Comparison Of The Application Of Pressure-controlled And Lung-protective Volume-controlled Ventilation In Lumbar Spine Surgery During Prone Position

Objective:Pressure-controlled ventilation（PCV）and lung-protective volume-controlled ventilation（LP-VCV）modes in lumbar spine surgery during prone position were compared in terms of their effects on mechanical ventilation and the occurrence of postoperative pulmonary complications（PPCs）.The authors explored whether the application of PCV in this type of surgery can also produce certain effects on lung protection.Methods:Forty patients who were scheduled to undergo lumbar spine operations during prone position were randomly assigned to the pressure-controlled ventilation group（Group P）and the lung-protective volume-controlled ventilation group（Group L）,with 20 patients in each group.The general characteristics of the two groups of patients,including gender,age（years）,height（cm）,weight（kg）,BMI（kg/m2）,ASA classification,and PPCs risk scores were recorded during the preoperative visit.V_T was calculated based on predicted body weight（PBW）.After the induction of anesthesia and before the patients turned to the prone position,both groups were ventilated with conventional VCV modes,and ventilation parameters were set as follows:VT=8ml/kg（PBW）,respiratory rate（f）was 12 breaths per minute,the fraction of inspired oxygen（Fi O2）was 100%,positive end-expiratory pressure（PEEP）was 0,and the inspiratory-expiratory ratio（I:E）was 1:2.After turning the patients to the prone position,the ventilation settings of Group L were VT=6～8ml/kg（PBW）,f=12～16 times per minute,PEEP=5cm H₂O,Fi O₂=60%（mixed with air）,I:E=1:2,and the recruitment maneuvers（RMs）were performed every 30 minutes.The V_T of Group P was set by adjusting the inspiration pressure(P_INS)（maximum 40cm H₂O）to form 6～8ml/kg（PBW）,other parameters were set as follows:f=12～16 times per minute,PEEP=0,Fi O₂=60%（mixed with air）and I:E=1:2.Data of respiratory mechanics at T1～T4including peak airway pressure(P_peak),plateau airway pressure(P_plat),driving pressure（Δp）,and dynamic lung compliance(C_dyn)were recorded.Arterial blood gases（ABG）were analyzed at T0,T1,T4,and T5;and p H,Pa CO₂,Pa O₂were recorded and oxygenation index（OI）was calculated according to the formula“Pa O₂/Fi O₂”.Fi O₂ was the value at the same time when arterial blood was sampled.MAP,Sp O₂,and HR were recorded at T0～T5;other indicators of the perioperative periods including operation time（h）,crystalloid fluid（ml）,colloid fluid（ml）,blood loss（ml）,blood transfusion（ml）,urine volume（ml）,and hospitalization time（days）were recorded.The occurrence of PPCs within 7 days after the operations were recorded.The respiratory mechanics,OI,perioperative indicators,and the occurrence of PPCs within 7 days after surgery were compared between the two groups.Results:P_peak（T1:12.7±3.0 vs 18.6±2.3,T2:13.1±3.1 vs 18.1±2.5,T3:13.4±3.1vs 18.6±2.8,T4:13.2±3.1 vs 19.0±2.3,p<0.05）and P_plat（T1:12.6±2.9 vs17.4±2.2,T2:13.0±3.1 vs 17.3±2.3,T3:13.2±3.0 vs 17.4±2.8,T4:13.2±3.1 vs17.8±2.0,p<0.05）were significantly lower during PCV than during LP-VCV;Δp and C_dyn were not significantly different between the two groups.There were no significant differences in p H,Pa O₂,and OI between the two groups;Pa CO₂ at T4 was significantly higher during PCV than during LP-VCV（53.7±3.7 vs 49.1±3.9,p<0.05）.There was no significant difference in Pa CO₂ between the two groups at the other three points.Pa CO₂ and p H in the two groups tended to increase and decrease respectively during the operations.There were no significant differences in perioperative indicators between the two groups;the occurrence of PPCs in the two groups during the postoperative follow-up were similar.Conclusion:Compared with lung-protective VCV mode,P_peak and P_plat were significantly lower when patients were ventilated with PCV mode in lumbar spine surgery during prone position.ΔP,Cdyn,and OI were not significantly different between the two groups.Postoperative pulmonary complications did not occur in both groups.This study demonstrated that PCV can be safely used in this type of surgery,and may have certain lung-protective effects similar to lung-protective VCV.However,V_T changed easily in surgery when using PCV mode.To obtain more valid evidence,the conclusions above need to be further verified.