Abstract
Pulmonary embolism (PE) is a potentially lethal pathology which is hard to exclude without expensive imaging techniques. Recent literature suggests the use of end-tidal PCO2 (PETCO2) as a useful parameter to exclude PE. Analysis of the entire curve of the PCO2 in expired air (volumetric capnography, VCap), contains more information.
VCap was performed in subjects seen at the emergency room with D-dimer > 500 µg/L or Wells-score > 4. The association with PE was tested with age, weight, height, Wells score, D-dimer, PETCO2, the calculated anatomic dead space (VDaw/Vt) and the slope of the alveolar phase of the VCap (slope III). Variables with p<0.10 were candidate variables for a multivariate logistic regression prediction model.
Of the 24 included subjects, PE was diagnosed in 10. Wells score, D-dimer and VDaw/Vt were associated with PE (p<0.10). Due to the small sample size, multivariate logistic regression was not performed. The cut-off value suggested by Riaz et al. of PETCO2 >4.3 kPa to exclude PE1, resulted in a PPV of 36% and a NPV of 50%.
In this ongoing study, contrary to the literature, PETCO2 was not related to PE. However, VCap derived dead space (VDaw/Vt) seems more promising.
No PE (N=14) | PE (N=10) | |
Median (IQR) | Median (IQR) | |
Age (y) | 55 (46 - 69) | 55 (44 - 70) |
Height (cm) | 173 (163 - 185) | 177 (168 - 182) |
Weight (kg) | 87 (75 - 99) | 74 (60 - 95) |
Wells score | 3.0 (0.0 - 3.3) | 4.3 (3.0 5.9) |
D-dimer (mug/L) | 862 (672 - 1784) | 4933 (1755 - 7327) |
PETCO2 (kPa) | 4.21 (3.30 - 4.46) | 4.25 (3.42 - 4.45) |
VDaw/Vt (%) | 31 (26 - 38) | 39 (35 - 46) |
Slope III (kPa/L) | 1.20 (0.78 - 2.53) | 1.55 (1.28 - 2.00) |
1 Riaz et al. Clin Med. 2014 Apr;14(2):128-33.
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