Masimo’s RD SET pulse oximetry sensors accurately measured oxygen saturation (SpO2) for both Black and white subjects when perfusion index (Pi) was normal and when Pi was low, according to a retrospective, peer-reviewed study published in the Journal of Clinical Monitoring and Computing.

Masimo says the analysis added to the body of evidence that Masimo SET pulse oximetry delivers accurate values across the skin tone range, with no clinically significant difference in accuracy or bias, even in challenging conditions.

For this newly published study, noting that low peripheral perfusion is a “recognized confounder of conventional pulse oximetry” and in light of concerns that low perfusion combined with dark skin pigmentation might decrease pulse oximetry’s accuracy, the investigators sought to determine whether accuracy on Black or White subjects was impacted by a subject’s perfusion index (Pi) with Masimo SET pulse oximetry. To that end, they abstracted Pi values from their dataset, and divided them into “low perfusion” (Pi ≤ 1) and “normal perfusion” (Pi > 1) groups. They then performed statistical analyses to determine bias (the mean difference between SpO2 and arterial oxygen saturation [SaO2]), precision (the standard deviation of the difference), and accuracy (root-mean-square error, or ARMS*). 

The researchers found that in the normal perfusion group, comparing SpO2 to SaO2 values, there was overall bias and precision of +0.18% ± 1.34%, with accuracy of 1.37% ARMS. For the subset of Black subjects, there was bias and precision of -0.26% ± 1.37%, and for White subjects, -0.12% ± 1.31%. In the low perfusion group, there was overall bias and precision of 0.48% ± 1.59%, with accuracy of 1.64% ARMS. For Black subjects, bias and precision were 0.19% ± 1.53%, and for White subjects, 0.91% ± 1.57%.

Based on their analysis, the authors concluded, “Masimo SET pulse oximeters with RD SET sensors are accurate for individuals of both Black and White races when Pi is normal, as well as during conditions when Pi is low. The ARMS for all conditions studied is well within FDA standards. This study was conducted in healthy volunteers during well-controlled laboratory desaturations, and results could vary under certain challenging clinical conditions.”

However, the authors noted that controlling conditions in the laboratory setting helps “minimize confounders that are present in clinical scenarios, allowing for greater focus on the topics of skin tone and Pi. Indeed, abnormal hemoglobin species (eg, carboxyhemoglobin and methemoglobin) [known clinical SpO2 confounders] were measured and reported in the earlier paper by Barker and Wilson, and the values were similar (statistically the same) between Black and White groups. Also, one can only ethically conduct desaturation studies using healthy volunteer subjects in a safe setting.”

*ARMS accuracy is a statistical calculation of the difference between device measurements and reference measurements. Approximately two-thirds of the device measurements fell within +/- ARMS of the reference measurements in a controlled study.