AB129. SOH25_AB_097. The effect of operating theatre lighting on pulse oximetry monitoring during surgery

Background: Pulse oximetry is an essential component of monitoring during anaesthesia. It is a rapid, non-invasive monitoring device which calculates the percentage of haemoglobin in arterial blood that is saturated with oxygen, and is traditionally placed on the fingertip during anaesthesia. The authors noted a case where a patient underwent general anaesthesia with routine monitoring for minor surgery. The patient was placed in the lithotomy position with pulse oximetry demonstrating a normal pulsatile waveform, and the patient’s arms were tucked and covered using a drawsheet. Upon illuminating the operating area, interference was noted on the pulse oximeter waveform, and no saturation values were displayed, despite the hands being shielded by the drawsheet. The operating lights were temporarily redirected away, with restoration of the normal plethysmograph and displayed saturations values. A new pulse oximeter was placed on the patient’s ear and surgery proceeded as normal.

Methods: We analysed the performance of the pulse oximeter under three different conditions: ambient light, direct surgical lighting, and indirect lighting with the hand covered.

Results: Marked interference from the lights was evident in both direct and indirect exposure to light emitting diode (LED) operating lights, with loss of saturation values and abnormal plethysmograph trace.

Conclusions: Pulse oximetry is a useful monitoring device but is prone to interference, for example from surgical lighting, especially of the LED type. Shielding the hands with a draw sheet is not a reliable method to diminish interference. Alternative probe placement or more robust shielding materials may be required during anaesthesia.

Keywords: Anaesthesia; oximetry; patient monitoring; patient safety; pulse oximetry