Birmingham gauge

The Birmingham gauge[1] is a wire gauge system, and is also used to specify thickness or diameter of hypodermic needles and tube products.

Terminology

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.[2] However, this should be distinguished from French gauge.

System

The gauge starts at the lowest gauge number of 5Ø or 00000, corresponding to the largest size of 0.500 inches (12.7 mm) to 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.[3] Concerning wire and fine tubing, 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 it began appearing in 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.

Sizes of hypodermic needles

Hypodermic needles are available in a wide variety of outer diameters described by gauge numbers. Smaller gauge numbers indicate larger outer diameters.[4] Inner diameter depends on both gauge and wall thickness. The following chart shows nominal inner diameter and wall thickness for regular-wall needles.[4][5] Thin-wall needles (not shown) have identical outer diameters but larger inner diameters for a given gauge.

Needle Nominal outer diameter Nominal inner diameter Nominal wall thickness Color
Not strictly defined, and may vary for a given gauge.
Gauge inches mm tol. inches (mm) inches mm tol. inches (mm) inches mm tol. inches (mm) ISO[6]
7 0.180 4.572 ±0.001 (±0.025) 0.150 3.810 ±0.003 (±0.076) 0.015 0.381 ±0.001 (±0.025)
8 0.165 4.191 ±0.001 (±0.025) 0.135 3.429 ±0.003 (±0.076) 0.015 0.381 ±0.001 (±0.025)
9 0.148 3.759 ±0.001 (±0.025) 0.118 2.997 ±0.003 (±0.076) 0.015 0.381 ±0.001 (±0.025)
10 0.134 3.404 ±0.001 (±0.025) 0.106 2.692 ±0.003 (±0.076) 0.014 0.356 ±0.001 (±0.025) Olive brown
11 0.120 3.048 ±0.001 (±0.025) 0.094 2.388 ±0.003 (±0.076) 0.013 0.330 ±0.001 (±0.025) Green-yellow
12 0.109 2.769 ±0.001 (±0.025) 0.085 2.159 ±0.003 (±0.076) 0.012 0.305 ±0.001 (±0.025) Pale blue
13 0.095 2.413 ±0.001 (±0.025) 0.071 1.803 ±0.003 (±0.076) 0.012 0.305 ±0.001 (±0.025) Purple
14 0.083 2.108 ±0.001 (±0.025) 0.063 1.600 ±0.003 (±0.076) 0.01 0.254 ±0.001 (±0.025) Pale green
15 0.072 1.829 ±0.0005 (±0.013) 0.054 1.372 ±0.0015 (±0.038) 0.009 0.229 ±0.0005 (±0.013) Blue-grey
16 0.065 1.651 ±0.0005 (±0.013) 0.047 1.194 ±0.0015 (±0.038) 0.009 0.229 ±0.0005 (±0.013) White
17 0.058 1.473 ±0.0005 (±0.013) 0.042 1.067 ±0.0015 (±0.038) 0.008 0.203 ±0.0005 (±0.013) Red-violet
18 0.050 1.270 ±0.0005 (±0.013) 0.033 0.838 ±0.0015 (±0.038) 0.0085 0.216 ±0.0005 (±0.013) Pink
19 0.042 1.067 ±0.0005 (±0.013) 0.027 0.686 ±0.0015 (±0.038) 0.0075 0.191 ±0.0005 (±0.013) Cream
20 0.03575 0.9081 ±0.00025 (±0.0064) 0.02375 0.603 ±0.00075 (±0.019) 0.006 0.1524 ±0.00025 (±0.0064) Yellow
21 0.03225 0.8192 ±0.00025 (±0.0064) 0.02025 0.514 ±0.00075 (±0.019) 0.006 0.1524 ±0.00025 (±0.0064) Deep green
22 0.02825 0.7176 ±0.00025 (±0.0064) 0.01625 0.413 ±0.00075 (±0.019) 0.006 0.1524 ±0.00025 (±0.0064) Black
22s 0.02825 0.7176 ±0.00025 (±0.0064) 0.006 0.152 ±0.00075 (±0.019) 0.0111 0.2826 ±0.00025 (±0.0064)
23 0.02525 0.6414 ±0.00025 (±0.0064) 0.01325 0.337 ±0.00075 (±0.019) 0.006 0.1524 ±0.00025 (±0.0064) Deep blue
24 0.02225 0.5652 ±0.00025 (±0.0064) 0.01225 0.311 ±0.00075 (±0.019) 0.005 0.1270 ±0.00025 (±0.0064) Medium purple
25 0.02025 0.5144 ±0.00025 (±0.0064) 0.01025 0.260 ±0.00075 (±0.019) 0.005 0.1270 ±0.00025 (±0.0064) Orange
26 0.01825 0.4636 ±0.00025 (±0.0064) 0.01025 0.260 ±0.00075 (±0.019) 0.004 0.1016 ±0.00025 (±0.0064) Brown
26s 0.01865 0.4737 ±0.00025 (±0.0064) 0.005 0.127 ±0.00075 (±0.019) 0.0068 0.1734 ±0.00025 (±0.0064)
27 0.01625 0.4128 ±0.00025 (±0.0064) 0.00825 0.210 ±0.00075 (±0.019) 0.004 0.1016 ±0.00025 (±0.0064) Medium grey
28 0.01425 0.3620 ±0.00025 (±0.0064) 0.00725 0.184 ±0.00075 (±0.019) 0.0035 0.0889 ±0.00025 (±0.0064) Blue-green
29 0.01325 0.3366 ±0.00025 (±0.0064) 0.00725 0.184 ±0.00075 (±0.019) 0.003 0.0762 ±0.00025 (±0.0064) Red
30 0.01225 0.3112 ±0.00025 (±0.0064) 0.00625 0.159 ±0.00075 (±0.019) 0.003 0.0762 ±0.00025 (±0.0064) Yellow
31 0.01025 0.2604 ±0.00025 (±0.0064) 0.00525 0.133 ±0.00075 (±0.019) 0.0025 0.0635 ±0.00025 (±0.0064) White
32 0.00925 0.2350 ±0.00025 (±0.0064) 0.00425 0.108 ±0.00075 (±0.019) 0.0025 0.0635 ±0.00025 (±0.0064) Deep green
33 0.00825 0.2096 ±0.00025 (±0.0064) 0.00425 0.108 ±0.00075 (±0.019) 0.002 0.0508 ±0.00025 (±0.0064) Black
34 0.00725 0.1842 ±0.00025 (±0.0064) 0.00325 0.0826 ±0.00075 (±0.019) 0.002 0.0508 ±0.00025 (±0.0064) Orange
Six hypodermic needles on Luer connectors. These needles are normally used with other medical devices, such as a syringe; from top to bottom:
  • 26G × ​1⁄2″ (0.45 × 12 mm) (brown)
  • 25G × ​5⁄8″ (0.5 × 16 mm) (orange)
  • 22G × ​1 1⁄4″ (0.7 × 30 mm) (black)
  • 21G × ​1 1⁄2″ (0.8 × 40 mm) (green)
  • 20G × ​1 1⁄2″ (0.9 × 40 mm) (yellow)
  • 19G × ​1 1⁄2″ (1.1 × 40 mm) (cream)

