A 42-year-old male with a history of epiglottitis 2 years ago (treated conservatively) presents for emergency appendicectomy. On airway assessment, the patient has a Mallampati score of III, inter-incisor distance of 3 cm, and thyromental distance of 6 cm. Awake fiberoptic intubation is planned. During the procedure, after topicalization with 4% lignocaine spray and 10% lignocaine gel, the patient develops sudden onset of stridor and respiratory distress. Which of the following is the MOST likely cause of this acute deterioration?