Upper airway neuromuscular compensation during sleep is defective in obstructive sleep apnea

Abstract

Obstructive sleep apnea is the result of repeated episodes of upper airway obstruction during sleep. Recent evidence indicates that alterations in upper airway anatomy and disturbances in neuromuscular control both play a role in the pathogenesis of obstructive sleep apnea. We hypothesized that subjects without sleep apnea are more capable of mounting vigorous neuromuscular responses to upper airway obstruction than subjects with sleep apnea. To address this hypothesis we lowered nasal pressure to induce upper airway obstruction to the verge of periodic obstructive hypopneas (cycling threshold). Ten patients with obstructive sleep apnea and nine weight-, age-, and sex-matched controls were studied during sleep. Responses in genioglossal electromyography (EMG(GG)) activity (tonic, peak phasic, and phasic EMG(GG)), maximal inspiratory airflow (V(I)max), and pharyngeal transmural pressure (P(TM)) were assessed during similar degrees of sustained conditions of upper airway obstruction and compared with those obtained at a similar nasal pressure under transient conditions. Control compared with sleep apnea subjects demonstrated greater EMG(GG), V(I)max, and P(TM) responses at comparable levels of mechanical and ventilatory stimuli at the cycling threshold, during sustained compared with transient periods of upper airway obstruction. Furthermore, the increases in EMG(GG) activity in control compared with sleep apnea subjects were observed in the tonic but not the phasic component of the EMG response. We conclude that sustained periods of upper airway obstruction induce greater increases in tonic EMG(GG), V(I)max, and P(TM) in control subjects. Our findings suggest that neuromuscular responses protect individuals without sleep apnea from developing upper airway obstruction during sleep.

Dissociation of electromyogram and mechanical response in sleep apnoea during propofol anaesthesia

“…Similarly, abundant observations demonstrated that dilator muscle EMG tends to increase in sleeping OSA patients during hypopnoeas and apnoeas, but this enhanced activity usually fails to restore pharyngeal patency before arousal [4,15,18,[21][22][23][24]. The finding that increasing GG-EMG activity fails to affect airflow below an individual threshold could be demonstrated also during sleep [15].…”

High-Flow, Heated, Humidified Air Via Nasal Cannula Treats CPAP-Intolerant Children With Obstructive Sleep Apnea

“…[37][38][39] The lack of sensation of nasal airflow, as by adenotonsillar hypertrophy or nasal obstruction common in the pediatric population, is associated with increased nasopharyngeal resistance and contributes to OSA, [40][41][42][43][44][45] suggesting that sensation of nasal airflow reduces airway resistance and elicits compensatory increase in pharyngeal tone. 36,46 Therefore, the delivery of heated and humidified air to the nasopharynx at higher than usual flow rates may activate, or reactivate, the protective airway reflex via nasopharyngeal mechanoreceptor or thermoreceptor stimulation, as well as reduce irritation, swelling, and congestion associated with dryness. 40,47 HFNC may reduce dead space and thus improve efficiency of gas exchange.…”

Acute Upper Airway Responses to Hypoglossal Nerve Stimulation during Sleep in Obstructive Sleep Apnea

“…First, the airflow response to peak stimulation was of sufficient magnitude to relieve upper airway obstruction during sleep and reduce sleep apnea severity. In patients with baseline levels of maximal inspiratory airflow during sleep-disordered breathing episodes of 50-250 ml/s, a mean increase of 294 ml/s would likely yield relatively normal levels of peak inspiratory airflow found in asymptomatic snoring and normal nonsnoring individuals during sleep (36,37). Second, flow changed instantaneously with stimulation and increased progressively with stimulus intensity, suggesting that increases in flow are a direct effect of stimulation rather than a result of arousals from sleep.…”