Abay Tomas Ysehak, Kyriacou Panayiotis A
IEEE Trans Biomed Eng. 2015 Sep;62(9):2187-95. doi: 10.1109/TBME.2015.2417863. Epub 2015 Mar 30.
In the last decades, photoplethysmography (PPG) has been used as a noninvasive technique for monitoring arterial oxygen saturation by pulse oximetry (PO), whereas near-infrared spectroscopy (NIRS) has been employed for monitoring tissue blood perfusion. While NIRS offers more parameters to evaluate oxygen delivery and consumption in deep tissues, PO only assesses the state of oxygen delivery. For a broader assessment of blood perfusion, this paper explores the utilization of dual-wavelength PPG by using the pulsatile (ac) and continuous (dc) PPG for the estimation of arterial oxygen saturation (SpO2) by conventional PO. Additionally, the Beer-Lambert law is applied to the dc components only for the estimation of changes in deoxyhemoglobin (HHb), oxyhemoglobin (HbO2), and total hemoglobin (tHb) as in NIRS. The system was evaluated on the forearm of 21 healthy volunteers during induction of venous occlusion (VO) and total occlusion (TO). A reflectance PPG probe and NIRS sensor were applied above the brachioradialis, PO sensors were applied on the fingers, and all the signals were acquired simultaneously. While NIRS and forearm SpO2 indicated VO, SpO2 from the finger did not exhibit any significant drop from baseline. During TO, all the indexes indicated the change in blood perfusion. HHb, HbO2, and tHb changes estimated by PPG presented high correlation with the same parameters obtained by NIRS during VO (r(2) = 0.960, r(2) = 0.821, and r(2) = 0.974, respectively) and during TO (r(2) = 0.988, r(2) = 0.940, and r(2) = 0.938, respectively). The system demonstrated the ability to extract valuable information from PPG signals for a broader assessment of tissue blood perfusion.
在过去几十年中，光电容积脉搏波描记法（PPG）已被用作通过脉搏血氧饱和度仪（PO）监测动脉血氧饱和度的无创技术，而近红外光谱法（NIRS）则用于监测组织血流灌注。虽然NIRS提供了更多参数来评估深部组织中的氧输送和消耗，但PO仅评估氧输送状态。为了更全面地评估血流灌注，本文探索了利用双波长PPG，通过传统PO使用脉动（交流）和连续（直流）PPG来估计动脉血氧饱和度（SpO2）。此外，仅将比尔-朗伯定律应用于直流分量，以像在NIRS中那样估计脱氧血红蛋白（HHb）、氧合血红蛋白（HbO2）和总血红蛋白（tHb）的变化。该系统在21名健康志愿者的前臂上进行了静脉阻塞（VO）和完全阻塞（TO）诱导期间的评估。在肱桡肌上方应用反射式PPG探头和NIRS传感器，在手指上应用PO传感器，并同时采集所有信号。当NIRS和前臂SpO2显示VO时，手指处的SpO2并未显示出相对于基线的任何显著下降。在TO期间，所有指标均表明血流灌注发生了变化。PPG估计的HHb、HbO2和tHb变化与VO期间（分别为r(2) = 0.960、r(2) = 0.821和r(2) = 0.974）以及TO期间（分别为r(2) = 0.988、r(2) = 0.940和r(2) = 0.938）通过NIRS获得的相同参数呈现出高度相关性。该系统展示了从PPG信号中提取有价值信息以更全面评估组织血流灌注的能力。
