Sé riè s, F., and I. Marc. Selected Contribution: Influence of genioglossus tonic activity on upper airway dynamics assessed by phrenic nerve stimulation. J Appl Physiol 92: [418][419][420][421][422][423] 2002.-Upper airway (UA) dynamics can be evaluated during wakefulness by using electrical phrenic nerve stimulation (EPNS) applied at end-expiration during exclusive nasal breathing by dissociating twitch flow and phasic activation of UA muscles. This technique can be used to quantify the

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... nce of nonphasic electromyographic (EMG) activity on UA dynamics. UA dynamics was characterized by using EPNS when increasing tonic EMG activity with CO 2 stimulation in six normal awake subjects. Instantaneous flow, esophageal and nasopharyngeal pressures, and genioglossal EMG activity were recorded during EPNS at baseline and during CO 2 ventilatory stimulation. The proportion of twitches presenting an inspiratory-flow limitation pattern decreased from 100% at baseline to 78.7 Ϯ 21.4% (P ϭ 10 Ϫ4 ) during CO2 rebreathing. During CO2 stimuli, maximal inspiratory twitch flow (V Imax) of flow-limited twitches significantly rose, with the driving pressure at which flow limitation occurred being more negative. For the group as a whole, the increase in V Imax and the decrease in pressure were significantly correlated with the rise in endexpiratory EMG activity. UA stability assessed by EPNS is dramatically modified during CO 2 ventilatory stimulation. Changes in tonic genioglossus EMG activity significantly contribute to the improvement in UA stability. electromyographic tonic activity; diaphragm twitch; electrical phrenic nerve stimulation UPPER AIRWAY (UA) STRUCTURES are largely involved in determining ventilatory characteristics and breathing stability. Whereas nasal and laryngeal levels are supported by rigid cartilaginous or bony structures, pha-