血壓為人類重要生命跡象之一，也是用來判斷生命穩定度的指標。大部分脊椎損傷的患者需要做傾斜床的訓練，在訓練過程當中可能會因為患者姿勢改變而使血壓產生不正常的變化；輕則造成患者不適，重則會使患者生命受到威脅，若能夠建構一套非侵入式的連續血壓估算系統，便能在患者再復健過程中連續監測患者的血壓值，並適時的給予警訊。
根據現有文獻顯示，脈衝傳導時間與血壓數據是呈現負相關，本研究最主要是依據這兩者之間的關聯性來建構非侵入式連續的血壓估算系統。本系統利用了自製光體積變化描述波形(Photoplethysmograph, PPG)感測器與濾波放大類比電路量測出手指近端與遠端兩組PPG訊號，利用美商國家儀器的訊號擷取卡取得類比訊號，透過LabVIEW圖控軟體來顯示波形、控制類比電路的直流準位與增益比，並計算兩組PPG訊號之間峰值的時間差。最後再將量測到的脈衝傳導時間代入關係式估算當下的血壓值。
本研究結果發現脈衝傳導時間與血壓值為高度負相關(R2=0.8)。除此之外，針對準確性的評估，本研究使用市售血壓計(Omron MX3)與系統推算之血壓值進行比較，發現系統所估算的血壓誤差值落在±10%內，此誤差範圍為一般市售血壓計可容許的誤差範圍。因此，利用脈衝傳導技術建構一套連續血壓估算系統具有相當高的可行性。

Blood pressure (BP) is one of the vital signs, and is an index that helps determining the stability of life. In this respect, some spinal cord injury patients need to take the tilt table test. When doing so, the posture changes abruptly, and may cause a patient’s BP to change abnormally. This may cause patients to feel discomfort, and even feel as though their life is threatened. Therefore, if a continuous non-invasive BP assessment system were built, it could help to alert health care professionals in the process of rehabilitation when the BP value is out of range.
According to research, the relationship between pulse transit time and BP is a negative relationship. Hence, in our research, BP assessed by the pulse transit technique was developed. In the system, we use a self-made photoplethysmograph (PPG) sensor and filter circuit to detect two PPG signals. LabVIEW was used to display the waveform and control the voltage level, as well as magnify and calculate the time difference; then, a DAQ card, produced by National Instruments, was used to obtain the analog signal. Finally, the BP can immediately be assessed by the trend line.
According to the results of this study, the relationship between the systolic BP and pulse transit time has a highly negative linear correlation (R2=0.8). Further, we used the trend line to assess the value of the BP and compared it to a commercial sphygmomanometer (Omron MX3); the error rate of the system was found to be in the range of ±10%, which is within the permissible error range of a commercial sphygmomanometer. Thus, to continuously monitor BP by the pulse transit technique is verified as having good feasibility.

[1] A. C. Guyton and J. E. Hall, “Human physiology the mechanisms of body function,” 1992.
[2] K. Kario, N. Yasui, and H. Yokoi, “Ambulatory blood pressure monitoring for cardiovascular medicine,” IEEE Engineering in Medicine and Biology Magazine, vol. 22, pp. 81-88, 2003.
[3] M. Fioravanti, D. Nacca, B. Golfieri, P. Lucia, and P. Cugini, “The relevance of continuous blood pressure monitoring in examining the relationship of memory efficiency with blood pressure characteristics,” Physiology and Behavior, vol. 59, pp. 1077-1084, 1996.
[4] 王相堯, “光體積變化描述波形在連續收縮壓量測之研究,” 國立臺灣大學電機工程系碩士論文, 2004.
[5] M. E. Safar, B. I. Levy, and H. Struijker-Boudier, “Current perspectives on arterial stiffness and pulse pressure in hypertension and cardiovascular diseases,” Circulation, vol. 107, (no. 22), pp. 2864-2869, 2003.
[6] A. Marinkovi, “Reconstructing the blood pressure waveform using a wearable photoplethysmograph sensor and hydrostatic pressure variations measured by accelerometers,” Master of Science dissertation, Dept. Mech. Eng., MIT, 2007.
[7] P. Fung, G. Dumont, C. Ries, C. Mott, and M. Ansermino, “Continuous noninvasive blood pressure measurement by pulse transit time,” Proceedings of the 26th Annual International Conference of the IEEE EMBS, vol. 1, pp. 738-741, 2004.
[8] J. Webster, Medical Instrumentation: Application and Design: Wiley. com, 2009.
[9] 張峰碩, “ 建構非侵入式連續血壓量測系統以評估血管系統之數學模型,” 中原大學醫學工程研究所碩士論文, 2005.
