SpO₂ monitoring in emergency and acute care: clinical utility, limitations, and interpretation pitfalls

Pulse oximetry provides a non-invasive numerical estimate of arterial oxygen saturation. It is simple to apply and interpret by clinicians at all levels, and its use has expanded substantially across prehospital care, emergency departments, acute care units, and household monitoring. Although pulse oximetry is portable, non-invasive, and cost-effective, its limitations are clinically important because it measures oxygen saturation rather than ventilation, oxygen delivery, or tissue oxygen utilization. Over-reliance on SpO₂ values for decisions related to oxygen administration, escalation of care, and clinical deterioration may conceal subtle but serious abnormalities. This review discusses the limitations of pulse oximetry in emergency and acute care settings, including sepsis, regional hypoperfusion, dyshaemoglobinemias, COVID-19, pulmonary embolism, hyperoxia, skin pigmentation-related bias, and other relevant clinical contexts. The central message is that SpO₂ should be interpreted as one component of a broader assessment bundle and should not substitute for comprehensive clinical evaluation.