Charrière (unit)
In medicine, Charrière (Ch) (also Charr.) Is a measure of the outer diameter of cannulas and catheters as well as tubes and guide wires . Three Charriere correspond to exactly one millimeter , or 1 Ch = 1 / 3 mm. The Charrière number is therefore always three times as large as the outer diameter in millimeters. If you divide the Charrière number by 3, you get the outer diameter of the cannula or catheter in millimeters. It was named after Joseph-Frédéric-Benoît Charrière . In the English-speaking world, the size is simply referred to as French (Fr) (because of its French origin) .
The circumference of a circle is calculated using the formula U = π d, where U is the circumference and d is the diameter. When determining the Charrière number, the number 3 was chosen as the multiplier between diameter and circumference instead of the exact value of π (3.14159265 ..). Thus, three charrière roughly correspond to the circumference in millimeters of a pipe with an outside diameter of one millimeter. Multiplying the outside diameter by π gives the actual circumference.
The size of cannulas is often specified in gauge .
See also
Individual evidence
- ↑ Erich Wintermantel, Suk-Woo Ha: Medical technology. Life Science Engineering. Springer, Munich 2009, ISBN 978-3-540-93935-1 , p. 1532.