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.