Normal Swallowing Acoustics Across Age, Gender, Bolus Viscosity, and Bolus Volume

Abstract

Cervical auscultation has been proposed as an augmentative procedure for the subjective clinical swallowing examination due to the tangible differences between normal and dysphagic swallowing sounds. However, the research is incomplete regarding cervical auscultation and swallowing acoustics in that the differences between the sounds of normal versus dysphagic swallowing have yet to be fully understood or quantified. The swallows of 96 reportedly healthy adults, balanced for gender and divided into younger, middle, and older age groups, were audio-recorded while ingesting several boluses of varying viscosity and volume. The audio signals were then analyzed to determine their temporal and acoustic characteristics. Results indicated increasing pharyngeal swallowing duration with increasing age, bolus viscosity, and bolus volume. In addition, an increased duration to peak intensity with increasing age was found in one of our two analyses, as well as with some of the more viscous versus less viscous boluses. Men and older persons produced higher peak intensities and peak frequencies than women and younger persons. Thin liquids were produced with more intensity than honey or more viscous boluses, and with greater frequency than mechanical soft solids. Larger volumes resulted in greater peak frequency values. Some of the acoustic measurements appear to be more useful than others, including the duration of the acoustic swallowing signal and the within-subjects peak intensity variable. We noted that differences in swallowing acoustics were more related to changes in viscosity rather than volume. Finally, within-participant observations were more useful than between-participant observations.

Contribuição da ausculta cervical para a avaliação clínica das disfagia orofaríngeas

“…The results showed that the swallowing time was longer in the group of elderly. In addition, the peak intensity was also more intense and the signal peak frequency was more acute in the group of the elderly, showing that an increased time in the pharyngeal phase occurs parallel to the increase of age 11 . Another study analyzed the duration of swallowing sounds in healthy subjects, 20 males and 10 females (age 37 ± 11).…”

“…Thus, it is evident an increasing number of studies with the purpose of studying the swallowing sounds and its correspondence with other physiological events in healthy subjects 9,11,[25][26][27] . The latter, relating the cervical auscultation findings with other assessment methods.…”

“…In a conventional way, this technique is performed by using a stethoscope. However, other instruments have been used recently, such as a microphone, the accelerometer and the Doppler sonar 11 . These transducer instruments allow the digitalization of the signal, a resource that enables the analysis of the sounds in a more objective way, considering their duration, signal frequency and the wave amplitude, among other aspects ,9,15,19,20 .…”

“…Despite the advantages, The use of oximeter to detect the risk of aspiration is based on the hypothesis that laryngo-tracheal aspiration would provoke a bronchospasm reflex, decreasing the respiratory perfusion and provoking a decrease in oxygen saturation 4,5 . In the case of cervical auscultation, performed with stethoscope located in specific points in this region, it allows for the acoustic analysis of the swallowing sounds, before, during, and after the food bolus goes through the pharynx, giving additional clues regarding the food entrance in the lower airway or not 3,4,[6][7][8][9][10][11][12][13] . Swallowing sounds occur during the pharyngeal phase due to the pressure on the oropharyngeal tract with its valves represented by the lips, velopharyngeal region, larynx and cricopharyngeal muscle 6 .…”

Dysphagia Screening: Contributions of Cervical Auscultation Signals and Modern Signal-Processing Techniques

“…The first analysis method is the most simplistic and extracts the most basic features and conclusions from the time domain recordings. For example, researchers have matched certain visual landmarks of a raw cervical auscultation signal with some specific physiological events [19], [37], [48], [69], [103], determined the onset and duration of a swallow [34], [68], [69], [94], [95], [97], [101], [110], [113], [114], or simply counted the number of swallows that occurred over a certain period [40], [95], [102], [104], [107], [111]. The second analysis method also uses simple features of the signal, but uses the subjective opinion of a trained expert listening to the acoustic signal rather than the researcher’s visual analysis of the signal waveform.…”