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Physiological Effects of High Altitude

What's high altitude ? It's considered to be between 5,000 and 11,500 feet (1,524 and 3,505.2 m) above sea level. Very high altitude is any altitude between 11,500 and 18,000 feet (5,486.4 m), and extreme altitude is anything above 18,000 feet.

Atmospheric pressure (which is measured with a barometer and is also known as barometric pressure ) is a measurement of air's force against a surface. At low elevations, the pressure is greater, since the molecules of air are compressed from the weight of the air above them. However, at higher elevations, there's less pressure and the molecules are more dispersed.

The percentage of oxygen in the air at sea level is the same at high altitudes -- roughly 21 percent. But because the air molecules are more dispersed, each breath delivers less oxygen to the body. When you take a breath at 12,000 feet (3,657.6 m), you're breathing in 40 percent less oxygen than at sea level. At 18,000, feet you're taking in 50 percent less oxygen. So during and shortly after physical activities (like mountain climbing or hiking), you should expect to feel short of breath at higher altitudes


At higher altitudes, our bodies make adjustments: creating more red blood cells to carry oxygen through the bloodstream, pushing air into normally unused portions of the lungs and producing citrate synthase , a special enzyme that helps the oxygen found in hemoglobin make its way into body tissue. High altitude also triggers an increase in our heartbeat, breathing and urination. The low humidity and low air pressure at high altitudes causes moisture from your skin and lungs to evaporate at a faster pace -- and your body's increased exertion requires even more water to keep it hydrated.

When your body loses fluid through its blood vessels, it tries to counteract the effect by holding water and sodium in its kidneys . As a result, even more fluid builds up in your body -- and more trickles out of your blood vessels . This fluid can get into body tissue and cause edema (swelling of the face, legs and feet). Edema is more common in women . There's no clear reason why, but researchers suspect it has something to do with their hormones and menstrual cycles. The condition isn't always an indicator of altitude sickness (it can occur from malnutrition and other illnesses at low altitudes), so it can be discounted as a precursor of altitude sickness if no other symptoms are present. While swelling may worsen with ascent, it usually resolves after descent.

As your sleeping body attempts to strike some balance between oxygen and carbon dioxide levels, it falls into periodic breathing. Periodic breathing is a cycle of decreased breathing, followed by a complete absence of breathing (from three to 15 seconds). Breathing resumes once carbon dioxide has sufficiently built up in your bloodstream to prompt your brain. Periodic breathing is fairly common at higher altitudes and is not itself a sign of altitude sickness, but it often leaves afflicted individuals feeling worn out upon waking.

Preventative Treatment

The best rule of thumb in preventative treatment? If you begin having symptoms, stay put until they disappear. If symptoms get worse, descend. Don't make any sudden changes in altitude -- someone who races up to an elevation of 15,000 feet (4,572 m) will be worse for the wear than someone who slowly acclimates himself or herself to 20,000 feet (6,096 m). If you need to stay at a given elevation, it's better to engage in some light activity than it is to sleep . Generally, your symptoms will worsen as you sleep.

The most important factor in determining your likelihood for altitude sickness is acclimatization . To become acclimated, sleep one night below 10,000 feet (3,048 m) after you begin your ascent. Above 10,000 feet, don't sleep more than 1,000 to 1,500 feet (304.8 to 457.2 m) higher than the elevation at which you previously slept. For every 3,000 feet (914.4 m) gained, sleep two consecutive nights at that altitude. The climbing maxim " climb high, sleep low " refers to the practice of ascending during the day to new heights and then descending at night to sleep. Dehydration is common at high altitudes and can prevent acclimatization. Drink plenty of water before and during your ascent.

There are some drugs you can take to prevent altitude sickness -- and a few that can alleviate mild to moderate symptoms that onset as you ascend.

  • Ibuprofen helps alleviate the pain of normal altitude-related headaches , but it will not affect the underlying causes of the headache. If you treat a headache but it gets worse, descend immediately.
  • Diamox can increase your rate of breathing, leading to increased oxygenation of your blood . It also diminishes symptoms -- especially when you're sleeping. If you're taking it preventively, you should take it a full day before your ascent to allow your body to begin processing it. Like all medications, it may cause side effects and allergic reactions, so you should try it first at low altitude to see if it affects you adversely. In most cases, a careful and cautious rate of ascent will not necessitate the use of Diamox.
  • Acetazolamide or low doses of oral furosemide treats edema in swollen faces, feet and legs.
  • And speaking of drugs, don't ingest alcohol or any other drug that may alter or decrease your rate of breathing.

Some people are advised to avoid high altitudes altogether. If you have heart disease , lung disease or sickle cell anemia , it's recommended that you not ascend to high altitudes. Diabetics can safely go to high altitudes but must be especially vigilant in monitoring their blood glucose levels -- glucose monitors may be adversely affected by high altitude, and altitude sickness may trigger ketoacidosis (a serious condition caused by a lack of insulin). The CDC recommends that pregnant women shouldn't attempt to go higher than 12,000 feet (3,657.6 m). Researchers don't know whether the effects of altitude sickness can afflict fetuses, but there are concerns that blood vessel leakage could harm them.

Source: http://health.howstuffworks.com/diseases-conditions/respiratory/altitude-sickness.htm

Don't let home without

  • Verify the situation of the visa
  • A copy of your passport
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  • Camera, a lot of movie or memory and supplementary batteries
  • Sunblock UV30 or higher
  • Sunglasses and hat
  • Insecticide for the tropical zones

Health and Sanity

Eating and drinking
In Bolivia the sanitary conditions for the sale and handling of foods are not always the best; we suggest not buying and ingesting foods in the streets. We recommend only eating in hotels and suggested restaurants. Drink only bottled water if it's possible.


Bolivia is a safe country- but as cities develop so does the petty thieving. For your security, please follow the following suggestions:

  • If you need to be transported from your Hotel to other places, it is advise to ask your hotel reception for a “radio taxi”.
  • When walking along the streets, or in public and crowed places, please don't get distracted and keep an eye on your things.
  • Never contact a tour or other tourist service in the street. Do so via authorized travel agents.
  • There are some delinquents trying to make tourist believe that they belong to the police or anti –narcotics forces, please be careful.
  • Always carry with you the name, address and telephone number of your hotel and travel agent in Bolivia .
  • Leave all important documents at your hotel security.
  • You must not give your credit card PIN (personal identification number) to anybody and at any place. Don't answer to any strange question referred to your credit card.

Norms for foreign currencies

The official currency in Bolivia is the boliviano. It co-exists with the North American dollar that is currency of free circulation and it can be changed in Banks and Money Exchange offices Money Exchange offices also accept transactions in Euros. People called “libre-cambistas” (people who change money in the streets) located in the streets and avenues, is not recommended to make transactions with them, due to the danger of receiving false currency, besides carrying out an inferior change to the official rate.

Emergency phone numbres - La Paz

Numeration area

Bolivia (591) - La Paz (2)







Touristic Police


Find and rescue service


Bolivian Red Cross

222-7818, 222-6936


281-0122, 281-0123

Natural Custom Expeditions 277-2546, 706-80189, 706-47427

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