心血管疾病持續成為世界上第一大死亡原因。在眾多危險因素中，動脈血壓，尤其是夜間血壓和血壓變化率，是心血管疾病發病率和死亡率的關鍵指標。 / 由於需要用到充氣式袖帶，現有的血壓測量技術只能提供瞬時血壓，並且使用起來極不舒適。因此，本文致力於研究另一種無袖帶式血壓測量方法。此方法的原理基於血壓波在血管上的傳導速度，即脈搏波傳導速度（PWV）取決於血壓作用下的血管力學特性。因此，血壓可以從脈搏波傳導速度，或者其倒數：脈搏波傳輸時間（PTT）估計得到。由於脈搏波傳導時間可以方便的從心電信號及光電容積描記信號獲取，這種新型的無袖帶式血壓測量技術近年來備受關注。 / 現有的基於脈搏波傳輸時間的血壓估計方法建立於一個被動的，薄壁的和均質的血管模型。但是，真實的血管卻是由彈性蛋白，膠原纖維和平滑肌共同組成的具有特殊層次結構的管道。事實上，以往許多研究已經表明了血管緊張度（VSM tone），即血管壁平滑肌細胞的激活程度，能顯著改變血管力學特性進而使脈搏波傳輸時間與血壓的關係惡化。特別地，血管緊張度主要受控于自主神經系統，尤其是交感神經系統。因此，本論文的目的在於研究自主神經系統對基於脈搏波傳輸時間的血壓估計的影響。 / 首先，基於血管微結構力學模型和Bramwell-Hill公式，本文建立了一個基於血管組分的脈搏波傳輸時間-血壓模型。并在此基礎上，推導出一個融合了血管結構和功能特性的解析數學公式來表徵脈搏波傳導時間和血壓的關係。仿真結果顯示，隨著血管緊張度增高，脈搏波傳輸時間-血壓曲綫會移向右上方，造成滯變現象（hysteresis）。 / 其次，爲了研究自主神經系統對血壓，脈搏波傳輸時間及心率的調節機制，本文利用時頻分析技術，對來自9個健康測試者跑步運動前後的實驗數據進行了分析。結果顯示，僅心率這一參數表現出運動中首先迷走神經活動減弱，然後交感神經增強的機制。此外，分析結果表明脈搏波傳輸時間與血壓的關係是頻率相關的。 / 爲了進一步研究自主神經系統在吞咽動作過程中對心血管參數的調控作用，本文設計了喝水實驗。對32個健康測試者的實驗數據分析結果表明，在喝水過程中，心率和血壓顯著上升，脈搏波傳輸時間顯著下降。另一方面，基於之前脈搏波傳輸時間與血壓的頻變關係的研究發現，本文設計了一種新的基於脈搏波傳輸時間，利用頻段特定的序列技術，來估計壓力反射敏感性（BRS）的新方法，並利用喝水實驗數據進行了驗證。結果顯示，利用此方法估計和利用傳統的利用血壓計算出的壓力反射敏感性具有高相關性（喝水前，中，后過程中，相關係數分別為0.90，0.70和0.81）。 / 最後，爲了驗證自主神經系統調控下的血管緊張度對脈搏波傳輸時間和血壓關係的影響，本文對來自46名測試者，其中包括17名心血管疾病患者，在人體仰臥姿態下的漸進式腳踏車運動實驗中的數據進行了分析。結果證實了仿真實驗中顯示的脈搏波傳輸時間和血壓的滯變現象。另外，本文提出了兩個新型量化指標衡量此滯變現象，即AreaN和ΔSBP20。結果顯示，相比于健康人，心血管疾病患者的滯變現象幅度顯著減弱，這與此類患者通常伴隨有交感神經系統過度活躍相關。基於以上發現，本文進一步提出利用AreaN和ΔSBP20來評估交感神經系統功能的建議。 / 綜上所述，本論文從理論和實驗的雙重角度研究了自主神經系統對脈搏波傳輸時間和血壓關係的影響。此工作將有利於提高基於脈搏波傳輸時間的血壓估計技術的準確度，并進一步對控制心血管疾病做出貢獻。 / Cardiovascular diseases (CVDs) remain the number one cause of death worldwide. Amongst various risk factors, arterial blood pressure (BP), especially BP measured during nighttime, and BP variability are major indicators of cardiovascular morbidity and mortality. / Most of the state-of-the-art BP meters are designed with an inflatable cuff, which provide snapshots of BP and are uncomfortable during measurements. An alternative cuffless BP measurement approach is therefore studied in this work. The estimation principle is derived based on the fact that velocity of a pressure wave propagating along an artery, i.e., pulse wave velocity (PWV) is related to the pressure-dependent mechanical property of the artery. Thus, BP can be possibly estimated from PWV, or its reciprocal, pulse transit time (PTT), which can be conveniently acquired from electrocardiogram and photoplethysmogram without using an inflatable cuff. / The current PTT-based BP estimation was built on a model that assumes the artery to be a passive, thin-wall and homogeneous tube. However, arterial wall in reality exhibits a specific layered structure and consists of elastin, collagen fibers and smooth muscles. In fact, the PTT-BP relationship was found by many studies to be easily deteriorated by vasoconstriction/dilation, which reflects the vascular smooth muscle (VSM) activation level, i.e., VSM tone. In particular, innervating most blood vessels, the autonomic nervous system (ANS), primarily sympathetic nervous system, plays an important role in determining the arterial mechanical behavior thus PTT-BP relationship via regulating the VSM tone. It is therefore the aim of this thesis to investigate the effects of ANS on the PTT-based BP estimation. / Firstly, a constituent-based PTT-BP model was developed in the thesis, based on the micro-structurally motivated arterial mechanical model and Bramwell-Hill equation. Specifically, analytic PTT-BP relationship incorporating arterial structural and functional properties was deduced. Theoretical effects of various arterial properties on the relationship have