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Aviation and Space Physiology (Part 2): Associated Disorders

By Patience Joseph Mamman

Mount Everest Summit
(Source: Wikipedia)

Disorders associated with High Altitudes

Acute Mountain Sickness

This is the common manifestation and disorders that take place when the body is exposed to high altitudes without acclimatization. There are 3 forms of this: mild, moderate and severe
Mild

  • Occurs at ascension of about 10, 000 feet or more.
  • Symptoms include headache, nausea, weakness, decreased appetite.
  • Onset is between 12-14 hours of reaching high altitudes.
  • Symptoms disappear within 3days.
  • The best cure is rest and allowing the body to acclimatize or descend to a lower altitude.

Moderate

  • Here in addition to the symptoms in mild mountain sickness, there is ataxia (loss of muscle coordination) leading to the ‘drunk man walk’ sign.
  • If this occurs it is advisable to descend to lower altitudes.
  • In 1-3 days the symptoms tend to resolve.

Severe

  • Severe ataxia
  • Inability to think clearly.
  • Fluid builds up in the lungs.
  • In such conditions the victim is immediately transported to very low altitudes preferably below 4000 ft.

High Altitude Pulmonary Edema.
This is caused by excessive fluid build up in the lungs. For some the lack of oxygen at high altitudes causes vasoconstriction which elevates the blood pressure and leakage of fluids into the tissues and organs. Symptoms include persistent cough, feeling of tightness in the chest, discomfort when trying to lie flat on the ground, gurgling sound when breathing. Remedy is immediate descent to seek medical attention.

High Altitude Cerebral Edema.
This occurs when the effect of high altitude and low air pressure causes fluid to leak out of the capillaries that surround the brain. This fluid then collects within the brain substance.

Symptoms of this include inability to think clearly, and severe ataxia(uncoordinated movements).
This situation is always treated as an emergency by immediately taking the victim to a low altitude to commence immediate treatments.

Some Preventive measures to minimize the onset of Acute Mountain Sickness.
1. If you begin to have symptoms do not proceed. Remain where you are or descend.
2. Drink plenty of water as dehydration is common.
3. Pain relief drugs and diuretics can also help ease some symptoms.

Acclimatization
This is the gradual adjustment the body makes to cope with the low oxygen partial pressure common at such heights. Such adjustments include:

  1. Increased pulmonary ventilation: On exposure to low partial pressure of oxygen, some receptors known as chemoreceptors are activated to cause increased ventilation of the alveoli through increased breathing rate. This mechanism helps increase the rate of ventilation to about 5 times the normal rate at the end of 2-5days of being at high altitudes.
  2. Increased red blood cells production and hemoglobin concentration: Low partial pressure of oxygen has been spotted as one of the key stimulants in the production of red blood cells. As the individual acclimatizes, his hemoglobin level rises from a normal value of about 15g/dl to about 20g/dl. Increased blood volume by about 20-30% results in a total increase of about 50% in hemoglobin level.
  3. Increased oxygen diffusing capacity: The normal diffusing capacity for oxygen across the pulmonary membrane is about 21ml/mmHg/min. This capacity can increase about 3 fold when the body is exposed to high altitudes. The increased blood volume to the capillaries causes an increase in surface area where gas exchange can take place.
  4. Increased Capillarity: Another adaptive feature that the body develops as it tries to cope with the change in altitude is the increase in number of capillaries in all body tissues. This is so that more oxygen can be delivered to the cells.
  5. Cellular Acclimatization: At high altitudes, the body also witnesses an increased production of mitochondria and oxidative enzymes in the cells. This is to help maximum utilization of the oxygen delivered to the cells for optimum functioning.

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Updated: January 15, 2017 — 3:13 pm
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