The following is the summary of “Racial Disparities in Occult Hypoxemia and Clinically Based Mitigation Strategies to Apply in Advance of Technological Advancements” published in the December 2022 issue of Respiratory Care by Chesley, et al.
Oxygen levels in patients are typically monitored by pulse oximetry. Even though people with darker skin pigmentation are more susceptible to measurement error from pulse oximetry, the problem is still poorly understood, and there are no clinically-proven treatments for reducing this error. Their goals were to determine the prevalence of occult hypoxemia in a racially mixed group of critically ill patients (defined as arterial oxygen saturation (Sao2) 88% when pulse oximeter oxygen saturation was between 92-96%), to assess the extent, nature, and consistency of measurement error, and to propose a strategy for reducing occult hypoxemia before better tools become available.
Researchers conducted a retrospective cohort analysis on patients in critical care at many institutions. A total of 105,467 paired observations on 7,693 participants revealed a racial disparity in the prevalence of concealed hypoxemia. Occult hypoxemia occurred in 7.9% of Black patients and 2.9% of white subjects, respectively (P<.001). There was wide variation in the accuracy of pulse oximeter readings throughout a patient interaction, with 67% of readings showing a range of intra-subject measurement errors of more than 4%. The intra-subject mistakes were reciprocal in nature in 75% of all interactions. At higher oxygenation ranges, Sao2 88% was seen less frequently (4.1% and 1.8% of observations among Black and white subjects at a pulse oximeter threshold of 94-98%, respectively).
However, with an oxygen saturation of 95-100%, the frequency of hyperoxemia (a partial pressure of arterial oxygen more than 110 mm Hg) increased, occurring in 42.3% of Black and 46.0% of white observations, whereas occult hypoxemia decreased. Occult hypoxemia was more prevalent in Black patients, while measurement error in pulse oximetry was shown to affect all racial groups. Measurement errors range widely in size and might even reverse the results of a measurement, making it impossible to devise a universal strategy for their correction. Investigators suggest that, until better monitoring tools become available, all patients have a pulse oximetry saturation objective of 94% to 98%.