There was a warning not long ago that oximeters were more unreliable and over estimated oxygen levels in some ethnic minorities. So worth keeping that in mind. Don't rely on them alone.
There is a growing body of evidence, going back three decades, that suggest there may be drawbacks when using pulse oximetry on darker skinned patients. In as early as 1990, a study revealed discrepancies in the reliability of a target SpO2 of 92% when comparing white and black patients receiving mechanical ventilation.
^Whilst a 92% target was suitable for white patients (n=25), a higher target of 95% was required in order to prevent significant hypoxaemia associated with this target in black patients (n=29). In addition, inaccurate pulse oximetry readings were more than two times more
common in black patients than white patients.^
Further trials revealed significant skin pigment related differences when testing three different models of pulse oximeters (Nellcor Inc., Novametrix Inc. and Nonin Inc.) and consistently identified overestimated SpO2 during hypoxia in dark-skinned individuals (n=11). A more recent study conducted in 2020, at the University of Michigan Hospital compared measures of oxygen saturation by pulse oximetry and arterial blood gas samples from adult inpatients receiving supplemental oxygen.
^The sample consisted of white patients (n=1333) and black patients (n=276) and revealed that of the patients who had an SpO2 reading
between 92% and 96%, black patients were three times more likely (11.7%) to have an arterial oxygen saturation of less than 88% than white patients^
Source - Pulse oximetry and racial bias: Recommendations for national healthcare, regulatory and research bodies (March 2021)