## 3 Results
### Varied Effects of ETT and SC on PEEP in Both Respiratory Systems  
A closed suctioning system usually can be connected to a ventilator during suctioning in patients with deteriorating respiratory systems to maintain higher PEEP. The experiment \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**(a) Obstructive Respiratory System Model**} \\ \hline  & \multicolumn{2}{c}{\(\bigtriangleup\)PIP (cm H\({}_{2}\)O)} & \multicolumn{6}{c}{\(\bigtriangleup\)PEEP (cm H\({}_{2}\)O)} & \multicolumn{6}{c}{\(\bigtriangleup\)**Vexp (L)**} \\ \hline  & **B** & **SE** & \(t\) & **B** & **SE** & \(t\) & **B** & **SE** & \(t\) \\ \hline Constant & 22.64 & 2.09 & 10.84 \({}^{**}\) & \(-\)0.52 & 0.38 & \(-\)1.34 & 1.50 & 0.34 & 4.38 \({}^{**}\) \\ ETT area (mm\({}^{2}\)) & \(-\)0.42 & 0.05 & \(-\)7.36 \({}^{**}\) & 0.00 & 0.01 & 0.19 & \(-\)0.03 & 0.01 & \(-\)3.48 \({}^{**}\) \\ SC area (mm\({}^{2}\)) & 0.24 & 0.12 & 2.09 \({}^{**}\) & 0.07 & 0.02 & 3.40 \({}^{**}\) & 0.26 & 0.02 & 13.52 \({}^{**}\) \\ R\({}_{\text{aw}}\) (cm H\({}_{2}\)O L\({}^{-1}\) s) & \(-\)0.10 & 0.02 & \(-\)4.19 \({}^{**}\) & 0.00 & 0.00 & 0.73 & \(-\)0.02 & 0.00 & \(-\)4.49 \({}^{**}\) \\ Mode & \(-\)4.86 & 0.61 & \(-\)7.95 \({}^{**}\) & \(-\)0.05 & 0.11 & \(-\)0.42 & 1.03 & 0.10 & 10.31 \({}^{**}\) \\ R\({}^{2}\) & & 0.63 & & & 0.13 & & & & 0.07 \\ \(p\) & \(<\)0.01 & & & & 0.04 & & & \(<\)0.01 & \\ \hline  & \multicolumn{6}{c}{**(b) Restrictive Respiratory System Model**} \\ \hline  & \multicolumn{2}{c}{\(\bigtriangleup\)PIP (cm H\({}_{2}\)O)} & \multicolumn{6}{c}{\(\bigtriangleup\)**PEEP (cm H\({}_{2}\)O)} & \multicolumn{6}{c}{\(\bigtriangleup\)**Vexp (L)**} \\ \hline  & **B** & **SE** & \(t\) & **B** & **SE** & \(t\) & **B** & **SE** & \(t\) \\ \hline Constant & 21.75 & 1.86 & 11.69 \({}^{**}\) & \(-\)0.34 & 0.30 & \(-\)1.16 & \(-\)0.68 & 0.64 & \(-\)1.04 \\ ETT area (mm\({}^{2}\)) & \(-\)0.49 & 0.05 & \(-\)9.48 \({}^{**}\) & 0.00 & 0.01 & 0.42 & \(-\)0.05 & 0.02 & \(-\)2.56 \({}^{**}\) \\ SC area (mm\({}^{2}\)) & 0.47 & 0.11 & 4.47 \({}^{**}\) & 0.06 & 0.17 & 3.84 \({}^{**}\) & 0.32 & 0.04 & 8.63 \({}^{**}\) \\ C\({}_{\text{rs}}\) (L cm H\({}_{2}\)O\({}^{-1}\)) & 22.98 & 11.99 & 1.92 & \(-\)5.19 & 1.96 & \(-\)2.65 \({}^{**}\) & 39.15 & 4.15 & 9.42 \({}^{**}\) \\ Mode & \(-\)7.35 & 0.54 & \(-\)13.52 \({}^{**}\) & \(-\)0.09 & 0.09 & \(-\)1.07 & 1.42 & 0.19 & 7.52 \({}^{**}\) \\ R\({}^{2}\) & & 0.72 & & & & & & 0.68 \\ \(p\) & \(<\)0.01 & & & & & & & \(<\)0.01 & \\ \hline \(\bigtriangleup\): delta (a variation level that the suctioning PIP, PEEP, and Vexp level subtract at baseline level); \(\bigtriangleup\)PIP: delta peak inspiratory pressure; \(\bigtriangleup\)Vexp: delta expiratory minute volume; \(\bigtriangleup\)PEEP: delta positive end-expiratory pressure; ETT area: endotracheal tube cross-section area; SC area: suction catheter cross-section area; C\({}_{\text{rs}}\): lung compliance; R\({}_{\text{aw}}\): airway resistance; Mode: VC-CMV (volume control continuous mandatory ventilation); PC-CMV (pressure control continuous mandatory ventilation). B: unstandardized regression coefficient; SE: standard error; \(t\) = \(t\) statistic, which evaluates the predictor; R\({}^{2}\): adjusted R-squared; mode of VC-CMV dummy variable is 0. The mode of the PC-CMV dummy variable is 1. \({}^{*}\)\(p\)\(<\) 0.05, \({}^{**}\)\(p\)\(<\) 0.01. & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Multiple regression analysis of factors affecting closed endotracheal suctioning: (**a**) Ventilator-related parameters of factors affecting the restrictive respiratory system; (**b**) Ventilator-related parameters of factors affecting the restrictive respiratory system. showed that PEEP levels for 6.5 mm and 7.0 mm were similar to 7.5 mm endotracheal tubes with suction catheters that could be kept at the set scale during closed suction in both ventilation modes (Figure 4). In the 8.0 mm endotracheal tube with a 12 Fr suction catheter, PEEP levels began to experience a slight variation in both pulmonary mechanics.