It is largely unknown how the tongue base and soft palate deform to alter the configuration of the oropharyngeal airway during respiration. This study is to address this important gap. After live sleep monitoring of 5 Yucatan and 2 Panepinto minipigs to verify obstructive sleep apnea (OSA), 8 and 4 ultrasonic crystals were implanted into the tongue base and soft palate to circumscribe a cubic and square region, respectively. The 3D and 2D dimensional changes of the circumscribed regions were measured simultaneously with electromyographic activity (EMG) of the oropharyngeal muscles during spontaneous respiration under sedated sleep. The results indicated that both obese Yucatan and Panepinto minipigs presented spontaneous OSA, but not in 3 non-obese Yucatan minipigs. During inspiration, the tongue base showed elongation in both dorsal and ventral regions but thinning and thickening in the anterior and posterior regions respectively. The widths showed opposite directions, widening in the dorsal but narrowing in the ventral regions. The soft palate expanded in both length and width. Compared to normal controls, obese/OSA ones showed similar directions of dimensional changes, but the magnitude of change was two times larger in the tongue base and soft palate, and obese/OSA Panepinto minipigs presented 10 times larger changes in all dimensions of both the tongue base and the soft palate. The opposite direction of the respiratory spatial relationship between these two structures was seen in obese/OSA as compared to normal minipigs.
Keywords: Tongue base; obesity; obstructive sleep apnea; respiration; soft palate.