High altitude sickness （in English and Chinese 中英文)

Translated and edited by: Joe Hing Kwok Chu

The problems of high altitude adaptation is mainly caused by low air pressure. The lower oxygen in the air causes:

1. the alveolar oxygen pressure reduction and

2. low blood oxygen.

Then the amount of oxygen in the blood decreases, resulting with the body reaction of:

1. Increasing respiratory rate, bringing more air into the lungs;

2. Increasing heart rate to increase cardiac output in order to increase the blood flow in the of the lungs and body arteries;

3. Gradually increasing  erythrocytes and hemoglobin, to improve blood oxygen transport capacity.

4. Increasing histamine production of the body to expand blood vessels to bring in more blood circulation.

Upon acute exposure to reduced ambient pressure of oxygen, there is an increase in catecholamines release. Hyperventilation (breathing too fast) can trigger the increase of catecholamines.  Among the catecholamines, norepinephrine increases progressively during rest and exercise peaking within of a week in high altitude. This increase of norepinephrine raises heart rate and blood pressure. Hyperventilation also trigger epinephrine (adrenaline) which can tighten the blood vessels and raise the blood pressure. The increase of norepinephrine and epinephrine increases sympathetic neural activity and causes the patients becoming hyper. Over production of histamine causes the over expansion of the blood vessels and causes leakage. If it leaks into the brain, it cause headache. It can also leak into the lungs. Over leaking into the lungs, the patients can die from drowning by their own liquid in the lungs.

Even with these adjustments, it is impossible for the new arrivals at the high altitude to maintain their normal body functions.

The problems can be eliminated after going back to the original lower altitude.
 

See climbing high mountain training.