The speed reflection and intensity of waves propagating in flexibletubes with aneurysm and stenosis: Experimental investigation

摘要

A localized stenosis or aneurysm is a discontinuity that presents the pulse wave produced by the contracting heart with a reflection site. However, neither wave speed (c) in these discontinuities nor the size of reflection in relation to the size of the discontinuity has been adequately studied before. Therefore, the aim of this work is to study the propagation of waves traversing flexible tubes in the presence of aneurysm and stenosis in vitro. We manufactured different sized four stenosis and four aneurysm silicone sections, connected one at a time to a flexible ‘mother’ tube, at the inlet of which a single semi-sinusoidal wave was generated. Pressure and velocity were measured simultaneously 25 cm downstream the inlet of the respective mother tube. The wave speed was measured using the PU-loop method in the mother tube and within each discontinuity using the foot-to-foot technique. The stenosis and aneurysm dimensions and c were used to determine the reflection coefficient (R) at each discontinuity. Wave intensity analysis was used to determine the size of the reflected wave. The reflection coefficient increased with the increase and decrease in the size of the aneurysm and stenosis, respectively. c increased and decreased withinstenosis and aneurysms, respectively, compared to that of the mother tube.Stenosis and aneurysm induced backward compression and expansion waves,respectively; the size of which was related to the size of the reflectioncoefficient at each discontinuity, increases with smaller stenosis and largeraneurysms. Wave speed is inversely proportional to the size of thediscontinuity, exponentially increases with smaller stenosis and aneurysms andalways higher in the stenosis. The size of the compression and expansionreflected wave depends on the size of R, increases with largeraneurysms and smaller stenosis.