A novel endothelial function test using Doppler flow: the snuff-box technique.
Precise measurement of Doppler estimated blood flow volume using the standard technique of flow-mediated vasodilation is not possible because the anatomic course of the brachial or radial artery goes against the principle of Doppler measurements that the insonation angle should be less than 30 degrees . The radial artery in the anatomic snuff-box area is useful for the measurement of Doppler signals as the insonation angle is less than 30 degrees and because the size of the artery allows observation of laminar flow. We introduce the snuff-box technique as a novel endothelial function test that enables measurement of both blood flow and diameter of the radial artery. Changes in diameter and blood flow volume during reactive hyperemia were examined in 15 healthy volunteers. Changes in blood flow determined using the snuff-box technique were compared with changes in forearm blood flow determined by plethysmography. The diameter of the radial artery increased from 2.3 +/- 0.2 mm at baseline to 2.8 +/- 0.4 mm at 60 s after deflation (P = 0.0017), and blood flow increased from 52.3 +/- 21.4 ml/min at baseline to 108.6 +/- 33.1 ml/min at 15 s after deflation (P = 0.0014). Percentile blood flow determined by the snuff-box technique correlated significantly with that determined by plethysmography (r = 0.824, P = 0.0002). Both blood flow volume and artery diameter can be measured with high reliability using the snuff-box technique, as has been shown in subjects with reactive hyperemia.