Basic Studies for Quantitative Evaluation Utilizing the Coordination between Swallowing and Respiratory Movements

Abstract

The coordination between swallowing and respiratory movements was studied in twenty-three young, nine elderly and two subjects with dysphagia. The swallowing was produced by administration of a small quantity of water (3 ml). Laryngeal and respiratory movements were recorded by mercury elastic strain gauges placed on the laryngeal cartilage and lateral rib cage, respectively.
In the young subjects, swallowing respiration occurred with retardation of 238±32 msec from the onset of upward movement of the larynx. Further, swallowing respiration shifted to the expiratory phase with retardation of 165±29 (mean±SEM) msec from the onset of downward movement of the larynx. This coordination between swallowing and swallowing respiration was maintained in the elderly subjects. In all the subjects, aspiration was never observed, It is therefore suggested that the coordination is necessary to produce complete swallowing. However, swallowing respiration was preceded by the laryngeal movement in the dysphagia subjects. Therefore the difference occurred with coordination between swallowing and respiration.
These results indicate that the inspiratory phase of swallowing respiration is produced after the elevation of the larynx, which produces complete respiratory passage occlusion and prevents water and bolus from entering the respiratory passage. We conclude that modification of the coordination seems one factor for aspiration and the method used in this research is useful for quantitative evaluation of dysphagia.