Sizes of catheters

This includes peripheral venous catheters and central venous catheters. The gauge compared to outer diameter is the same as for needles, but the color coding is different.

GaugeOuter diameter (mm)Maximum flow rate (ml/min)Color
142.10250-300Orange
161.65200Grey
181.2775-120[7]Green[7]
200.9040-80[7]Pink[7]
220.7155[7]Blue[7]
240.5635[7]Yellow[7]
260.4613-15[7]Black[7]

See also
  • Wire gauge, including other systems

References
  1. Page 400 in: Steven M. Yentis, Nicholas P. Hirsch, James Ip (2013). Anaesthesia and Intensive Care A-Z E-Book: An Encyclopedia of Principles and Practice. FRCA Study Guides (5 ed.). Elsevier Health Sciences. ISBN 9780702053757.CS1 maint: multiple names: authors list (link)
  2. "'French', 'gauge' and millimeters". University of California, San Francisco. Retrieved 2018-02-03.
  3. Machinery's Handbook 27. New York, NY: Industrial Press, Inc. 2004. p. 2520.
  4. "Syringe Needle Gauge Chart". Sigma Aldrich. Retrieved 20 March 2012.
  5. "Hypodermic Needle Gauge Chart". Medical Tube Technology, Inc. Retrieved 20 March 2012.
  6. "ISO 6009:2016 Hypodermic needles for single use -- Colour coding for identification". International Organization for Standardization. Publication date: 2016-08
  7. Page 110 in: Edward Doyle (2007). Paediatric Anaesthesia. OUP Oxford. ISBN 9780199202799.

Further reading
  • ISO 9626: Stainless steel needle tubing for the manufacture of medical devices, 1st ed. Geneva: International Organization for Standardization, 1991: 1–2.
  • ISO 9626: Stainless steel needle tubing for the manufacture of medical devices, Amendment 1. Geneva: International Organization for Standardization, 2001: 1–2.
  • Wonsik Ahn; Jae-Hyon Bahk; Young-Jin Lim (2002). "The "Gauge" System for the Medical Use". Anesthesia & Analgesia. 95 (4): 1125. doi:10.1097/00000539-200210000-00076.
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