Sublingual electrical stimulation of the tongue during wakefulness and sleep

Pharyngeal obstruction in patients with obstructive sleep apnea (OSA) is th ought to result from decreased upper airway muscle tone during sleep. The g oal of the present study was to estimate the role of the tongue muscles in maintaining pharyngeal patency during sleep. Using non-invasive, sub-lingua l surface electrical stimulation (ES), we measured tongue protrusion force during wakefulness and upper airway resistance during sleep in seven health y subjects and six patients with OSA. During wakefulness, ES produced simil ar protrusion forces in healthy subjects and patients with OSA. ES of the a nterior sublingual surface, causing preferential contraction of the geniogl ossus, resulted in smaller effects than combined ES of the anterior and lat eral surface, which also stimulated tongue retractors. During sleep, trans- pharyngeal resistance decreased and peak inspiratory flow rate increased fr om 319 +/- 24 to 459 +/- 27 and from 58 +/- 16 to 270 +/- 35 ml/sec for hea lthy subjects and OSA patients, respectively (P < 0.001). However, ES was u sually unsuccessful in reopening the upper airway in the presence of comple te apneas. We conclude that non-invasive ES of the tongue improves flow dyn amics during sleep. Combined activation of tongue protrusors and retractors may have a beneficial mechanical effect. The magnitude of responses observ ed suggests that in addition to the stimulated muscles, other muscles and/o r forces have a substantial impact on pharyngeal patency. (C) 2001 Elsevier Science B.V. All rights reserved.