以非接觸光學法量測血液流速並估算平均動脈壓

Using non-contact optical method to measure blood flow velocity and estimate mean arterial pressure

陳冠融(Guan-Rong Chen)

指導教授 ： 李世光

共同指導教授 ： 吳光鐘(Kuang-Chong Wu)

國立臺灣大學/工學院/應用力學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202102251

摘要

目前最為廣泛的血壓量測方法為聽音診斷法及示波振幅法，這兩種方法於量測過程中均須使用脈壓袖帶以阻斷血流，過程中可能會造成受試者的不適且無法進行連續性地監控，故有許多研究致力於開發非接觸式的連續監控血壓方法，先前曾有研究透過材料力學及流體力學的觀點，推導出以血液體積流率、脈衝傳遞時間(Pulse Transit Time, PTT)、心率及血管管徑變化等作為參數之血壓迴歸模型，其中血液體積流率參數僅使用光體積描記法(Photoplethysmography, PPG)之波形斜率作為參考依據，因此本研究將使用非接觸光學方法進行人體血液流速之量測，並結合各項生理參數進行迴歸分析，期望使原始血壓迴歸模型更為完善。
本研究將使用光纖搭載環形器之雷射都卜勒流速儀(Laser Doppler Flowmetry, LDF)進行流速之量測，為了驗證光學系統可行性及都卜勒散射理論之正確性，於人體量測之前，預先進行管流流速量測實驗以簡化及模擬人體量測時之光學行為，透過分析干涉訊號之功率譜及計算結果得知，平均流速與其功率譜一次矩成正比關係，其結果與理論相符合。此外，由隨時間變化之流速分析結果可以得知此LDF具備了良好的相對流速快慢之分辨率，並可將其應用於人體血流量測。
於人體量測上除了LDF進行血液流速量測外，還另外搭配商用儀器量測心電圖(Electrocardiography, ECG)及 PPG，以獲取PTT及心率。將所量測到之各項生理參數代入使用血液流速參數之迴歸模型中以評估平均動脈壓(Mean Arterial Pressure, MAP)，並與使用PPG波形斜率之迴歸模型進行比較與分析，經單一受試者和複數受試者迴歸後的統計結果顯示，使用血液流速之迴歸模型比起使用PPG波形斜率之迴歸模型具備了更好的預測能力，且於每位受試者之迴歸結果均為血液流速參數為影響MAP高低之主要因素，因此證明了使用血液流速資訊作為迴歸參數確實對於模型上有顯著的改善。

關鍵字

連續血壓量測 ； 血液流速 ； 平均動脈壓 ； 雷射都卜勒流速儀 ； 迴歸模型

並列摘要

Nowadays, the most widely used blood pressure measurement methods are auscultatory method and oscillometric method. Both of these methods use cuff to occlude the blood flow during the measurement, which cause the subject to feel uncomfortable and cannot be monitored continuously. Therefore, many studies have proposed the development of non-contact continuous blood pressure monitoring methods. Previous studies have proposed a blood pressure regression model with parameters such as blood volume flow rate, pulse transit time (PTT), heart rate, and vessel diameter changes from the viewpoints of material mechanics and fluid mechanics. Among them, the blood volume flow rate only uses the slope of Photoplethysmography (PPG) waveform as the basis. Therefore, this study will use non-contact optical methods to measure the human blood flow velocity, and combined with the regression analysis of various physiological parameters. It is expected that the original blood pressure regression model can be improved.
In this study, a laser Doppler flowmetry (LDF) with a fiber and circulator will be used to measure the flow velocity. In order to verify the feasibility of the optical system and the correctness of the Doppler scattering theory, the pipe flow velocity measurement experiment is carried out to simplify and simulate the optical behavior of the human body before the human body measurement. By analyzing the power spectrum of the interference signal and the calculation results, it is known that the mean flow velocity is proportional to the first moment of the power spectrum. The experimental results are consistent with the theory. In addition, through the analysis results of the flow velocity over time, it can be known that this LDF has a good resolution of relative flow velocity and can be applied to human blood flow measurement.
In human body measurement, in addition to using LDF to measure the blood velocity, commercial instruments are also used to measure electrocardiography (ECG) and PPG to obtain PTT and heart rate. Combined these parameters into the regression model using the blood flow velocity to evaluate the mean arterial pressure (MAP), and compared with the regression model using the slope of PPG waveform. The statistical results show that the regression model using blood flow velocity has better predictive ability than the using slope of PPG waveform either in the results of single subject or multiple subjects regression results. Moreover, the blood flow velocity is the main factor that affects the level of MAP for each subject. In summary, using blood flow velocity as a regression parameter has a significant improvement on the model.

並列關鍵字

continuous blood pressure monitoring ； blood flow velocity ； mean arterial pressure ； laser Doppler flowmetry ； regression model

參考文獻

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