The influence of CO2 on genioglossus muscle after-discharge following arousal from sleep : Hypocapnia and genioglossus muscle after-discharge.

The influence of CO2 on genioglossus muscle after-discharge following arousal from sleep : Hypocapnia and genioglossus muscle after-discharge.

Sleep. 2017 Oct 06;:

Authors: Cori JM, Rochford PD, O'Donoghue FJ, Trinder J, Jordan AS

Abstract
Objectives: 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 post-arousal 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.
Methods: 24 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 five minutes on continuous positive airway pressure (4cmH2O). Inspiratory pressure support was increased until PETCO2 was ≥2mmHg 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.
Results: 11 participants (4 female) provided data. Pre-arousal PETCO2 was less (p<.05) during hypocapnia (40.74±2.37) than normocapnia (43.82±2.89), with differences maintained post-arousal. After-discharge, defined as an increase in genioglossus activity above pre-arousal 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 six breaths during normocapnia. However, when peak activity following the return to sleep was compared between CO2 conditions no individual breath differences were observed.
Conclusions: Post-arousal genioglossal after-discharge may protect against upper airway collapse during sleep. Steady-state CO2 levels minimally influence post-arousal genioglossus after-discharge.

PMID: 29029284 [PubMed - as supplied by publisher]

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