Modulation of swallowing reflex by lung volume changes

We investigated the effects of changes in lung volume on coordination of re spiration and swallowing in 11 healthy subjects. Swallowing reflexes were e licited by bolus injections of a small amount of distilled water(1 mi) and by continuous infusion of distilled water (3 ml/min) into the pharynx at th ree different levels of lung volume. The lung volume was changed by applica tion of negative extrathoracic pressure (0, -20, and -40 cm H2O). We found that increases in lung volume prolonged the latency of swallows elicited by bolus injection of water and decreased the number of swallows during conti nuous infusion of water. In addition, the preponderant coupling of swallows with the expiratory phase observed before application of negative extratho racic pressure was lost during application of negative extrathoracic pressu re. These results may indicate that lung inflation has an inhibitory influe nce on the swallowing reflex, and modulates the timing of swallowing in ref erence to the respiratory cycle.