結合非侵入式光學量測血流速及光體積變化描記圖法以監測連續血壓

Abstract

心血管疾病其中一普遍指標為血壓數值，現今最為主流血壓量測法是透過非侵入式的壓脈帶之血壓計作為量測，其中包括聽音診斷法和振盪法，然而這兩種方法在量測上有些許缺點，如操作上的不便性或是無法連續即時監控血壓，因此，本研究利用近紅外(Near Infrared, NIR)光波段的光纖雷射都卜勒流速儀(Laser Doppler Flowmetry, LDF)量測手腕橈動脈血管內血流流速變化，且同時架設半導體泵浦固體雷射，將光源針對手腕部位，量測手腕的光體積變化描計圖法(Photoplethysmograph, PPG )訊號，藉以分析人體動脈血管管徑變化及心率，透過上述等生理訊號建立血壓迴歸模型。 本研究藉由手腕橈動脈血管及血流變化的關係來作為估算血壓的重要參考訊號，因此選用不同波段的近紅外光比較不同光源之間訊號的品質，最後選擇1064 nm 波段作為光源進行量測。使用光纖雷射都卜勒流速儀為確保光學系統穩定以及準確性，先以體外進行驗證，以塑膠微粒及管流模擬人體血流實驗，且將搭載探頭於精密位移平台上，為確保訊號穩定性。藉由分析光纖環形器所得干涉訊號，實驗結果證實，平均管流速與所分析訊號有高度正相關。 最後在估算血壓迴歸模型上，本研究量測結果，僅透過少部分的生理訊號及參數，便有很好的預估能力表現，由其是個別受試者舒張壓和平均動脈壓模型，其最好的預測結果RMSE小於5 mmHg，且結果和參考值具有正相關性，研究結果表明對於此光學波段及光學量測方法為有效合理量測生理訊號，且透過此方法進行舒張壓和平均動脈壓的估算。

Cardiovascular diseases are commonly indicated by blood pressure values, with the most prevalent current method of measurement being non-invasive, it is known that blood pressure monitors utilizing sphygmomanometers include auscultatory and oscillometric methods. However, these two methods present certain drawbacks in their measurements, such as inconvenience in operation or inability to continuously monitor blood pressure in real-time. Therefore, this study employs the use of Near Infrared (NIR) light in the form of a Laser Doppler Flowmetry (LDF) to measure variations in blood flow velocity within the radial artery in the wrist. Simultaneously, a diode-pumped solid-state laser is set up, directing its light source to the wrist area to measure photoplethysmographic (PPG) signals of volumetric changes of light in the wrist, hence analyzing variations in the diameter of human arterial vessels and heart rate. A blood pressure regression model is established through these physiological signals. In this study, the relationship between the radial artery in the wrist and variations in blood flow was utilized as a crucial reference signal for estimating blood pressure. To achieve a favorable signal-to-noise ratio, different wavelengths of near-infrared (NIR) light were compared, and ultimately, the 1064 nm wavelength was selected as the optimal light source for measurement. A fiber optic laser Doppler flowmetry system was employed to ensure stability and accuracy in the optical system. Validation was initially conducted ex vivo by simulating human blood flow experiments using plastic micro-particles and pipe flow. The probe was mounted on a precision displacement platform to ensure signal stability. By analyzing the interference signals obtained from the fiber optic ring resonator, the experimental results confirmed a strong positive correlation between the average pipe flow speed and the analyzed signal. Finally, in the estimation of the blood pressure regression model, the measurement results of this study showed that using only a small set of physiological parameters, individual subjects' diastolic and mean arterial pressure models exhibited good predictive performance. The best prediction results yielded an RMSE (root mean square error) of less than 5 mmHg, and the results demonstrated a positive correlation with the reference values. These findings indicate that this optical wavelength and optical measurement method effectively and reasonably measure physiological signals, allowing for the estimation of diastolic and mean arterial pressure through this approach.