What is used to confirm occlusion during the modified Allen test?

The modified Allen test is a clinical procedure used to evaluate the patency of the radial and ulnar arteries, typically before an arterial blood gas sample is taken from the radial artery or prior to procedures such as arteriovenous fistula creation. The test assesses the collateral circulation of the hand.

To confirm occlusion during the modified Allen test, an SAO2 monitor, which measures oxygen saturation, is utilized. When the occlusion of the ulnar artery is performed, if the radial artery is patent (open and functioning), the hand’s oxygen saturation should remain adequate, reflecting good collateral circulation from the ulnar artery. A drop in the oxygen saturation can indicate compromised blood flow, thus confirming ulnar artery occlusion.

The other options provide tools and techniques that do not directly measure the oxygenation of the blood or the adequacy of perfusion in the hand. For instance, a blood pressure cuff can help achieve arterial occlusion but does not directly assess the blood flow after the release; a digital thermometer measures temperature and does not have relevance to blood flow confirmation; and a stethoscope is typically used for auscultation rather than for measuring hemodynamic parameters like oxygen saturation. Thus, the use of an SAO