The Birmingham gauge is a wire gauge system, and is also used to specify thickness or diameter of hypodermic needles and tube products.
8-583: Birmingham gauge is also known as the Stubs Iron Wire Gauge or Birmingham Wire Gauge . It is not the same as, though similar to, the Stubs Steel Wire Gauge . Birmingham gauge is often simply termed Gauge , with the abbreviation G . However, this should not be confused with French gauge . The gauge starts at the lowest gauge number of 5Ø or 00000, corresponding to the largest size of 0.500 inches (12.7 mm), and runs to
16-413: A given gauge. Rapid blood transfusion through 23G or smaller needles can cause hemolysis (rupturing of red blood cells). This includes peripheral venous catheters . The gauge compared to outer diameter is the same as for needles, but the color coding is different. French gauge The French scale , French gauge or Charrière system is commonly used to measure the size of a catheter . It
24-426: A larger external diameter. This is contrary to Birmingham gauge , where an increasing gauge corresponds to a smaller diameter needle. The French size is a measure of the outer diameter of a catheter (not internal drainage channel, or inner diameter ). 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
32-704: A medical setting in the early 20th century. Another common needle gauge system is the French catheter scale . Needle wire gauge was derived from the Stubs Iron Wire Gauge. Hypodermic needles are available in a wide variety of outer diameters described by gauge numbers. Smaller gauge numbers indicate larger outer diameters. Inner diameter depends on both gauge and wall thickness. The following chart shows nominal inner diameter and wall thickness for regular-wall needles. Thin-wall needles (not shown) have identical outer diameters but larger inner diameters for
40-443: Is most often abbreviated as Fr , but can often be seen abbreviated as Fg , FR or F . It may also be abbreviated as CH or Ch (for Charrière , its inventor). However, simply gauge , G or GA generally refers to Birmingham gauge . The Charrière is measured by the ''outer'' diameter, and is defined as 1 Fr = 1/3 mm, and thus 1 mm = 3 Fr; therefore the diameter of a round catheter in millimetres can be determined by dividing
48-547: The French size by 3. The French units roughly correspond to the outer circumference of the catheter (see table below). For example, if the French size is 9, the diameter is 9/3 = 3.0; mm. It is seen that the French unit is fully redundant with the metric system but introduces potential for rounding errors . This metrication problem is further complicated by the mixed use of metric and imperial units in medical professions using catheters. An increasing French size corresponds to
56-511: The gauge number is used to specify the outside diameter of the product, whereas for larger mechanical tubing the gauge number specifies the wall thickness independent of the overall size of the tube. In medicine , the Birmingham gauge specifies the outside diameter of hypodermic needles , catheters , cannulae and suture wires. It was originally developed in early 19th-century England for use in wire manufacture, and began appearing in
64-430: The highest gauge number of 36, corresponding to the smallest size of 0.004 inches (0.10 mm). Size steps between gauges range from 0.001 inches (0.025 mm) between high gauge numbers to 0.046 inches (1.2 mm) between the two lowest gauge numbers and do not correspond to a particular mathematical pattern, although for the most part the steps get smaller with increasing gauge number. Concerning wire and fine tubing,
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