12th May 2024

A 3-year-old boy presents to the emergency department in the middle of the night with a barking cough, stridor, and difficulty breathing.

A 3-year-old boy presents to the emergency department in the middle of the night with a barking cough, stridor, and difficulty breathing. His parents report that he developed a low-grade fever and cold-like symptoms a few days ago, but the cough and breathing difficulties worsened rapidly over the past few hours. On examination, the child appears anxious and is sitting upright, leaning forward, and breathing with his mouth open.

Which underlying mechanism is most likely responsible for his clinical presentation?