5. Central Arterial Pressure The applanation tonometry from the radial artery is a non-invasive method assessing arterial stiffness, which is predictive of vascular disease. A portion of the artery pressure wave travelling towards the extremities is reflected back from peripheral impedance points. In healthy individuals, the reflected wave returns to the aorta during diastole. When arteries become stiff, the transit time for de incident and reflected waves is reduced. Thus, the reflected wave returns to the aorta during systole of the same cardiac cycle augmenting the central blood pressures. This augmenting of central pressure can be quantified by augmentation index (AIx). AIx has been associated with cardiovascular risk, predicts the presence or absence of coronary artery disease40. Higher values of AIx indicate increased wave reflection from periphery or earlier return of the reflected wave as a result of increased pulse velocity, which can be contributed to an increased arterial stiffness. In young healthy individuals, the systolic arterial pressure (aortic) is about 20 mmHg less than the peripheral systolic pressure (brachial).