Comparative analysis of aortic impedance and wave reflection in ferrets and dogs

Our modified version of the T-tube arterial model (consisting of two parallel, loss-free transmission paths terminating in lumped loads of complex and frequency-dependent nature) was applied to experimental measurements of ascending aortic pressure and of ascending and descending aortic flows taken from dogs and ferrets. Our aim was to provide quantitative evaluation of the aortic pressure and flow pulse wave components as they relate to the distribution of arterial properties and relate to wave travel and reflection in mammalians of consistently different size and shape. Estimated effective lengths (distances to effective reflection sites) of the head-end (d(h)) and body-end (d(b)) transmission paths were approximately 12 and 30 cm, respectively, in the dog and 6.5 and 13 cm, respectively, in the ferret. These lengths and distributions of estimated arterial properties were consistent with the difference in the body size and with the more central location of the heart in the ferret's body than it is in the dog's body. In both animal species the ascending aortic pressure and flow waves could be interpreted in terms of forward and reflected components arising from the two distinct effective reflection sites, although the higher d(h)/d(b) ratio in the ferret determined the presence of one broad, indistinct minimum in the modulus of ascending aortic impedance in the frequency range from 0 to 10 Hz, rather than two distinct minima as observed in the dog.