NHA Phlebotomy Certification Practice Exam

A properly tied tourniquet should:

1. Permit arterial flow and block venous flow

2. Block arterial and venous flow

3. Prevent backflow

4. Permit venous flow and block arterial flow

The correct answer is: Permit arterial flow and block venous flow

A properly tied tourniquet is designed to facilitate the collection of blood by creating a temporary vascular occlusion that helps engorge the veins, making them more prominent and easier to access. The goal of using a tourniquet is to block venous flow while still allowing arterial flow to occur, which is why arterial blood continues to enter the arms or legs when the tourniquet is in place. When the tourniquet is applied correctly, it restricts the return of blood from the veins to the heart, but allows the arteries to keep supplying blood to the site. This enables the veins to fill with blood, aiding in the identification and puncturing of a suitable vein for blood draw. The ideal situation is one where the veins remain distended but arterial circulation is maintained, preventing tissue damage or complications from excessive restriction. This understanding demonstrates why the statement about permitting arterial flow while blocking venous flow is accurate, as it aligns with the proper technique for venipuncture and ensures the safety and comfort of the patient.