A syndrome arising from too rapid a release of nitrogen from solution in the blood, as a result of decompression. The problem is generally associated with deep-sea divers, but astronauts must be protected from the bends by sufficient cabin pressure to prevent nitrogen from forming painful gas bubbles.

During the Apollo–Soyuz Test Project, astronauts transferring from the space shuttle to the docking module had to increase the module's atmospheric pressure slowly to about two-thirds of sea-level pressure to avoid the bends.