Definition
A medical condition caused by nitrogen dissolved in the body's tissues and blood coming out of solution and forming bubbles when surrounding pressure drops too quickly. In aviation it occurs when a pilot ascends to high altitude (typically above 18,000 feet, but possible lower) or flies soon after scuba diving. Symptoms range from joint pain and skin itching to neurological problems, breathing difficulty, and collapse.
Plain English
When the air pressure around you drops too fast, gas that was dissolved in your blood and tissues turns into bubbles, like opening a fizzy drink. Those bubbles can cause pain, dizziness, breathing trouble, or worse.
Context Anchor
Seen in high-altitude physiology discussions, especially when learning about oxygen use, pressurization, rapid climbs, and flying after scuba diving.
Derivation
From Latin 'de-' (away from) and 'comprimere' (to press together). 'Decompression' literally means the release of pressure. The term came from deep-sea divers in the 1800s who got sick when they came up too fast — the same mechanism that affects pilots climbing too high too quickly.
Why Pilots Care
Untreated DCS can produce joint pain, dizziness, confusion, or incapacitation, directly threatening flight safety.
Analogy
Think of a sealed bottle of soda. While the cap is on, the gas stays dissolved in the liquid. Pop the cap quickly and bubbles form everywhere. Your body works the same way when pressure drops too fast.
Grounding Statement
Picture climbing to very high altitude: the air pressure around the body falls, and gas that was dissolved in body tissues can start forming bubbles.
Intuition Check
DCS is not just being short of oxygen. Oxygen may help, but the key problem is gas bubbles forming because pressure dropped.
Example Sentence 1
After a rapid climb to 25,000 feet in an unpressurized cabin, the pilot reported joint pain and was treated for suspected DCS upon landing.
Example Sentence 2
Proper preflight planning and cabin pressurization reduce the risk of DCS on high-altitude flights.