Effects Of Different Levels Of Positive End-expiratory Airway Pressure On Atelectasis And Oxygenation Function In Elderly Patients Undergoing Laparoscopic Surgery

Objective:To investigate the effect of different levels of positive end-expiratory airway pressure（PEEP）guided by driving pressure（ΔP）on atelectasis and oxygenation function in elderly gynecological laparoscopic surgery.Methods:This study included elderly patients who underwent gynecological laparoscopic surgery in a certain hospital from February 2022 to December 2022.The ASA classification is I-II,the age is greater than or equal to 65 years old,,and the BMI is18-24 kg/m².They were divided into fixed PEEP group（group C）and individualized PEEP group（group P）with 33 patients each.After general anesthesia and endotracheal intubation,the patient was ventilated in volume-controlled ventilation mode with a tidal volume of 6-8 m L/kg,Fi O₂ of 30%,and an inspiratory-expiratory ratio of 1:2.Group C took PEEP of 5 cm H₂O until the end of the operation;PEEP of group P was first gradually increased from 0-10 cm H₂O,the titration interval was 2 cm H₂O,and the titration time of each interval was 2 minutes,and the plateau of each PEEP level at the end of 2 minutes was recorded Plateau pressure（plat）,the driving pressure value was calculated by the formula:ΔP=plat-PEEP,and the PEEP corresponding to the minimum driving pressure in the patient guidance process was selected as the optimal PEEP value of group P until the end of the operation.The main observation time points were the day before operation（T0）,10 minutes after tracheal intubation（T1）,10 minutes after pneumoperitoneum（T2）,40 minutes after pneumoperitoneum（T3）,10 minutes after extubation（T4）,and After 24h（T5）.The main outcome measure was the lung ultrasound score（Lung ultrasound score,LUS）at T0,T4,T5.The secondary observation indicators were the oxygenation index at T1,T2 and T3,the plateau pressure corresponding to each PEEP level in group P,the optimal PEEP value in group P,the mean arterial pressure and heart rate at T1,T2,T3 and T4,And the pulmonary complications within 7 days after operation.Results:1.General information:There was no statistical difference between the two groups in terms of basic information such as age,height,weight,and operation time（P>0.05）.2.LUS scores at T0,T4,and T5:The results of two-factor repeated measures analysis of variance showed that there was an interaction effect between group and time（F=41.896,P<0.05）.Inter-group comparison:at T4,the LUS score of group P was significantly lower than that of group C,and the difference was statistically significant（P<0.05）;at T0 and T5,there was no significant difference in the LUS scores of group C and P（P>0.05）;Intra-group comparison:In group C,the LUS score at T4 was significantly higher than T0 and T5,and the difference was statistically significant（P<0.05）;the LUS score at T5 was significantly higher than T0,and the difference was statistically significant Significant（P<0.05）;in group P,the LUS score at T4 was significantly higher than T0 and T5,the difference was statistically significant（P<0.05）;the LUS score at T5 was significantly higher than T0,the difference was statistically significant（P<0.05）.3.Oxygenation index at T1,T2,and T3:Two-factor repeated measures analysis of variance was used,and there was an interaction effect between group and time（F=22.200,P<0.05）.Comparison between groups:at T3,the oxygenation index of group P was significantly higher than that of group C,and the difference was statistically significant（P<0.05）;at T1 and T2,there was no significant difference in oxygenation index between groups C and P significance（P>0.05）;intra-group comparison:in group C,the oxygenation index at T3 was significantly lower than T1 and T2（P<0.05）;in group P,the oxygenation index at T3 was significantly lower than T1,T2（P<0.05）.4.Plateau pressure corresponding to different PEEP levels:As PEEP gradually increased from 0,2,4,6,8,and 10 cm H₂O,the plateau pressure showed an increasing trend.5.The optimum PEEP value of group P:8cm H₂O（6-10 cm H₂O）.6.Mean arterial pressure and heart rate at T1,T2,T3,and T4:There was no significant difference in mean arterial pressure and heart rate between group P and group C at T1,T2,T3,and T4（P>0.05）.7.Pulmonary complications within 7 days after operation:1 case of hypoxemia occurred in group C,0 cases of hypoxemia occurred in group P,no atelectasis,acute pneumonia,pulmonary infection and Acute Respiratory Distress Syndrome.Conclusion:Compared with fixed PEEP,individualized PEEP guided by driving pressure can significantly improve lung atelectasis and oxygenation function in elderly laparoscopic gynecological surgery without causing mechanical lung injury and hemodynamic fluctuations.