What is the primary purpose of using a tourniquet during a blood draw?

The primary purpose of using a tourniquet during a blood draw is to make veins more prominent. When the tourniquet is applied, it temporarily restricts venous blood flow, which causes blood to accumulate in the veins and leads to their expansion. This makes the veins easier to see and palpate, facilitating the identification of a suitable site for the blood draw.

The use of a tourniquet is common practice in venipuncture as it helps healthcare providers find a suitable vein, thereby improving the chances of a successful blood draw on the first attempt and minimizing discomfort for the patient. The other options describe different aspects of the procedure but do not capture the primary function of the tourniquet itself in this context.