## 3 Results
### Varied Effects of ETT and SC on Vexp in Both Types of Respiratory Systems  
Closed endotracheal suctioning significantly reduced lung volume loss by handling the suctioning procedure in terms of suctioning pressure and time. The study examined the expiratory minute volume (Vexp) and the control of suction pressure time. Figure 5  
Figure 4: The effects of 7.5 mm and 8.0 mm ETT with 10 Fr, 12 Fr, and 14 Fr SC on PEEP in different respiratory systems: (**a**) Changes in airway resistance of pulmonary mechanics for the obstructive system; (**b**) Changes in lung compliance of pulmonary mechanics for the restrictive system in VC-CMV and PC-CMV. PC-CMV: pressure control continuous mandatory ventilation, this mode set inspiratory pressure at 20 cm H\({}_{2}\)O with inspiratory time at 1 sec; VC-CMV: volume control continuous mandatory ventilation, this mode is set to VT 0.6 L with peak flow 60 Lpm; C: control group (0.08 L cm H\({}_{2}\)O\({}^{-1}\) of \(\mathrm{C_{rs}}\) and 5 cm H\({}_{2}\)O\(\cdot\)L\({}^{-1}\)\(\cdot\)s of \(\mathrm{R_{aw}}\)); PEEP: positive end-expiratory pressure placed 10 cm H\({}_{2}\)O (solid line); \(\mathrm{R_{aw}}\): airway resistance; \(\mathrm{C_{rs}}\): lung compliance; ETT: endotracheal tube; SC: suction catheter; 7.5 mm\(-\)10 Fr: 7.5 mm ETT paired with 10 Fr SC, and so on. The closed suctioning procedure was repeated three times. The error bars represent the standard deviation of 30 breaths in each of the pulmonary mechanic scenarios (five airway resistance levels and six lung compliance levels). The independent samples \(t\)-test was used to compare with the control group. * \(p\) < 0.05, ** \(p\) < 0.01.  
shows that the Vexp level decreased in both progressively declining respiratory systems during PC-CMV. The distance between the Vexp curves of VC-CMV and PC-CMV with a 6.5 mm endotracheal tube was less than with an 8.0 mm endotracheal tube. Moreover, the distance between the two curves with the restrictive respiratory system was less than with the obstructive respiratory system. In the obstructive respiratory system (Figure 5a), the Vexp level in lower R\({}_{\text{aw}}\) was higher than in higher R\({}_{\text{aw}}\) during PC-CMV. The distance between the two curves (VC-CMV and PC-CMV) of Vexp had a more extensive range for lower R\({}_{\text{aw}}\). However, the curve distance diminished when R\({}_{\text{aw}}\) exceeded 20 cm, H\({}_{2}\)O\(\cdot\)s\(\cdot\)L\({}^{-1}\) of. In the restrictive respiratory system (Figure 5b), the Vexp level was higher in higher C\({}_{\text{rs}}\) than lower C\({}_{\text{rs}}\) during PC-CMV. In addition, the distance between the two curves in Vexp increased in line with the rise of C\({}_{\text{rs}}\), but the two curves began descending along with the C\({}_{\text{rs}}\) progressive decline to 0.02 L\(\cdot\)cm H\({}_{2}\)O\({}^{-1}\). When the C\({}_{\text{rs}}\) decreased to 0.01 L\(\cdot\)cm H\({}_{2}\)O\({}^{-1}\), the Vexp of PC-CMV was equal to that of VC-CMV. Figure 5: Comparison of the changes in Vexp effects in different respiratory systems and ventilation modes. Various ETTs paired with SCs for CSS conducted endotracheal suctioning in airway resistance of pulmonary mechanics for the obstructive system (**a**) and lung compliance of pulmonary mechanics for the restrictive system (**b**) with VC-CMV or PC-CMV. PC-CMV: pressure control continuous mandatory ventilation, this mode set inspiratory pressure at 20 cm H\({}_{2}\)O with inspiratory time at 1 sec; VC-CMV: volume control continuous mandatory ventilation, this mode is set to VT 0.6 L with peak flow 60 Lpm; C: control group (0.08 L\(\cdot\)cm H\({}_{2}\)O\({}^{-1}\) of C\({}_{\text{rs}}\) and 5 cm H\({}_{2}\)O\(\cdot\)L\({}^{-1}\)-s of R\({}_{\text{aw}}\)); Vexp: expiratory minute volume; R\({}_{\text{aw}}\): airway resistance; C\({}_{\text{rs}}\): lung compliance; ETT: endotracheal tube; SC: suction catheter; 6.5 mm\(\,-\)08 Fr: 6.5 mm ETT paired with 08 Fr SC, and so on. The closed suctioning procedure was repeated three times.