Definition
A bluish discoloration of the skin, fingernails, and lips caused by insufficient oxygen in the blood. In aviation medicine, it is recognized as a visible late-stage symptom of hypoxia.
Plain English
Skin, lips, or fingernails turning a bluish color because the blood does not have enough oxygen.
Context Anchor
Seen in aeromedical discussions, especially when learning the symptoms of hypoxia at altitude.
Derivation
From the Greek 'kyanos' meaning 'dark blue,' plus the suffix '-osis' meaning 'condition.' Literally 'a blue condition' — which is exactly what a pilot would see on the fingernails or lips of someone running short on oxygen.
Why Pilots Care
It is an early visible sign of hypoxia that signals the need to descend or use supplemental oxygen before judgment and consciousness are lost.
Grounding Statement
If someone at altitude develops bluish lips or fingernails, treat it as a possible oxygen problem, not as a normal reaction to being cold.
Intuition Check
Cyanosis is not just looking pale or cold. It specifically means a bluish color linked to too little oxygen in the blood.
Example Sentence 1
The instructor pointed out that cyanosis in the fingernails is one of the visible signs of hypoxia during high-altitude flight.
Example Sentence 2
Cyanosis appeared during the altitude chamber flight, confirming the onset of hypoxia.