Evaluation of equal ratio ventilation on laryngeal mask airway during endoscopic surgery for prostate cancer by lung and gastric ultrasound

Objective To evaluate the impacts of equal ratio ventilation (ERV) mode on lung morphology, gastric inflation and laryngeal mask airway ventilation during laparoscopic radical prostatectomy by lung ultrasound（LUS） and gastric ultrasound. Methods A prospective study was performed in 60 patients with prostate cancer undergoing laparoscopy from June 2021 to May 2022 in Nanjing First Hospital. The patients were randomly divided into ERP group (group E) and conventional ventilation group (group C,n=30, each). After induction of routine intravenous anesthesia and mechanical ventilation with laryngeal mask airway, and the ventilation mode was set as follows: the inspiratory-to-expiratory ratio in group E was 1∶1, while that in group C was 1∶2. After anesthesia induction (T0), 30 minutes after surgery begin (T1), 60 minutes after surgery begin (T2) and 10 minutes after surgery (T3), the peak airway pressure (Ppeak), airway plateau pressure(Pplat), mean airway pressure (Pmean),end-expiratory partial pressure of carbon dioxide (PETCO2) and minute ventilation (MV) were observed and compared between two groups. The LUS score, the cross-sectional area of gastric antrum and fundus and the incidence of airway complications were recorded in two groups. Results At T1 and T2, Ppeak in group E was significantly lower than that in group C(P＜0.05), and Pmean was significantly higher than that in group C(P＜0.05). There was no significant difference in PETCO2 and MV between two groups at different time points (P＞0.05). The LUS and the incidence of atelectasis in group E were statistically lower than those in group C (P＜0.05), and there was no significant difference in the cross-sectional area of gastric antrum and fundus（P＞0.05） and the incidence of airway complications（30.0% vs 32.1%，χ2=0.031，P=0.860) between two groups. Conclusion ERV mode during laparoscopic radical prostatectomy can reduce Ppeak, leakage rate of laryngeal mask, atelectasis and LUS scores without increasing the incidence of gastric inflation and laryngeal mask-related adverse complications.