Genioglossus Motor Control following the Return to Sleep after Brief Arousal
Authors List
Amy S Jordan1,2, Andrew Dawson1, Joanne Avraam1,2, Christian L Nicholas1,2, Amanda Kay1, Therese Thornton1, Nicole Feast1, Monika Fridgant1, Fergal J O’Donoghue2,3, and John Trinder1*.
1. Melbourne School of Psychological Sciences, The University of Melbourne, Parkville, Victoria, Australia. (Where the work was performed.)
2. Department of Respiratory and Sleep Medicine and Institute for Breathing and Sleep, Austin Health, Heidelberg, Victoria, Australia.
3. Faculty of Medicine, The University of Melbourne, Parkville, Victoria, Australia.
* Deceased
Rationale
Arousal from sleep has been shown to elicit a prolonged increase in genioglossus muscle activity that persists following the return to sleep and may protect against airway collapse. We hypothesised that this increased genioglossal activity following return to sleep after an arousal is due to persistent firing of inspiratory single motor units (MUs) recruited during the arousal.
Methods
34 healthy participants were studied overnight while wearing a nasal mask/pneumotachograph to measure ventilation and with 4 intramuscular genioglossus MU electrodes. During stable N2 and N3 sleep, auditory tones were played to induce brief (3-15s) AASM arousals. Ventilation and genioglossus MUs were quantified for 5 breaths before the tone, during the arousal and for 10 breaths after the return to sleep.
Results
A total of 1089 tones were played and gave rise to 239 MUs recorded across arousal and the return to sleep in 20 participants (age 23±4.2 years and BMI 22.5±2.2kg/m2). Ventilation was elevated above baseline during arousal and the first post-arousal breath (p<0.001) whereas genioglossal activity was elevated for 5 breaths following the return to sleep (p<0.001). Increased genioglossus activity on return to sleep occurred due to recruitment of previously silent MUs with an inspiratory pattern, as well as MUs with an inspiratory pattern developing an expiratory component. Small 2-3Hz increases in firing frequency of inspiratory modulated MUs also occurred. However, MUs with an Expiratory or constant firing pattern (Tonic) were not recruited at arousal and either did not change firing frequency or had reduced firing frequency.
Conclusions
The motor control of inspiratory MUs appears different to that of expiratory/tonic MUs during arousal and on the return to sleep. The prolonged increase in genioglossus activity that occurs on return to sleep after brief arousal from sleep is a result of increased activity of inspiratory MUs. Strategies to increase inspiratory genioglossus MU activity may be beneficial in preventing airway collapse.
Funding: This work was funded by the Australian Research Council: Discovery Project Grant 160101398
Amy S Jordan1,2, Andrew Dawson1, Joanne Avraam1,2, Christian L Nicholas1,2, Amanda Kay1, Therese Thornton1, Nicole Feast1, Monika Fridgant1, Fergal J O’Donoghue2,3, and John Trinder1*.
1. Melbourne School of Psychological Sciences, The University of Melbourne, Parkville, Victoria, Australia. (Where the work was performed.)
2. Department of Respiratory and Sleep Medicine and Institute for Breathing and Sleep, Austin Health, Heidelberg, Victoria, Australia.
3. Faculty of Medicine, The University of Melbourne, Parkville, Victoria, Australia.
* Deceased
Rationale
Arousal from sleep has been shown to elicit a prolonged increase in genioglossus muscle activity that persists following the return to sleep and may protect against airway collapse. We hypothesised that this increased genioglossal activity following return to sleep after an arousal is due to persistent firing of inspiratory single motor units (MUs) recruited during the arousal.
Methods
34 healthy participants were studied overnight while wearing a nasal mask/pneumotachograph to measure ventilation and with 4 intramuscular genioglossus MU electrodes. During stable N2 and N3 sleep, auditory tones were played to induce brief (3-15s) AASM arousals. Ventilation and genioglossus MUs were quantified for 5 breaths before the tone, during the arousal and for 10 breaths after the return to sleep.
Results
A total of 1089 tones were played and gave rise to 239 MUs recorded across arousal and the return to sleep in 20 participants (age 23±4.2 years and BMI 22.5±2.2kg/m2). Ventilation was elevated above baseline during arousal and the first post-arousal breath (p<0.001) whereas genioglossal activity was elevated for 5 breaths following the return to sleep (p<0.001). Increased genioglossus activity on return to sleep occurred due to recruitment of previously silent MUs with an inspiratory pattern, as well as MUs with an inspiratory pattern developing an expiratory component. Small 2-3Hz increases in firing frequency of inspiratory modulated MUs also occurred. However, MUs with an Expiratory or constant firing pattern (Tonic) were not recruited at arousal and either did not change firing frequency or had reduced firing frequency.
Conclusions
The motor control of inspiratory MUs appears different to that of expiratory/tonic MUs during arousal and on the return to sleep. The prolonged increase in genioglossus activity that occurs on return to sleep after brief arousal from sleep is a result of increased activity of inspiratory MUs. Strategies to increase inspiratory genioglossus MU activity may be beneficial in preventing airway collapse.
Funding: This work was funded by the Australian Research Council: Discovery Project Grant 160101398
