High Altitude: Acclimatization & Sickness:


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                            "Climb high, sleep low" - If symptoms increase, go down, down, down!


Travelling at high altitude can be dangereous....... 


Almost everyone who travels to Central or Western Tibet will suffer fro the effects of altitude.  Although Lhasa is one of the lowest places in Central Tibet, it is still 4’000m (13.000 ft) above sea level.  Katmandu is 4,500 ft above seal level. How greatly one is affected by altitude varies from person to person and depends in part on how gradually one has made the ascent into Tibet.  Obviously, acclimatization is much more difficult if you fly in than if you drive.  It also tends to strike people who overexert themselves in the first few days above 3,000m (9,800 ft).  


 The so-called “early mountain sickness” usually develops during the first two or three days at high altitude.  Its symptoms include headache, nausea and loss of appetite, sleeplessness, and difficulty breathing.  People will be affected in different ways and not all the symptoms need to be present.  If you experience some or all of the symptoms, you definitely should not go any higher until they have disappeared.  To be safe, it is best to plan for three days of relatively reduced activity upon first arriving in Central Tibet (this is assuming that you are flying in).  Headache medication, avoidance of alcohol, cigarettes and heavy food and direct intake of oxygen can help alleviate these symptoms.  The drug Acetazolamide (also know as Diamox) is often used nowadays both preventatively (in casts of quick ascent) and as a treatment for mild symptom of altitude sickness.  Most people experience no side effects with this drug, and it has the added advantage that it does not mask more serious developments of illness.  Before your trip to Tibet, you should consider obtaining a course of Acetazolamide from your doctor.  Even without any drugs, most people get over the initial symptoms quite soon but it usually takes 6 weeks for a complete adaptation to occur. 


The so-called early mountain sickness can sometimes develop into acute mountain sickness, which may involve the life threatening conditions of pulmonary or cerebral edema-waterlogged lungs or brain.  These are serious occurrences that can result in death if not treated immediately.  They are liable to occur only if the symptoms of early mountain sickness are ignored and you continue to ascend.  The symptoms of pulmonary edema are as follows:  weakness, tiredness, shortness of breath, increased respiratory and heart rates, dry cough at first followed by cough with watery or bloody sputum later, noisy and bubbly treating, congested chest and dark blue fingernails and lips.  If pulmonary edema is diagnosed (not all symptoms need to be present), you must descend to a lower altitude immediately.  If the symptoms develop while you are in Lhasa, go straight to the hospital.  From there it is probable that you will be flown out of the country, either to Chengdu or to Nepal. 


The symptoms of cerebral edema are extreme tiredness, vomiting, severe headaches, difficulty in walking, abnormal speech and behavior, drowsiness and unconsciousness.  If cerebral edema is diagnosed (again not all of the symptoms need be present), you must descend immediately and stay down.  Descent should not be delayed for any reason and someone should accompany the patient.  No medication is a substitute for descent.  If in Lhasa, go straight to a hospital, from where descent by air will be arranged.  Although early mountain sickness is common pulmonary and cerebral edema (acute mountain sickness) are not.  The greatest risk is for those with heart or lung diseases.  It is advisable that before leaving for Tibet such persons, the elderly and people with chronic illnesses consult their doctor.   


What is High Altitude?

Altitude is defined on the following scale High (8,000 - 12,000 feet [2,438 - 3,658 meters]), Very High (12,000 - 18,000 feet [3,658 - 5,487 meters]), and Extremely High (18,000+ feet [5,500+ meters]). Since few people have been to such altitudes, it is hard to know who may be affected. There are no specific factors such as age, sex, or physical condition that correlate with susceptibility to altitude sickness. Some people get it and some people don't, and some people are more susceptible than others. Most people can go up to 8,000 feet (2,438 meters) with minimal effect. If you haven't been to high altitude before, it's important to be cautious. If you have been at that altitude before with no problem, you can probably return to that altitude without problems as long as you are properly acclimatized.

