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Volumetric Capnography as a Screening Test for Pulmonary Embolism in the Emergency Department

2004; Elsevier BV; Volume: 125; Issue: 3 Linguagem: Inglês

10.1378/chest.125.3.841

1931-3543

Franck Verschuren, Giuseppe Liistro, René Coffeng, F. Thys, Jean Roeseler, Francis Zech, Marc Reynaert,

Chronic Obstructive Pulmonary Disease (COPD) Research

Study objective To compare the diagnostic performance of volumetric capnography (VCap), which is the plot of the expired CO2 partial pressure against the expired volume during a single breath, with the Paco2 to end-tidal CO2 (EtCO2) gradient, in the case of suspected pulmonary embolism (PE). Design Single-center, prospective study. Setting Emergency department of a teaching hospital. Patients A total of 45 outpatients with positive enzyme-linked immunosorbent assay d-dimer levels of > 500 ng/mL. The diagnosis of PE was confirmed in 18 outpatients according to a validated procedure based on the ventilation-perfusion lung scan and/or spiral CT scanning. Interventions Curves of VCap were obtained from a compact monitor connected to a computer. A sequence of four to six stable breaths allowed the calculation of the following several variables: alveolar dead space fraction; the ratio of alveolar dead space (VDalv) to airway dead space (VDaw); the VDalv to physiologic dead space (VDphys) fraction; the slope of phase 3; and the late dead space fraction (Fdlate) corresponding to the extrapolation of the capnographic curve to a volume of 15% of the predicted total lung capacity. Results The mean (± SD) Paco2-EtCO2 gradient was 5.3 ± 0.7 mm Hg in the PE-positive group and 2.8 ± 0.7 mm Hg in the PE-negative group (p = 0.019). Four variables of the VCap exhibited a statistical difference between both groups, as follows: the VDalv/VDaw fraction; the slope of phase 3; the VDalv/VDphys fraction; and the Fdlate, which was 8.2 ± 3.3% vs −7.7 ± 2.8%, respectively (p = 0.000011). The diagnostic performance expressed as the mean area under a receiver operating characteristic curve comparison was 75.9 ± 7.4% for the Paco2-EtCO2 gradient and 87.6 ± 4.9% for the Fdlate (p = 0.02). Conclusion Fdlate, a variable of VCap, had a statistically better diagnostic performance in suspected PE than the Paco2-EtCO2 gradient. VCap is a promising computer-assisted bedside application of pulmonary pathophysiology. Future research should define the place of this technique in the diagnostic workup of PE, especially in the presence of positive d-dimers. To compare the diagnostic performance of volumetric capnography (VCap), which is the plot of the expired CO2 partial pressure against the expired volume during a single breath, with the Paco2 to end-tidal CO2 (EtCO2) gradient, in the case of suspected pulmonary embolism (PE). Single-center, prospective study. Emergency department of a teaching hospital. A total of 45 outpatients with positive enzyme-linked immunosorbent assay d-dimer levels of > 500 ng/mL. The diagnosis of PE was confirmed in 18 outpatients according to a validated procedure based on the ventilation-perfusion lung scan and/or spiral CT scanning. Curves of VCap were obtained from a compact monitor connected to a computer. A sequence of four to six stable breaths allowed the calculation of the following several variables: alveolar dead space fraction; the ratio of alveolar dead space (VDalv) to airway dead space (VDaw); the VDalv to physiologic dead space (VDphys) fraction; the slope of phase 3; and the late dead space fraction (Fdlate) corresponding to the extrapolation of the capnographic curve to a volume of 15% of the predicted total lung capacity. The mean (± SD) Paco2-EtCO2 gradient was 5.3 ± 0.7 mm Hg in the PE-positive group and 2.8 ± 0.7 mm Hg in the PE-negative group (p = 0.019). Four variables of the VCap exhibited a statistical difference between both groups, as follows: the VDalv/VDaw fraction; the slope of phase 3; the VDalv/VDphys fraction; and the Fdlate, which was 8.2 ± 3.3% vs −7.7 ± 2.8%, respectively (p = 0.000011). The diagnostic performance expressed as the mean area under a receiver operating characteristic curve comparison was 75.9 ± 7.4% for the Paco2-EtCO2 gradient and 87.6 ± 4.9% for the Fdlate (p = 0.02). Fdlate, a variable of VCap, had a statistically better diagnostic performance in suspected PE than the Paco2-EtCO2 gradient. VCap is a promising computer-assisted bedside application of pulmonary pathophysiology. Future research should define the place of this technique in the diagnostic workup of PE, especially in the presence of positive d-dimers.