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

      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).


      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.

      Key words


      CI (confidence interval), ELISA (enzyme-linked immunosorbent assay), EtCO2 (end-tidal CO2), Fdlate (late dead space fraction ExpCO2 15%), TLC (extrapolated CO2 partial pressure at an exhaled volume of 15% of the estimated total lung capacity), PE (pulmonary embolism), ROC (receiver operating characteristic), TLC (total lung capacity), VCap (volumetric capnography), VDalv (alveolar dead space), VDalv/Vtalv (alveolar dead space fraction), VDaw (airway dead space), VDphys (physiologic dead space), / (ventilation-perfusion ratio), Vt (tidal volume)
      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic and Personal
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to CHEST
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Robin ED
        • Julian DG
        • Travis DM
        • et al.
        A physiological approach to the diagnosis of acute pulmonary embolism.
        N Engl J Med. 1959; 260: 586-591
        • Nutter DO
        • Massumi RA
        The arterial-alveolar carbon dioxide tension gradient in diagnosis of pulmonary embolus.
        Dis Chest. 1966; 50: 380-387
        • Vereerstraeten J
        • Schoutens A
        • Tombroff M
        • et al.
        Value of measurement of alveolo-arterial gradient of PCO2compared to pulmonary scan in diagnosis of thromboembolic pulmonary disease.
        Thorax. 1973; 28: 306-312
        • Hatle L
        • Rokseth R
        The arterial to end-expiratory carbon dioxide tension gradient in acute pulmonary embolism and other cardiopulmonary diseases.
        Chest. 1974; 66: 352-357
        • Colp C
        • Stein M
        Re-emergence of an “orphan” test for pulmonary embolism.
        Chest. 2001; 120: 115-119
        • Fletcher R
        • Jonson B
        • Cumming G
        • et al.
        The concept of deadspace with special reference to the single breath test for carbon dioxide.
        Br J Anaesth. 1981; 53: 77-78
        • Fletcher R
        Deadspace, invasive and non-invasive.
        Br J Anaesth. 1985; 57: 245-249
        • Kline JA
        • Israel EG
        • Michelson EA
        • et al.
        Diagnostic accuracy of a bedside D-dimer assay and alveolar dead-space measurement for rapid exclusion of pulmonary embolism: a multicenter study.
        JAMA. 2001; 285: 761-768
        • Rodger MA
        • Jones G
        • Rasuli P
        • et al.
        Steady-state end-tidal alveolar dead space fraction and D-dimer: bedside tests to exclude pulmonary embolism.
        Chest. 2001; 120: 115-119
        • Wells P
        • Ginsberg JS
        • Anderson DR
        • et al.
        Use of a clinical model for safe management of patients with suspected pulmonary embolism.
        Ann Intern Med. 1998; 129: 997-1005
        • de Moerloose P
        • Desmarais S
        • Bounameaux H
        • et al.
        Contribution of a new, rapid, individual and quantitative automated D-dimer ELISA to exclude pulmonary embolism.
        Thromb Haemost. 1996; 75: 11-13
        • Brown MD
        • Rowe BH
        • Reeves MJ
        • et al.
        The accuracy of the enzyme-linked immunosorbent assay D-dimer test in the diagnosis of pulmonary embolism: a meta-analysis.
        Ann Emerg Med. 2002; 40: 133-144
        • Eriksson L
        • Wollmer P
        • Olsson CG
        • et al.
        Diagnosis of pulmonary embolism based upon alveolar dead space analysis.
        Chest. 1989; 96: 357-362
      1. Standardized lung function testing: report working party.
        Bull Eur Physiopathol Respir. 1983; 19: 1-95
        • Hull RD
        • Hirsh J
        • Carter CJ
        • et al.
        Diagnostic value of ventilation-perfusion lung scanning in patients with suspected pulmonary embolism.
        Chest. 1985; 88: 819-828
        • Mayo JR
        • Remy-Jardin M
        • Muller NL
        • et al.
        Pulmonary embolism: prospective comparison of spiral CT with ventilation-perfusion scintigraphy.
        Radiology. 1997; 205: 447-452
        • Hanley JA
        Receiver operating characteristic (ROC) methodology: the state of the art.
        Crit Rev Diagn Imag. 1989; 29: 307-335
        • Lee M-LT
        • Rosner BA
        The average area under correlated receiver operating characteristic curves: a non parametric approach based on generalized two-sample Wilcoxon statistics.
        Appl Stat. 2001; 50: 337-344
        • Perrier A
        • Desmarais S
        • Miron MJ
        • et al.
        Non-invasive diagnosis of venous thromboembolism in outpatients.
        Lancet. 1999; 353: 190-195
        • Perrier A
        • Desmarais S
        • Goehring C
        • et al.
        D-dimer testing for suspected pulmonary embolism in outpatients.
        Am J Respir Crit Care Med. 1997; 156: 492-496
        • Burki NK
        The dead space to tidal volume ratio in the diagnosis of pulmonary embolism.
        Am Rev Respir Dis. 1986; 133: 679-685
        • Olsson K
        • Jonson B
        • Olsson CG
        • et al.
        Diagnosis of pulmonary embolism by measurement of alveolar dead space.
        J Intern Med. 1998; 244: 199-207
        • Anderson JT
        • Owings JT
        • Goodnight JE
        Bedside noninvasive detection of acute pulmonary embolism in critically ill surgical patients.
        Arch Surg. 1999; 134: 869-874
        • Kline JA
        • Meek S
        • Boudrow D
        • et al.
        Use of the alveolar dead space fraction (Vd/Vt) and plasma D-dimers to exclude acute pulmonary embolism in ambulatory patients.
        Acad Emerg Med. 1997; 4: 856-863
        • Kline JA
        • Arunachlam M
        Preliminary study of the capnogram waveform area to screen for pulmonary embolism.
        Ann Emerg Med. 1998; 32: 289-296
        • Johanning JM
        • Veverka TJ
        • Bays RA
        • et al.
        Evaluation of suspected pulmonary embolism utilizing end-tidal CO2and D-dimer.
        Am J Surg. 1999; 178: 98-102
        • Patel MM
        • Rayburn DB
        • Browning JA
        • et al.
        Neural network analysis of the volumetric capnogram to detect pulmonary embolism.
        Chest. 1999; 116: 1325-1332
        • Kline JA
        • Kubin AK
        • Patel MM
        • et al.
        Alveolar dead space as a predictor of severity of pulmonary embolism.
        Acad Emerg Med. 2000; 7: 611-617
        • Elliott CG
        Pulmonary physiology during pulmonary embolism.
        Chest. 1992; 101: 163S-171S
        • Grunkemeier GL
        • Ruyun J
        Receiver operating characteristic curve analysis of clinical risk models.
        Ann Thorac Surg. 2001; 72: 323-326