Effects of swallowing on the pattern of continuous respiration in human adults

Swallowing must interact with respiration so that a swallow causes minimal or no disturbance of continual respiration. In order to study the coordinate control of swallowing and respiration, we investigated the effects of spontaneous and water-induced swallows on the pattern of ongoing respiration in 8 adult human subjects. Swallows were identified by submental electromyograms and visual observation of the characteristic laryngeal movements. Both spontaneous and water-induced swallows occurred during all phases of the respiratory cycle, but approximately 80% of swallows occurred during the expiratory phase. No essential difference between spontaneous and water-induced swallows in the effects of the swallowing on respiration was observed. A swallow coinciding with the expiratory phase prolonged the duration of the same expiration that had been interrupted, whereas a swallow coinciding with the inspiratory phase interrupted the inspiration immediately and was followed by a short expiratory duration. There was a positive correlation between the time from the onset of the expiration to the onset of the swallowing and the duration of the expiration interrupted by the swallowing, indicating that the later the onset of the swallowing takes place, the more is the expiration prolonged. The duration of respiratory cycle in the breaths immediately following the swallow was not affected by the swallow, but there was a considerable increase in the tidal volume of the postswallowing breaths. These results suggest that the changes in respiratory pattern induced by the act of swallowing may depend on some mechanism that regulates the coordination of respiration and swallowing.