Electrical stimulation of the lingual musculature in obstructive sleep apnea

The influence of lingual muscle activity on airflow dynamics in the upper airway was examined in nine patients with obstructive sleep apnea. Muscles that retract the tongue (hyoglossus and styloglossus) and protrude the tongue (genioglossus) were selectively stimulated electrically during sleep with fine wire electrodes placed intramuscularly transorally. We confirmed that stimulation with 50 Hz and 40-mu s pulse duration did not elicit changes in electroencephalographic patterns or heart rate or alter airflow after the stimulation burst had ceased. The highest stimulus intensity that did not arouse patients from sleep was then utilized to examine the effect of lingual muscle recruitment on airflow dynamics during steady-state periods of inspiratory airflow limitation. When applying a stimulus burst during single inspirations, maximal inspiratory airflow decreased by 239 +/- 177 ml/s (P < 0.05) during retractor stimulation, whereas maximal inspiratory airflow increased by 217 +/- 93 ml/s during protrusor stimulation (P < 0.001) compared with breaths immediately before and after the stimulated breath. When consecutive inspirations were stimulated repeatedly, protrusor stimulation decreased the frequency of obstructive breathing episodes in four patients breathing at 3.9 +/- 3.4 (SD) cmH(2)O nasal pressure. The findings suggest that stimulation of the lingual muscles can increase or decrease airflow depending on the specific muscles stimulated without arousing patients from sleep.