French catheter scale

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French catheter scale

From Wikipedia, the free encyclopedia  The French scale or French gauge system is commonly used to measure the size of a catheter. It is most often abbreviated as Fr, but can often be seen abbreviated as Fg, Ga, FR or F. It may also be abbreviated as CH or Ch (for Charrière, its inventor). The French size is three times the diameter in millimeters. A round catheter of 1 French has an external diameter of  13 mm, and therefore the diameter of a round catheter in millimetres can be determined by dividing the French size by 3: D (mm) = Fr / 3 or Fr = D (mm) * 3 For example, if the French size is 9, the diameter is 9/3 = 3.0; mm. From the basic math equation C = πd, it follows that the catheter’s circumference in mm is only slightly (about 4.7%) greater than the French size. An increasing French size corresponds to a larger external diameter. This is contrary to needle-gauge size, where an increasing gauge corresponds to a smaller diameter needle. The French size is a measure of the external diameter of a catheter (not internal drainage channel). So, for example, if a two-way catheter of 20 Fr is compared to a 20 Fr three-way catheter, they both have the same external diameter but the two-way catheter will have a larger drainage channel than the three-way. Three-way catheters accommodate an extra channel for irrigation within a similar external diameter. 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.
French
Gauge
Circumference
(mm)
Diameter
(mm)
Diameter
(inches)
33.1410.039
44.191.3330.053
55.241.6670.066
66.2820.079
77.332.3330.092
88.342.6670.105
99.4230.118
1010.473.3330.131
1111.523.6670.144
1212.5740.158
1313.614.3330.170
1414.664.6670.184
1515.7150.197
1616.765.3330.210
1717.815.6670.223
1818.8560.236
1919.906.3330.249
2020.946.6670.263
2223.047.3330.288
2425.1380.315
2627.238.6670.341
2829.329.3330.367
3031.42100.393
3233.5110.6670.419
3435.6011.3330.445
参考
ゲージ換算表

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