The Study of Transesophageal Oxygen Saturation Monitoring

Introduction

Oxygen saturation (SpO₂) is the percentage of oxyhemoglobin (HbO₂) with respect to the sum of hemoglobin (Hb) and HbO₂ in blood, which is an important physiological parameter to assess human health condition. Therefore, oximetry has become an indispensable guardianship and diagnostic equipment and there is a wide range of applications in clinical practice, such as surgery, anaesthesia and intensive care units (ICU) (Kyriacou, 2006). There are some reports that Oximeters are placed in fingers, foreheads (Kim et al., 2007), tongues (Jobes & Nicolson, 1988), faces (O'Leary et al., 1992) and other parts of body surface to monitor oxygen saturation. However, in some cases, such as trauma (burn), surgery, or the unstable peripheral circulation, there are some limitations in clinical applications (Kyriacou et al., 2002; Ahrens, 1999; Pal et al., 2005).

Before this study, Zhu et al. (2005) had verified the feasibility of transesophageal pulse oximetry through the animal experiments, then, the human experiments that monitoring pulmonary artery through trachea could be achieved (Wei et al., 2005). In this work, based on the anatomical relationship that the esophagus was close to the descending aorta (Kyriacou et al., 2003), a method of transesophageal SpO₂ monitoring was proposed, to provide a new method for in vivo monitoring. As the blood vessels of descending aorta and left ventricular are larger than surface vessels, which means that the light absorption of internal vessels is larger, so we expected that the signals from these parts would be more stable and sensitive, to make the SpO₂ monitoring accurate and timely. Also, more biological information was expected to be obtained from the signal waveforms.