Bends is a painful and dangerous condition caused by the formation of gas bubbles in the bloodstream and body tissues. It can occur when the air pressure surrounding the body decreases too rapidly. Bends is also called decompression sickness or caisson disease. It is most common among underwater divers and people who work in construction caissons (see Caisson ). Such people may get bends if they return too quickly to the water surface or ground level. People in aircraft also may experience bends if pressurization in the cabin fails.
When air pressure drops too rapidly, nitrogen that was in solution in body fluids comes out of solution and forms bubbles. The bubbles stretch or break tissues or impair the circulation of blood through capillaries. Common symptoms of bends include pain in the joints of bones, itching or tingling of the skin, breathing problems, and partial or total paralysis. Less common symptoms include dizziness, nausea, vomiting, convulsions, and coma. Bends can be fatal in some cases.
Astronauts who perform activities outside their spacecraft wear special suits that enclose only a low pressure of gas. Before such extravehicular activity, astronauts breathe pure oxygen for three or four hours to allow nitrogen to leave the body. This reduces the chances of getting bends during the activity. Similarly, caisson workers and divers may breathe pure oxygen before and during their ascent to the surface.
Bends is treated by increasing the air pressure, usually in a sealed pressure chamber. Increasing the pressure compresses the nitrogen bubbles and causes some nitrogen to go back into solution in body fluids. The pressure is slowly lowered so that the nitrogen leaves the body without excessive bubbling.