been evaluated by simulation. The results revealed that PTT-BP curve will shift to the top right when VSM tone elevates, producing PTT-BP hysteresis. / Next, the mechanism of regulation of BP, PTT as well as heart rate (HR) by ANS was evaluated in 9 normotensive subjects in treadmill exercise by using time-frequency technique. Vagal withdrawal and subsequent sympathetic activity enhancement by exercise have been observed in only HR. In addition, the results indicate a frequency-dependent PTT-BP relationship. / Then we conducted water drinking experiments in a total of 32 healthy subjects to investigate the ANS controlled cardiovascular responses by the act of swallowing. Significant increment in HR and BP, and decrease in PTT were observed during drinking. On the other hand, considering the frequency-dependent nature of PTT-BP relationship, a novel method that estimates baroreflex sensitivity (BRS) from PTT based on the band-specified sequence technique has been proposed. The results showed high correlations between BRS estimated from BP and PTT. (γ=0.90, 0.70 and 0.81 before, during and after drinking respectively). / Lastly, the effects of ANS mediated VSM tone on the PTT-BP relationship were validated in 46 subjects including 17 patients with CVDs in graded bicycle exercise stress test in supine position. The results demonstrated PTT-BP hysteresis as predicted by the simulation. Furthermore, two novel parameters, i.e., AreaN and ΔSBP20 were proposed to evaluate the hysteresis phenomenon. Significant attenuation was observed in CVD patients with sympathetic overactivity. The two quantifications were proposed accordingly to be indices for assessing sympathetic function. / To conclude, this work addressed the effects of ANS on the PTT-BP relationship from both theoretical and experimental aspects. The work can help to improve the accuracy of PTT-based BP estimation and CVD control. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Liu, Qing. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Abstract --- p.i / Acknowledgement --- p.v / List of figures --- p.vi / List of tables --- p.x / List of abbreviations --- p.xi / Chapter Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- Current Status of Blood Pressure Management --- p.1 / Prevalence of Cardiovascular Diseases --- p.1 / Healthcare System Transformation --- p.2 / Blood Pressure A Crucial Role in CVD Control --- p.4 / Chapter 1.2. --- Overview of Blood Pressure Measurement Techniques --- p.7 / Chapter 1.3. --- Motivations and Objectives of the Thesis --- p.15 / Chapter 1.4. --- Organization of the Thesis --- p.16 / References: --- p.17 / Chapter Chapter 2. --- Basics of Cardiovascular System, Autonomic Nervous System and PTT-BP Relationship --- p.20 / Chapter 2.1. --- Cardiovascular System --- p.20 / Heart Physiology --- p.20 / Arterial Physiology --- p.24 / Chapter 2.2. --- Autonomic Nervous System --- p.35 / Autonomic Histology and Pharmacology --- p.35 / Autonomic Nervous Control of Cardiovascular System --- p.37 / Assessment of ANS Activity --- p.41 / Chapter 2.3. --- PWV and Its Relationship with BP --- p.43 / Pulse Wave Velocity --- p.44 / PWV-BP Relationship --- p.50 / Chapter 2.4. --- Section Summary --- p.54 / References: --- p.55 / Chapter Chapter 3. --- A Model-based Study on the Effects of Arterial Properties on the Relationship between Pulse Transit Time and Blood Pressure --- p.62 / Chapter 3.1. --- Introduction to Constitutive Modeling of Arteries --- p.62 / Experimental Methods --- p.63 / Modeling of