IEEE Trans Biomed Circuits Syst. 2018 Aug;12(4):904-917. doi: 10.1109/TBCAS.2018.2829708. Epub 2018 May 15.
Acquiring a precise percentage of oxygen saturation (SpO2) from a finger-probe pulse oximeter is dependent on both artifact-free red and infrared photoplethysmoghaphic (PPG) signals. Nonetheless, in real-life situations, these PPG signals are corrupted by a motion artifact (MA) signal that is generated from either finger or hand movement. To resolve this MA interference, the cause of the adulteration of PPG signals by the MA signal is examined. The MA signal is found to behave like an additive noise. Additionally, the frequency responses of the MA and PPG signals show that these signals are in the same frequency band. Hence, instead of direct current, a sinusoidal wave alternating current is proposed to drive an LED source in order to shift the PPG frequency band away from the MA frequency band. Experimentally, a commercial finger-probe pulse oximeter is employed. To determine the performance of the presented scheme, the resulting PPG signals are compared with those from employing the old-fashioned LED-driving method. In addition, the accuracy is verified by computing the SpO2 value. The results reveal that the proposed approach successfully retains the fundamental morphologies of the PPG structures when motion occurs. Moreover, the calculated SpO2 values from the proposed technique provide an average error of approximately 1.4%, whereas the conventional method yields a mean error approximately 4.2%.
从指夹式脉搏血氧仪获取精确的血氧饱和度（SpO2）百分比，取决于无伪迹的红光和近红外光光电体积描记图（PPG）信号。然而，在实际情况下，这些 PPG 信号会受到运动伪影（MA）信号的干扰，这些伪影信号是由手指或手部运动产生的。为了解决这个 MA 干扰问题，需要检查导致 PPG 信号被 MA 信号污染的原因。结果发现，MA 信号表现为一种附加噪声。此外，MA 和 PPG 信号的频率响应表明，这些信号处于相同的频带内。因此，不是采用直流，而是提出采用正弦波交流来驱动 LED 光源，以将 PPG 频带从 MA 频带移开。实验中，采用了商用指夹式脉搏血氧仪。为了确定所提出方案的性能，将得到的 PPG 信号与采用老式 LED 驱动方法的信号进行了比较。此外，通过计算 SpO2 值来验证准确性。结果表明，当发生运动时，所提出的方法成功地保留了 PPG 结构的基本形态。此外，所提出技术计算出的 SpO2 值的平均误差约为 1.4%，而传统方法的平均误差约为 4.2%。
