[Objective] Pharyngeal swallows consist of consecutive pharyngeal swallows (CPS) and isolated pharyngeal swallows (IPS). CPS is a swallow with consecutive oral and pharyngeal stages, while IPS is a swallow without oral bolus transport by the tongue. The objective of this study is to compare the trajectory of the hyoid bone between CPS and IPS.
[Subjects and Methods] Fifty-three healthy subjects who gave informed consent were enrolled in this study. A videofluoroscopic examination of swallowing (VF) was performed in lateral projection in an upright posture. A mixture of semi-solid food and liquid was administered two times to each subject. The first and second swallows were divided into CPS and IPS upon agreement of one physiatrist and two dentists. The trajectory of the hyoid bone during swallowing was measured. The maximum distance of the horizontal and vertical axes, and the distance and time from onset to the end of the motion of the hyoid bone to antero-superior direction between CPS and IPS were compared.
[Results] Among 106 trials in 53 subjects, IPS occurred 26 times and CPS 80 times in the first swallows. All second swallows were CPS. In comparison of the trajectory of the hyoid bone between 18 subjects (26 trials) who had IPS and 20 subjects (30 trials) who had CPS in the first swallows, the maximum distance of horizontal and vertical axes, and the distance and time from onset to the end of the motion of the hyoid bone to antero-superior direction were found to be significantly smaller in IPS than CPS.
[Conclusion] IPS was a small and quick movement compared to CPS and seemed to occur for airway protection purposes.
