Biphasic flow volume curve due to obstruction of main bronchus by bronchogenic cyst

Abstract The biphasic curve or bicompartmental flow volume obtained during the forced maneuver is the characteristic of the obstruction of a main bronchus. We report the case of a 64-year-old woman, with progressive dyspnea, coughing and wheezing localized in the left hemithorax, who had been diagnosed with bronchial asthma and was not responding to treatment. The flow volume curve showed an end inspiratory arm configuration compatible with unilateral obstruction of a main bronchus. Chest computed tomography with three-dimensional reconstruction showed a left main bronchus compression by a cyst formation, the bronchoscopy confirmed the obstruction. At surgery a bronchogenic cyst was resected. After the procedure, dyspnea, cough, expectoration and wheezing disappeared. The postoperative flow volume curve showed a normal configuration. We are not aware of a previous report of a biphasic flow volume curve due to a mediastinal bronchogenic cyst. The flow volume curve is a noninvasive procedure useful in the diagnosis of unilateral obstruction of a main bronchus.