French catheter scale: Difference between revisions
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
[[Image:French catheter scale.gif|thumb|right|350px|Sizing scale of the French catheter system]] | [[Image:French catheter scale.gif|thumb|right|350px|Sizing scale of the French catheter system]] | ||
{{SI}} | |||
{{CMG}} | {{CMG}} | ||
Revision as of 21:58, 11 March 2009
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Please Take Over This Page and Apply to be Editor-In-Chief for this topic: There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [2] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Overview
The French catheter scale (most correctly abbreviated as Fr, but also often abbreviated as FR or F) is commonly used to measure the outer circumference of cylindrical medical instruments including catheters. In the French Gauge system as it is also known, the diameter in millimeters of the catheter can be determined by dividing the French size by 3, thus an increasing French size corresponds with a larger diameter catheter. The following equations summarize the relationships:
D(mm) = Fr/3 or Fr = D(mm)*3
For example, if the French size is 9, the diameter is 3 mm. Note: the French scale is equal to the diameter in mm multiplied by three, not the circumference (diameter times π) as is sometimes thought.
This is contrary to needle-gauge size, where the diameter is 1/gauge inches; thus the larger the gauge needle, the more narrow the bore of the needle.
The Stubs Iron Wire Gauge system is also commonly used in a medical setting and is in fact more common for measuring needles, even though many find the Stubs system to be more confusing because the scale is non-linear and inversely proportional.
The French Gauge was devised by Joseph-Frédéric-Benoît Charrière, a 19th century Parisian maker of surgical instruments, who defined the "diameter times 3" relationship.
In some countries (especially French speaking), this unit is called Charriere and abbreviated as Ch.
1 F is equivalent to 0.33 mm = .013" = 1/77" of diameter. Thus the size in French units is roughly equal to the circumference of the catheter in millimetres.
| French Gauge |
Diameter (mm) |
Diameter (inches) |
| 3 | 1 | 0.039 |
| 4 | 1.35 | 0.053 |
| 5 | 1.67 | 0.066 |
| 6 | 2 | 0.079 |
| 7 | 2.3 | 0.092 |
| 8 | 2.7 | 0.105 |
| 9 | 3 | 0.118 |
| 10 | 3.3 | 0.131 |
| 11 | 3.7 | 0.144 |
| 12 | 4 | 0.158 |
| 13 | 4.3 | 0.170 |
| 14 | 4.7 | 0.184 |
| 15 | 5 | 0.197 |
| 16 | 5.3 | 0.210 |
| 17 | 5.7 | 0.223 |
| 18 | 6 | 0.236 |
| 19 | 6.3 | 0.249 |
| 20 | 6.7 | 0.263 |
| 22 | 7.3 | 0.288 |
| 24 | 8 | 0.315 |
| 26 | 8.7 | 0.341 |
| 28 | 9.3 | 0.367 |
| 30 | 10 | 0.393 |
| 32 | 10.7 | 0.419 |
| 34 | 11.3 | 0.445 |
References
This chart taken from Texloc