Causes of Altitude sickness

Hypoxia or insufficient oxygen to the tissues is the root cause of Altitude sickness .

The absolute percentage of oxygen in the air is the same, but as altitude increases, the number of molecules in the specific volume of air decreases.¹

At sea level, the arterial oxygen partial pressure is 90–95 mmHg and oxygen saturation is 97%. The figures fall to 40 mmHg and 71%, respectively at 18,000 feet above sea level (prior to eventual acclimatization).

As the patient’s arterial partial pressure of oxygen begins to fall, the body attempts to compensate, by the process of hyperventilation, which helps the patient adapt, also producing water loss and decreased arterial partial pressure of carbon dioxide. Respiratory alkalosis and nocturnal periodic breathing occur. Tachycardia, hypertension, and increased venous tone develop.

Eventually, as the patient becomes acclimatized, the blood becomes thicker, and the percentage of red cells rises from 45% to over 50%.²

Written by: Healthplus24 team
Date last updated: July 03, 2011

• Management of Altitude Sickness
• Symptoms of Altitude Sickness