Mechanical Behavior: Pressure-Radius Relationship --- p.64 / Chapter 3.2. --- A Novel Constitutive Model of the Relationship between PTT and BP --- p.76 / Chapter 3.3. --- Simulation Study of Effects of Arterial Properties on the PTT-BP Relationship --- p.82 / Chapter 3.4. --- Section Summary --- p.93 / References: --- p.94 / Chapter Chapter 4. --- Evaluation Study on the Autonomic Nervous System Control of Heart Rate, Blood Pressure and Pulse Transit Time Before and After Dynamic Exercise --- p.96 / Chapter 4.1. --- Introduction --- p.96 / Chapter 4.2. --- Methodology --- p.98 / Experiment Protocol --- p.98 / Signal Processing and Spectral Estimation --- p.99 / Chapter 4.3. --- Results --- p.101 / Chapter 4.4. --- Discussion --- p.104 / Chapter 4.5. --- Section Summary --- p.108 / References: --- p.110 / Chapter Chapter 5. --- Investigation on Autonomic Nervous System Control of Heart Rate, Blood Pressure and Pulse Transit Time During Water Drinking --- p.113 / Chapter 5.1. --- Responses of HR, BP and PTT during Water Drinking --- p.113 / Chapter 5.1.1. --- Introduction --- p.113 / Chapter 5.1.2. --- Methodology and Results --- p.115 / Chapter 5.1.3. --- Discussion and Conclusion --- p.118 / Chapter 5.2. --- Potential Application of PTT in Baroreflex Sensitivity Assessment --- p.121 / Chapter 5.2.1. --- Introduction --- p.121 / Chapter 5.2.2. --- Methodology --- p.122 / Chapter 5.2.3. --- Discussion and Conclusion --- p.125 / Chapter 5.3. --- Section Summary --- p.127 / References: --- p.129 / Chapter Chapter 6. --- Experimental Validation of the ANS Effects on the Relationship between Pulse Transit Time and Blood Pressure in Human Stress Test --- p.131 / Chapter 6.1. --- Introduction --- p.131 / Chapter 6.2. --- Methodology --- p.133 / Chapter 6.3. --- Results --- p.137 / Chapter 6.4. --- Discussion and Conclusion --- p.139 / Chapter 6.5. --- Section Summary --- p.144 / References: --- p.145 / Chapter Chapter 7. --- Conclusions and Suggestions for Future Work --- p.148 / Chapter 7.1. --- Summary --- p.148 / Chapter 7.1.1. --- A model-based study on the effects of arterial properties on the PTT-BP relationship --- p.148 / Chapter 7.1.2. --- Evaluation study on the ANS control of HR, BP and PTT before and after dynamic exercise --- p.149 / Chapter 7.1.3. --- Investigation on ANS control of HR, BP and PTT during water drinking --- p.150 / Chapter 7.1.4. --- Experimental validation of the ANS mediated VSM tone on the PTT-BP relationship --- p.151 / Chapter 7.2. --- Suggestions for Future Work --- p.152 / Chapter 7.2.1. --- Modifications on the constituent-based PTT-BP model --- p.152 / Chapter 7.2.2. --- Improvement of PTT-based BP estimation by considering VSM tone effects --- p.153 / Chapter 7.2.3. --- Improvement of PTT-based BP estimation by considering the frequency-dependent PTT-BP relationship --- p.154 / Chapter 7.2.4. --- Validation of the PTT-BP hysteresis quantifications to be indicators of sympathetic function --- p.154 / References: --- p.155 / Appendix --- p.156 / List of Publications --- p.156
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_328100 |
| Date | January 2013 |
| Contributors | Liu, Qing, Chinese University of Hong Kong Graduate School. Division of Electronic Engineering. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography |
| Format | electronic resource, electronic resource, remote, 1 online resource (xiv, 157 leaves) : ill. (some col.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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