Volumetric or time-based capnography for excluding pulmonary embolism in outpatients?
(2009) Journal of thrombosis and haemostasis : JTH — Vol. 8, n° 1, p. 60-67 (2010)
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- Summary. Background: Volumetric capnography is technically more demanding but theoretically more performant than the time-based alveolar deadspace fraction (PaCO(2)-EtCO(2))/PaCO(2) as bedside diagnostic tool for ruling-out pulmonary embolism (PE) in outpatients. Objective: We compared both diagnostic accuracies, combined to clinical probability evaluation, in patients with a suspicion of PE and positive ELISA D-dimer results. Patients and methods: In this clinical multicenter trial with prospective inclusion and three-month follow-up, alveolar deadspace fraction was compared by ROC analysis with other parameters derived from volumetric capnography. Results: Capnography was performed in 239 patients, of which 205 tests (86%) were conclusive. The prevalence of PE was 33%. The ROC curve analysis for alveolar deadspace fraction was 0.73+/-0.04. The diagnostic performances of parameters from volumetric capnography were not significantly better. 16% (95% CI 12%-21%) of patients presented a (PaCO(2)-EtCO(2))/PaCO(2) ratio under the cut-off value of 0.15 with a low clinical probability. This combination excluded PE with a sensitivity of 96% (95% CI 89%-99%) and a negative likelihood ratio of 0.17 (95% CI 0.09-0.33). Conclusion: Volumetric capnography failed to achieve better performances than the alveolar deadspace fraction (PaCO2-EtCO2)/PaCO2 for excluding PE in outpatients with positive D-dimers. Future studies should clarify the safety of ruling out PE in patients combining a low clinical probability with positive D-dimers and a (PaCO2-EtCO2)/PaCO2 ratio under the cut-off value of 0.15.
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Verschuren, F., Sanchez, O., Righini, M., Heinonen, E., Le Gal, G., Meyer, G., Perrier, A., & Thys, F. (2009). Volumetric or time-based capnography for excluding pulmonary embolism in outpatients? Journal of thrombosis and haemostasis : JTH, 8(1), 60-67. https://doi.org/10.1111/j.1538-7836.2009.03667.x (Original work published 2010)