Definition
An abnormally rapid heart rate, typically defined as a resting heart rate above 100 beats per minute in adults. It can be caused by physical exertion, stress, low oxygen levels, exposure to certain gases such as carbon dioxide, or underlying medical conditions.
Plain English
Your heart beating faster than it should when you are at rest.
Context Anchor
Seen in safety warnings about carrying dry ice in an aircraft, where dry ice can turn into carbon dioxide gas and affect the people on board.
Derivation
From the Greek 'tachys' meaning 'fast' and 'kardia' meaning 'heart.' The same 'tachy-' root appears in 'tachometer,' the cockpit instrument that measures engine RPM — both relate to measuring how fast something is turning over.
Why Pilots Care
It can appear as an early symptom of carbon dioxide buildup or low oxygen in the cabin, reducing a pilot's ability to think clearly and respond safely.
Grounding Statement
Picture sitting calmly in the aircraft, not exercising, but your heart suddenly starts racing; that is the condition this word names.
Intuition Check
Tachycardia does not mean a heart attack by itself. It means an unusually fast heartbeat, which can have several causes and should be taken seriously in flight.
Example Sentence 1
While transporting dry ice, the pilot noticed tachycardia and a headache, recognized the symptoms of CO2 buildup, and increased cabin ventilation immediately.
Example Sentence 2
Tachycardia was listed among the warning signs that required immediate descent to lower altitude.