## 4 Results  
This study enrolled 27 very severe OSA patients with 24 men and 3 women between 29 and 63 years of age (mean = 47.4; standard deviation (SD) = 10.6). The mean BMI was 28.5 with a standard deviation of 3.5 kg/m\({}^{2}\). All patients received ZPP with one-layer closure and partial open tongue-base resection. Twenty-five received routine septomeatoplasty. One patient underwent UPPP at another hospital before visiting our clinic. Three and one patients underwent routine endoscopic sinosurgery and adenoidectomy, respectively.  
After the surgery, the mean AHI (with 1 SD; the same for the follows) was reduced from \(73.8\pm 10.3\) to \(33.2\pm 20.4\) events/h (\(p<0.001\)). The mean AHI reduction was 40.5, with a 95% confidence interval of 31.9 to 49.1 events/h. Figure 1 illustrated the individual AHI reductions. In these AHIs (including central and mixed indexes), the mean obstructive apnea index reduced 35.7 events/h, with a 95% confidence interval of 28.1 to 43.3 events/h (\(p<0.001\)) (Figure 2). The hypopnea index almost remained the same, with a small change of 2.2 events/h (\(p=0.6562\)) (Figure 3). The mean portion of hypopnea in AHI increased from 29.1 \(\pm\) 23.9 to 77.3 \(\pm\) 25.1% (\(p<0.001\)) (Figure 4). The mean increase was 48.2%, with a 95% confidence interval of 37.7 to 58.8%. The mean desaturation index decreased from 62.5 \(\pm\) 12.5 to 24.4 \(\pm\) 16.3 events/h (mean reduction was 38.1, with a 95% confidence interval of 30.6 to 45.6 events/h, \(p<0.001\)) (Figure 5), and the mean SpO\({}_{2}\) desaturation was cut down from 10.0 \(\pm\) 5.0 to 5.8 \(\pm\) 1.9% (mean reduction was 4.2%, with a 95% confidence interval of 2.3 to 6.1%, \(p<\) 0.001) (Figure 6). The mean SpO\({}_{2}\) improved from 92.3 \(\pm\) 3.4 to 94.7 \(\pm\) 1.5% (mean improvement was 2.4%, with a 95% confidence interval of 1.0 to 3.8%, \(p=0.0014\)) (Figure 7). A correlation of the data revealed that the improvement of mean SpO\({}_{2}\) was positively related to the proportional increase of hypopnea/AHI,  
Figure 4: Individual portion change of hypopnea in AHI. After the surgery, the mean hypopnea portion increased 48.2%, \(p<0.001\).  
Figure 3: Individual hypopnea index did not reveal a significant change after the surgery.  
Figure 5: Individual change of desaturation index. After the surgery, the mean desaturation frequency cut 38.1 events/h, \(p<0.001\).  
Figure 6: Individual change of mean SpO\({}_{2}\) desaturation. After the surgery, the mean desaturation severity reduced 4.2%, \(p<0.001\).  
Nineteen out of 27 patients did not qualify the classical surgical success because each had a postoperative AHI > 20 events/h, although all had AHI reductions > 50%. In these 19 \"non-surgical success\" patients, the mean SpO2 improved from 91.7 \(\pm\) 3.7 to 94.3 \(\pm\) 1.6% (\(p\) = 0.0087) (Figure 9). Among the remaining eight patients, the AHI reduced from 73.0 \(\pm\) 13.0 to 10.5 \(\pm\) 5.6 events/h and qualified as \"surgical success\". However, the improvement of mean SpO2 from 93.8 \(\pm\) 2.0 to 95.7 \(\pm\) 0.8% did not show statistical significance (\(p\) = 0.0625).  
Figure 8: Scatter plot and correlation of proportion change of hypopnea/AHI (defined here as (postoperative-preoperative)/preoperative fraction of hypopnea in AHI) vs. change of mean SpO2 (defined here as (postoperative-preoperative)/preoperative mean SpO2). It shows that the improvement of mean SpO2 was positively related to the proportional increase of hypopnea/AHI.  
Figure 7: Individual change of mean SpO2. After the surgery, the mean O2 saturation improved 2.4%, \(p\) = 0.0014.