Effects of tongue electrical stimulation on pharyngeal mechanics in anaesthetized patients with obstructive sleep apnoea

The tongue plays a significant role in the maintenance of a patent airway. The purpose of this study was to examine the effects of tongue musculature contraction on the static mechanical properties of the pharynx in patients with obstructive sleep apnoea (OSA). During hyperventilation-induced apnoea in seven OSA patients anaesthetized with sevoflurane, the static pressure/area relationships of the oropharynx were obtained by means of step changes in airway pressure while endoscopically measuring cross-sectional area. At each airway pressure, the tongue was electrically stimulated via electrodes placed bilaterally. Tongue electrical stimulation (TES) did not further dilate the oropharyngeal area at higher airway pressure (3.2+/-1.9 versus 3.0+/-2.1 cm(2)), although the narrowed oropharyngeal area at lower airway pressures increased during TES (0.8+/-9.0) versus 1.7+/-1.8 cm(2), p<0.05). Accordingly, the slope of the pressure/area relationship decreased during TES (0.24+/-0.20 versus 0.12+/-0.09 cm(2).cmH(2)O(-1), p<0.05). In conclusion, electrical stimulation of the tongue stiffens the retroglossal airway wall in patients with obstructive sleep apnoea.