EXPONENTIALLY TAPERED T-TUBE MODEL OF SYSTEMIC ARTERIAL SYSTEM IN DOGS

This study determines the role of an asymmetric T-tube model as a repr esentation of arterial mechanical properties. The model consists of tw o non-uniform tubes connected in parallel. The non-uniform properties of each tube include geometric and elastic tapering and each tube term inates in a complex load. Pulsatile pressure and flow velocity of the ascending aorta were measured in 10 closed-chest, anaesthetized dogs. An exponentially tapered transmission line is used to describe the non -uniform properties of the vasculature. The phase constant is a functi on of position along the path length due to geometric and elastic tape rs. This non-uniform T-tube model makes it possible to fit the measure d pressure waveform in the ascending aorta. Model parameters could be estimated and used to interpret the physical properties of the arteria l system. The mathematical and experimental modal impedance spectra ar e similar. There is a close correspondence between the impedance param eters derived from the non-uniform T-tube model and values computed fr om measurements on dogs. The results suggest that inclusion of tube ta pering improves the mathematical model so that it closely represents t he experimentally derived arterial impedance in closed-chest dogs. We conclude that the non-uniform properties of wave-transmission paths ma y play an important role in governing the behaviour of an asymmetric T -tube for the description of the arterial system.