Dynamics of oropharyngeal structures during respiration with the volume-altered tongue base of minipigs

This study aimed to analyze the functional adaptations of tongue base volumetric enlargement and reduction on the kinematics of oropharyngeal structures during respiration in a minipig model.

Six same-sex sibling pairs of 8-to-9-month-old Yucatan minipigs were studied. Of each pair, one was diet-induced obese with a BMI>50 (obesity-associated volume enlargement) while the other was normal-weight and underwent partial ablation of the tongue base volume (volume-reduction). Real-time X-ray video fluoroscopic images (30 frames/s) were recorded under sedation, at baseline (before surgery) and 5 weeks postoperatively. Selected landmarks of the soft palate, epiglottis, tongue base, and pharyngeal wall were digitized frame by frame for 25-30 respiratory cycles. Directional movements and distance changes of these oropharyngeal structures were analyzed within the defined coordinate system using video-analysis software. Correlations between areas of airway spaces during respiration and biometric measurements of the dissected tongue at week 5 were included.

During respiratory phases, movement distances of the soft palate and the pharyngeal wall were significantly larger in the volume-reduced group than in the volume-enlarged group at baseline (p<0.05). These moving distances were also larger compared to those of the volume-enlarged group at both time points. Similarly, distance changes during inspiration between structures (soft palate-pharyngeal wall, soft palate-tongue base, and epiglottis-pharyngeal wall) were significantly larger at week 5 than at baseline (p<0.05) in both groups. Positive correlations during respiratory phases were detected between tongue volume and velopharyngeal width in the volume-reduced group (r=0.86, p<0.05). Negative correlations occurred between retromolar space area and tongue thickness in the volume-enlarged group (r=-0.9, p<0.05).

These results suggest that oropharyngeal spatial dynamics are enhanced in the tongue base volume-reduced minipigs, with altered moving patterns during respiration. In contrast, smaller distance changes observed over time in the volume-enlarged group suggest continuous airway narrowing and potential restriction of airway dynamics.