Aviation and Space Physiology (Part 1): Introduction

By Patience Joseph Mamman

The field or discipline called Physiology is a life science that deals basically with study of functions in living things, whether plants or animals. Physiology in a general sense is simply one of the branches of life science that focuses majorly on understanding how a living entity functions.

Space, High altitude and Aviation physiology is a field of physiology that deals with how the body works or adjusts when exposed to high altitudes. One key thing to note is as you ascend high up in the sky, the atmospheric pressure drops. At about 16,000 feet above sea level, the oxygen saturation in the blood drops to about half its original value at sea level.

The reason behind this is phenomenon is explained thus: The percentage of oxygen at sea level and at high altitudes is the same, but what causes the drop is the reduction in the atmospheric pressure. At high altitudes, the air molecules are more dispersed than compressed as we see at sea levels. This dispersed nature of air molecules makes it difficult to get in the amount of oxygen adequate enough for respiration to take place successfully.

To cope with this, there are certain adjustments the body makes:

  1. At high altitudes, breathing rate (hyperventilation) increases to get in more oxygen into the lungs.
  2. Increased heart beat to help push out more blood to help circulate oxygen to the tissues to avoid tissue death.
  3. After an individual has begun to acclimatize there is increased production of red blood cells.

Hypoxia and Its Acute Effects
Hypoxia refers to a condition of low oxygen delivery to tissues. It relates to space and aviation physiology in the sense that as you go higher in altitude, there is a drop in the atmospheric pressure. This in turn makes less oxygen available for tissue functions which are what precipitates the bodily malfunctions experienced at high altitudes.

When a person who has never risen to a high altitude whether by flying or climbing is suddenly exposed to such the body reacts in a certain way due to the sudden exposure to low oxygen levels and this in turn produces the following effects:

  • Beginning at a height of about 12000 feet drowsiness, lassitude, mental fatigue, headache and nausea begins to occur.
  • At about 18, 000 feet above sea level the person begins to experience minor seizures
  • At above 23, 000 feet above sea level in the unacclimatized person, coma results and death if nothing is done to return back to lower altitudes.