Evaluation of oesophageal pulse oximetry in patients undergoing cardiothoracic surgery*

Abstract

SummaryPulse oximetry probes placed peripherally may fail to give accurate values of blood oxygen saturation when the peripheral circulation is poor. Because central blood flow may be preferentially preserved, we investigated the oesophagus as an alternative monitoring site. A reflectance blood oxygen saturation probe was developed and evaluated in 49 patients undergoing cardiothoracic surgery. The oesophageal pulse oximeter results were in good agreement with oxygen saturation measurements obtained by a blood gas analyser, a CO-oximeter and a commercial finger pulse oximeter. The median (IQR [range]) difference between the oesophageal oxygen saturation results and those from blood gas analysis were 0.00 ()0.30 to 0.30 [)4.47 to 2.60]), and between the oesophageal oxygen saturation results and those from CO-oximetry were 0.75 (0.30 to 1.20 [)1.80 to 1.80]). Bland-Altman analysis showed that the bias and the limits of agreement between the oesophageal and finger pulse oximeters were )0.3% and )3.3 to 2.7%, respectively. In five (10.2%) patients, the finger pulse oximeter failed for at least 10 min, whereas the oesophageal readings remained reliable. The results suggest that the oesophagus may be used as an alternative monitoring site for pulse oximetry even in patients with compromised peripheral perfusion.

Measuring venous oxygenation using the photoplethysmograph waveform

“…They developed a special-purpose esophageal PPG probe [10] and used this probe to collect PPG waveforms on patients undergoing coronary artery bypass surgery and postoperative care in the intensive care unit [11,12]. All patients were undergoing positive pressure ventilation.…”

“…The PPG probe used by Kyriacou et al consisted of a miniature circuit board containing a photodetector and two LEDs with center wavelengths 655 nm (Red) and 880 nm (IR) [11,12]. This unit was placed in a sterile size-20 French gauge stomach tube and advanced down the esophagus of an anesthetized patient.…”

Estimation of instantaneous venous blood saturation using the photoplethysmograph waveform

“…Oesophageal PPG data, collected in previous studies 2003;Kyriacou;2013), from twelve ASA (American Society of Anaesthesiologists) 2 4 anaesthetised patients (aged 26 to 81) undergoing elective cardiothoracic surgery with positive pressure ventilation were analysed in this work. The data were acquired following local research ethics committee approval and patient consent.…”

“…For each patient, approximately 100 minutes of ECG and PPG data was collected at a sampling rate of 100 Hz. The purpose of the previous studies Kyriacou et al (2002bKyriacou et al ( , 2003 was to investigate the oesophagus as a viable site for measuring blood oxygenation saturation Kyriacou et al (2002b).…”

“…The authors (Walton et al;2010) have analysed PPG signals from the oesophagus of ten patients undergoing coronary artery bypass surgery and postoperative care in the intensive care unit 2002b, 2003. They proposed time and frequency domain algorithms for the estimation of arterial and regional venous saturation.…”