Effect of lung inflation on levator veli palatini muscle activity.

Palatal movements play a critical role in regulating oropharyngeal airflow during breathing. We hypothesized that these movements are coordinated with breathing movements via afferent signals from the lung. However, the control of palatal movements in relation to the lung remains unclear. This study was designed to define, by electromyographic techniques, the relationship between palatal movement and lung action during respiration. We performed tracheotomies on 12 mongrel dogs anesthetized with sodium pentobarbital and found that lung inflation augmented the activity of the levator veli palatini muscle (LVP). Two kinds of discharges were recognized during the expiratory pause following lung inflation. One was a continuous, low-amplitude discharge induced during apnea following lung inflation. The other was a transient, high-amplitude discharge which appeared immediately after lung inflation. Both of these response activities were eliminated by bilateral vagotomy. We thus concluded that palatal movements, which can regulate expiratory airflow resistance and cause switching from nasal to oral airflow, are under the control of vagal afferent signals from the lung.