Regulation of Upper Airway Muscle Activity Across the Lung Volume Range in Healthy Young Adults

Speech is a voluntary task that requires fine motor control of ~50 muscles, including muscles of the tongue. One tongue muscle, the genioglossus (GG), has been well studied as an airway dilator that defends the airway in sleep (Remmers 1980). The results of this work highlights the GG's role in airway defense and factors that augment (PaCO2) or inhibit (pulmonary stretch receptor feedback) GG activity (Bailey et al. 2001). We recorded GG electromyographic (EMG) activity across the lung volume range testing the hypothesis that tongue muscle activation declines with lung volume in respiratory and volitional movements. We measured EMG activity across voluntary e.g., meaningful speech (phrases), speech sound devoid of meaning (sustained vowels) and respiratory tasks performed across the vital capacity range (0-80%VC). We show that GG EMG activity is variable across adults but is greatest for tasks performed at the lowest lung volumes. Our results are consistent with results in the rodent that show greatest GG EMG in the absence of lung inflation attributed to release from vagal inhibition (Bailey et al. 2001) and provide additional new insights into airway muscle control during high airflow (speech) relative to low airflow (controlled breathing) tasks