Volumetric capnography in the exclusion of pulmonary embolism at the emergency department: A pilot study

The analysis of the PCO2 in expired air as a function of the exhaled volume (volumetric capnography) might result in a more specific exclusion tool for pulmonary embolism (PE) in addition to the Wells-score and D-dimer. A novel combination of volumetric capnography parameters (VCO2 slopeIII RR × / ) should be decreased in PE and could possibly be used to decrease the number of requested computed tomography pulmonary angiograms (CTPA). Volumetric capnography measurements were performed on consecutive patients seen in the emergency department for which, due to suspected PE (due to increased D-dimer level or Wells-score), a CTPA was ordered. A total of 30 subjects were included, of which in 13 PE was seen on CTPA. Median PETCO2 was 4.36 kPa (IQR 3.92-4.88) in the no PE group versus 4.07 kPa (IQR 3.37-4.39) in the PE group (p = 0.086). Median of the novel parameter VCO2 slopeIII RR ×- / was 1.85 min.kPa dl?1 (IQR 1.21-3.00) in the no PE group versus 1.18 min.kPa dl?1 (IQR 0.61-1.38) in the PE group (p = 0.006). Using a threshold for the new parameter of 1.90 min.kPa dl?1 or higher to exclude PE resulted in a negative predictive value of 100% (95% CI: 77%-100%) and would have potentially excluded PE in 47% (95% CI: 26%-69%) of the no PE group without the need for CTPA. This pilot study introduces a novel parameter VCO2 slopeIII RR × / which is significantly decreased in PE subjects. Future studies regarding validation and addressing aspects such as reproducibility and normalization after treatment are needed to confirm its usability in excluding PE in the emergency department.