Kyriacou P A, Moye A R, Choi D M, Langford R M, Jones D P
Department of Medical Electronics and Physics, St. Bartholomew's and The Royal London School of Medicine and Dentistry, Queen Mary and Westfield College, UK.
Physiol Meas. 2001 Feb;22(1):223-32. doi: 10.1088/0967-3334/22/1/325.
Pulse oximeter probes placed peripherally may fail to give accurate values of arterial blood oxygen saturation (SpO2) when peripheral perfusion is poor. Since central blood flow may be preferentially preserved, the oesophagus was suggested as an alternative monitoring site. A reflectance oesophageal photoplethysmographic (PPG) probe and a multiplexed data acquisition system, operating simultaneously at two wavelengths and incorporating an external three-lead electrocardiogram (ECG) reference channel, has been developed. It has been used to investigate the suitability of the oesophagus as a possible monitoring site for SpO2 in cases of compromised peripheral perfusion. Oesophageal PPG signals and standard ECG traces were obtained from 16 anaesthetized patients and displayed on a laptop computer. Measurable PPG signals with high signal-to-noise ratios at both infrared and red wavelengths were obtained from all five oesophageal depths investigated. The maximum PPG amplitude occurred at 25 cm from the upper incisors in the mid-oesophagus. The measured pulse transit times (PTTs) to the oesophagus were consistent with previous measurements at peripheral sites and had a minimum value of 67 +/- 30 ms at a depth of 30 cm. There was broad agreement between the calculated values of oesophageal SpO2 and those from a commercial finger pulse oximeter.
当外周灌注较差时，置于外周的脉搏血氧饱和度探头可能无法给出动脉血氧饱和度（SpO2）的准确值。由于中心血流可能会优先得到维持，有人提出将食管作为一个替代监测部位。已开发出一种反射式食管光电容积脉搏波描记（PPG）探头和一个多路复用数据采集系统，该系统能同时在两个波长下运行，并包含一个外部三导联心电图（ECG）参考通道。它已被用于研究在周围灌注受损的情况下，食管作为SpO2可能的监测部位的适用性。从16名麻醉患者身上获取了食管PPG信号和标准ECG轨迹，并显示在一台笔记本电脑上。在所研究的所有五个食管深度处均获得了在红外和红色波长下具有高信噪比的可测量PPG信号。最大PPG振幅出现在食管中部距上切牙25厘米处。测得的食管脉搏传输时间（PTT）与之前在外周部位的测量结果一致，在30厘米深度处的最小值为67±30毫秒。食管SpO2的计算值与商用手指脉搏血氧饱和度仪的测量值之间存在广泛的一致性。
