Electrical Impedance Tomography Was Used To Compare The Effects Of Oxygen Concentration On Pulmonary Ventilation And Oxygenation Function Of Gynecological Laparoscopic Surgery During General Anesthesia Induction

Objective Electroimpedance tomography(EIT)was used to compare the effects of different oxygen concentration during general anesthesia induction on the distribution of lung ventilation uniformity,oxygenation function,safe time of non-ventilation period,respiratory mechanics and postoperative pulmonary complications in patients undergoing laparoscopic gynecological surgery.To find the best inhaled oxygen concentration during the induction of general anesthesia,in order to provide reference for the selection of oxygen concentration during clinical induction.Methods A total of 100 non-smoking women aged 30 to 65 years who were scheduled to undergo elective endoscopic gynecologic surgery due to benign disease,ASAI or grade II,with a body mass index(BMI)18~30 kg/m2,and good pulmonary function were recruited.By random number table method,they were divided into four groups: A(Fi O2= 40%),B(Fi O2= 60%),C(Fi O2= 80%)and D(Fi O2= 100%),with 25 cases in each group.Inhaled oxygen was given at different concentrations during induction,and 40% during maintenance and recovery.The proportion of pulmonary ventilation in the Region of Interest(ROI)was measured by electrical impedance tomography at entry(T0),after tracheal intubation(T1),after the construction of the pneumoperitoneum(T2),pneumoperitoneum established 30 min(T3),before extubation(S1),15 min after the extubation(S2),and calculate the Impedance Ratio(IR).The pulmonary ventilation was divided from ventral to dorsal into 4 regions(ROIⅠ、ROIⅡ 、 ROI Ⅲ 、 ROI Ⅳ).The safe time of anaeration period was recorded.Respiratory mechanics,including peak inspiratory pressure(Ppeak),airway platform pressure(Pplat)and dynamic pulmonary compliance,were recorded during mechanical ventilation.Sp O2,end-of-expiratory carbon dioxide(Pet CO2),blood pressure and heart rate were recordedat each time point.The arterial blood gas was analyzed at T0,T1,T2 and S2,and the oxygenation index(Pa O2/ Fi O2)was calculated.Pulmonary complications were assessed on postoperative day 1 and 3.The obtained data were analyzed by SPSS 26.0 statistical software.Results A total of 96 patients were included in this study,4 of whom were excluded due to data loss due to intraoperative EIT bandage displacement and poor signal.Twenty-three patients were included in group A,24 in group B,25 in group C,and 24 in group D.EIT entilation distribution,according to the results of four groups of patients at T0 time ROI Ⅰ-Ⅳ and IR values were no statistical difference.Compared with the T0 moment,four groups of ROI in T1,T2,T3,S1 time ROIⅠand ROI Ⅱ all increase,ROI Ⅲ and ROI Ⅳ are reduced,the IR value increases,and especially in T1 and T2(P < 0.05).Compared with A,B,C three groups,group D in T1 and T2 obviously increase ROI Ⅰand ROI Ⅱ area ventilation;ROI Ⅲ and ROI Ⅳ area ventilation significantly reduced(P < 0.05);IR value of group D also increased at every moment after T0 compared with group A,B and C(P < 0.05).The results of arterial blood gas showed that at T1,compared with group D,oxygenation index of group C increased,while oxygenation index of groups A and B decreased(P < 0.05).At T2,PETCO2 in the four groups increased compared with that at T0 and T1,and there was no statistically significant difference between the four groups.The safety time of non-ventilation period showed that group C and D were better than group A and B(P < 0.05).There was no significant difference between groups C and D.Respiratory mechanics and hemodynamic results had no significant difference among the four groups.Respiratory dynamics and hemodynamics index results showed that compared with T1,lung compliance of all groups at T2 decreased,while PETCO2,peak inspiratory pressure and airway plateau pressure increased(P < 0.05).The mean arterial pressure at T1 was lower than before(T0)(P < 0.05).There was no significant difference in the above respiratory mechanics and hemodynamics indexes among the four groups.Conclusion Mechanical ventilation causes pulmonary ventilation to move from the dorsal to the ventral region,resulting in a decrease in pulmonary ventilation uniformity.Inhaled oxygen concentration of 80% during induction period has minimal effect on pulmonary ventilation uniformity,can obtain optimal oxygenation,and does not affect the safe time of non-ventilation period.