Symptoms of upper airway obstruction at presentation include positional dyspnea, exercise induced dyspnea, cough, wheeze, chest discomfort, stridor, and hemoptysis. Symptoms tend to correlate with tracheal diameter; exercise-induced symptoms usually occur at 8 mm (normal diameter, 10 to 25 mm), stridor at rest at 5 mm, and a marked decrease in peak flow at 5 mm. On physical examination in a patient with upper airway obstruction, one may hear wheeze, which is a high pitched sound or vibration that is continuous for 250 ms. Wheeze can be local/diffuse, inspiratory/expiratory, or episodic/chronic. Stridor is a subset of wheezing described as a loud musical sound of constant pitch heard predominantly during inspiration, and is most typical for patients with extrathoracic airway obstruction. Our patient had stridor only when challenged with exercise. The mechanism of stridor in our patient is based on the Bernoulli principle; airway velocity must increase through a constricted region to maintain a constant flow rate. The increase in velocity leads to a decreased airway pressure in the constricted region and allows for further collapse in that constricted region. Thus, our patient, during exercise, had increased velocity across the stenotic area that resulted in decreased airway pressure, a larger discrepancy between the atmospheric and tracheal pressures, and a resultant increase in stridor.