Abstract
RATIONALE: Most children with obstructive sleep apnea are able to sustain stable breathing during portions of sleep, despite an anatomic predisposition toward airway collapse. This suggests that additional determinants of airway patency are active, such as neuromuscular compensation. OBJECTIVES/METHODS: Using a custom intraoral surface electrode to record pharyngeal dilator muscle activity (the genioglossus [EMGgg]), we evaluated the muscle, ventilatory, and arousal responses to negative-pressure challenges during sleep in 19 healthy control children. MEASUREMENTS AND MAIN RESULTS: In response to these challenges, we observed (1) marked variability in individual EMGgg responsiveness (peak EMGgg [mean+/-SD], 214+/-101% baseline), which was consistent within subjects; (2) a relationship between EMGgg activity and inspiratory flow and airway collapsibility; (3) reflex increases in flow (peak flow increase from challenge breaths 1-5 [mean+/-SD], 49+/-41% baseline) and respiratory rate often sufficient to sustain minute ventilation near baseline levels, without arousal; and (4) arousal threshold to be highest in stage 4, intermediate in stage 2, and lowest in REM sleep. CONCLUSIONS: Healthy children have wide variation in upper airway neuromuscular compensatory responses and arousal thresholds that could represent intermediate phenotypes affecting the expression of sleep apnea. Children with robust upper airway neuromuscular responsiveness, or a very high arousal threshold, may be able to sustain minute ventilation when challenged with negative airway pressure.