RT Journal Article SR Electronic T1 Bedside end-tidal CO2 tension as a screening tool to exclude pulmonary embolism JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 735 OP 741 DO 10.1183/09031936.00084709 VO 35 IS 4 A1 A. R. Hemnes A1 A. L. Newman A1 B. Rosenbaum A1 T. W. Barrett A1 C. Zhou A1 T. W. Rice A1 J. H. Newman YR 2010 UL http://erj.ersjournals.com/content/35/4/735.abstract AB End tidal carbon dioxide tension (PET,CO2) is a surrogate for dead space ventilation which may be useful in the evaluation of pulmonary embolism (PE). We aimed to define the optimal PET,CO2 level to exclude PE in patients evaluated for possible thromboembolism. 298 patients were enrolled over 6 months at a single academic centre. PET,CO2 was measured within 24 h of contrast-enhanced helical computed tomography, lower extremity duplex or ventilation/perfusion scan. Performance characteristics were measured by comparing test results with clinical diagnosis of PE. PE was diagnosed in 39 (13%) patients. Mean PET,CO2 in healthy volunteers did not differ from PET,CO2 in patients without PE (36.3±2.8 versus 35.5±6.8 mmHg). PET,CO2 in patients with PE was 30.5±5.5 mmHg (p<0.001 versus patients without PE). A PET,CO2 of ≥36 mmHg had optimal sensitivity and specificity (87.2 and 53.0%, respectively) with a negative predictive value of 96.6% (95% CI 92.3–98.5). This increased to 97.6% (95% CI 93.2–99.) when combined with Wells score <4. A PET,CO2 of ≥36 mmHg may reliably exclude PE. Accuracy is augmented by combination with Wells score. PET,CO2 should be prospectively compared to D-dimer in accuracy and simplicity to exclude PE.