What Causes Altitude Illnesses

The concentration of oxygen at sea level is about 21% and the barometric pressure averages 760 mmHg. As altitude increases, the concentration remains the same but the number of oxygen molecules per breath is reduced. At 12,000 feet (3,658 meters) the barometric pressure is only 483 mmHg, so there are roughly 40% fewer oxygen molecules per breath. In order to properly oxygenate the body, your breathing rate (even while at rest) has to increase. This extra ventilation increases the oxygen content in the blood, but not to sea level concentrations. Since the amount of oxygen required for activity is the same, the body must adjust to having less oxygen. In addition, for reasons not entirely understood, high altitude and lower air pressure causes fluid to leak from the capillaries which can cause fluid build-up in both the lungs and the brain. Continuing to higher altitudes without proper acclimatization can lead to potentially serious, even life-threatening illnesses.


The major cause of altitude illnesses is going too high too fast. Given time, your body can adapt to the decrease in oxygen molecules at a specific altitude. This process is known as acclimatization and generally takes 1-3 days at that altitude. For example, if you hike to 10,000 feet (3,048 meters), and spend several days at that altitude, your body acclimatizes to 10,000 feet (3,048 meters). If you climb to 12,000 feet (3,658 meters), your body has to acclimatize once again. A number of changes take place in the body to allow it to operate with decreased oxygen.

  • The depth of respiration increases.
  • Pressure in pulmonary arteries is increased, "forcing" blood into portions of the lung which are normally not used during sea level breathing.
  • The body produces more red blood cells to carry oxygen,
  • The body produces more of a particular enzyme that facilitates
  • the release of oxygen from hemoglobin to the body tissues.

Prevention of Altitude Illnesses

Prevention of altitude illnesses falls into two categories, proper acclimatization and preventive medications. Below are a few basic guidelines for proper acclimatization.

  • If possible, don't fly or drive to high altitude. Start below 10,000 feet (3,048 meters) and walk up.
  • If you do fly or drive, do not over-exert yourself or move higher for the first 24 hours.
  • If you go above 10,000 feet (3,048 meters), only increase your altitude by 1,000 feet (305 meters) per day and for every 3,000 feet (915 meters) of elevation gained, take a rest day.
  • "Climb High and sleep low." This is the maxim used by climbers. You can climb more than 1,000 feet (305 meters) in a day as long as you come back down and sleep at a lower altitude.
  • If you begin to show symptoms of moderate altitude illness, don't go higher until symptoms decrease (& Don't go up until symptoms go down").
  • If symptoms increase, go down, down, down!
  • Keep in mind that different people will acclimatize at different rates. Make sure all of your party is properly acclimatized before going higher.
  • Stay properly hydrated. Acclimatization is often accompanied by fluid loss, so you need to drink lots of fluids to remain properly hydrated (at least 3-4 quarts per day). Urine output should be copious and clear.
  • Take it easy; don't over-exert yourself when you first get up to altitude. Light activity during the day is better than sleeping because respiration decreases during sleep, exacerbating the symptoms.
  • Avoid tobacco and alcohol and other depressant drugs including, barbiturates, tranquilizers, and sleeping pills. These depressants further decrease the respiratory drive during sleep resulting in a worsening of the symptoms.
  • Eat a high carbohydrate diet (more than 70% of your calories from carbohydrates) while at altitude.
  • The acclimatization process is inhibited by dehydration, over-exertion, and alcohol and other depressant drugs.

(This information is only for education and awareness only and not a substitute for medical training)


Further Reading Sources:

- www.high-altitude-medicine.com

- www.traveldoctor.co.uk/altitude.html

- www.mountaineering.ie/features/general/highaltitude.html

- www.traveldoctor.co.uk/exposure.html


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              "The impossible is achieved through the process of self-perfection called meditation" - Swami Chinmayananda