What primarily causes decompression sickness?

Decompression sickness, commonly known as "the bends," primarily occurs due to a rapid ascent leading to the formation of nitrogen bubbles in the body. When a diver descends, the pressure increases, and nitrogen, which is part of the breathing gas (such as air), is absorbed into the body's tissues. At greater depths, more nitrogen is dissolved in the tissues. If a diver ascends too quickly, the pressure decreases rapidly, and the nitrogen that was previously dissolved can come out of solution and form bubbles in the bloodstream and tissues.

These nitrogen bubbles can cause various symptoms and complications, including joint pain, dizziness, and even life-threatening conditions. This phenomenon is the result of the laws of gas behavior, specifically Henry’s Law, which states that the amount of gas that dissolves in a liquid is directly proportional to the pressure of the gas above the liquid. Therefore, managing ascent rates is crucial to prevent these dangerous nitrogen bubbles from forming, confirming that rapid ascent is the key factor in the occurrence of decompression sickness.

In contrast, the other options relate to dive conditions but do not directly lead to the formation of nitrogen bubbles in the manner that an uncontrolled ascent does.