Elastic Water Hammer Effect in Arterial Network: Origin of the Tidal and the Dicrotic Wave in Blood Pressure Waveforms

Arterial blood pressure (ABP) and photoplethysmography (PPG) signals are extensively utilized in this domain to explore new biological markers for improved healthcare. Nonetheless, the interpretation of waveform morphology remains unclear for researchers and physicists, making it challenging to associate waveform features with physiological mechanisms. Two signal components are commonly observed in the electronically recordings, yet their origins are not universally agreed upon: the tidal wave (TDW) and the dicrotic wave (DCW). While these components are strongly correlated with vasomotor states, their origins have often been hypothesized to result from wave reflection phenomena. However, within the context of an elastic arterial network, this hypothesis appears unlikely to occur. One overlooked physical mechanism during blood flow is the water hammer effect, which manifests with both positive and negative pressure variations. The current study investigated this mechanism in view of the origin of tidal and dicrotic waves during different hemodynamic states. The analysis consisted of high-quality recordings of arterial blood pressure (ABP) and blood flow velocity tracing obtained from 20 patients undergoing surgical procedures. As a result, tidal wave indicates to be originated from the negative water hammer effect, resulting from the discontinuity in blood flow induced by the closure of semilunar valves. Conversely, the dicrotic wave indicates to appear due to the positive water hammer effect, which occurs during right atrium contraction by sudden interruption of blood flow continuity. These findings provide an accurate understanding of waveform morphologies to be exploit for an improved cardiovascular evaluation.