USE OF 2 OXIMETERS TO INVESTIGATE A METHOD OF MOVEMENT ARTIFACT REJECTION USING PHOTOPLETHYSMOGRAPHIC SIGNALS

Oxygen haemoglobin saturations and plethysmograph signal amplitudes we re recorded from two oximeters placed on the fingers and toes of 10 pa tients undergoing oesophagectomy, to assess a method of removing motio n artefact from saturation recordings. By examining changes in the ple thysmograph amplitude that preceded changes in saturation, episodes of desaturation caused by movement artefacts were removed from the data. The reliability of the method was then determined by scrutinizing two concurrent oximetric profiles from each patient. A total of 1600 h of data were evaluated Desaturations occurring contemporaneously in both oxygen saturation profiles were presumed genuine, whereas a desaturat ion occurring in only one of the profiles was classified as artefactua l. Our method had a sensitivity of 96%, a positive predictive power of 98% and a specificity of 60%. We modified the method to increase spec ificity and re-evaluated our data. We found that a useful increase in specificity was associated with a considerable decline in sensitivity.