Electro-Optical Techniques for the Investigtion of Oesophageal Photoplethysmographic Signals and Blood Oxygen Saturation in Burns

Pulse oximetry is widely used in anaesthesia and intensive care monitoring. It is a valuable, non-invasive optical monitoring technique used for continuous measurement of arterial blood oxygen saturation (SpO2). Sites for pulse oximeter sensors are frequently difficult to find in patients with major thermal injury. Therefore blood oxygen saturation readings are often unobtainable at just the time when they would be most valuable. An oesophageal SpO2 probe has been designed to record reliable photoplethysmographic (PPG) signals and SpO2 values from the oesophagus of burned patients. Seven adult patients were studied. Good quality oesophageal PPG signals with large amplitudes were measured from various depths within the oesophagus. The optimal monitoring oesophageal depth ranged from 13 cm to 20 cm, measured from the upper lip. It was found that the oesophageal pulse oximeter saturation results were in good agreement with those from the CO-oximeter. This study suggests that the oesophagus can be used as an alternative site for monitoring arterial blood oxygen saturation by pulse oximetry in burned patients.