Wave Travel and Reflection
Both pressure and flow are travelling waves: they vary in time over the cardiac cycle and depend on location. The time delay Δt of pressure, flow or diameter waves allows calculation of Pulse Wave Velocity, PWV = distance/Δt. The pulse pressure (systolic-diastolic pressure) increases towards the periphery, called amplification, and results from wave reflections. The different wave shapes of pressure and flow also result from wave reflection. Reflections occur at all changes in arterial geometry: size, bifurcations, and changes in wall properties. Pressure and flow at any location can be separated into their forward and reflected components. Reflections of pressure and flow are equal in magnitude but ‘inversed’: when reflection is positive for pressure, it is negative for flow.
KeywordsWave propagation Wave separation Local reflection coefficient Global reflection coefficient Forward and backward waves Pressure transmission Pressure amplification Characteristic impedance
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