Oscillatory Flow Impedance in Electrical Analog of Arterial System: Representation of Sleeve Effect and Non-newtonian Properties of Blood.

• A great variety of mathematical and physical models of the human arterial system has been introduced, since the start of investigations in this field, with the dual purpose of gaining a better quantitative understanding of arterial performance and deriving clinical information in cases that deviate from normal." They can basically be divided in two groups: the "windkessel" models, the main characteristic of which is the analogy with the air chamber as used in fire engines, and those dealing with the equations of oscillatory motion of fluid streaming through tubes, the transmission models. Whereas one of the main purposes of utilizing models in the past has been the derivation of stroke volume, it is generally felt nowadays that a model should be more sophisticated and should have counterparts of the essential hemodynamic quantities in the actual system such as pressure-flow relationships, reflection coefficients, pulse wave velocity, etc. The "windkessel" models cannot be expected to do this because they lack, in their original concept, a representation of pulse wave velocity while subsequent attempts to introduce this quantity must be considered as unrealistic. One way of coming to some sort of simulation of the pulse wave, as it travels down the ar-