Noninvasive Measurement and Quantitative Analysis of Dynamic Arterial Stiffness Using Minute Vibration

• Main Authors: Hung-mao Su, 蘇弘貿
• Other Authors: Jia-jung Wang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/38502667537627058804

碩士 === 義守大學 === 生物醫學工程學系碩士班 === 96 === Human arterial hardening appears more significant when their age is increased or when they suffer from cardiovascular diseases. Up to now, there is no reliable way to evaluate the degree of the arterial stiffness (elastance) in the clinical setting. Thus, the purpose of this thesis is to develop a noninvasive apparatus for measuring the arterial wall properties by means of minute vibration technique, and to quantitatively analyze the dynamic arterial elastance. The measuring apparatus consisted mainly of a micro-vibration generator, a force-sensing device, an oscillometric blood pressure measuring device, a photo-plethysmographic device, analog-to-digital and digital-to-analog converters, and a personal computer. The characteristics of arterial wall were assumed to be governed by three components, including the inertia, viscosity, and elastance. According to the concept of force balance, the force generated by the arterial wall should be equal to the sum of the forces from the three components. With the apparatus, the arterial wall was stimulated by a minute sinusoidal displacement with various frequencies (40, 45, 50, 55, 60, 80, and 85 Hz). Based on the linear relationship between the responsive contact force (Y-axis) and square angular frequency (X-axis), the wall elastance could be obtained from the intercept of the Y-axis. In the eighteen subjects, the dynamic range of the radial wall elastance was found between 0.705×106 and 3.778×106 dyne/cm, and the average of maximum elastance was 1.879×106 ± 0.854×106 dyne/cm in baseline conditions. As an air cuff around one upper arm was pressurized to 10 mmHg over the subject’s diastolic pressure, the dynamic radial wall elastance varied from 1.243×106 to 6.557×106 dyne/cm, and the average of maximum elastance became 3.017×106 ± 1.779×106 dyne/cm for the eighteen subjects. In brachial artery occlusion experiments, it was found that the radial wall elastance during the brachial artery occlusion was decreased as compared with that in the baseline conditions. In addition, the dynamic curve of the radial wall elastance computed in this study resembled radial blood pressure waveform. Briefly, a noninvasive apparatus using the minute vibration technique is successfully established, and used to measure the subjects’ time-varying radial wall compliance (inversely proportional to elastance) in this thesis. It suggests that the apparatus proposed in the study has potential in future applications.