Effect of posture on deglutitive biomechanics in healthy individuals

The purpose of this study was to assess displacement of oropharyngeal structures, particularly the hyoid bone and velum, and variations in timing of the pharyngeal stage of swallowing in the upright versus the supine position. Twelve Caucasian adult subjects between 19 and 27 years of age participated. Subjects were recorded swallowing 7 cc of liquid barium in the upright and supine positions. The hyoid bone had a significantly greater amount of anterior displacement while in the supine position compared to that of the upright position (p < 0.01). While in the upright position, the velum comes to a fully elevated position at nearly the same time as the initiation of the pharyngeal swallow (within an average of 27 ms of each other), whereas in the supine position the velum continues to elevate on average 115 ms after the initiation of the pharyngeal swallow. Results indicated a significant difference (p < 0.05) in the amount of velar movement from rest to the fully elevated position between the upright and supine positions for female subjects. The results from the study demonstrate variations in hyoid displacement, velar movement, and bolus movement through the pharynx with respect to the two body positions and the subjects' gender.