Does ambient light affect the accuracy of pulse oximetry?

OBJECTIVE Determine whether ambient light affects the accuracy of pulse oximetry readings. DESIGN Prospective, repeated-measures study. SETTING A photographic darkroom. SUBJECTS Forty-five faculty and students at a university, none of whom had pale skin, dark skin, or evidence of cardiopulmonary disease. Any nail polish was removed. METHODS Five light sources were individually tested: incandescent, quartz-halogen, infrared, fluorescent, and bilirubin light. A pulse oximetry probe was placed on the subject's finger, and the finger and probe were placed sideways under each light source, on a predetermined mark. RESULTS The greatest difference in pulse oximetry reading between any of the light sources was 0.5%. Repeated-measures analysis of variance yielded a p value of 0.204. CONCLUSIONS Ambient light has no statistically significant effect on pulse oximetry readings. Even had the differences been statistically significant, the magnitude of the differences was small and thus clinically unimportant.