The word “capnography” is derived from a Latin twist based on an original Greek concept. The Greeks first wrote about combustion centers throughout the body that they said released a byproduct called “Kapnos,” or in Latin, “Capnos;” both are words for “smoke.” What the Greeks called “combustion,” we now call metabolism and what they called “smoke,” today is termed carbon dioxide.
Capnography is a device that is placed at the lips to detect the presence of carbon dioxide in exhaled air, called “End-Tidal Carbon Dioxide” or ETCO2 for short. Older, qualitative “colorimetric” capnography devices simply changed color when sensing the presence of carbon dioxide. Today’s EMS monitors use quantitative technology that combines a numerical readout (capnometer) with a waveform to measure and display the pressure of carbon dioxide in exhaled air. ETCO2 is a pressure measurement in mmHg and not a percentage or “count” like parts per million.
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Above photo by Rick McClure