What is the purpose of using a tourniquet during venipuncture?

Using a tourniquet during venipuncture serves the specific purpose of engorging the veins for easier access. By applying a tourniquet, blood flow is partially restricted in the area above the venipuncture site, causing the veins to become swollen or engorged with blood. This makes the veins more prominent and easier to locate, which is crucial for successfully inserting the needle.

The engorgement of veins not only facilitates easier access but also improves the likelihood of obtaining a sufficient volume of blood for laboratory testing. It is important to note that the tourniquet should be removed as soon as the needle is inserted to prevent complications such as hemoconcentration or tissue damage.

Other options like decreasing blood pressure, preventing bleeding, or helping in sample preservation do not accurately describe the role of the tourniquet in the venipuncture process.