Decompression sickness, commonly called the bends, affects scuba divers who descend to depths at which nitrogen is not properly expelled from their bodies. When leaving the water, the diver needs to manage the ascent properly so the nitrogen has the time needed to leave the body without causing damage. If the ascent occurs too rapidly, divers can suffer severe injuries or death.
Decompression sickness occurs because our air contains 79% nitrogen and 21% oxygen (plus a few miscellaneous gasses). Typically, we breathe the air, and our bodies absorb oxygen through the lungs while expelling the unused nitrogen. Nitrogen comes in and goes out but does not impact our bodies.
When scuba diving, however, we pull in oxygen, but the nitrogen is not expelled and gets stored in our lungs. If a diver ascends too quickly, the nitrogen does not have time to slowly dissolve from the lungs, forming bubbles that damage our tissues. The damage to our tissues is very painful and typically causes victims to bend over in pain, leading to decompression sickness to be called the bends.
To avoid decompression sickness, scuba divers ascend in steps, pausing at each step to allow the nitrogen to escape the lungs in a managed and safe process. When this process occurs as expected, divers experience few aftereffects of scuba diving.
