Cori Jennifer M, Rochford Peter D, O'Donoghue Fergal J, Trinder John, Jordan Amy S
Melbourne School of Psychological Sciences, University of Melbourne, Parkville, Victoria, Australia.
Institute for Breathing and Sleep and Austin Health, Heidelberg, Victoria, Australia.
Sleep. 2017 Nov 1;40(11). doi: 10.1093/sleep/zsx160.
Ventilatory after-discharge (sustained elevation of ventilation following stimulus removal) occurs during sleep but not when hypocapnia is present. Genioglossus after-discharge also occurs during sleep, but CO2 effects have not been assessed. The relevance is that postarousal after-discharge may protect against upper airway collapse. This study aimed to determine whether arousal elicits genioglossus after-discharge that persists into sleep, and whether it is influenced by CO2.
Twenty-four healthy individuals (6 female) slept with a nasal mask and ventilator. Sleep (EEG, EOG, EMG), ventilation (pneumotachograph), end-tidal CO2 (PETCO2), and intramuscular genioglossus EMG were monitored. NREM eucapnia was determined during 5 minutes on continuous positive airway pressure (4 cmH2O). Inspiratory pressure support was increased until PETCO2 was ≥2 mm Hg below NREM eucapnia. Supplemental CO2 was added to reproduce normocapnia, without changing ventilator settings. Arousals were induced by auditory tones and genioglossus EMG compared during steady-state hypocapnia and normocapnia.
Eleven participants (4 female) provided data. Prearousal PETCO2 was less (p < .05) during hypocapnia (40.74 ± 2.37) than normocapnia (43.82 ± 2.89), with differences maintained postarousal. After-discharge, defined as an increase in genioglossus activity above prearousal levels, occurred following the return to sleep. For tonic activity, after-discharge lasted four breaths irrespective of CO2 condition. For peak activity, after-discharge lasted one breath during hypocapnia and 6 breaths during normocapnia. However, when peak activity following the return to sleep was compared between CO2 conditions no individual breath differences were observed.
Postarousal genioglossal after-discharge may protect against upper airway collapse during sleep. Steady-state CO2 levels minimally influence postarousal genioglossus after-discharge.
通气后放电（刺激移除后通气持续升高）出现在睡眠期间，但低碳酸血症存在时则不会出现。颏舌肌后放电也出现在睡眠期间，但尚未评估二氧化碳的影响。其相关性在于觉醒后放电可能防止上气道塌陷。本研究旨在确定觉醒是否会引发持续至睡眠期的颏舌肌后放电，以及它是否受二氧化碳影响。
24名健康个体（6名女性）佩戴鼻罩并使用呼吸机入睡。监测睡眠（脑电图、眼电图、肌电图）、通气（呼吸流速仪）、呼气末二氧化碳分压（PETCO2）和颏舌肌肌内肌电图。在持续气道正压通气（4 cmH2O）下5分钟内确定非快速眼动期正常碳酸血症。增加吸气压力支持直至PETCO2比非快速眼动期正常碳酸血症低≥2 mmHg。添加补充二氧化碳以重现正常碳酸血症，且不改变呼吸机设置。通过听觉音调诱导觉醒，并在稳态低碳酸血症和正常碳酸血症期间比较颏舌肌肌电图。
11名参与者（4名女性）提供了数据。低碳酸血症期间（40.74±2.37）觉醒前PETCO2低于正常碳酸血症期间（43.82±2.89）（p<0.05），觉醒后差异依然存在。后放电定义为颏舌肌活动高于觉醒前水平的增加，在重新入睡后出现。对于紧张性活动，后放电持续4次呼吸，与二氧化碳状态无关。对于峰值活动，低碳酸血症期间后放电持续1次呼吸，正常碳酸血症期间持续6次呼吸。然而，当比较重新入睡后的峰值活动时，在不同二氧化碳状态下未观察到个体呼吸差异。
觉醒后颏舌肌后放电可能在睡眠期间防止上气道塌陷。稳态二氧化碳水平对觉醒后颏舌肌后放电影响极小。
