Positive pulse reflection in an elastic model from a wider segment with higher resistance

¹ Department of Physiology, Medical College of Georgia, Augusta, Georgia

It has been shown in earlier work from this laboratory that a standing or resonant wave is set up in the dog's aorta that causes simultaneous augmentation of the systolic pressure in the lower parts of the aorta. It has been hypothesized that this is due to reflection of the pulse wave from the peripheral arterioles. On theoretical premise, the possibility of such reflection has been denied by various authors, on the grounds that the aggregate cross-sectional area of the arterioles is greater than that of the aorta and that reflection in such a region should be negative rather than positive. A model has been constructed of a distensible rubber tube, the end of which can be open or closed with a stopper or a bundle of capillary tubes with aggregate cross-sectional area larger and resistance to flow greater than those of the distensible tube. With tube distended to 20 cm H₂O, pulse-wave trains were generated in the tube with the end either open or closed. Pulse waves at the two ends of the tube were recorded simultaneously and recordings showed that with the open tube negative reflection took place, whereas with the tube closed the reflection was unequivocally positive.