What is the actual physical cause of decompression sickness?

Decompression sickness, often referred to as "the bends," occurs when there is bubble formation and growth in the body tissues as a consequence of changes in pressure. When a diver ascends too quickly after being at depths where the pressure is higher, dissolved gases, primarily nitrogen, can come out of solution and form bubbles in the bloodstream and tissues.

Under normal conditions, gas dissolved in the bloodstream is balanced with the external pressure; however, during rapid ascent, the decrease in pressure can lead to a supersaturation of the gases. As a result, these gases come out of solution and form bubbles, which can cause various symptoms and health complications. The formation of these bubbles can obstruct blood vessels and result in pain, tissue damage, and potentially severe consequences, depending on their size and location.

Understanding that bubble formation and growth is the direct physical cause of decompression sickness emphasizes the importance of controlled ascent rates and safety stops to allow dissolved gases to safely exit the body while maintaining a balance with the surrounding environmental pressure.