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Birmingham gauge

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The Birmingham gauge,[1] officially the Birmingham Wire Gauge and often abbreviated as G or ga,[2] is unit or wire gauge used to measure the thickness or diameter of wires and tubing, including hypodermic needles and other medical tube products.

Terminology

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The Birmingham gauge is also known as the Stubs Iron Wire Gauge or Birmingham Wire Gauge and is distinct from the Stubs Steel Wire Gauge and the British Standard Wire Gauge. It is commonly referred to simply as gauge (abbreviated as G),[3] but this should not be confused with the French gauge, a separate system used for measuring the outer diameter of catheters.

System

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The Birmingham gauge ranges from 5/0 or 00000, the lowest gauge number corresponding to the largest size of 0.500 inches (12.7 mm), to 36, the highest gauge number corresponding to the smallest size of 0.004 inches (0.10 mm). The increments between gauge sizes are not linear and vary.[2] At higher gauge numbers, the increment between the two highest gauges is 0.001 inches (0.025 mm), while at lower gauge numbers, the increment between the two lowest gauges is 0.046 inches (1.2 mm). This progression does not follow a mathematical formula but instead reflects historical manufacturing practices in the wire drawing industry, where the size increments were determined by practical tooling, such as a draw plate, and production constraints.[4] In applications involving wires and fine tubing, the gauge number refers to the product's outside diameter. For larger mechanical tubing, however, the gauge number indicates the wall thickness, independent of the tube's overall size.

In medicine, the Birmingham gauge is widely used to specify the outer diameter of hypodermic needles, catheters, cannulae, and suture wires. However, catheters are more commonly defined using the French catheter gauge. The Birmingham gauge was originally developed in early 19th-century England for wire manufacturing and became common in medical settings in the early 20th century.

The Birmingham gauge system is also recognized in international medical standards, such as ISO 6009:2016, which includes a color-coding system for hypodermic needles. This standardization helps ensure accurate identification and compatibility of medical equipment.

Sizes of hypodermic needles

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Hypodermic needles are available in a wide variety of outer diameters described by gauge numbers. Smaller gauge numbers indicate larger outer diameters.[5] Inner diameter depends on both gauge and wall thickness. The following chart shows nominal inner diameter and wall thickness for regular-wall needles.[5][6] Thin-wall needles (not shown) have identical outer diameters but larger inner diameters for a given gauge.

