Why do scuba divers form air bubbles in their blood stream?

Answer 1

When diving, Scuba divers breathe gas under pressure. The greater pressure causes the nitrogen in the breathing gas to dissolve in their bodily tissues (the body metabolises the oxygen).

When the diver ascends from depth, the pressure is reduced, and so the gas comes out of the tissues and into the bloodstream, where the diver expels it through his lungs. Normally these bubbles are very small (sometimes called "micro" bubbles or "silent" bubbles) and present no risk to the diver.

Normal off-gassing in this was is not harmful, but if a diver stays too deep for too long, the rapid release of gas can form larger bubbles which can cause decompression sickness. In minor cases this can cause discomfort and localised swelling, which can normally be resolved with oxygen. Severe cases can lead to permanent tissue damage, paralysis and even death. This is why divers are trained to understand no-decompression limits and to utilise tables or dive computers to keep them safely within margins.