利用結構光投影法實現非接觸式橈動脈表面振動測量及連續血壓監測

Abstract

當前的血壓量測方法中可信度較高且運用廣泛的方法是聽音診斷法及示波振幅法，每次量測皆需要以袖帶阻斷血流，過程除了不舒服外也不適合連續量測血壓，因此，許多研究致力於開發非接觸式連續監控血壓的方法，這當中以光體積描記法量測之血液容積波形搭配脈衝傳導時間法最為被看好，但血壓成因複雜，若只考慮血液容積與心率等因素並不足以量測正確血壓。 本實驗開發了適用於微米級小尺度動態量測之實驗方法與架構，透過結構光投影法中的傅立葉轉換輪廓術以非接觸式的方法量測手腕橈動脈表面皮膚之振動波形，作為血管管徑變化量之參數以利後續改良血壓回歸模型。在本實驗之架構中，使用DLP投影機投射週期約為0.1295 mm之條紋結構光搭配每秒拍攝46 幀的相機，與待測物之間呈現三角關係，待測物產生的形變會使條紋相位產生變化並記錄於連續拍攝之影像中，因此，便可從影像之頻譜域中選取承載相位變化之條紋頻率範圍，進行解相後得到相位資訊，再從相位變化資訊與實際高度做轉換，得到脈搏表面振幅之波形。 本實驗將量測結果與商用儀器量測之心電圖、光體積描記波形做比較與驗證，評估心率、心臟變異率與週期之均方根誤差等生理訊號，證實本研究開發之方法能有足夠的精度描述脈搏振動波形，最後代入改良後的血壓回規模型，發現加入管徑變化因素的血壓回歸模型，三位受試者與收縮壓之相關係數分別從0.111提升至0.692、0.716提升至0.957、0.0961提升至0.251，與舒張壓之相關係數則分別從0.314提升至0.707、0.064提升至0.72、0.0627提升至0.291，因此本研究之研究結果能對於血壓回歸模型有非常顯著的改善。

Among the current blood pressure measurement methods, the most reliable and widely used methods were Auscultatory and Oscillometric. However, both these measurements required a cuff to block the blood flow and the process was uncomfortable and not suitable for continuous measurement. Therefore, to realize continuous blood pressure measurement in non-contact way, many researches were devoted to the development of such as arterial tonometry, vascular unloading technique and pulse transit time methods, especially pulse transit time methods. In pulse transit time methods, the velocity between Photoplethysmography in two position was considered as an important indicator. But it was still not sufficient to measure the correct blood pressure. In this research, an experimental method which was suitable for dynamic micron-level measurement was developed. The Fourier transform profilometry was used to measure the vibration waveform of the skin on the radial artery in a non-contact way. In addition, the vibration waveform as a parameter of radial artery diameter change was used to improve the model of blood pressure regression. The method, based on a triangular configuration, used a digital light processing (DLP) projector with 0.1295 mm structure light fringe pattern and a camera with frame rate of 46 fps. The fringe pattern with pre-defined spatial carrier frequency was projected on the subject's wrist. In the configuration design, instantaneous pulsation-induced skin vibrations of subtle amplitude can be observed and recorded within each frame of the fringe pattern. Using a two-dimensional Fourier transform, and chose a frequency region of interest (ROI) filter to collect the spectrum magnitude embedded with the deformation data to deliver the phase retrieval. After using a phase-to-height conversion, the results of the full-field dynamic vibrational field were analyzed. Several indicators such as heart rhythm (HR), heart rate variable (HRV), and root mean squared errors (RMSE) were adopted to compare the pulsation signal with the ECG and PPG signals. Combining these indicators proved that the method developed in this research can be adequate accurately describe the pulse vibration waveform. Finally, it is found that the blood pressure model with radial artery diameter oscillation factors will increase the correlation coefficient with systolic blood pressure and diastolic blood pressure, so the results of this study can significantly improve the blood pressure regression model.