Asthma or not? The value of flow volume loops in evaluating airflow obstruction.

Large airway obstruction can present with symptoms typically associated with asthma, including cough, dyspnea, or wheezing. Obstruction of the large airways should be considered in the differential diagnosis of patients with difficult to manage asthma, particularly those with known risk factors for tracheal disease, atypical clinical features, or lack of response to standard asthma therapy. Spirometry and flow volume loops are valuable diagnostic tools in this evaluation. This article discusses two cases in which large airway obstruction mimicked asthma and reviews the characteristic flow volume loop patterns associated with large airway lesions.