Electromyographic activity of the hyoepiglotticus muscle in dogs

We examined the respiratory-related electromyographic (EMG) activity of the hyoepiglotticus muscle using fine wire bipolar electrodes, inserted perorally in five anaesthetised (IV chloralose) tracheostomised dogs studied in the prone, mouth open position. The integrated HE EMG was measured in arbitrary units (a.u.) during resting breathing via the upper airway, and on a breath-by-breath basis during progressive increases in respiratory drive induced by infusion of CO2 into the inspired gas. The HE demonstrated inspiratory activity which increased linearly in relation to ventilation (r = 0.85 +/- 0.06, p < 0.001) due to an increase in both phasic (8.8 +/- 1.8 to 32.4 +/- 9.2 a.u.) and tonic (0.2 +/- 0.1 to 26.3 +/- 13.3 a.u.) activity (both p < 0.05). In addition, HE EMG developed substantial phasic expiratory activity (1.3 +/- 1.1 to 13.8 +/- 4.4 a.u., p < 0.05). We conclude that the canine HE exhibits inspiratory and expiratory related activity which is augmented during increased respiratory drive. These findings imply active control of epiglottic position during breathing in dogs.