Neuroscience Research Australia (NeuRA), Sydney, NSW, Australia.
School of Medical Sciences, University of New South Wales, Sydney, NSW, Australia.
J Physiol. 2020 Feb;598(3):567-580. doi: 10.1113/JP278433. Epub 2020 Jan 15.
Impaired pharyngeal anatomy and increased airway collapsibility is a major cause of obstructive sleep apnoea (OSA) and a mediator of its severity. Upper airway reflexes to changes in airway pressure provide important protection against airway closure. This study shows increased pharyngeal collapsibility and attenuated genioglossus reflex responses during expiration in people with OSA.
Upper airway collapse contributes to obstructive sleep apnoea (OSA) pathogenesis. Pharyngeal dilator muscle activity varies throughout the respiratory cycle and may contribute to dynamic changes in pharyngeal collapsibility. However, whether upper airway collapsibility and reflex responses to changes in airway pressure vary throughout the respiratory cycle in OSA is unclear. Thus, this study quantified differences in upper airway collapsibility and genioglossus electromyographic (EMG) activity and reflex responses during different phases of the respiratory cycle. Twelve middle-aged people with OSA (2 female) were fitted with standard polysomnography equipment: a nasal mask, pneumotachograph, two fine-wire intramuscular electrodes into the genioglossus, and a pressure catheter positioned at the epiglottis and a second at the choanae (the collapsible portion of the upper airway). At least 20 brief (∼250 ms) pressure pulses (∼-11 cmH O at the mask) were delivered every 2-10 breaths during four conditions: (1) early inspiration, (2) mid-inspiration, (3) early expiration, and (4) mid-expiration. Mean baseline genioglossus EMG activity 100 ms prior to pulse delivery and genioglossus reflex responses were quantified for each condition. The upper airway collapsibility index (UACI), quantified as 100 × (nadir choanal - epiglottic pressure)/nadir choanal pressure during negative pressure pulses, varied throughout the respiratory cycle (early inspiration = 43 ± 25%, mid-inspiration = 29 ± 19%, early expiration = 83 ± 19% and mid-expiration = 95 ± 11% (mean ± SD) P < 0.01). Genioglossus EMG activity was lower during expiration (e.g. mid-expiration vs. mid-inspiration = 76 ± 23 vs. 127 ± 41% of early-inspiration, P < 0.001). Similarly, genioglossus reflex excitation was delayed (39 ± 11 vs. 23 ± 7 ms, P < 0.001) and reflex excitation amplitude attenuated during mid-expiration versus early inspiration (209 ± 36 vs. 286 ± 80%, P = 0.009). These findings may provide insight into the physiological mechanisms of pharyngeal collapse in OSA.
咽腔解剖结构异常和气道 collapsibility 增加是阻塞性睡眠呼吸暂停（OSA）的主要原因，也是其严重程度的中介因素。上气道对气道压力变化的反射为气道闭合提供了重要保护。本研究显示，OSA 患者在呼气时咽腔 collapsibility 增加，颏舌肌反射反应减弱。
上气道塌陷导致阻塞性睡眠呼吸暂停（OSA）发病机制。咽腔扩张肌的活动在整个呼吸周期中发生变化，可能导致咽腔 collapsibility 的动态变化。然而，OSA 患者在整个呼吸周期中，上气道 collapsibility 和对气道压力变化的反射反应是否存在差异尚不清楚。因此，本研究定量分析了不同呼吸周期阶段上气道 collapsibility 和颏舌肌肌电图（EMG）活动及反射反应的差异。12 名中年 OSA 患者（2 名女性）佩戴标准多导睡眠图设备：鼻罩、呼吸量计、两根细金属丝肌内电极置于颏舌肌，以及一个位于会厌和另一个位于后鼻孔的压力导管（上气道可塌陷部分）。在四种情况下，每 2-10 次呼吸时，每呼吸 20 次左右（面罩约-11cmH2O）的短（约 250ms）压力脉冲：（1）早期吸气，（2）中期吸气，（3）早期呼气，和（4）中期呼气。在脉冲输送前 100ms 记录颏舌肌肌电图的基线平均活性，并对每种情况进行定量分析。上气道 collapsibility 指数（UACI）定义为负压脉冲期间（下鼻甲-会厌压力）/（下鼻甲压力）的 100×，在整个呼吸周期中变化（早期吸气=43±25%，中期吸气=29±19%，早期呼气=83±19%，中期呼气=95±11%（均值±标准差）P<0.01）。呼气时颏舌肌 EMG 活性较低（例如，中期呼气与中期吸气相比=76±23%与 127±41%），P<0.001）。同样，颏舌肌反射兴奋延迟（39±11ms 与 23±7ms，P<0.001），中期呼气时反射兴奋幅度减弱（209±36%与 286±80%，P=0.009）。这些发现可能为 OSA 患者咽腔塌陷的生理机制提供了深入的了解。
