[Flow-volume curve as an aid to diagnosis in double aortic arch masquerading as asthma in a young adult].

We describe a young adult with double aortic arch who for several years had experienced stridor during exercise. He had been given a diagnosis of exercise-induced asthma, also known as hyperventilation syndrome. Antiasthmatic drugs, including inhaled corticosteroids and a short-acting bronchodilator, in addition to antidepressants, did not improve his symptoms. He had a history of allergic rhinitis and a familial history of asthma, but no signs of asthma as assessed by expectorated sputum and airway responsiveness (Dmin). However, flow-volume curves demonstrated a pattern consistent with upper airway constriction. Computed tomography confirmed severe tracheal narrowing caused by a double aortic arch. Compressive tracheal narrowing was also evaluated by fiber-optic tracheobronchoscopy. A treadmill exercise study induced respiratory distress with audible stridor that resolved itself without intervention. He underwent surgical division of the left aortic arch, which relieved the stridor during exercise. The flow-volume curve improved but constriction was still indicated even at 1.5 years after surgery. Double aortic arch should be considered in the differential diagnosis of drug-resistant stridor. This case re-emphasizes the value of flow-volume curves for diagnosing upper-airway obstruction.