Racial and ethnical discrepancy in hypoxemia detection in patients on extracorporeal membrane oxygenation

Objective: To determine whether there is racial/ethnical discrepancy between pulse oximetry (SpO₂) and oxygen saturation (SaO₂) in patients receiving extracorporeal membrane oxygenation (ECMO).

Methods: This was a retrospective observational study at a tertiary academic ECMO center with adults (>18 years) on venoarterial (VA) or venovenous (VV) ECMO. Datapoints were excluded if oxygen saturation ≤70% or SpO₂-SaO₂ pairs were not measured within 10 minutes. The primary outcome was the presence of a SpO₂-SaO₂ discrepancy between different races/ethnicities. Bland-Altman analyses and linear mixed-effects modeling, adjusting for prespecified covariates, were used to assess the SpO₂-SaO₂ discrepancy between races/ethnicities. Occult hypoxemia was defined as SaO₂ <88% with a time-matched SpO₂ ≥92%.

Results: Of 139 patients receiving VA-ECMO and 57 patients receiving VV-ECMO, we examined 16,252 SpO₂-SaO₂ pairs. The SpO₂-SaO₂ discrepancy was greater in VV-ECMO (1.4%) versus VA-ECMO (0.15%). In VA-ECMO, SpO₂ overestimated SaO₂ in Asian (0.2%), Black (0.94%), and Hispanic (0.03%) patients and underestimated SaO₂ in White (-0.06%) and nonspecified race (-0.80%) patients. The proportion of SpO₂-SaO₂ measurements considered occult hypoxemia was 70% from Black compared to 27% from White patients (P < .0001). In VV-ECMO, SpO₂ overestimated SaO₂ in Asian (1.0%), Black (2.9%), Hispanic (1.1%), and White (0.50%) patients and underestimated SaO₂ in nonspecified race patients (-0.53%). In linear mixed-effects modeling, SpO₂ overestimated SaO₂ by 0.19% in Black patients (95% confidence interval, 0.045%-0.33%, P = .023). The proportion of SpO₂-SaO₂ measurements considered occult hypoxemia was 66% from Black compared with 16% from White patients (P < .0001).

Conclusions: SpO₂ overestimates SaO₂ in Asian, Black, and Hispanic versus White patients, and this discrepancy was greater in VV-ECMO versus VA-ECMO, suggesting the need for physiological studies.