[Swallowing sound signal: description in normal and laryngectomized subjects]

Recently, we described three sound components in the pharyngeal swallowing sound. The aim of the present study was to identify the origin of these components using modern techniques providing numeric, synchronized acoustic-radiological data in a normal population and in a partial supracricoid laryngectomized population (SCL group) and a total laryngectomized (TL group) population in pre- and postoperative situations.

We enrolled 15 normal subjects (10 men and five women; mean age, 29.5+/-8 years), 11 patients in the SCL group (11 men; mean age, 62; range, 45-75 years), and nine patients in the TL group (three women, six men; mean age, 56; range, 39-73). An X-ray camera was connected to a video acquisition card to obtain acoustic-radiological data (2 images/s). The microphone was attached to each subject's skin overlying the lateral border of the cricoid. The subjects were asked to swallow 10 ml of a barium suspension. We performed the acoustic-radiological analysis using Visualisation and Cool Edit Pro software. Each sound component was associated with a specific position of the bolus and the moving anatomic structure. Three sound components were identified: the laryngeal ascension sound (LAS), the upper sphincter opening sound (USOS), and the laryngeal release sound (LRS). We quantified the total duration of the pharyngeal sound and its components, as well as the duration of the interval.

The average duration of the normal pharyngeal sound was 690+/-162 ms and was significantly decreased in the TL group (296+/-105 ms) and increased in the SCL group (701+/-186 ms). The USOS was present in 100% of the recordings. A typical profile of the swallowing sound for each group was obtained.

This study allowed us to determine the origin of the three main sound components of the pharyngeal swallowing sound with respect to movements in anatomic structures and the different positions of the bolus, and to describe the main variations induced by a partial and a total laryngectomy.