Swallowing Onset Detection: Comparison of Endoscopy- and Accelerometry-Based Estimations

The swallowing process involves the coordinated activation of several muscles to ensure the transfer of nutrients from the mouth to the stomach. A proper segmentation of swallowing into its constituent phases is relevant to obtain a quantitative biomechanical and electrophysiological description of this sensorimotor task. The aim of the study was to design a non-invasive measurement framework integrating electromyographic and acceleration measurements to detect the swallowing onset and event-related muscular symmetry indexes during the oropharyngeal phase. Therefore, the experimental protocol included: surface electromyography (sEMG), accelerometry and Fiberoptic Endoscopic Examination of Swallowing (FEES) as a clinical gold standard. A comparative study on five healthy subjects was performed in order to evaluate the results of the accelerometer-based segmentation with respect to those obtained through the gold standard. Results showed that the accelerometer-based method consistently underestimated the swallowing onset (204 ± 192 ms, mean and standard deviation). Despite this bias towards the onset estimation, sEMG symmetry indexes computed from the accelerometer- and FEES-based onset exhibited comparable values. These preliminary results suggest that the observed underestimation is not relevant in order to study symmetry differences in swallowing muscular activation. Thus, the acceleration measurements can provide a possible non-invasive alternative to the FEES-based segmentation for the extraction of event-related symmetry indexes during the oropharyngeal phase of swallowing.