I know that our bodies use most of the oxygen we breathe in during a dive but, wouldn't our tissues, under pressure, absorb more oxygen than we need? For instance, in normal circumstances, we don't use all the oxygen in each breath and we exhale some (this is what 'rebreathers' are for, right?)
Couldn't any gas we breathe in under pressure cause decompression sickness when we decompress?
Read this, from NASA:
"Astronauts put on their spacesuits several hours before a spacewalk. The suits are pressurized. This means that the suits are filled with oxygen.
Once in their suits, astronauts breathe pure oxygen for a few hours. Breathing only oxygen gets rid of all the nitrogen in an astronaut's body. If they didn't get rid of the nitrogen, the astronauts might get gas bubbles in their body when they walked in space. These gas bubbles can cause astronauts to feel pain in their shoulders, elbows, wrists and knees. This pain is called getting "the bends" because it affects the places where the body bends. Scuba divers can also get "the bends."