Figure. Scatterplots of Paired Pulse Oximetry (SpO₂) and Arterial Blood Oxygen Saturation (SaO₂) Observations for Black or African American Patients and White Patients.

Black solid lines represent the line of equality and the trend line for the given set of paired data points. Blue solid lines denote the following quadrants: true positive includes patients whose paired SaO₂ and SpO₂ measurements both indicate hypoxemia (SpO₂ <92% and SaO₂ <88%). True negative includes patients whose SaO₂ and SpO₂ both indicate normoxemia. False positive includes patients whose SaO₂ is normoxemic but whose SpO₂ may suggest hypoxemia. False negative includes patients whose Sao₂ is hypoxemic but whose SpO₂ wrongly suggests normoxemia, placing the patient at risk of undertreatment (withholding supplemental O₂).