## 4 Discussion
\begin{table}
\begin{tabular}{l l l l l l l l l l l l} \hline \multicolumn{8}{c}{**VOTE Classification**} \\ \hline  & **0** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** & \(p\) \\ \hline \hline T & & & & & & & & & & & \\ \hline Non Resp. & 92 (71.9\%) & 24 (18.8\%) & 12 (9.4\%) & & & & & & & & 0.008 \\ \hline Resp. & 162 (78.3\%) & 41 (19.8\%) & 4 (1.9\%) & & & & & & & & \\ \hline E & & & & & & & & & & & \\ \hline Non Resp. & 98 (76.6\%) & 10 (7.8\%) & 4 (3.1\%) & 2 (1.6\%) & 1 (0.8\%) & 4 (3.1\%) & 5 (3.9\%) & 2 (1.6\%) & 2 (1.6\%) & 0 (0.0\%) & 0.005 \\ \hline Resp. & 190 (91.8\%) & 6 (2.9\%) & 0 (0.0\%) & 0 (0.0\%) & 0 (0.0\%) & 5 (2.4\%) & 3 (1.4\%) & 2 (1.0\%) & 0 (0.0\%) & 1 (0.5\%) & \\ \hline \end{tabular} Non Resp.: non-responders to mandibular advancement simulator during DISE; Resp.: responder to mandibular advancement simulator during DISE.  
\end{table} 
Table 6: _Cont._number of collapses (non-responders: 89.1%; responders: 80.2%; \(p=0.034\)). This result could be explained by considering the nature of oropharynx obstructions. In fact, we also analyzed the distribution of the patterns and degrees of airway narrowing, with a qualitative evaluation as proposed by [PERSON] [18]. At the oropharynx level, non-responders show a higher percentage of patients with complete latero-lateral obstruction while in responders the percentage of partial latero-lateral obstruction is higher (\(p=0.003\)). Similarly, for VOTE classification the two groups differ at the velopharynx obstruction with a higher presence of complete circular obstruction in non-responders. These differences are peculiar. The complete obstruction of the latero-lateral oropharynx walls is the main indication for CPAP or pharyngeal surgery, especially in the last years with new techniques like functional expansion pharyngoplasty [28; 29]. Differently, the complete circular obstruction is not a privileged therapy option. It is commonly observed in obese patients, where the presence of fat at the neck level is relevant, and/or in patients with loss of muscle responsiveness. Typically, there is no single therapy sufficient to address this condition. Instead, a combined therapeutic approach is preferred, with MAD considered an adjunct to other treatments that alone would fail to achieve optimal therapeutic outcomes [25]. These results appear to align with the finding by [PERSON] et al. [25], who identified complete lateral orophyngeal collapse as an adverse baseline DISE phenotype associated with MAD treatment outcomes. Concerning the obstructive sites with the TMA simulator in situ, the two groups differ significantly for velopharynx, oropharynx, and epiglottis collapse. On the contrary, there was not a difference in the percentage of obstructions at the tongue level. As a trend the obstruction improved equally in both responders and non-responders, suggesting that MAD is equally effective at the tongue level. Therefore, we can hypothesize that the difference in response to mandibular advancement between the groups is due to obstructions present at other levels. Interestingly, tongue base collapse has been described as a beneficial baseline DISE phenotype associated with MAD treatment outcomes [25]. Moreover, without the TMA simulator, there was no difference between the groups in the velopharynx obstruction percentage. After mandibular advancement the difference is significant, suggesting that MAD therapy could be effective at the velopharynx level. There is still considerable variation across studies on the recommended initial mandibular position for MAD therapy, but the use of a TMA simulator during DISE allows to determine a good candidate for treatment responsiveness and, also, a minimal protrusion from which clinicians could subsequently start MAD titration for each patient. The concept is to achieve the highest reduction in the AHI while reducing patient discomfort and potential side effects [30; 31; 32].