ELECTRICAL-STIMULATION OF THE LINGUAL MUSCULATURE IN OBSTRUCTIVE SLEEP-APNEA

The influence of lingual muscle activity on airflow dynamics in the up per airway was examined in nine patients with obstructive sleep apnea. Muscles that retract the tongue (hyoglossus and styloglossus) and pro trude the tongue (genioglossus) were selectively stimulated electrical ly during sleep with fine wire electrodes placed intramuscularly trans orally. We confirmed that stimulation with 50 Hz and 40-mu s pulse dur ation did not elicit changes in electroencephalographic patterns or he art 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 li mitation. When applying a stimulus burst during single inspirations, m aximal inspiratory airflow decreased by 239 +/- 177 ml/s (P < 0.05) du ring retractor stimulation, whereas maximal inspiratory airflow increa sed by 217 +/- 93 ml/s during protrusor stimulation (P < 0.001) compar ed with breaths immediately before and after the stimulated breath. Wh en consecutive inspirations were stimulated repeatedly, protrusor stim ulation decreased the frequency of obstructive breathing episodes in f our 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 with out arousing patients from sleep.