A: The bends, or decompression illness, was originally described among "Caisson Workers". These workers would work underwater in tunnels made of stone which were then pumped free of water. During this time the caisson worker would be breatehing air at a much increased pressure. When the shift was over, the caisson worker would ascend through the water. Upon reaching the surface workers often experienced severe pain, most noted in the back, and often walked in a bent over posture due to the pain.

It was not until 100 years later that the exact mechanism of this injury was determined. It is the same mechanism that causes decompression sickness, or the bends in SCUBA divers.

When a diver breathes compressed air at depth, the amount of Nitrogen that can be dissolved in the blood is much higher, due to the pressure exerted by the water. When the diver ascends, this dissolved nitrogen will quickly form into bubbles of gas in the bloodstream. When the bubbles are trapped in the muscles or joints, it causes severe pain.

There are two types of decompression sickness, DCS I involves only the joints and limbs, where DCS II also involves the brain or spinal column.

Decompression sickness can be prevented by meticulous attention to Navy diving tables. Note however, that these tables are developed for healthy young divers, and individuals with a higher body fat may take longer to equalize their nitrogen. In addition, flying can excacerbate or precipitate the symptoms, as most commercial aircraft are pressurized to an altitude equivilent of about 2500m.

Treatement of DCS involves recompression with 100% oxygen and controlled decompression in a decompression chamber. Recompression will improve symptoms by decreasing the size of the nitrogen bubbles and promote diffusion of nitrogen back into body tissues.