Mechanisms of oronasal airflow partitioning in dogs.
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.
Department of Respiratory Medicine, Westmead Hospital, NSW, Australia.
T C
TC
Amis
N
N
O'Neill
T
T
Van der Touw
A
A
Brancatisano
D000768:Anesthesia, General; D000818:Animals; D004285:Dogs; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D007821:Laryngeal Muscles / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D009055:Mouth / Q000033:anatomy & histology / Q000502:physiology*; D009296:Nasal Cavity / Q000033:anatomy & histology / Q000502:physiology*; D010160:Palate, Soft / Q000033:anatomy & histology / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology*; D012132:Respiratory Muscles / Q000294:innervation / Q000502:physiology*