A 24-year-old elite female athlete presents with episodic dyspnea and chest tightness during high-intensity training, often accompanied by inspiratory stridor. She has been treated for presumed asthma without improvement. Spirometry with flow-volume loop shows flattening of the inspiratory limb with normal expiratory flow. Flexible laryngoscopy performed during an acute episode reveals paradoxical adduction of the vocal cords. The pattern marked **D** in the diagram suggests this vocal cord pathology. Which of the following is the most appropriate initial management for this condition?