The Search for Optimal Oxygen Saturation Targets in Critically Ill Patients: Observational Data from Large ICU Databases

Abstract

Background While low oxygen saturations are generally regarded as deleterious, recent studies in intensive care unit (ICU) patients have shown that a liberal oxygen strategy increases mortality. However, the optimal oxygen saturation target remains unclear. We therefore aimed to elucidate this optimal range with real world data.

Methods Replicate retrospective analyses of two electronic medical record databases were done: eICU Collaborative Research Database (eICU-CRD) and the Medical Information Mart for Intensive Care III (MIMIC). Only patients with at least 48 hours of oxygen therapy were included. Nonlinear regression was used to analyze the association between median pulse oximetry-derived oxygen saturation (SpO2) and hospital mortality. We derived an optimal range of SpO2 and analyzed the association between the percentage of time within the optimal range of SpO2 and hospital mortality. All models adjusted for age, body mass index, gender, and SOFA score. Subgroup analyses included ICU types, main diagnosis, and comorbidities.

Results We identified 26,723 patients from eICU-CRD and 8,564 patients from MIMIC. The optimal range of SpO2 was 94–98% in both eICU-CRD and MIMIC. The percentage of time patients were within the optimal range of SpO2 was associated with decreased hospital mortality (odds ratio of 80% versus 40% of the measurements within the optimal range: 0.42, 95% CI 0.40 to 0.43, for eICU-CRD and 0.53, 95% CI 0.50 to 0.55 for MIMIC). This association was consistent across subgroup analyses.

Conclusions The optimal range of SpO2 was 94–98% and should inform future trials of oxygen therapy.