Racial and skin color mediated disparities in pulse oximetry in infants and young children

Abstract

Race-based and skin pigmentation-related inaccuracies in pulse oximetry have recently been highlighted in several large electronic health record-based retrospective cohort studies across diverse patient populations and healthcare settings. Overestimation of oxygen saturation by pulse oximeters, particularly in hypoxic states, is disparately higher in Black compared to other racial groups. Compared to adult literature, pediatric studies are relatively few and mostly reliant on birth certificates or maternal race-based classification of comparison groups. Neonates, infants, and young children are particularly susceptible to the adverse life-long consequences of hypoxia and hyperoxia. Successful neonatal resuscitation, precise monitoring of preterm and term neonates with predominantly lung pathology, screening for congenital heart defects, and critical decisions on home oxygen, ventilator support and medication therapies, are only a few examples of situations that are highly reliant on the accuracy of pulse oximetry. Undetected hypoxia, especially if systematically different in certain racial groups may delay appropriate therapies and may further perpetuate health care disparities. The role of biological factors that may differ between racial groups, particularly skin pigmentation that may contribute to biased pulse oximeter readings needs further evaluation. Developmental and maturational changes in skin physiology and pigmentation, and its interaction with the operating principles of pulse oximetry need further study. Importantly, clinicians should recognize the limitations of pulse oximetry and use additional objective measures of oxygenation (like co-oximetry measured arterial oxygen saturation) where hypoxia is a concern.

Keywords: Disparity; Infants; Oxygen; Pulse Oximeter; Race; Skin Pigmentation.

Figure 1.

Schematic diagram of light absorbance by a pulse oximeter. (A) In clinical states with good cardiac function, the onset of the cardiac systole, as denoted by the onset of the QRS complex coincides with the onset of the increase of the arterial blood volume. The amount of red and IR light absorbed in the arterial compartment also rises and falls with systole and diastole, respectively, due to the increase and decrease in blood volume. The volume that increases with systole is also known as the pulsatile or “alternating current” (AC) compartment and the compartment in which the blood volume does not change with the cardiac cycle is known as the non-pulsatile or “direct current” (DC) compartment. (B) A cross-sectional diagram of an artery and a vein displaying the pulsatile (AC) and non-pulsatile (DC) compartments of the blood vessels. Note that only the artery has a pulsatile (AC) component. (C) A diagram of a calibration (standard) curve of the Red:IR Modulation Ratio in relation to the ${\text{SpO}}_2$. Increased red light absorbance (increased R) is associated with increased deoxyhemoglobin, i.e., lower ${\text{SpO}}_2$ [Image reproduced with permission].

Figure 2.

Simulated data illustrating statistics used in pulse oximeter validation studies. The triangles on the solid black line A indicate the reference or actual values of arterial oxygen saturation (${\text{SaO}}_2$) ranging from 70-100%. The dotted line B (yellow) shows Mean Bias which is the average of individual absolute deviations (${\text{SpO}}_2$-${\text{SaO}}_2$) along the entire data set. The grey circles depict pulse oximeter readings (${\text{SpO}}_2$). B1 and B2 indicate deviations of individual datapoints from the reference values (${\text{SpO}}_2$-${\text{SaO}}_2$) at two different ${\text{SaO}}_2$ measurement points. ${\mathrm{B}}_1>{\mathrm{B}}_2$ showing higher individual deviation at lower ${\text{SaO}}_2$. The solid line C (yellow) indicates the best fit line through the entire ${\text{SpO}}_2$ dataset as a function of ${\text{SaO}}_2$. Precision is represented by the scatter around line C, which is the standard deviation of the residuals. A residual is the difference of one ${\text{SpO}}_2$ data point from the best-fit line (line C).

Figure 3.

Flow diagram of literature search

Figure 4a and 4b.

The CIELAB color space diagram shows the quantitative relationship of colors on three axes: L* value indicates lightness, and a* and b* are chromaticity coordinates. On the color space diagram, L* is represented on a vertical axis with values from + (black) to − (white). The a* value indicates red-green component of a color, where a* (positive) and a* (negative) indicate red and green values, respectively. The yellow and blue components are represented on the b* axis as b* (positive) and b* (negative) values, respectively. At the center of the plane is neutral or achromatic. The distance from the central axis represents the chroma (C*), or saturation of the color. The angle on the chromaticity axes represents the hue. The L*, a*, and b* values can be transcribed to dermatological parameters. Figure 4c. ITA° classification provides objective quantification and classification of skin color into six groups: very light, light, intermediate, tanned, brown, and dark (Del Bino, 2013). CIE, Commission Internationale de l’Eclairage. ITA, Individual Typology Angle.