Effect Of Driven Pressure-guided Ventilation On Lung Function In Patients Undergoing Cardiopulmonary Bypass Under Different Inhalation Oxygen Concentrations

Object:To explore the effect of driving pressure guided ventilation strategy under different inspired oxygen concentrations on pulmonary function in patients undergoing median thoracotomy cardiac surgery under cardiopulmonary bypass,and to provide reference for the selection of inspired oxygen concentration and ventilation strategy during operation.Methods:A total of 80 patients,aged 30 to 75 years old,male or female,ASAⅢorⅣ,NYHAⅡorⅢ,body mass index（BMI）18～28 kg/m²were selected for elective open-heart surgery under cardiopulmonary bypass from June 2022 to January 2023.The patients were randomly divided into 4 groups A,B,C and D（n=20）.Patients in4 groups were connected to anesthesia machine after intubation,and respiratory parameters were set as the following ones:volume control mode,gas flow rate 2L/min,VT 8ml/kg（per predicted body weight）,（I:E）1:2,set 20%inspiratory pause time and adjust the ventilation rate per minute to maintain intraoperative P_ETCO₂no higher than 40mm Hg.The inhaled oxygen concentration（Fi O₂）of group A and Fi O₂of group C were set at 50%and 80%respectively,and 5cm H₂O positive end-expiratory pressure（PEEP）was applied for ventilation.Fi O₂of group B was set at50%and Fi O₂of group D was set at 80%,which were all combined with individualized PEEP of driving pressure（DP）oriented for ventilation.For group B and D,PEEP was titrated once after endotracheal intubation,cardiopulmonary bypass shutdown and chest closure,and then maintained.General information like operation time,cardiopulmonary bypass time,blood transfusion and infusion,postoperative catheter time and postoperative hospital stay were collected.Record 10minutes after endotracheal intubation（T₁）,10 minutes after CPB downtime（T₂）,before going out of the room（T₃）in patients with blood oxygen saturation（Sp O₂）,P_ETCO₂,mean arterial pressure（MAP）,PEEP,the airway peak pressure(P_peak),DP,respiratory compliance（Crs）.In T₁,T₂,T₃,and 24 h after surgery（T₄）when extracting the artery of patients with 1 ml of blood gas analysis,record the arterial oxygen partial pressure（Pa O₂）,artery carbon dioxide partial pressure（Pa CO₂）,oxygen index（OI）,alveolar artery blood oxygen partial pressure（A-a DO₂）.Pulmonary ultrasound examinations were performed at time points T₀（before anesthesia induction）,T₃and T₄,and lung ultrasound scores（LUSS）were recorded.The incidence of pulmonary complications within 7 days after surgery was collected through postoperative follow-up.Results:1.General information:There was no significant difference in general data among the four groups（P>0.05）.2.Respiratory parameters:At T₁,T₂and T₃,the PEEP of group B was 6（6,8）cm H₂O,7（6,8）cm H₂O and 8（6,8）cm H₂O,respectively,and the PEEP of group D was 8（6,8）cm H₂O.Compared with group A,DP was decreased and Crs was increased at T_1-3in group B,DP was decreased at T₃in group D,and Crs was increased at T_1-3（P<0.05）.Compared with group B,DP increased and Crs decreased in group C at T_1-3.Compared with group C,DP was decreased and Crs was increased in group D at T_1-3（P<0.05）.Compared with T₁,Crs of the four groups were decreased and P_peakwas increased at T₂,while DP of groups A,B and D was increased.Compared with T₂,in T₃,P_peakincreased and DP decreased in groups B and D,while Crs increased in groups A and D（P<0.05）.3.Arterial blood gas analysis:Compared with group A,OI in group B increased at T₃,Pa O₂and A-a DO₂in group C increased at T_1-3,Pa O₂in group D increased at T_1-3,and A-a DO₂increased at T_2-3.Compared with group B,Pa O₂and A-a DO₂in group C and D were increased at T_1-3,while OI in group C was decreased at T₃.Compared with group C,Pa O₂and OI in group D were increased at T₃,while A-a DO₂was decreased（P<0.05）.Compared with T₁,Pa O₂and OI of the four groups were decreased at T₂,while A-a DO₂of groups A,B and D were increased.Pa O₂and OI of the four groups were decreased at T₃,while A-a DO₂of groups A,B and D were increased（P<0.05）.4.Lung ultrasound score（LUSS）:At T₄,the LUSS of group A was higher than that of group B,and that of group C was higher than that of group B and D（P<0.05）.Compared with T₀,LUSS in 4 groups was increased at T₃and T₄（P<0.05）.5.Postoperative pulmonary complications（PPCs）:There was no significant difference in the overall incidence of PPCs among the four groups within 7 days,but the incidence of atelectasis in groups A and C was higher than that in groups B and D（P<0.05）.Conclusion:1.Under the same ventilation strategy,there is no significant difference in the effect of 50%or 80%inspired oxygen concentration on pulmonary function in patients undergoing cardiac surgery with cardiopulmonary bypass.2.Driving pressure-guided ventilation strategy can increase lung compliance,reduce intrapulmonary shunt,improve oxygenation,and reduce the incidence of postoperative atelectasis in patients undergoing cardiac surgery with cardiopulmonary bypass.