This study tests the hypothesis that the surface electromyographic (EMG) activity of upper airway dilators would respond to inspiratory loading in a healthy humans model of ventilator trigger asynchrony. EMG activity was measured in levator alae-nasi, genioglossus, parasternal, scalene and diaphragm muscles in eight subjects. They breathed quietly through a face mask and then were connected to a mechanical ventilator. Recordings were performed during nasal breathing against negative pressure triggers (-2.5%, -5% and -10% of maximal inspiratory pressure) and during oro-nasal breathing with a "-10% trigger". Scalene, alae-nasi and genioglossus EMG activity level increased with the "-10% trigger". While no breathing route dependence was found in scalene, the significant increase was only found for nasal breathing in alae-nasi and for oro-nasal breathing in genioglossus. The dyspnea intensity was significantly correlated with the EMG activity level of these three muscles. Surface EMG of airway dilator muscles could be used as a complementary tool to assess inspiratory drive during mechanical ventilation.
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