Influence of Bubble-Containing Thickened Liquid on Swallowing Dynamics

Thickened liquid (TL) is commonly used to aid swallowing and prevent aspiration in dysphagia patients. We hypothesized that incorporating air bubbles into TL (TLB) could reduce viscosity and pharyngeal residue, improving swallowing dynamics. This study included 24 adults (17 males, 7 females; mean age: 75.8 ± 11.4 years) with Dysphagia Severity Scale scores of 3 or 4, excluding those with laryngeal penetration or aspiration when swallowing 4 mL of TL. Test samples consisted of TL with 3% wt/vol thickening agent and TLB. Type E viscosity and texture profile analysis were conducted. The subjects were administered 4 ml of thickened liquid and 4 ml of thickened liquid with bubbles three times each in a random order. Swallowing dynamics were evaluated using videofluoroscopy, measuring hyoid displacement, velocity, duration, pharyngeal transit time, upper esophageal sphincter (UES) opening width, and pharyngeal residue ratios. No significant differences were observed in adhesion or cohesion between TL and TLB, while viscosity and specific gravity tended to be lower for TLB. Compared to TL, TLB significantly increased hyoid anterior displacement and velocity (p = 0.03, p < 0.01, respectively), shortened movement duration (p < 0.01), and widened UES opening (p < 0.01). Additionally, pyriform sinus residue ratio significantly decreased (p = 0.02). These findings suggest that TLB positively influences swallowing dynamics and reduces pharyngeal residue.