Decompression sickness or the bends are the symptoms associated with a rapid decrease in surrounding pressure. This most often occurs in scuba divers but also can occur in airplane pilots. When the diver breathes compressed air, extra oxygen and nitrogen enter the blood stream. If the surrounding pressure decreases rapidly during the diver's trip to the surface, the bubbles are not completely absorbed and remain in the blood stream and tissue. These nitrogen bubbles are the cause of the symptoms of the bends. Certain factors increase the risk of developing the bends. Those include smoking, alcohol use, age greater than 30, obesity, poor physical fitness and cold water diving.