The diagnostic role of capnography in pulmonary embolism

The aim of this study was to evaluate the diagnostic contribution of alveolar dead space fraction (AVDSf) measured using capnography in patients admitted with suspected pulmonary embolism (PE). A total of 58 patients who were admitted to our hospital with suspected PE between October 2006 and January 2008 were included in this study. All patients were assessed using the Wells clinical score, capnography, computed tomographic pulmonary angiography, D-dimer measurement, lower-extremity venous Doppler ultrasonography, and V/Q scintigraphy. Forty patients (69%) had PE based on computed tomographic pulmonary angiography findings. The AVDSf value with the highest sensitivity and specificity, which was at the same time statistically significant, was 0.09. This value was consistent with the AVDSf value obtained using receiver operating characteristic analysis. In our study, the sensitivity of capnography was 70%, with a specificity of 61.1%, positive predictive value of 80%, and negative predictive value of 47.8%. The use of AVDSf in combination with any of the several scoring systems that evaluate clinical likelihood of PE and D-dimer levels resulted in higher sensitivity and specificity rates for the diagnosis of PE.