Pulmonary embolism risk stratification: pulse oximetry and pulmonary embolism severity index

Background: Risk stratification of pulmonary embolism (PE) patients is important to determine appropriate management.

Objectives: We evaluated two published risk-stratification tools in emergency department (ED) PE patients: a pulse oximetry cutoff below 92.5% oxygen (at 5280 feet elevation) and the Pulmonary Embolism Severity Index (PESI).

Methods: Electronic medical records of all patients diagnosed with PE were abstracted to identify their triage vital signs, co-morbidities, and adverse short-term outcomes (AO) either requiring interventions (defined as respiratory failure, hypotension requiring pressors, and hemodynamic impairment requiring thrombolytics) or resulting in death. We applied these models to our ED PE patients and assessed their performance.

Results: There were 168 PE patients identified, with an overall AO rate of 7.1% (12/168), including a 3.0% mortality rate. A room-air pulse oximetry cutoff of 92.5%, for values measured at 5280 feet, classified 89/136 patients as low risk, 1.1% of which had an AO, and 47/136 patients as high risk, of which 10.6% had AO. This pulse oximetry cutoff had a sensitivity of 83% (95% confidence interval [CI] 36-99%), specificity of 68% (95% CI 58-76%), and a negative predictive value (NPV) of 99% (95% CI 93-100%). PESI classified 91/168 patients as low risk (class I or II): 2.2% had AO but none died, and 77/168 were classified as high risk (class III, IV, or V), with an AO rate of 13.0%. A PESI cutoff score of II had a sensitivity of 83% (95% CI 52-98%), specificity of 57% (95% CI 49-65%), and NPV of 98% (95% CI 92-100%).

Conclusion: Both PESI and pulse oximetry measurements are moderately accurate identifiers of low-risk patients with PE.