Decompression illness (DCI), also known as “the bends” or caisson disease, is a illness that occurs when bubbles form in your body’s tissues because of an excessive quantity of inert gas (nitrogen or helium) due to inadequate decompression following the exposure to increased pressure. During a dive, your body’s tissues absorb nitrogen or helium from your breathing gas in proportion to the surrounding pressure. As long as you remain at pressure (depth), the inert gas does not present any problems. If the pressure is reduced too quickly, from a rapid ascent for example, the inert gas can come out of solution and form bubbles in your body’s tissues and bloodstream. Once bubbles are formed they may or may not produce symptoms based on their eventual growth. When symptoms occur, they relate to the area in the body where the bubble is located.
DCI can occur as a result of violating no decompression limits and not properly decompressing during your ascent, ascending too rapidly on a no decompression dive, pushing dive tables to their limits, skipping or shortening decompression stops during a staged decompression dive, or pushing the limits on tables or dive computers when making repetitive dives. But, DCI can also occur even when you follow all of the recommended guidelines and safety factors.