Reflection and transmission pulse oximetry during compromised peripheral perfusion

The performance of a reflection pulse oximeter and a transmission pulse oximeter was assessed during open-heart surgery when cardiac output, peripheral temperature, pulse pressure, and systolic pressure were low and vascular resistance was high. Before and after extracorporeal circulation (ECC) there was no difference in ability of the sensors to obtain readings and no difference in the accuracy of those readings. During partial ECC, especially after coronary artery bypass grafting, the reflection sensor gave readings earlier and at a lower pulse pressure. In addition, the transmission sensor failed to give any readings for 2 patients on partial ECC, for whom the reflection sensor did give readings. The accuracy of heart rate (HR) data was comparable for both sensors before ECC; however, during partial ECC, the reflection sensor tended to give values closer to the electrocardiographic HR. The accuracy of saturation data given by the reflection oximeter was comparable to that of the transmission oximeter. It is concluded that the accuracy of the saturation and HR data provided by the two methods of pulse oximetry are comparable, but that the reflection sensor is more likely to obtain readings under conditions of poorer peripheral circulation.