Final answer:
The smaller the gauge number of a cannula, the bigger the catheter, similar to how electrical wire gauges work with higher numbers indicating thinner wires.
Step-by-step explanation:
When selecting a cannula for IV access, nurses must understand that the smaller the gauge number, the bigger the catheter. This means that the numerical value of the gauge is inversely proportional to the diameter of the catheter. This concept is similar to the way electrical wires are measured, where higher gauge numbers indicate thinner wires, as shown in Figure 9.11 depicting a device for measuring the gauge of electrical wires.
It is important to note, however, that in medical settings, the choice of cannula size depends on the type of fluid being infused, the patient's vein size, and the purpose of the intravenous therapy. For example, a larger gauge (which, again, is a smaller number) might be chosen for rapid infusions or blood transfusions, while a smaller gauge (a larger number) could be appropriate for slower infusions or paediatric patients.