go higher, your respiration rate rises as the oxygen level in the atmosphere drops. As a result, your body will lose more body fluid as water vapor from lungs than usual. This can lead to dehydration and may contribute to the symptoms of altitude sickness.

Avoid Alcohol Consumption

Although there is no significant evidence that alcohol can worsen the effects of acute mountain sickness, it is still considered best to avoid alcohol when traveling at high altitudes particularly before bed.

Alcohol causes dehydration which can lead to altitude sickness.

Alcohol can cause respiratory depression which totally negates the normal human physiology at high altitudes.

However, these effects are rare. But still, to be safe, it is best to consume alcohol after 48 hours of ascending to a particular altitude.

Medications

Diamox aka Acetazolamide is one of the most commonly used medicines. It is used to prevent and reduce the symptoms of high altitude sickness and can also be used as prophylaxis.

Acetazolamide is a carbonic anhydrase inhibitor. Carbonic anhydrase as discussed above is an enzyme that converts carbon dioxide present in the blood to bicarbonate. This bicarbonate alkalizes the blood leading to respiratory alkalosis which can cause mountain sickness.  

Inhibition of carbonic anhydrase enzyme can cause an increase in acidity of blood which can stimulate breathing. This leads to increased uptake of oxygen in the blood.

If the headache is severe, symptomatic treatment with analgesics such as aspirin, ibuprofen or other NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) can be given.

For nausea and vomiting, an antihistamine such as Promethazine (25-50 mg) is useful.

However, if symptoms worsen, it is better to descent to a lower altitude where symptoms start to fade. Descending 500m to 1000m is usually effective