A 50-year-old male returns to see his sleep physician 1 year after undergoing upper airway surgery in order to treat his obstructive sleep apnea (OSA). He is still experiencing daytime sleepiness and his partner reports that while his snoring has improved since the surgery, it is still present and disrupting their sleep. A repeat sleep study shows the surgery has reduced the apnea-hypopnea index by 10 events/hr (from 35 to 25 events/hr).

Which of the following endotypes best explains this patient’s poor response to upper airway surgery?