A 23-year-old woman presents to the clinic for repeat assessment of wheezing symptoms and shortness of breath on exertion. She reports no "triggers" that bring on the symptoms, and they usually only occur in the spring and then resolve spontaneously. She is a lifetime nonsmoker and feels well in between episodes. There is no personal or family history of atopy or asthma. On physical examination, the vital signs and cardiac exam are normal. The lungs are clear on auscultation and there is no wheeze on forced expiration. Which of the following is the most likely mechanism of wheezing in this woman?