Abstract:Abstract: Objective?To investigate the predictive value of the change of airway peak pressure (Ppeak) for gas-related complications of peroral endoscopic myotomy (POEM), and provide reference for early diagnosis of gas-related complications.?Methods?A retrospective study was performed on the clinical data of 38 achalasia (AC) patients receiving POEM from January 2014 to April 2019. We divided all the patients into groups according to the presence or absence of gas-related complications and their severity. Group A: no gas-related complications, Group B: mild gas-related complications (mediastinal emphysema or/and Subcutaneous emphysema), Group C: moderate (mediastinal and subcutaneous emphysema combined with pneumoperitoneum), Group D: severe (combined with pneumothorax). The Ppeak was recorded at 1 min after successful anesthesia intubation (T1), 10 min after the tunnel was dissected (T2), tunnel dissection was completed (T3), 10 min after myotomy (T4) and myotomy was completed (T5) for each patient. Meanwhile, the rise of Ppeak within 1min was more than thirty percent, which was set as a significant increase. Firstly, the influencing factors of gas-related complications were analyzed. The Ppeak at different time points during the operation of each group of patients was compared. At the same time, the sensitivity, specificity, positive and negative predictive value for predicting gas-related complications caused by significant increase of Ppeak were calculated.?Results?The differences between the two groups that had or not had gas-related complications were statistically significant (P?0.05) in the past treatment history, whether it was an S-shaped esophagus, the establishment method of tunnel entrance and the operation time. And the independent risk factor is operative time. In the four groups of patients, Ppeak appeared an upward trend in T1~T3 and T4~T5 and a downward trend in T3~T4. Moreover, the increase degrees of Ppeak of group C and group D in T2~T3 period were significantly higher than that of group A and group B. Ppeaks of Group C and group D were significantly higher than group A and group B at T3, T4 and T5 (P?0.05). Group B was higher than group A and group D was higher than group C at T5. The difference was statistically significant (P?0.05). During the operation, the sensitivity was (78.57%, 22/28), specificity was (80.00%, 8/10), positive predictive value was (91.67%, 22/24) and negative predictive value was (57.14%, 8/14) for predicting gas-related relative complications caused by significant increase of Ppeak.?Conclusion?Intraoperatively Ppeak monitoring has high clinical value in terms of predicting gas-related complications and perioperative risks can be decreased by prevention and intervention in early stage.