What to expect when you are at high altitudes?


The hectic lifestyle, demanding jobs and lot of mental pressure has made us looking for respite in travelling to calm mountain places or engaging in adventurous sports such as mountain climbing. Since most of us are not used to living at high altitudes our body is not acclimatized or in simpler words not used to living at high altitudes.

If you are planning to backpack and go for mountain climbing this vacation than you should surely know these facts so as to have minimal hazardous effects on the body. As we move up the atmospheric pressure decreases. At sea level, the barometric pressure or atmospheric air pressure is 760 mm Hg; at 10,000 feet 523 mm Hg; and at 50,000 feet only 87 mm Hg. Thus increase in altitude, decreases the atmospheric air pressure drastically. This decrease in air pressure also causes the proportionate decrease in atmospheric oxygen. Since oxygen in optimal amount is most important for living, this decrease causes many health related problems.

How decreased oxygen affects health?

With decreased atmospheric pressure there is also decreased oxygen availability at high altitudes. This means there is less binding of oxygen with the haemoglobin and there is hypoxia as well. The effects of hypoxia are soon observed in person who is not used to living at increased altitudes. These effects can be observed as early as 12000 feet. The major symptoms of hypoxia are-

  1. Drowsiness
  2. Lassitude
  3. Muscle fatigue
  4. Headache
  5. Nausea and vomiting
  6. Confusion
  7. Impaired judgement
  8. Impaired memory
  9. Poor motor coordination

These effects are seen in people who are used to living in plains or lowlands and are not used to living at high altitudes. You should seek medical advice at the nearest healthcare centre as these symptoms start getting worse if not taken care of. These symptoms may lead to muscle twitching or seizures if not taken care of above 18000 feet and may even lead to death above 23000 feet.

What is acclimatization?

As we have discussed these problems of hypoxia and mountain sickness are seen more in people who are not acclimatized or in simpler words are not used to living in high altitudes. The person who is born in that particular environment is better acclimatized than a person who has been living in the same place for even ten or fifteen years. The reason behind this being that acclimatization starts taking place as soon as the child is born. Since there is an increased oxygen demand at higher altitude due to decreased atmospheric pressure and reduced partial pressure of oxygen, the chest size is relatively increased to increases the vital capacity of the lungs and there is decrease in body size to reduce the overall oxygen demand of the body. The heart has to put an extra effort to pump the blood because of the increased oxygen demand. This causes increase in heart size as well. To meet the oxygen demand there is also an increased level of haemoglobin in blood as compared to person living in plains. So we can say that a person who is native of that place especially high altitude is better acclimatized than any other individual because of the physiological adaptations that start taking place in infancy. This makes some of the natives live comfortably in Andes and Himalayas above 12000 feet.

The body functions, breathing, heart rate, muscle oxygen demand and work capacity of muscles get so well adapted or acclimated in the natives that they can work well in extreme environment whereas survival is the biggest key for unacclimatized individuals.

When and how does mountain sickness occur?

The mountain sickness occurs in individuals who are not acclimatized. It may begin in first few hours to about 2 days after ascent. Mountain sickness can be acute or chronic.

Acute mountain sickness

Acute mountain sickness presents itself with symptoms that shows up themselves in few hours after the ascent. The symptoms are same as for hypoxia which includes drowsiness, lassitude, muscle fatigue, headache, nausea, vomiting, confusion and impaired judgement. The cause for acute mountain sickness can be briefly described as follows:

  • Acute cerebral oedema: Hypoxia causes the vasodilation of the local blood vessels. This causes the dilation of the arteries, arterioles, capillaries which results in increased capillary pressure thereby causing the fluid to leak into cerebral tissues. Therefore it results into cerebral oedema which causes the major symptoms of headache, drowsiness, mental confusion and disorientation.
  • Acute pulmonary oedema: The exact cause for the pulmonary oedema is still unknown but it is suggested that severe hypoxia causes the constriction of pulmonary arterioles. This constriction causes the blood to forcibly flow through non constricted arterioles which in return causes the increased local capillary pressure and resulting oedema due to perfusion of the fluids and dysfunction of the lungs which can be fatal if not treated. Allowing the person to breathe oxygen usually reverses the process within hours.

Chronic Mountain Sickness

Chronic mountain sickness develops in people who are not acclimatized and live at high altitudes for a long time. If not treated the acute mountain sickness progresses into chronic mountain sickness. Chronic mountain sickness causes following effects on the body:

  • Red cell mass and hematocrit are raised which increases the density and viscosity of the blood, which results in decreased blood flow to the tissues.
  • There is marked increases in pulmonary arterial pressure because of the vasoconstriction of the arterioles
  • The right side of the heart becomes greatly enlarged due to pooling of blood
  • The peripheral arterial pressure begins to fall
  • Congestive heart failure ensues
  • Death often follows unless the person is removed to a lower altitude.

This is the reason why you should take a training course in mountaineering and trek low peaks first and then gradually go for higher peaks. So if you feel that your mountain sickness is getting worse with increasing altitude it's best to consult a healthcare professional immediately and if required it’s better to move back to lowlands.

Now you are ready to enjoy, have fun and have a HAPPY AND HEALTHY VACATION!! BON VOYAGE...


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