Is Oxygen Saturation Variable of Simplified Pulmonary Embolism Severity Index Reliable for Identification of Patients, Suitable for Outpatient Treatment

Introduction: The pulmonary embolism severity index (PESI) or simplified version (sPESI) are widely validated risk scores for the identification of eligible patients for outpatient treatment. Saturation is one of these criteria. For this metric, saturation of 90% or greater is assigned zero points. However, 90% saturation does not always exclude hypoxemic respiratory failure.

Objective: The aims of this study were first was to define corresponding partial arterial oxygen pressure (PaO ) values according to saturation in pulmonary embolism (PE) patients, and the second was to define a target saturation that can exclude hypoxemic respiratory failure and enable secure discharge of PE patients from emergency departments.

Methods: This is a retrospective study. To determine the optimal saturation value by which to detect hypoxemic respiratory failure, we generated receiver operating characteristic (ROC) curves and calculated the negative predictive value.

Results: Total of 65 patients were included in this study. Mean PaO levels from SaO 89% to SaO 93% were 52.8, 57.1, 57.3, 61, and 63.8 mmHg, respectively. ROC curve analysis revealed SaO level of 91.5% to be optimal target saturation for excluding respiratory failure with 84.6% specificity and 89.7% sensitivity; area under the curve was 0.885 (95% CI 0.796-0.975). The negative predictive value was 80% for SaO level of 92%.

Conclusion: Patients with PE may be in respiratory failure despite an oxyhemoglobin saturation of ≥90%. Although saturation is likely more important than precise PaO in tissue oxygenation, clinicians should be aware of the physiological effects of hypoxemia and take this into account before making outpatient treatment decisions.