Oxygen levels in patients are typically monitored by pulse oximetry. However, there has been little research done on why people with darker skin pigmentation are more likely to have measurement inaccuracy with pulse oximetry, and there are no currently available evidence-based clinical mitigation techniques to address this problem. The goal of this study was to determine the prevalence of occult hypoxemia in a racially diverse population of critically ill patients (defined as arterial oxygen saturation (SaO2) less than 88% when pulse oximeter oxygen saturation was between 92-96%), to analyze the extent, direction, and consistency of measurement error, and to devise a strategy to minimize occult hypoxemia prior to technological advances. Researchers conducted a retrospective cohort analysis on patients in critical care at many institutions. Their analysis of 105,467 paired observations from 7,693 participants reveals a racial disparity in the prevalence of concealed hypoxemia. Occult hypoxemia was more common in blacks (7.9%) than in whites (2.9%; P<.001). The range of intra-subject measurement errors for pulse oximeters was greater than 4% points in 67% of all patient contacts. About 75% of all interactions featured a symmetrical distribution of errors within the same subject. At higher oxygenation ranges, SaO2 less than 88% was observed in fewer cases (4.1% and 1.8% of observations among Black and white subjects at a pulse oximeter threshold of 94-98%, respectively). Increases in the frequency of hyperoxemia (arterial oxygen partial pressure > 110 mm Hg) were found in 42.3% of Black and 46.0% of white observations, even though occult hypoxemia was lowered even further at oxygenation saturation range 95-100%. All races experience measurement errors when using pulse oximetry. However, Black patients were more likely to have occult hypoxemia. The magnitude and direction of measurement error might vary greatly, making targeted corrections impossible. For the time being, until better tools become available, they advise setting a target saturation level of 94–98% for pulse oximetry.
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