Left tracheal diverticulum showing a central airway obstruction pattern on pulmonary function testing: a case report

Upper respiratory tract disease and intratracheal tumors commonly cause central airway obstruction patterns on the flow–volume curves obtained during pulmonary function testing. We herein describe a rare case in which a central airway obstruction pattern was attributed to slowly progressive tracheal lumen narrowing caused by chronic inflammation in the surrounding area rather than enlargement of the tracheal diverticulum. In our patient, the flow–volume curve demonstrated an expiratory plateau pattern consistent with moderate central airway obstruction, despite no remarkable changes on chest computed tomography (CT). A 73-year-old woman diagnosed with a tracheal diverticulum was followed as an outpatient. Although her subjective symptoms did not worsen, her flow–volume curves obtained during pulmonary function testing indicated central airway obstruction. Annual chest CT showed no significant changes; however, tracheal narrowing due to inflammation around the tracheal diverticulum was suspected. Therefore, surgical treatment, including laser therapy, was considered. We report a rare case of a tracheal diverticulum diagnosed >10 years previously that exhibited a central airway obstruction patterns on the flow–volume curves obtained during pulmonary function testing. Pulmonary function testing and flow–volume curves are valuable for monitoring airway obstruction. In particular, expiratory plateauing on the flow–volume curve may indicate moderate central airway obstruction even when chest CT findings remain unchanged.