Devices that are inserted through natural opening | Devices that are inserted through unnatural opening |
Number increase, diameter increase | Number increase, diameter decrease |
Diameter order- 12G < 14G < 16G < 18G | Diameter order- 12G > 14G > 16G > 18G |
1. Ryles tube- in nose / mouth 2. Suction catheter- in nose / mouth 3. Gudel airway- in mouth 4. Foley catheter- in uretha | 1. IV cannula - in veins |

IV Cannula Color | Gauge Size | Outer Diameter (mm) | Flow Rate (ml/min) | Typical Use |
Orange | 14 G | 2.1 | 270 | Rapid fluid replacement, emergency use |
Grey | 16 G | 1.8 | 180 | Blood transfusions, surgery |
Green | 18 G | 1.3 | 90 | Blood transfusions, major trauma |
Pink | 20 G | 1.1 | 60 | General use, blood transfusions, IV fluids |
Blue | 22 G | 0.9 | 36 | IV medications, pediatric use |
Yellow | 24 G | 0.7 | 20 | Neonatal, pediatric, or elderly patients |
Purple | 26 G | 0.6 | 13 | Neonatal, fragile veins |