Two Levels Of Positive End-expiratory Pressure Combined With Lung Recruitment Maneuver In General Anesthesia For Obese Patients In Prone Position

Objective:To evaluate the effect of two different levels of positive end-expiratory pressure（PEEP）combined with lung recruitment maneuver（RM）on general anesthesia for obese patients in prone position.Methods:Ninety obese patients with body mass index（BMI）≥28kg/m²who would undergo general anesthesia for spinal surgery were randomly divided into control group（Group C,PEEP=5 cm H₂O）,experimental group 1（E1,PEEP=5cm H₂O combined with lung recruitment）and experimental group 2（E2,PEEP=10 cm H₂O combined with lung recruitment）,with 30 patients in each group.All patients were given low tidal volume（6～8 m L/kg）mechanical ventilation based on predicted body weight（PBW）.The hemodynamic index,respiratory mechanics index,arterial blood gas analysis index of the three groups of patients before anesthesia（T0）,at 10 minutes of mechanical ventilation in supine position after tracheal intubation（T1）,at 10 minutes of mechanical ventilation in prone position after tracheal intubation（T2）,at 1hour（T3）and at 30 minutes after tracheal extubation（T4）;the lung ultrasound score（LUS）at T0,T4,24 hours after operation（T5）and 48hours after operation（T6）was counted;the incidence of respiratory complications within 5 days after operation was analyzed.Results:Intra-group comparison:the heart rate（HR）and mean arterial pressure（MAP）of the three groups were lower than T0 at T1,T2 and T3（P<0.05）,and there was no significant difference between T4 and T0（P>0.05）;the partial pressure of arterial oxygen（Pa O₂）and oxygenation index（OI）of the three groups increased at T1,T2 and T3,decreased at T4,and reached the highest at T2.The above indexes had significant differences between each time point and T0（P<0.05）;compared with T0,the levels of alveolar-arterial oxygen gradient（A-a DO₂）in group C and E1 were significantly higher at T1,T2,T3 and T4（P<0.05）.The level of A-a DO₂in E2 group was higher than that in T0 at T1,T2 and T3（P<0.05）,but there was no significant difference between T4 and T0（P>0.05）;the peak airway pressure（Ppeak）,airway plateau pressure（Pplat）,and driving pressure（ΔP）of the three groups increased in T2 and T3,and the highest in T3;the levels of lung dynamic compliance（Cdyn）in the three groups decreased in T2 and T3,and the lowest in T3.The above indexes had significant differences at T2 and T3 compared with T1（P<0.05）;compared with T0,the LUS of the three groups were significantly higher at T4,T5 and T6（P<0.05）,but significantly lower at T6 than at T4 and T5（P<0.05）.T5 had a downward trend compared with T4,but the difference was not statistically significant（P>0.05）.Comparison between groups:there was no significant difference in HR and MAP levels among the three groups at each time point（P>0.05）;the levels of Pa O₂and OI in E2 group were higher than those in C group at T2,and higher than those in C group and E1 group at T3 and T4（P<0.05）;the A-a DO₂levels in E2 group were lower than that in group C at T2 and T3,and lower than that in group C and E1 at T4（P<0.05）;The levels of Ppeak,Pplat and Cdyn in E2 group were higher than those in the other two groups,while the levels ofΔP were lower in T1,T2 and T3 than in the other two groups（P<0.05）;the LUS of E2 group was lower than that of the other two groups at T4 and T5,and lower than that of C group at T6（P<0.05）;there was no significant difference between group C and group E1（P>0.05）.There was no significant difference in the incidence of respiratory complications among the three groups within 5 days after operation（P>0.05）.Conculsion:For obese patients undergoing prone position surgery under general anesthesia,high level PEEP combined with lung recruitment maneuver can improve lung compliance and oxygenation,improve oxygen reserve and recovery of lung function,reduceΔP and the incidence of atelectasis within24～48 hours after surgery,but can not significantly reduce the incidence of postoperative respiratory complications.