Prognostic Value of Pulse Oximetry Differences

This is a prospective observational cohort study conducted in a single ED to evaluate the prognostic significance of inter-site differences in pulse oximetry in adult patients presenting with dyspnea.

Adult patients (≥19 years) presenting with dyspnea and classified as Korean Triage and Acuity Scale (KTAS) levels 1-3 will be enrolled at the time of ED admission. During initial vital sign assessment at ED presentation, SpO₂ will be simultaneously measured at the finger, earlobe, and forehead, along with the corresponding perfusion index at each site.

The primary exposure of interest is the difference between finger and earlobe SpO₂ (ΔSpO₂). Additional inter-site SpO₂ differences involving forehead measurements will also be evaluated. Clinical and physiological data at presentation will be collected prospectively, while outcome data will be obtained through retrospective medical record review.

The primary outcome is the mean difference in ΔSpO₂ between patients with poor outcomes-defined as all-cause mortality from ED admission to hospital discharge or intensive care unit (ICU) admission-and those with favorable outcomes. Secondary outcomes include the associations of ΔSpO₂ with mortality, ICU admission, endotracheal intubation, serum lactate levels, and perfusion index, as well as the predictive performance of ΔSpO₂ using logistic regression and receiver operating characteristic (ROC) analysis. The prognostic value of ΔSpO₂ will also be compared with established early warning scores such as NEWS.

Inclusion criteria

• Adult patients aged 19 years or older presenting to the emergency department with dyspnea, classified as KTAS level 1-3

Exclusion criteria

• Patients in whom SpO₂ measurements were not obtained simultaneously
• Patients in whom arterial blood gas analysis was not ordered at initial evaluation
• Pregnant patients
• Patients with facial trauma or hand trauma
• Patients with amputation, injury, or burns at the measurement sites
• Patients wearing nail polish
• Patients with dyshemoglobinemia
• Non-Korean nationality
• Patients who did not provide consent to participate in the study