Figure 1

Flow-mediated dilation. Flow-mediated dilation (FMD) measures endothelial function by inducing a temporary ischemia in a brachial artery and observing the amount of vasodilation following the stressor event. After a baseline measurement of the artery diameter via an ultrasound probe, a sphygmomanometer blood pressure cuff is positioned on the right forearm 2 cm below the elbow and inflated to 250 mmHg to produce ischemia in the forearm. The cuff is deflated after some minutes, usually 5, thus causing a reactive hyperemia which in turn produces a shear stress stimulus that induces the endothelium to release nitric oxide as a vasodilator. FMD is considered as diameter after reactive hyperemia - basal diameter/basal diameter × 100. The figure shows the diameter (upper part) and shear rate (lower part) of brachial artery during FMD before (grey-shaded part on the left), during (black-shaded part), and after (grey-shaded part on the right) ischemia.