Pulmonary thromboembolism is a common condition. Its diagnosis usually requires pulmonary scintigraphy, computed angiotomography, pulmonary arteriography and, in order to rule out other diagnoses, the measurement of D-dimer levels. Due to the fact that these diagnostic methods are not available in most Brazilian hospitals, the validation of other diagnostic techniques is of fundamental importance. We describe a case of a woman with chronic pulmonary hypertension who experienced a pulmonary thromboembolism event. Pulmonary scintigraphy, computed angiotomography and pulmonary arteriography were used in the diagnosis. The D-dimer test result was positive. Volumetric capnography was performed at admission and after treatment. The values obtained were compared with the imaging test results.345328332Owings, J.T., Kraut, E., Battistella, F., Cornelius, J.T., O'Malley, R., Timing of the occurrence of pulmonary embolism in trauma patients (1997) Arch Surg, 132 (8), pp. 862-866. , discussion 866-7Chemla, D., Castelain, V., Hervé, P., Lecarpentier, Y., Brimioulle, S., Haemodynamic evaluation of pulmonary hypertension (2002) Eur Respir J, 20 (5), pp. 1314-1331Moreira, M.M., Terzi, R.G.G., Vieira, R.W., Petrucci Jr, O., Fração tardia do espaço morto (fDlate) antes e após embolectomia pulmonar. (2005) Rev Bras Cir Cardiovasc, 20 (1), pp. 81-84Rodger, M.A., Jones, G., Rasuli, P., Raymond, F., Djunaedi, H., Bredeson, C.N., Steady-state end-tidal alveolar dead space fraction and D-dimer: Bedside tests to exclude pulmonary embolism (2001) Chest, 120 (1), pp. 115-119Eriksson, L., Wollmer, P., Olsson, C.G., Albrechtsson, U., Larusdottir, H., Nilsson, R., Diagnosis of pulmonary embolism based upon alveolar dead space analysis (1989) Chest, 96 (2), pp. 357-362Grimby, G., Söderholm, B., Spirometric studies in normal subjects. III. Static lung volumes and maximum voluntary ventilation in adults with a note on physical fitness (1963) Acta Med Scand, 173 (2), pp. 199-206Thys, F., Elamly, A., Marion, E., Roeseler, J., Janssens, P., El Gariani, A., PaCO(2)/ETCO(2) gradient: Early indicator of thrombolysis efficacy in a massive pulmonary embolism (2001) Resuscitation, 49 (1), pp. 105-108Verschuren, F., Heinonen, E., Clause, D., Roeseler, J., Thys, F., Meert, P., Volumetric capnography as a bedside monitoring of thrombolysis in major pulmonary embolism (2004) Intensive Care Med, 30 (11), pp. 2129-2132