Definition
A form of decompression sickness in which dissolved nitrogen comes out of solution in the body's tissues and bloodstream as the surrounding pressure drops, forming bubbles that can lodge in joints, muscles, the lungs, the skin, or the central nervous system. It typically becomes a risk for pilots flying at cabin altitudes above about 18,000 feet, especially after recent scuba diving.
Plain English
When pressure around the body drops too quickly, the nitrogen that is normally dissolved in your blood and tissues can fizz out as tiny bubbles, much like opening a soda bottle. Those bubbles can cause pain, breathing trouble, skin problems, or serious nervous system symptoms.
Context Anchor
Seen in pressurized-aircraft and high-altitude flight discussions, especially when studying rapid cabin pressure loss or flight at altitudes where the body is exposed to much lower pressure.
Derivation
Evolved here means released or given off, from the Latin evolvere meaning to roll out. The phrase describes gas being rolled out of solution, which captures what is actually happening inside the body as pressure drops.
Why Pilots Care
Failure to recognize or prevent this condition during unpressurized flight or emergency descents can result in incapacitation, requiring immediate descent and medical attention.
Analogy
Think of a sealed soda bottle. While it is closed, the gas stays dissolved in the liquid. Open it quickly and bubbles appear everywhere. The body behaves the same way when pressure drops too far, too fast.
Grounding Statement
Picture a high-altitude cabin pressure loss: as the pressure around you drops, gas that was dissolved in your body may start forming bubbles instead of staying dissolved.
Intuition Check
“Evolved” does not mean the sickness slowly developed or improved over time. Here it means gas came out of solution and formed bubbles because the surrounding pressure decreased.
Example Sentence 1
Because she had been scuba diving the day before, she delayed her cross-country flight to reduce the risk of evolved gas decompression sickness.
Example Sentence 2
Proper pre-breathing of oxygen before high-altitude flight reduces the risk of evolved gas decompression sickness during any sudden loss of cabin pressure.