The Effect of Chin-Down Position and Bolus Volume on Swallow-Induced Respiratory Measures in Young Healthy Adults

Abstract

Though head positioning strategies are widely used in the rehabilitation of swallowing dysfunction, little is yet known about its effect on the respiratory-swallow interaction. We hypothesised that a chin-down positioning would alter the respiratory behaviour in healthy young individuals. In a within-group study, we compared the characteristics of nasal airflow and its coordination with swallow events before, after, and during the swallow of liquid in a group of 30 young healthy individuals. The measures were obtained with simultaneous recording of surface electromyography, nasal airflow, and swallow sound recording during spontaneous drinking of 5, 15, and 20 ml water. Duration of swallowing apnoea (SAD) and the slope (Spre & Spost), duration (Dpre & Dpost), and direction (Expiration/Inspiration) of respiratory phases surrounding the apnoea were obtained. The statistical comparisons revealed that chin-down position significantly prolonged breathing arrest (SAD) and pharyngeal transit time (event interval) during swallow. The Dpost of large volume swallows were shorter indicating a quick resumption of breathing, indicating high post-swallow respiratory demand. The other statistically significant differences in various event intervals suggested the influence of chin-down position and bolus volume on the oral and pharyngeal transit time. Also, there was an increase in the incidence of inspiratory swallows in the chin-down position with large bolus volumes. We conclude that the chin-down position can provide longer airway decoupling but may increase the respiratory demand during swallows. Use of smaller bolus volumes should be recommended for chin-down swallows in persons with respiratory distress and dysphagia.