Decompression Sickness

Under high atmospheric pressure, a higher than normal amount of nitrogen can dissolve in the plasma. If the ascent to the surface occurs at a fast rate, than this nitrogen comes out of solution forming minute gas bubbles. This quite similar to when a bottle of champagne or fizzy drink is opened. The dissolved gas is liberated and bubbles are released. The nitrogen bubbles can then lodge in joints and small vessels causing pain and the possibility of brain damage. This is know as decompression sickness or "bends". Decompression sickness can be avoided if the ascent to the surface occurs at a slow rate, so that the dissolved nitrogen can be safely eliminated through the lungs. In those individuals that have suffered a decompression sickness episode, slow decompression can be achieved inside a hyberbaric chamber.

For deep sea diving, the air mixture inside the air tanks is made up of a mixture of Helium and Oxygen without nitrogen. Helium is utilised as it has the peculiar characteristic of being less soluble in water at increased pressure.