Quantitative assessment of the reactive function in peripheral microcirculation and its computer modeling

• Main Authors: Yue-Tin Tsai, 蔡岳庭
• Other Authors: Jia-Jung Wang
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/3r5446

碩士 === 義守大學 === 生物醫學工程學系 === 105 === Microcirculation is a fundamental unit of the human circulatory system, responsible for transporting oxygen and nutrition to all tissues. If the perfusion in peripheral microcirculation is not enough, vascular abnormality and even tissue necrosis will be caused. Thus, it is necessary to early quantify the microcirculatory reactivity. The thesis established one assessment system for quantifying the reactivity of the peripheral microcirculation. We recruited 25 healthy subjects to participate three items of lower-extremity physiological stress, including the local heating, the arterial occlusion, and the Valsalva maneuver. The laser Doppler Flowmetry (LDF) was used to record the microvascular LDF oscillation signals on the surface of the foot bottom. The LDF signals were analyzed by both the time-domain techniques, and the frequency-time methods (including the fast Fourier transform, FFT and the wavelet transform,WT). In the thesis, six specific frequency bands that governed the microcirculatory characteristicswere further explored. The six bands (0.005 to 2.0 Hz) were associated with the cardiac activity(0.6-2.0Hz), the respiratory activity(0.15-0.6Hz), the myogenic activity(0.05-0.15 Hz), the sympathetic activity(0.021-0.05Hz), the endothelial NO-dependent metabolic activity(0.0095-0.021Hz) and theendothelial non-NO-dependent metabolic activity(0.005-0.0095Hz), respectively. In the time-domain analysis, both the initial peak and the plateau values in the LDF signalswithin the 30-min local heating course (up to 44oC) were found to be significantly greater than the 10-min baseline amplitude. Also, the composite vasodilatation indexes corresponding to the initial peak and the plateau periods were 154564 % and 23993 %, respectively. In the 3-min arterial occlusion, the amplitude (7655 PU) of LDF signals smaller in the 10-min baselinewas significantly than that (214116 PU)in thereactive period, but greater than that (4.124 PU) in the occlusion period (all p<0.05). Meanwhile, the composite vasodilatation and vasoconstriction indexes were found to be 217213 % and 926 %, respectively. In the FFT analysis, the LDF signals recorded in the reactive period after 3-min occlusion had significantly greater cardiac activity-related spectral power density area and average power density than those in the 10-min baseline (4.907.18 vs. 0.300.56, p<0.05;57.026.2 vs. 21.618.2, p<0.05). In the WT analysis, the LDF signals recorded in the heating period had significantly less endothelial NO-nondependent activity-related average power percentage (13±12%) than that (15±13%) in the 10-min baseline (p<0.05). Furthermore, an analog circuit that modeled the lower extremity circulatory system was established to study the effect of lower extremity arterial occlusion on the peripheral microcirculation. In conclusion, a measuring system for quantifying the reactivity of the peripheral microcirculation is constructed. Through the lower-extremity physiological stress and with the FFT and WT methods, we are able to observe the change in the six special mechanisms in the regulation of microcirculation before and after stimulation, by assessing their composite and individual microvascular reactivity. This may help us to quantify the endothelial function of microcirculation, and then to diagnose its initial dysfunction. Furthermore, the proposed Lower limb circulation model can be used to investigate the role of individual hemodynamic parameter and its effect on the blood pressure and flow in the circulation model.