Irvine, California-based Masimo evaluated its pulse oximetry’s performance in varying skin pigmentation. It observed no clinically significant accuracy or bias between Black and White subjects.
The results come as the FDA increasingly scrutinizes whether some pulse oximeters may be less accurate among people with darker skin. Over the summer, Democratic U.S. senators called on the agency to study the issue more.
The Journal of Clinical Monitoring and Computing published the retrospective trial. It studied subjects using Masimo SET pulse oximetry and Masimo RD SET sensors.
Masimo CSO Dr. Steven Barker and CMO Dr. William Wilson performed the retrospective analysis. It utilized Masimo laboratory data obtained from self-identified Black and White volunteer subjects.
Investigators reviewed data collected between October 2015 and July 2021. Data included 7,183 paired samples (3,201 Black and 3,982 White) collected from 75 subjects (39 Black and 36 White). Subjects received screening with the same criteria to remove potential bias based on health conditions.
All subjects underwent the same hypoxia protocol. Investigators obtained noninvasive oxygen saturation (SpO2) from Masimo SET pulse oximeters with RD SET sensors. They time-matched those values with simultaneously taken arterial blood gas (ABG) samples analyzed using an ABL-835 blood gas analyzer.
The data
The investigators analyzed data to determine the bias, precision and accuracy for both groups. They observed a negative bias of 0.2% for Black subjects, compared to 0.05% for White subjects. Masimo said that difference is not clinically significant and the values are numerically indistinguishable. This is because the SpO2 display resolution is 1% on commercially available pulse oximeters (both from Masimo and other manufacturers).
Investigators also found a precision of 1.4% for Black subjects compared to 1.35% for White subjects. Accuracy came in at 1.42% for Black subjects and 1.35% for White subjects. Results fall in line with the accuracy specifications for the RD SET sensors.
Barker and Wilson explained that Masimo’s multiple signal-processing engines work together to overcome limitations in pulse oximetry. These limitations contribute to disparities in measurements based on skin color.
Addressing limitations
During the early stages of the COVID-19 pandemic, pulse oximeters became a useful tool for obtaining certain metrics that may indicate infection. Reports suggested disparities in pulse oximetry depending on skin color.
At the time (December 2020), Masimo told MassDevice that the company undertook a research effort to improve accuracy. The company said then that its RD SET sensors demonstrated similar accuracy on different skin pigmentations.
Based on the recent analysis, the company said its advanced technique allows for a more accurate picture of the pulsatile (arterial) signal. It reduces the impact of static absorbers such as skin pigment, bone density, and tissue thickness.
“In conclusion, this retrospective study of healthy human volunteers monitored with Masimo RD SET pulse oximeter sensors showed an absence of clinically significant differences in accuracy between Black and White subjects,” concluded Barker and Wilson.
The authors suggested that additional prospective clinical studies should be conducted to validate their results in critically ill patients utilizing Masimo SET pulse oximeters and those from other manufacturers.
