Tongue protrusion strength in arousal state is predictive of the airway patency in obstructive sleep apnea

Abstract

Contraction of the genioglossus affects either tongue protrusion strength or dilating forces of the upper airway. The upper airway in patients with obstructive sleep apnea (OSA) is thought to collapse during sleep, at least in part because of a sleep related reduction in genioglossus muscle activity. Thus, although tongue protrusion strength by genioglossus activity during sleep contributes to the maintenance of airway patency in patients with OSA, the relationship between tongue protrusion strength in the arousal state and obstructive sleep apnea has not been fully elucidated. Conventional method of tongue protrusion strength cannot be used to evaluate in edentulous subjects and/or subjects with the decreased biting force. In this study, employing a novel measurement method that does not require biting a transducer, we investigated relationships between the tongue protrusion strength and polysomnographic findings. We enrolled twenty normal subjects and 26 subjects with OSA. All subjects completed the measurement of tongue protrusion strength. Each subject with OSA was evaluated by full polysomnography. The degree of tongue protrusion strength was assessed by maximum voluntary contraction against the tongue depressor connected with a strain gauge dynamometer. The tongue protrusion strength was negatively correlated with obstructive apnea time, apnea index (AI) and the percent of sleep stage 2 (r = −0.61, p < 0.0001, r = −0.41 p = 0.03 and r = −0.39 p = 0.04, respectively). Tongue protrusion strength measured in the arousal state is predictive of the airway patency during sleep in OSA.