Characterizing the Racial Discrepancy in Hypoxemia Detection in Venovenous Extracorporeal Membrane Oxygenation: An Extracorporeal Life Support Organization Registry Analysis

Abstract

Purpose: Skin pigmentation influences peripheral oxygen saturation (SpO₂) compared to arterial saturation of oxygen (SaO₂). Occult hypoxemia (SaO₂ ≤ 88% with SpO₂ ≥ 92%) is associated with increased in-hospital mortality in venovenous-extracorporeal membrane oxygenation (VV-ECMO) patients. We hypothesized VV-ECMO cannulation, in addition to race/ethnicity, accentuates the SpO₂-SaO₂ discrepancy due to significant hemolysis.

Methods: Adults (≥ 18 years) supported with VV-ECMO with concurrently measured SpO₂ and SaO₂ measurements from over 500 centers in the Extracorporeal Life Support Organization Registry (1/2018-5/2023) were included. Multivariable logistic regressions were performed to examine whether race/ethnicity was associated with occult hypoxemia in pre-ECMO and on-ECMO SpO₂-SaO₂ calculations.

Results: Of 13,171 VV-ECMO patients, there were 7772 (59%) White, 2114 (16%) Hispanic, 1777 (14%) Black, and 1508 (11%) Asian patients. The frequency of on-ECMO occult hypoxemia was 2.0% (N = 233). Occult hypoxemia was more common in Black and Hispanic patients versus White patients (3.1% versus 1.7%, P < 0.001 and 2.5% versus 1.7%, P = 0.025, respectively). In multivariable logistic regression, Black patients were at higher risk of pre-ECMO occult hypoxemia versus White patients (adjusted odds ratio [aOR] = 1.55, 95% confidence interval [CI] = 1.18-2.02, P = 0.001). For on-ECMO occult hypoxemia, Black patients (aOR = 1.79, 95% CI = 1.16-2.75, P = 0.008) and Hispanic patients (aOR = 1.71, 95% CI = 1.15-2.55, P = 0.008) had higher risk versus White patients. Higher pump flow rates (aOR = 1.29, 95% CI = 1.08-1.55, P = 0.005) and on-ECMO 24-h lactate (aOR = 1.06, 95% CI = 1.03-1.10, P < 0.001) significantly increased the risk of on-ECMO occult hypoxemia.

Conclusion: SaO₂ should be carefully monitored if using SpO₂ during ECMO support for Black and Hispanic patients especially for those with high pump flow and lactate values at risk for occult hypoxemia.

Keywords: Arterial blood gas; Hypoxemia; Pulse oximetry; Racial/ethnical disparities; Venovenous extracorporeal membrane oxygenation.

Fig. 1

Creation of study cohort from the ELSO Registry (1/2018–5/2023)

Fig. 2

Forest plots of odds ratios and 95% confidence intervals from the multivariable logistic regression for occult hypoxemia in A pre-ECMO SpO₂-SaO₂ and B on-ECMO SpO₂-SaO₂ pairs. Pre-ECMO and on-ECMO SpO₂-SaO₂ measurements were extracted from the same patient

Fig. 3

Boxplots showing pulse oximetry (SpO₂) overestimates arterial blood gas (SaO₂) in Black, Asian, and Hispanic venovenous (VV)-extracorporeal membrane oxygenation (ECMO) patients, compared to White VV-ECMO patients. Purple color = White patients. Green color = Black patients. Turquoise color = Hispanic patients. Red color = Asian patients. Solid black line represents the median value while the upper and lower limits of the boxes represent the 75% and 25% quartiles, respectively. White patients were used as the reference comparator. **** and *** represent P values < 0.0001 and < 0.001, respectively