Improvement of novel noninvasive measurement of endothelial function: ezFMD

Endothelial dysfunction is considered as an early event in the development of atherosclerosis and vascular diseases. The conventional non-invasive method used to assess endothelial function, namely, measurement of flow-mediated dilatation (FMD), needs an ultrasound system, which is expensive, and high levels of technical skill. We developed the novel method, measurement of the ezFMD, for the assessment of endothelial function. ezFMD estimates the degree of vasodilatation from the cuff oscillation signal transmitted by the cuff attached to the upper arm. The objective of this study was to clarify the factors influencing the variability of ezFMD, improve the repeatability of ezFMD measurement, and determine the correlation between ezFMD and FMD. We assumed that the following two factors are variable factors, and investigated the following two factors to improve the measurement accuracy. (1) brachial artery occlusion by cuff pressure for oscillation measurement; (2) change of the arterial wall viscosity at dilatation. Repeatability was improved by using the mean pressure method. Also, the correlation was improved by calculating the oscillation amplitude from the pulse wave area. These results suggest that ezFMD has potential for clinical use.