A Study of the Relationship between Marcohemodynamics and Microhemodynamics

• Main Authors: Ming-Yie Jan, 詹明宜
• Other Authors: Wei-Kung Wang, Ph.D.
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/58415359700871033617

博士 === 國立臺灣大學 === 電機工程學研究所 === 88 === According to the WHO report, in the developed countries, the circulatory diseases are the main causes of death. In haemodynamic research, most approaches based on the Navior-Stoke equation investigate the precise movement of a small element of liquid in the artery. Meanwhile, both the viscous force and inertial force would attenuate the blood pressure wave. However, the pulsatile blood pressure is amplified from aorta to the downstream artery. The strange phenomenon is regarded as by superposition of the reflected waves generated by the vascular branches and the impedance of peripheral vascular beds. If the flow does act the key role in the circulation, the peripheral vascular fluxes, which have to flow through a complex network and be interfered by the numerous reflected waves, would be constant and no phase could be detected. On the contrary, according to the radial resonance theory, each organ or vascular bed has its own natural frequency; through the coupling by the long-wavelength blood pressure, the peripheral vascular fluxe is driven by the coupled blood pressure. Thus, it would be pulsatile and the fluxes in the same vascular bed would be coherent. In this study, refer to the blood pathway, there are two critical conditions about the peripheral blood flux perfused by the arterial blood pressure. First, the flux in the most perfused renal cortical surface relates to the abdominal aortic blood pressure. Second, the flux in the skin of a foot relates to the radial blood pressure. We used a laser Doppler flowmetry (LDF) to measure the blood fluxes on different sites of the observed tissues and a pressure transducer simultaneously measured the blood pressure waves. The results show that the peripheral blood flux not only is pulsatile but also has constant phase relation with arterial blood pressure; moreover, all blood fluxes in the same tissue are coherent. It is coincident with the inference of the radial resonance and the coupled resonance theory. Furthermore, the driving efficience of the pulsatile blood pressure in renal cortical surface was evaluated. We define a flux-to-pressure-area-ratio (FPAR) to evaluate the efficiency that the pulsatile blood pressure drives the renal cortical fluxe. The result shows that the higher the pulsatile blood pressure, the more the driven flux is, and it seems that there is a threshold of blood pressure pulsatile index (BPPI) that the driving efficiency would be amplified abruptly. That implies the pulsatility plays a role in lowering the vessel resistance of PVBs and it could also regulate the blood pressure in large arteries. As a result, we further infer that if the precapillary openings are obstructed or the peripheral blood vessels become stiffer the pulsatile pressure will be induced to become higher so as to keep the blood perfusion could be responsible for the hypertension.