Gauge,
G 		Nominal outer diameter Nominal inner diameter[a] Nominal wall thickness[a] ISO 6009
color[7]
(inch) (mm) (inch) (mm) (inch) (mm)
7 0.180 ± 0.001 4.572 ± 0.025 0.150 ± 0.003 3.810 ± 0.076 0.015 ± 0.001 0.381 ± 0.025 (undefined)
8 0.165 ± 0.001 4.191 ± 0.025 0.135 ± 0.003 3.429 ± 0.076 0.015 ± 0.001 0.381 ± 0.025 (undefined)
9 0.148 ± 0.001 3.759 ± 0.025 0.118 ± 0.003 2.997 ± 0.076 0.015 ± 0.001 0.381 ± 0.025 (undefined)
10 0.134 ± 0.001 3.404 ± 0.025 0.106 ± 0.003 2.692 ± 0.076 0.014 ± 0.001 0.356 ± 0.025 Olive brown
11 0.120 ± 0.001 3.048 ± 0.025 0.094 ± 0.003 2.388 ± 0.076 0.013 ± 0.001 0.330 ± 0.025 Green-yellow
12 0.109 ± 0.001 2.769 ± 0.025 0.085 ± 0.003 2.159 ± 0.076 0.012 ± 0.001 0.305 ± 0.025 Pale blue
13 0.095 ± 0.001 2.413 ± 0.025 0.071 ± 0.003 1.803 ± 0.076 0.012 ± 0.001 0.305 ± 0.025 Purple
14 0.083 ± 0.001 2.108 ± 0.025 0.063 ± 0.003 1.600 ± 0.076 0.010 ± 0.001 0.254 ± 0.025 Pale green
15 0.0720 ± 0.0005 1.829 ± 0.013 0.0540 ± 0.0015 1.372 ± 0.038 0.0090 ± 0.0005 0.229 ± 0.013 Blue-grey
16 0.0650 ± 0.0005 1.651 ± 0.013 0.0470 ± 0.0015 1.194 ± 0.038 0.0090 ± 0.0005 0.229 ± 0.013 White
17 0.0580 ± 0.0005 1.473 ± 0.013 0.0420 ± 0.0015 1.067 ± 0.038 0.0080 ± 0.0005 0.203 ± 0.013 Red-violet
18 0.0500 ± 0.0005 1.270 ± 0.013 0.0330 ± 0.0015 0.838 ± 0.038 0.0085 ± 0.0005 0.216 ± 0.013 Pink
19 0.0420 ± 0.0005 1.067 ± 0.013 0.0270 ± 0.0015 0.686 ± 0.038 0.0075 ± 0.0005 0.191 ± 0.013 Cream
20 0.03575 ± 0.00025 0.9081 ± 0.0064 0.02375 ± 0.00075 0.603 ± 0.019 0.00600 ± 0.00025 0.1524 ± 0.0064 Yellow
21 0.03225 ± 0.00025 0.8192 ± 0.0064 0.02025 ± 0.00075 0.514 ± 0.019 0.00600 ± 0.00025 0.1524 ± 0.0064 Deep green
22 0.02825 ± 0.00025 0.7176 ± 0.0064 0.01625 ± 0.00075 0.413 ± 0.019 0.00600 ± 0.00025 0.1524 ± 0.0064 Black
22s 0.02825 ± 0.00025 0.7176 ± 0.0064 0.00600 ± 0.00075 0.152 ± 0.019 0.01110 ± 0.00025 0.2826 ± 0.0064 (undefined)
23 0.02525 ± 0.00025 0.6414 ± 0.0064 0.01325 ± 0.00075 0.337 ± 0.019 0.00600 ± 0.00025 0.1524 ± 0.0064 Deep blue
24 0.02225 ± 0.00025 0.5652 ± 0.0064 0.01225 ± 0.00075 0.311 ± 0.019 0.00500 ± 0.00025 0.1270 ± 0.0064 Medium purple
25 0.02025 ± 0.00025 0.5144 ± 0.0064 0.01025 ± 0.00075 0.260 ± 0.019 0.00500 ± 0.00025 0.1270 ± 0.0064 Orange
26 0.01825 ± 0.00025 0.4636 ± 0.0064 0.01025 ± 0.00075 0.260 ± 0.019 0.00400 ± 0.00025 0.1016 ± 0.0064 Brown
26s 0.01865 ± 0.00025 0.4737 ± 0.0064 0.00500 ± 0.00075 0.127 ± 0.019 0.00680 ± 0.00025 0.1734 ± 0.0064 (undefined)
27 0.01625 ± 0.00025 0.4128 ± 0.0064 0.00825 ± 0.00075 0.210 ± 0.019 0.00400 ± 0.00025 0.1016 ± 0.0064 Medium grey
28 0.01425 ± 0.00025 0.3620 ± 0.0064 0.00725 ± 0.00075 0.184 ± 0.019 0.00350 ± 0.00025 0.0889 ± 0.0064 Blue-green
29 0.01325 ± 0.00025 0.3366 ± 0.0064 0.00725 ± 0.00075 0.184 ± 0.019 0.00300 ± 0.00025 0.0762 ± 0.0064 Red
30 0.01225 ± 0.00025 0.3112 ± 0.0064 0.00625 ± 0.00075 0.159 ± 0.019 0.00300 ± 0.00025 0.0762 ± 0.0064 Yellow
31 0.01025 ± 0.00025 0.2604 ± 0.0064 0.00525 ± 0.00075 0.133 ± 0.019 0.00250 ± 0.00025 0.0635 ± 0.0064 White
32 0.00925 ± 0.00025 0.2350 ± 0.0064 0.00425 ± 0.00075 0.108 ± 0.019 0.00250 ± 0.00025 0.0635 ± 0.0064 Deep green
33 0.00825 ± 0.00025 0.2096 ± 0.0064 0.00425 ± 0.00075 0.108 ± 0.019 0.00200 ± 0.00025 0.0508 ± 0.0064 Black
34 0.00725 ± 0.00025 0.1842 ± 0.0064 0.00325 ± 0.00075 0.0826 ± 0.019 0.00200 ± 0.00025 0.0508 ± 0.0064 Orange
  1. ^ a b Not strictly defined, and may vary for a given gauge.
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)

Rapid blood transfusion through 23G or smaller needles can cause hemolysis (rupturing of red blood cells).[8]

Sizes of catheters

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

Gauge Outer diameter
(mm) 		Maximum flow rate
(ml/min) 		Color
14 2.0 250–300 Orange
16 1.7 180 Grey
18 1.3 75–120[9] Green[9]
20 1.1 40–80[9] Pink[9]
22 0.9 42-55[9] Blue[9]
24 0.7 20-35[9] Yellow[9]
26 0.6 10-13[9] Black[9]

See also

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References

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  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 978-0-7020-5375-7.{{cite book}}: CS1 maint: multiple names: authors list (link)
  2. ^ a b Pöll, J. S. (1999). "The story of the gauge". Anaesthesia. 54 (6): 575–581. doi:10.1046/j.1365-2044.1999.00895.x. ISSN 1365-2044.
  3. ^ "'French', 'gauge' and millimeters". University of California, San Francisco. Archived from the original on 2017-08-18. Retrieved 2018-02-03.
  4. ^ Machinery's Handbook 27. New York, NY: Industrial Press, Inc. 2004. p. 2520.
  5. ^ a b "Syringe Needle Gauge Chart". Sigma Aldrich. Retrieved 20 March 2012.
  6. ^ "Hypodermic Needle Gauge Chart". Medical Tube Technology, Inc. Archived from the original on 10 October 2004. Retrieved 20 March 2012.
  7. ^ "ISO 6009:2016 Hypodermic needles for single use -- Colour coding for identification". International Organization for Standardization. Publication date: 2016-08
  8. ^ Miller, Michal A.; Schlueter, Annette J. (2004). "Transfusions via hand-held syringes and small-gauge needles as risk factors for hyperkalemia". Transfusion. 44 (3): 373–381. doi:10.1111/j.1537-2995.2004.00653.x. ISSN 0041-1132. PMID 14996194. S2CID 22956171.
  9. ^ a b c d e f g h i j Page 110 in: Edward Doyle (2007). Pediatric Anesthesia. OUP Oxford. ISBN 978-0-19-920279-9.

Further reading

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  • 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. PMID 12351319.
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