## 3 Results  
None of the pigs showed any anatomical variations, ear injuries, or disease on pre-procedural endoscopic examinations. The stent placements were technically successful in all pigs, with no procedure-related complications. Although mucosal injuries with touch bleeding were observed in two (33.3%) of the six specimens during sheath insertion, all metallic guiding sheaths were successfully located in the nasopharyngeal orifice of the ET under endoscopic guidance. In the right-side ETs treated with the larger 3.5-mm-diameter stents, the proximal ends of the stents protruded from the orifice by approximately 1-2 mm. In the left-side ETs, two of the three smaller 2.5-mm-diameter stents were located within the cartilaginous portion of the ET, while one stent was located in the cartilaginous portion of the ET with the proximal tip slightly protruding into the nasopharyngeal orifice of the ET. The longest luminal diameters at the three different stent levels and the decrease rates at each site are presented in Table 1 and Figure 2, with representative examples shown in Figure 3. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Stent Diameter/Site** & **Location** & **Luminal Diameter (mm)** & **Decrease Rate (\%)** \\ \hline \multirow{3}{*}{3.5 mm/Right ET} & Proximal & 3.48 \(\pm\) 0.06 & 0.9 \(\pm\) 0.8 \\ \cline{2-4}  & Middle & 2.54 \(\pm\) 0.17 & 27.4 \(\pm\) 7.6 \\ \cline{2-4}  & Distal & 2.15 \(\pm\) 0.14 & 38.6 \(\pm\) 4.1 \\ \hline \multirow{3}{*}{2.5 mm/Left ET} & Proximal & 2.49 \(\pm\) 0.04 & 0.4 \(\pm\) 0.6 \\ \cline{2-4}  & Middle & 1.73 \(\pm\) 0.21 & 30.8 \(\pm\) 8.3 \\ \cline{2-4}  & Distal & 1.42 \(\pm\) 0.18 & 43.2 \(\pm\) 7.1 \\ \hline \end{tabular} Note. Data are means \(\pm\) standard deviation.  
\end{table} 
Table 1: Mean luminal diameters and decrease rates at the proximal, middle, and distal portions of the placed stents in a porcine Eustachian tube (ET) model. Figure 3: Coronal computed tomography image showing segments of the stented ETs, where the stents were present in the (**1**) proximal, (**2**) middle, and (**3**) distal portions. The axial CT images of the proximal portions of the stents show fully expanded stents in both ETs (red circles). The axial CT images show a gradual decrease from the proximal to the distal portion of the stented ET. Figure 2: Longest luminal diameter of the stent measured at the proximal, middle, and distal portions of the porcine Eustachian tube (ET) model. The mean luminal diameters (\(\pm\)SD) of the proximal, middle, and distal portions of the stents in the right-side ETs using larger-diameter (3.5 mm) stents were 3.48 \(\pm\) 0.06, 2.54 \(\pm\) 0.17, and 2.15 \(\pm\) 0.14 mm, respectively. In the left-side ETs using smaller-diameter (2.5 mm) stents, these values were 2.49 \(\pm\) 0.04, 1.73 \(\pm\) 0.21, and 1.42 \(\pm\) 0.18 mm, respectively. The diameters of the inserted stents differed significantly by stent location and original diameter. The excised specimens with the placed stent showed no mucosal injuries in the ETs. The distal portions of the stents were severely collapsed in gross observation of the inserted stents (Figure 4). The stents gradually collapsed from the proximal to the distal portions. The shapes of the inserted stents were influenced by the stent sizes and anatomic configuration of the ET. The histological images showed severe inflammatory cell infiltration around the stent strut. Tissue hyperplasia with increased submucosal fibrosis progressed through the stent strut (Figure 5a-c). Follow-up endoscopic images demonstrated that stent migration did not occur at 4 weeks after stent placement. However, the proximal end of the stent was filled with secretion (Figure 5d). Figure 4: **(a)** Photograph showing a mid-sagittal sectioned cadaveric porcine head with the metallic guiding sheath (arrowheads) facing the orifice of the ET (arrow). **(b,c)** The photographs show the placed stent (arrows) in the ET and the extracted stent from the ET of the (**d**) frontal and (**e**) lateral views.