RESPIRATORY-RELATED ACTIVITY OF SOFT PALATE MUSCLES - AUGMENTATION BYNEGATIVE UPPER AIRWAY PRESSURE

We studied respiratory-related activity of the soft palate muscles in 10 anesthetized tracheostomized supine dogs. Moving time average (MTA) electromyographic (EMG) activity was measured in the palatinus (PAL), levator veli palatini (LP), and tenser veli palatini (TP) with bipola r fine-wire electrodes and in the diaphragm with bipolar hook electrod es. Measurements were made during tracheostomy breathing and nasal bre athing with the mouth sealed (NB). During tracheostomy breathing, all soft palate muscles displayed respiratory-related phasic inspiratory a nd expiratory as well as tonic EMG activity. During NB, peak inspirato ry EMG activity increased in PAL, LP, and TP because of an increase in both phasic inspiratory and tonic MTA activity. In contrast, phasic e xpiratory activity did not change. A constant negative pressure equal to peak inspiratory tracheal pressure during NB was applied to the cau dal end of the isolated upper airway with the nose occluded. This was associated with soft palate muscle responses qualitatively similar to the responses during NB but accounted for only 39, 25, and 32% of the magnitude of the peak inspiratory MTA EMG responses to NB in PAL, LP, and TP, respectively. Our results demonstrate that the soft palate mus cles exhibit respiratory-related activity in common with other upper a irway muscles. Furthermore, such activity is augmented in each soft pa late muscle during NB, and negative upper airway pressure makes a subs tantial contribution to the recruitment of soft palate muscle activity .