Neural memory of the genioglossus muscle during sleep is stage-dependent in healthy subjects and obstructive sleep apnea patients.
J Physiol. 2018 Jul 18;:
Authors: Taranto-Montemurro L, Sands SA, Grace KP, Azarbarzin A, Messineo L, Salant R, White DP, Wellman DA
RATIONALE: Several studies have shown that obstructive sleep apnea (OSA) improves during slow wave sleep (SWS) for reasons that remain unclear. Recent studies have identified forms of neural memory such as short-term potentiation or after-discharge that can occur in response to upper airway obstruction. Neural memory may play a role in the development of stable breathing during SWS by increasing upper airway muscles activity in this sleep stage. We hypothesize that the after-discharge of the genioglossus muscle following upper airway obstruction is enhanced during SWS compared to non-REM stage 2 (N2).
METHODS: During sleep, we performed 5-breath drops in continuous positive airway pressure (CPAP-drop) to simulate obstructive events and reflexively activate the genioglossus. Immediately afterwards, CPAP was returned to an optimal level. Once the post-drop ventilation returned to eupnea, the genioglossus after-discharge was measured as the time it took for genioglossus activity to return to baseline levels.
RESULTS: 171 CPAP-drops were analysed from a group of 16 healthy subjects and 19 OSA patients. A mixed-model analysis showed that after-discharge duration during SWS was 208% (95% CI: 112% to 387%, P = 0.022) greater than during N2 after adjusting for covariates (ventilatory drive, CPAP levels). There was also a non-significant trend for a -35% reduction in after-discharge duration following an arousal versus no-arousal from sleep (95% CI: -59.5% to 5%, P = 0.08).
CONCLUSION: Genioglossus after-discharge is 2-fold greater in SWS versus N2, which could partly explain the breathing stabilization described in OSA patients during this sleep stage. This article is protected by copyright. All rights reserved.
PMID: 30022493 [PubMed – as supplied by publisher]