Vessel Segment

The relation between the pressure drop and flow of a uniform segment of blood vessel is shown in the Figure in the box. The relation consists of a longitudinal impedance, which is described by Womersley’s oscillatory flow theory [1, 2], and a transverse impedance [3], describing the pressure-area (or volume) relation of the segment. The combination of longitudinal and transverse impedances gives characteristic impedance and wave propagation (Appendix 4).