Amis T C, O'Neill N, Van der Touw T, Brancatisano A
Department of Respiratory Medicine, Westmead Hospital, NSW, Australia.
Respir Physiol. 1996 Jul;104(2-3):169-77. doi: 10.1016/0034-5687(96)00029-1.
We examined the integrated (MTA) electromyographic activity (EMG) of the hyoepiglotticus (HE) muscle and the soft palate muscles (SPM) during CO2 administration in 6 anaesthetised prone, mouth open dogs. As ventilation increased nasal flow (VN) as a percentage of total flow (VT), i.e. VN/VT%, decreased. Breath-by-breath peak inspiratory and peak expiratory HE EMG activity was strongly and inversely correlated with VN/VT% (both r > 0.8, p < 0.001), whereas the correlation between SPM MTA EMG activity and VN/VT% was highly variable. Severing of the HE muscles halved the rate at which VN/VT% was reduced with respect to increasing ventilation while electrical stimulation of HE muscle contraction resulted in a fall in VN/VT% to near zero levels. Active control of epiglottic position appears to be an important mechanism controlling the patency of the epiglottic-soft palate seal and thus the oronasal partitioning of airflow in dogs.
