Accuracy of Pulse Oximetry and Risk Factors Associated with Discrepancy from Arterial Oxygenation in Asian Patients in the ICU: An Observational Study.

Abstract

Background: Oxygen administration is often guided by pulse oximeter readings. However, inaccuracies have been reported, particularly in patients with darker skin tones. During the COVID-19 pandemic, racial and ethnic disparities in hypoxemia detection emerged, with studies showing a higher incidence of hidden hypoxemia in Black and Hispanic patients. However, limited data exists regarding the Asian population.

Research question: How accurate are SpO₂ readings in Asian patients with critical illness, and what factors contribute to discrepancies with SaO₂?

Study design and methods: We conducted a single-center observational study in an ICU at a tertiary care hospital in Japan, including all adult patients admitted from October 2013 through September 2021. We collected data from electronic records and analyzed for agreement between SpO2 and SaO₂ using modified Bland-Altman plots. We performed multivariable regression analysis to identify factors associated with SpO₂-SaO₂ differences. We used cubic splines to model associations between the differences and mortality. To further explore potential mechanisms of dissociation, subgroups of patients with chronic dialysis and sepsis were analyzed.

Results: Clinical data from 10,698 patients admitted to the ICU were analyzed. The mean bias between SpO₂ and SaO₂ was -1.23%, with the largest discrepancies occurring 24.7 hours after ICU admission. Hidden hypoxemia (SaO₂ <88%, SpO₂ ≥88%) occurred in 0.8% of patients, and serious hidden hypoxemia (SpO₂ ≥92%) occurred in 0.6%. Overestimation of SaO₂ was associated with high creatinine levels, particularly among patients with chronic hemodialysis, whereas underestimation was associated with sepsis, mechanical ventilation, and signs of impaired systemic perfusion. We observed a U-shaped relation between the SpO₂ and SaO₂ differences and mortality, indicating a non-linear association.

Interpretation: Dissociation between SpO2 and SaO2 in Asian patients in the ICU was small; however, overestimation and underestimation were associated with increased mortality risk, particularly among patients with chronic hemodialysis or impaired peripheral perfusion.