Reconstruction of pressure and flow waves in the artery

Cardiac arrests were induced in 22 rabbits by applying electrical stimulations to the vagus nerve while electrocardiogram (ECG), and blood pressure (BP) and blood flow (BF) either from the carotid artery or from the femoral artery were monitored continuously. Under the assumption that the arterial system is a linear and time-in-variant (LTI) system, the "single-pulse-response" (SPR), i.e. the response to a single ventricular contraction of BP (Pm0) and BF (Qm0) were calculated by subtracting the wave from itself after being shifted backward by one R-R interval. Pm0 and Qm0 were then used to construct the original waves by summing successive SPR's at a repetitive period of one R-R interval. The result showed that both pressure and flow waves in the carotid artery and in the femoral artery could be successfully reconstructed from the corresponding SPR's. The result was compared to the voltage across the capacitor in the two-element windkessel model when a train of impulses were given, beginning from the zero-state. We concluded (1) the arterial system, being a physical system, can be treated as an engineering system, and (2) the observed BP and BF in the artery can be regarded as the summation of arterial responses to repetitive pulses generated by the left ventricle and be analyzed accordingly.