We tested the hypothesis that stimulating the genioglossus by repetitive transcranial magnetic stimulation (rTMS) during the ascendant portion of the inspiratory flow of airflow-limited breaths would sustain the recruitment of upper airway dilator muscles over time and improve airway dynamics without arousing obstructive sleep apnea (OSA) patients. In a cross-sectional design, 9 OSA patients underwent a rTMS trial during stable non-rapid eye movement (NREM) sleep. Submental muscle motor threshold (SUBMT) and motor-evoked potential were evaluated during wakefulness and sleep. During NREM sleep, maximal inspiratory flow, inspiratory volume, inspiratory time, shifts of electroencephalogram frequency and pulse rate variability were assessed under three different stimulation paradigms completed at 1.2 sleep SUBMT stimulation output: 1) 5Hz-08 (stimulation frequency: 5 Hz; duration of train stimulation: 0.8 s), 2) 25Hz-02 (stimulation frequency: 25 Hz; duration of train stimulation: 0.2 s) and 3) 25Hz-04 (stimulation frequency: 25 Hz; duration of train stimulation: 0.4 s). SUBMT increased during NREM sleep (wakefulness: 23.8 ± 6.1%; NREM: 26.8 ± 5.2%; P=0.001). Two distinct airflow patterns were observed in response to rTMS: with and without initial airflow drops, without other airflow variables change regardless the stimulation paradigm applied. Finally, rTMS-induced cortical and/or autonomic arousal were observed in 36%, 26% and 35% of all delivered rTMS trains during 5Hz-08, 25Hz-02 and 25Hz-04 stimulation paradigms, respectively. In conclusion, rTMS does not provide any airflow improvement of flow-limited breaths as seen with single and consecutive TMS of upper airway dilator muscles. However, rTMS trains were free of arousals in the majority of cases.
- upper airway dilator muscles
- obstructive sleep apnea
- repetitive transcranial magnetic stimulation
- motor-evoked potentials
- Copyright © 2015, Journal of Applied Physiology