Advanced Phlebotomy Practice Test

The test assess collateral circulation to the hand before radial artery puncture. Its purpose is to make sure the hand will still be well perfused if the radial artery is used for sampling. By temporarily blocking both the radial and ulnar arteries and then releasing one, you observe whether blood flow returns quickly to the hand. A prompt return of color indicates adequate collateral flow through the ulnar artery and palmar arches, meaning it’s safe to use the radial artery. If color does not return promptly, collateral circulation is insufficient, raising the risk of ischemia if radial access is pursued. This test isn’t about measuring how much oxygen is in the blood, nor does it assess venous return or nerve function. Those assessments involve different tests and purposes.