Temporal dimensions of oxygen saturation exposure and clinical outcomes in critically ill patients: a retrospective...

Most studies on SpO₂ exposure patterns focus solely on SpO₂ intensity and neglect exposure duration. We systematically investigated the associations between SpO₂ exposure patterns and clinical outcomes from both intensity and temporal dimensions in critically ill patients.

In this retrospective cohort study, 121,758 critically ill patients were analyzed. The patient data were obtained from three databases: SICdb (n = 11,324) for continuous exposure analysis using heatmaps, MIMIC-IV (n = 50,110) for cumulative exposure analysis, and eICU (n = 60,324) for validation. We examined the relationships between SpO₂ exposure and 28-day mortality using Cox regression and logistic regression models. Restricted cubic spline analysis was performed using time-weighted SpO₂ as a continuous variable to examine the continuous association between SpO₂ values and mortality risk.

Both analytical approaches revealed a U-shaped relationship between SpO₂ and mortality. Heatmap analysis revealed a SpO₂ of 93.5-97% as optimal, whereas Cox regression showed that a SpO₂ of 96-97% conferred the strongest protection (HR 0.714, 95% CI 0.694-0.733; P < 0.001). Prolonged exposure to SpO₂ > 98% had a diminishing effect, whereas SpO₂ < 93.5% increased mortality risk (HR 1.236, P < 0.001). External validation confirmed these findings (AUC 0.813).

Our study confirms a U-shaped relationship between SpO₂ and outcomes, emphasizing that oxygenation assessments should consider both intensity and duration. A prolonged SpO₂ above 98% or below 94% should be avoided in critically ill patients.