Theoretical and Experimental Investigation of a Method to Detect an Aortic Aneurysm from Pulse Waves

Early identification of aortic aneurysms is important for effective treatment. Although imaging systems have the ability to identify aortic aneurysms, high cost prevents their use for screening. On the other hand, pulse waves can be measured easily, and because pulse wave velocity is affected by the aortic aneurysm, there is a possibility to find an aortic aneurysm by pulse wave measurement. The aim of this study is to propose a method to find an aortic aneurysm from the pulse wave and to develop a measurement device. The aortic aneurysm causes the expansion of artery. The basic theory is based on the wave of a mechanical reactance silencer. The transfer functions of a pulse wave between brachial artery and anterior tibial artery were investigated. The transmission loss is increased by increase of the inner radius of an aortic aneurysm. The interval frequency of local minimum points of the transfer function correlates with the length of an aortic aneurysm. When the stiffness decreases, the characteristic impedance decreases, the pulse wave velocity decreases and the frequencies of the local peaks become low. It is therefore possible to estimate the size of an aortic aneurysm from the transfer function. The method to find an aortic aneurysm from the pulse wave was investigated theoretically and experimentally with silicone tubes. The relation between the transfer function and the pathological arterial change was clarified. This method can be used for diagnosis of aortic aneurysms.