Application Of Protective Lung Ventilation Strategy In Prone Position Operation Of Obese Patients

Objective:To investigate the effect of protective lung ventilation strategy on oxygenation and respiratory mechanics in obese patients undergoing prone surgery under general anesthesia.Methods:100 obese patients[28≤BMI≤35（kg/m²）]（ASA II or III）who underwent prone low spine surgery under general anesthesia were randomly divided into5 groups.Intermittent positive pressure ventilation（IPPV）is adopted,Fi O₂is100%,I:E is 1:2,and fresh air flow is 2L/min.（Group A）conventional ventilation,VT 9ml/kg,no PEEP;（Group B）low VT+low PEEP+RM,VT6ml/kg,PEEP 5cm H₂O,RM every 30min（manual control,pressure set to30cm H₂O,duration 30s）;（Group C）low VT+high PEEP+RM,VT 6ml/kg,group C₁:PEEP 10cm H₂O;Group C₂:PEEP 12cm H₂O;Group C₃:PEEP 14cm H₂O,RM every 30min.Adjust RR to make Pet CO₂fluctuate between 30～40mm Hg.T₀,T₁,T₂,T₃,T₄and T₅were marked before anesthesia induction,mechanical ventilation in prone position for 5min,30min,60min,skin suture and 30min after extubation;Arterial oxygen partial pressure（Pa O₂）and arterial carbon dioxide partial pressure（Pa CO₂）at T₀,T₃and T₅were recorded,and oxygenation index（OI）and alveolar arterial oxygen partial pressure difference（A-a DO₂）were calculated;On the other hand,the peak airway pressure（Ppeak）and plateau pressure（Pplat）at T₁,T₂,T₃and T₄were recorded,and the driving pressure（DP）and pulmonary dynamic compliance（Cdyn）were calculated;The occurrence of continuous hypotension and change of ventilator setting were recorded.Results:Compared with T₀,OI and A-a DO₂in each group increased significantly at T₃,OI in group B was significantly lower than other groups（P<0.05）,A-a DO₂was significantly higher than other groups（P<0.05）,but there was no significant difference between groups A,C₁,C₂and C₃.There was no significant difference in OI and A-a DO₂between groups at T₅;Compared with T₀,Pa CO₂in each group increased significantly at T₅（P<0.05）.Comparison of DP from T₁to T₄:group A>group B=group C₁>group C₂=group C₃（P<0.05）;Comparison of Pplat and Ppeak from T₁to T₄:Group C₃>group A=group C₁=group C₂>group B（P<0.05）;Comparison of Cdyn from T₁to T₄:group C₁=group C₂=Group C₃>group B>group A（P<0.05）;Compared with T₁,Cdyn in group A at T₄was significantly lower（P<0.05）.There were 28 cases of continuous hypotension during operation（6 cases in group A,3 cases in group B,4 cases in group C₁,7 cases in group C₂and 8cases in group C₃）,and there was no significant difference in the incidence among the groups;Changes to ventilator settings not occurred.Conclusion:Compared with traditional ventilation and other levels of PEEP,the protective lung ventilation strategy of 12～14cm H₂O PEEP can reduce the driving pressure during prone mechanical ventilation in obese patients,and improve perioperative lung compliance.The risk of hemodynamic instability don’t increase.However,it can’t optimize patients’intraoperative and early postoperative oxygenation.