Multi-site Vibration Signal Analysis for Estimating Post-Swallow Residue: A Pilot Study

This pilot study investigated whether multi-site acoustic signal analysis could detect post-swallow residue and aimed to identify the most effective sensor location and parameters for detection. Three contact microphone-based acoustic sensors and one air-conduction-based conventional audio recorder were positioned at four anatomical sites: the jugular notch, near the pyriform sinus, near the vallecular sinus, and over the right deltoid muscle. Patients with dysphagia were recorded during pre-swallow, thin-fluid swallowing, and yogurt (YP) swallowing conditions. Acoustic parameters, including harmonic-to-noise ratio (HNR), noise-to-harmonic ratio, jitter, shimmer, and formant frequencies, were extracted from each recording. The videofluoroscopic swallowing study findings served as the reference standard for detecting pharyngeal residue. Pre-swallow and post-YP swallowing conditions yielded the most reliable acoustic indicators of post-swallow residue. Among the sensor locations, the right-lateral vallecular sinus sensor demonstrated the highest accuracy in reflecting pharyngeal retention. HNR emerged as the most robust single parameter, with high values paradoxically associated with the presence of residue. Multisite acoustic analysis, particularly HNR measurement from a vallecular sinus-placed sensor in the pre-swallow or post-YP swallowing state, may serve as a noninvasive and accessible method for detecting post-swallow residue in patients with dysphagia. Notably, the vallecular sensor demonstrated the highest diagnostic performance, suggesting that a simplified single-sensor approach may be feasible, although this requires validation in larger-scale studies. Largescale studies are needed to validate these findings and assess the feasibility of real-time dysphagia screening.