What role does adding the tourniquet play in blood collection?

Adding a tourniquet plays a crucial role in the process of blood collection primarily by enhancing the visibility of veins. When a tourniquet is applied to the upper arm, it compresses the veins, causing them to engorge with blood. This engorgement makes the veins more prominent and easier to locate, which is particularly helpful in patients who may have smaller or deeper veins. The increased visibility facilitates the successful insertion of the needle into the vein, reducing the chances of multiple punctures and minimizing discomfort for the patient.

While there are other factors to consider, such as preventing contamination or maintaining proper blood flow, the primary function of the tourniquet in this context is to improve vein visibility, making blood collection more efficient and effective.