Does using a forehead or finger sensor during the six minute walk test impact oxygen saturation measurement?

Abstract

Background: Finger sensors are often used to record oxygen saturation (SPO2) in 6 minute walk tests (6MWT) but measurement errors may occur especially in patients with poor perfusion. Aims: To determine if during a 6MWT, SPO2 and heart rate (HR) differ between forehead and finger sensors and if poor peripheral perfusion is a contributing factor. Signal quality of two sensors was also compared. Methods: 80 patients with either pulmonary vascular disease or interstitial lung disease performed the 6MWT. SPO2 and HR readings were taken simultaneously by both sensors at 30 second intervals during 6MWT. Occurrences of poor signal were noted. Patients were examined to classify their perfusion status by examination of hands and measurement of capillary refill time. Mixed two way repeated measures analysis of variance (ANOVA) was performed for significant differences and interactions between sensor readings (see Table 1). Wilcoxon rank sum test demonstrated there was a higher occurence of poor signal quality measurements in the finger sensor (189/1040) particularly in patients with poor perfusion (122) compared with the forehead sensor (35/1040) (p Conclusion: The finger sensor was more prone to error with higher occurence of poor signal quality during the 6MWT. The forehead sensor recorded higher values for SPO2 and HR. Surprinsgly; the ANOVA results suggest poor perfusion was not a contributing factor. This may be due to limatations in the methods used to classify perfusion and warrants futher study.