where Δ𝑃 is the pressure change, ΔV is the volume change and D is the
distensibility coefficient.
Herein, simultaneous measurement of two variables is essential for
example, pressure and flow velocity (Doppler) or pressure and diameter
(wall tracking). These are further investigated in Section 3. of this
paper. A significant two-site method such as velocity-encoded MRI
includes transit time [73], flow-area [79], and
cross-correlation techniques [80]. In this method, flow pulses are
measured at dual sites over multiple cycles and ensemble averaging are
employed for accurate results. Further, specific devices employed
pressure/displacement waves for PWV estimation; for example Complior
[81], SphygmoCor [82,83], PulsePen [84]. However, these
devices use manual external tape measurements and therefore, error
prone.
Additionally, consumption of meals [85], caffeine [86], and/or
cigarette [87] influenced arterial stiffness.