Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University, Aachen 52074, Germany.
IEEE Trans Biomed Eng. 2012 Jul;59(7):2003-10. doi: 10.1109/TBME.2012.2196276. Epub 2012 Apr 25.
Pulse oximetry is a well-established, noninvasive photoplethysmographic method to monitor vital signs. It allows us to measure cardiovascular parameters, such as heart rate and arterial oxygen saturation, and is considered an essential monitoring tool in clinical routine. However, since many of the conventional systems work in transmission mode, they can only be applied to the thinner or peripheral parts of the body, such as a finger tip. This has the major disadvantage that, in case of shock-induced centralization and a resulting drop in perfusion, such systems cannot ensure valid measurements. Therefore, we developed a reflective in-ear sensor system that can be worn in the ear channel like a headphone. Because the sensor is integrated in an ear mold and positioned very close to the trunk, reliable measurement is expected even in case of centralization. An additional advantage is that the sensor is comfortable to wear and has considerable resistance to motion artifacts. In this paper, we report on hypoxia studies with ten healthy participants which were performed to analyze the system with regard to the detection of heart rate and arterial oxygen saturation. It was shown earlier that, due to the high signal quality, heart rate can easily be detected. Using the conventional calculation principle, based on Beer-Lambert's law combined with a single-point calibration method, we now demonstrate that the detection of arterial oxygen saturation in the human ear canal is possible using reflective saturation sensors.
脉搏血氧仪是一种成熟的、非侵入性的光电容积脉搏波法，用于监测生命体征。它允许我们测量心血管参数，如心率和动脉血氧饱和度，并且被认为是临床常规中必不可少的监测工具。然而，由于许多传统系统采用传输模式，它们只能应用于较薄或身体的外围部位，如指尖。这主要的缺点是，在休克引起的中央化和由此导致的灌注下降的情况下，这些系统不能确保有效的测量。因此，我们开发了一种反射式入耳式传感器系统，可以像耳机一样佩戴在耳道中。由于传感器集成在耳模中并被定位得非常靠近躯干，因此即使在中央化的情况下，也有望进行可靠的测量。另一个优点是传感器佩戴舒适，对运动伪影具有相当大的抵抗力。在本文中，我们报告了十名健康参与者的缺氧研究，这些研究旨在分析该系统在检测心率和动脉血氧饱和度方面的性能。先前已经表明，由于信号质量高，很容易检测到心率。现在，我们使用传统的计算原理，基于 Beer-Lambert 定律结合单点校准方法，证明了使用反射饱和度传感器在人体耳道中检测动脉血氧饱和度是可行的。
