Effect Of Individualized Positive End-expiratory Pressure Guided By Driving Pressure On Lung Protection After Laparoscopic Radical Gastrectomy For Elderly Patients

Objective To explore the effect of individualized positive end expiratory pressure guided by driving pressure on lung protection after laparoscopic radical gastrectomy for elderly patients.Methods A total of 64 patients undergoing elective laparoscopic radical gastrectomy for gastric cancer were selected.Both groups were treated with pressure control-volume assured ventilation（PCV-VG）mode,the tidal volume was 6ml/kg,and the inspired oxygen concentration was 60%.After pneumoperitoneum,manual lung recruitment was performed in both groups,and the APL valve was set at 40 cm H₂O,recruitment manoeuvres was repeated 3 times,each time lasted for 30s.InΔP group,PEEP was increased by 4,6,8,10,12,14 and 16cm H₂O after recruitment manoeuvers.Each PEEP level was maintained for 10 respiratory cycles.The driving pressure corresponding to the last respiratory cycle（ΔP=Pplat-PEEP）was recorded,and the PEEP corresponding to the lowestΔP was selected until extubation.In group C:PEEP=5cm H₂O.Mean arterial pressure（MAP）,heart rate（HR）,peak airway pressure（Ppeak）,plateau airway pressure（Pplat）and PEEP were recorded at 5min after intubation（T₁）,immediately after PEEP titration（T₂）,1h after the start of surgery（T₃）,2h after the start of surgery（T₄）,and 10min after pneumoperitoneum release（T₅）.The driving pressure（ΔP）and lung dynamic compliance（Cdyn）were calculated.Arterial blood samples were collected at T_1-5 for blood gas analysis,arterial partial pressure of oxygen（Pa O₂）was recorded,and oxygenation index（OI）was calculated.The percentages of area in center of ventilation（Co V）,dependent silent spaces（DSS）,and non-dependent silent spaces（NSS）monitored by electrical impedance tomography（EIT）were recorded before anesthesia induction and after extubation.Pulmonary function was assessed before operation and at 1,3,and 5 days after operation.The incidence of pulmonary complications（PPCs）within 7 days after surgery was recorded.The modified clinical pulmonary infection score（m CPIS）was recorded on the second day after operation.Results1.Comparison of general situations There was no differences in baseline characteristics,operation time,and intraoperative infusion volume between the two groups（P>0.05）.2.Comparison of hemodynamics at different time points Compared with T₁,HR of the two groups increased at T_4-5,and the difference was statistically significant（P<0.05）.3.Comparison of respiratory mechanics and OI at different time points There was no significant difference in respiratory mechanics and OI between the two groups at T₁（P>0.05）.Compared with T₁,Ppeak,Pplat andΔP increased and Cdyn decreased at T_2-5,while OI decreased at T₄（P<0.05）.Compared with group C,Ppeak,Pplat and Cdyn in group T_2-5 were increased（P<0.05）,ΔP was decreased（P<0.05）,and OI in group T_3-5 was increased（P<0.05）.4.Comparison of pulmonary electrical impedance tomography indices at different time points Compared with before anesthesia induction,the percentage of area Co V decreased and the percentage of area DSS increased in both groups after extubation（P<0.05）.Compared with group C,the percentage of area DSS in groupΔP decreased after extubation（P<0.05）.There was no significant difference in the percentage of area NSS between groups（P>0.05）. 5.Comparison of postoperative pulmonary function There was no significant difference in preoperative FVC,FEV₁ and PEF between 2groups（P>0.05）.Compared with the preoperative results,FVC in the 2 groups was decreased 1 day,3 day and 5 day after surgery,and FEV₁ and PEF in the 2 groups were decreased 1 day and 3 day after surgery（P<0.05）.Compared with C group,FVC inΔP group was higher 1 day after operation（P<0.05）. 6.The incidence of PPCs within 7 days after surgery PPCs occurred in 5 patients（15.6%）inΔP group at 7 days after operation,which was lower than 13 patients（40.6%）in C group（P<0.05）. 7.Comparison of m CPIS on the second postoperative day There was no difference in m CPIS score between the two groups before operation（P>0.05）.Compared with before operation,the m CPIS scores of the two groups increased on the second day after operation（P<0.05）.Compared with group C,the m CPIS score was significantly decreased at 2 days after operation in groupΔP（P<0.05）.Conclusion Individualized PEEP guided by drive pressure can improve lung compliance,reduce drive pressure,improve oxygenation function and early postoperative lung function,reduce the area of atelectasis in the early postoperative period,reduce the incidence of postoperative lung complications.