[10] K. Meigas, R. Kattai, and J. Lass, “Continuous blood pressure monitoring using pulse wave delay,” Proceedings of the 23rd Annual International Conference of the IEEE EMBS, vol. 4, pp. 3171-3174, 2001.
[11] J. Lass, K. Meigas, D. Karai, R. Kattai, J. Kaik, and M. Rossmann, “Continuous blood pressure monitoring during exercise using pulse wave transit time measurement,” Proceedings of the 26th Annual International Conference of the IEEE EMBS, vol. 1, pp. 2239-2242, 2004.
[12] D. B. McCombie, “Development of a wearable blood pressure monitor using adaptive calibration of peripheral pulse transit time measurements,” Degree of Doctor of Philosophy dissertation, Dept. Mech. Eng., MIT, 2008.
[13] J. Allen, “Photoplethysmography and its application in clinical physiological measurement,” Physiological Measurement, vol. 28, pp. R1-R39, 2007.
[14] 陳耀勳, “心率, PPG 和非侵入脈搏波信號之相關性研究,” 逢甲大學自動控制工程所碩士論文, 2005.
[15] D. Prokop, A. Cysewska-Sobusiak, and A. Hulewicz, “Application of a multi-sensor set for comparative evaluation of the photoplethysmographic waveforms,” First International Conference on Sensor Device Technologies and Applications, pp. 242-245, 2010.
[16] H. H. Asada, P. Shaltis, A. Reisner, S. Rhee, and R. C. Hutchinson, “Mobile monitoring with wearable photoplethysmographic biosensors,” Engineering in Medicine and Biology Magazine, IEEE, vol. 22, pp. 28-40, 2003.
[17] F. H. Huang, P. J. Yuan, K. P. Lin, H. H. Chang, and C. L. Tsai, “Analysis of reflectance photoplethysmograph sensors,” World Academy of Science, Engineering and Technology, vol. 5, pp. 1266-1269, 2011.
[18] H. Jiang, “Motion-artifact resistant design of photoplethysmograph ring sensor for driver monitoring,” Master of Science dissertation, Dept. Mech. Eng., MIT, 2003.
[19] X. F. Teng and Y. T. Zhang, “The effect of applied sensor contact force on pulse transit time,” Physiological Measurement, vol. 27, pp. 675-684, 2006.
[20] X. F. Teng and Y. T. Zhang, “Theoretical study on the effect of sensor contact force on pulse transit time,” IEEE Transactions on Biomedical Engineering, vol. 54, pp. 1490-1498, 2007.
[21] 洪偉翎, “下肢加壓循環器幫浦壓力變化對脊髓損傷患者姿勢性低血壓之影響之研究,” 國立臺灣大學機械工程學研究所碩士論文, 2005.
[22] 邱雅芳, “自主神經異常反射症狀之護理,” 榮總護理, vol. 23, (no. 2), pp. 142-146, 2006.
[23] M. S. Hansen, “Boundary Conditions for 3D Fluid-Structure Interaction Simulations of Compliant Vessels,” Master of Science dissertation, Department of Structural Engineering, NTNU, 2013.
[24] W. Nichols, M. O'Rourke, and C. Vlachopoulos, McDonald's blood flow in arteries: theoretical, experimental and clinical principles: CRC Press, 2011.
[25] D. J. Hughes, C. F. Babbs, L. A. Geddes, and J. D. Bourland, “Measurements of Young's modulus of elasticity of the canine aorta with ultrasound,” Ultrasonic Imaging, vol. 1, pp. 356-367, 1979.
[26] M. W. Chen, T. Kobayashi, S. Ichikawa, Y. Takeuchi, and T. Togawa, “Continuous estimation of systolic blood pressure using the pulse arrival time and intermittent calibration,” Medical and Biological Engineering and Computing, vol. 38, (no. 5), pp. 569-574, 2000.
[27] J. G. Webster, Design of pulse oximeters: CRC Press, 2002.
[28] B. R. Teja, “Calculation of Blood Pulse Transit Time from PPG,” Bachelor of Technology, Department of Biotechnology and Medical Engineering, REC Rourkela, 2012.
[29] 詹皓羽, “光體積變化描記圖之心血管功能診斷應用,” 中原大學電機工程研究所碩士論文, 2004.
[30] J. E. Naschitz, S. Bezobchuk, R. Mussafia-Priselac, S. Sundick, D. Dreyfuss, I. Khorshidi, A. Karidis, H. Manor, M. Nagar, and E. R. Peck, “Pulse transit time by R-wave-gated infrared photoplethysmography: review of the literature and personal experience,” Journal of Clinical Monitoring and Computing, vol. 18, pp. 333-342, 2004.
[31] G. Y. Jeong, K. H. Yu, and N. G. Kim, “Continuous Blood Pressure Monitoring using Pulse Wave Transit Time,” Measurement, vol. 4, pp. 7, 2005.