Effect Of Transpulmonary Pressure Guided Individualized Positive End-expiratory Pressure On Postoperative Pulmonary Function In Laparoscopic Radical Colorectal Cancer

Objective:The main objective of this study was to investigate the effects of applying individualized PEEP during laparoscopic radical colorectal cancer surgery on patients’perioperative pulmonary function and postoperative pulmonary complications,and to provide a theoretical basis for proposing effective individualized PEEP titration measures.Methods:From November 2021 to August 2022,70 patients who underwent elective laparoscopic radical rectal cancer were divided into two groups of 35 patients each,the control group（group N）and the individualized PEEP group（group P）,using the random number table method.After CO₂pneumoperitoneum injection and position adjustment,the PEEP value for group N was set at a fixed 5 cm H₂O and maintained until the end of surgery;after pneumoperitoneum administration and position adjustment,the"optimal"PEEP value was titrated using the PSM method for group P and maintained until the end of surgery.General data were collected and compared,and the preoperative（T₀）ARISCAT scores were recorded;the blood gas analysis results were recorded at T₀and 1h after PEEP administration（T₅）and the corresponding indexes were recorded;before pneumoperitoneum administration（T₁）,5 min after pneumoperitoneum administration（T₂）,5 min after PEEP administration（T₃）,30 min after PEEP administration（T₄）,and 1h after PEEP administration（T₅）were recorded.The respiratory mechanics and hemodynamic parameters before pneumoperitoneum（T₁）,5 min after pneumoperitoneum（T₂）,5 min after PEEP（T₃）,30 min after PEEP（T₄）,1 h after PEEP（T₅）and 5 min before extubation（T₆）.Pulmonary ultrasound was used and ultrasound scores（LUS scores）were calculated at T₀and 30 min after extubation（T₇）,and norepinephrine dosage,duration of surgery,pneumoperitoneum,fluid intake and output,and pulmonary complications during mechanical ventilation were recorded for 7 days after surgery.Results:The study initially included 70 patients who underwent laparoscopic radical colorectal cancer,of which one case in group N was excluded due to intraoperative conversion to open abdomen,and one case in group P was excluded due to the inability to obtain clear images by pulmonary ultrasound for postoperative subcutaneous emphysema.68 patients were finally included in group N and group P.The differences in general data（age,sex,and BMI）,surgery-related indicators（volume of infusion,bleeding,urine volume,operation time,pneumoperitoneum time,and norepinephrine use）,and ARISCAT scores were not statistically significant（p>0.05）,There were no statistically significant differences（p>0.05）between the N and P groups in terms of general information（age,sex,and BMI）,surgical parameters（fluid volume,bleeding,urine volume,operative time,pneumoperitoneum,and norepinephrine use）,and ARISCAT score.In terms of gas exchange,OI was significantly higher in the P group and A-a DO₂was significantly lower in the P group at T₇compared with the N group（p<0.05）,and there was no statistically significant difference in Pa CO₂changes between the P and N groups（p>0.05）.In respiratory mechanics,Cdyn was significantly higher in the P group than in the N group at T₃,T₄and T₅（p<0.05）;At T₃to T₆,the Pmean of patients in group P was significantly higher than that in group N,and the difference was statistically significant（p<0.05）.In terms of hemodynamics,the differences in HR and MAP changes between the P and N groups at different time points were not statistically significant（p>0.05）.In terms of assessment of pulmonary atelectasis,the LUS score was significantly lower in the P group at T₇（p<0.05）.In terms of pulmonary complications within 7 d postoperatively,there was no statistically significant difference in the incidence of PPCs between the P and N groups（p>0.05）.Conclusion:In conclusion,early application of individualized PEEP titration strategy after pneumoperitoneum and postural adjustment in patients undergoing laparoscopic radical resection of colorectal cancer can increase early postoperative Cdyn,improve oxygenation and reduce the degree of atractasis,which has a certain lung protective effect.