Final answer:
A butterfly needle is a medical device used for venipuncture in patients with fragile veins to minimize discomfort and vein damage.
Step-by-step explanation:
A butterfly needle is used for patients with fragile veins. A butterfly needle, also known as a winged infusion set, is a device specifically designed for venipuncture—the process of obtaining intravenous access for the purpose of intravenous therapy or for blood sampling.
Butterfly needles have flexible "wings" that allow the healthcare provider to maintain stability and control when accessing a vein, reducing the risk of the needle moving or causing damage to the vein walls. Butterfly needles come in a variety of sizes, measured in gauges, and a smaller gauge number indicates a larger diameter needle. Medical professionals select the gauge based on the viscosity of the fluid being administered or drawn and the patient's vein size and condition.