The Effect Of Regular Recruitment Maneuver Combined With Individualized Positive End-expiratory Pressure On Atelectasis In Elderly Patients Undergoing Laparoscopic Radical Resection Of Colorectal Cancer

Object:To evaluate the effect of individualized positive end-expiratory pressure（PEEP）guided by driving pressure（DP）combined with or without the regular recruitment maneuver（RM）on atelectasis in elderly patients undergoing laparoscopic radical colorectal resection using lung ultrasound.Methods:Sixty-two patients aged 65-85 years,ASA statusⅠ-Ⅲ,who planned to undergo laparoscopic radical resection of colorectal cancer in the Trendelenburg position were randomly divided into an experimental group（RRM group,n=31）and a control group（C group,n=31）.Initial ventilator settings included tidal volume（VT）of 6 ml/kg of predicted body weight,PEEP of 5 cm H₂O,Fi O₂of 0.5,inspiratory/expiratory ratio（I:E）of 1:2,inspiratory pause time of 30%,and ventilatory rate of 12 breaths/min.In both groups,a RM was applied once after pneumoperitoneum was established and the patients were transferred to the Trendelenburg position,followed by individualized PEEP titration guided by the lowest DP immediately,and the optimal PEEP was determined and maintained at this level until the end of the surgery.After pneumoperitoneum deflation,patients in both groups underwent another RM.The different interventions were:in the RRM group,additional RM was administered every 30 minutes from the beginning of pneumoperitoneum,while in the C group,no additional RM was administered.All RM used an incremental PEEP method:adjusted to pressure control mode with a ventilation rate of 10 breaths/min,an I:E ratio of 1:1,and a constant inspiratory driving pressure of 20 cm H₂O by increasing PEEP from 5 to 15 cm H₂O at 5 cm H₂O intervals for five respiratory cycles（30s）at each PEEP level.The time points of observation and recording were:before induction of anesthesia（T0）,30 min after pneumoperitoneum establishment（T1）,1.5 h after pneumoperitoneum establishment（T2）,at the end of the procedure（T3）,45 min after admission to the post-anesthesia resuscitation unit（PACU）（T4）.LUS was recorded at T0,T3,and T4.The results of blood gas analysis（including PH,Pa O₂,Pa CO₂,and Pa O₂/Fi O₂）and hemodynamic parameters（including MAP and HR）at time points T0-T5 were recorded.Ventilator parameters（Ppeak,Ppalt,and lung dynamic compliance[Cdyn]）were recorded at T1-T3.The incidence of hypotension during RM,the use of vasoactive agents during operation,hypoxic saturation events（Sp O₂<94%,unscheduled oxygen supplementation was required）in PACU,and the incidence of pulmonary complications（POPC）within the first 7 days after operation were recorded.Results:The median value of individualized PEEP was 9 cm H₂O in both groups（P>0.05）.Compared with the C group,LUS was significantly lower in the RRM group at T3 and T4（P<0.05）.At T2 and T3,Ppeak and Ppalt were lower in the RRM group（P<0.05）,while Pa O₂/Fi O₂and Cdyn were higher（P<0.05）.There was no significant difference in MAP and HR between the two groups at different time points（P>0.05）.The incidence of hypotension and the use of vasoactive agents during RM were similar between the two groups（P>0.05）.In addition,the RRM group had a lower incidence of hypoxic saturation events in PACU（P<0.05）.However,there was no significant difference in POPC incidence between the two groups（P>0.05）.Conclusion:During individualized PEEP ventilation in elderly patients undergoing laparoscopic radical resection of colorectal cancer,an additional RM delivered every 30 minutes during surgery was more advantageous in reducing atelectasis than the two RM administered at the beginning and end of the pneumoperitoneum.At the same time,it is more conducive to improving intraoperative oxygenation and respiratory mechanics without increasing the use of vasoactive drugs.However,further research is needed to determine whether the physiological benefits of regular RM can reduce POPC.