Effect Of Compliance Guided An Optimal Positive End-Expiratory Pressure On Arterial Oxygenation And Intrapulmonary Shunt During One-lung Ventilation

Objective To observe the effect of compliance guided an optimal Positive End-Expiratory Pressure（PEEP）on arterial oxygenation and intrapulmonary shunt during one-lung ventilation（OLV）,and discuss the lung protective effect of optimal PEEP during one-lung ventilation.Methods Sixty patients undergoing thoracic surgery were randomly allocated to the study or control group.Patients were monitored for electrocardiogram,pulse oximetry,and non-invasive blood pressure,20 gauge cannula needle for radial artery catheterization under local anesthesia,monitoring ABP.,the right subclavian vein was selected for catheterization under local anesthesia,monitoring CVP.Anesthesia was induced with sufentanil 0.4μg/kg,propofol 2 mg/kg,and cisatracurium 0.3mg/kg.The trachea was intubated with a double-lumen tube（DLT）,37F for male and35F for female patients.Tube position was confirmed by bronchoscopy in the supine and lateral positions.Anesthesia was maintained with sevoflurane 1.0–1.5 vol%,propofol 2-4 mg/（kg·h）and remifentanil 0.1–0.2μg/（kg·min）and intermittent cisatracurium 0.06-0.1 mg/kg.The lungs were initially ventilated using a volume-controlled ventilation mode,two-lung ventilation（TLV）:tidal volume（VT）8ml/kg,respiratory rate 12-14 bpm,inspiratory:expiratory（I:E）ratio 1:2,in 60%oxygen without PEEP.During OLV,VT was reduced to 6 ml/kg,OLV was initiated at the moment of skin incision.Both groups received an alveolar recruitment maneuver（increase inspiratory pressure to 30cmH₂O for 10s）at the 10min after one-lung ventilation.After the alveolar recruitment maneuver,the study group titrate PEEP from 4cmH2O,increased in 2cmH2O steps and hold at each step for 1min,and the static pulmonary compliance（Cst）would be record.Optimal PEEP was determined until the maximal static pulmonary compliance was obtained.In the control group at PEEP level of 5 cmH₂O was established and maintained during the study period.Blood gas analyses,respiratory variables,and hemodynamic variables were recorded at 6 different time points:10 min after TLV（T₀）,10min after OLV（T₁）,30min after PEEP（T₂）,60min after PEEP（T₃）,10min after the end OLV（T₄）and 20min after extubation（T5）.Results1.There were no significant differences in MAP,HR,CVP between the two groups（P>0.05）.2.In the study group,optimal PEEP during the PEEP titration trial was 7.8（±1.2）cmH2O,which was significantly different from the 5 cm H2O used in the control group（95%CI of the difference was+2.4 to+3.3 cm H₂O,P<0.001）.3.The static pulmonary compliance（Cst）in study group was higher than that in control group at T₂,T₃（P<0.05）,no significant differences were found at T₀,T₁,T₄between two groups（P>0.05）.4.Intrapulmonary shunt fraction（Qs/Qt）in study group was lower than that in control group at T₂,T₃,T₄（P<0.05）,no significant differences were found at T₀,T₁,T₅between two groups（P>0.05）.5.PaO₂/FiO₂ in study group was higher than that in control group at T₂,T₃,T₄,T₅（P<0.05）,no significant differences were found at T₀,T₁ between two groups（P>0.05）.6.PaO₂ in study group was higher than that in control group at T₂,T₃,T₄,T₅（P<0.05）,no significant differences were found at T₀,T₁ between two groups（P>0.05）.7.There were no significant differences in V_D/V_T and Pmean between the two groups（P>0.05）.8.There were no significant differences in length of stay days of indwelling drainage tube between the two groups（P>0.05）.Postoperative pulmonary complications were2 cases（7.1%）in study group,and were 7cases（25%）in control group respectively.Conclusion In conclusion,compared with constant 5cmH₂O,compliance guided an optimal PEEP may improve arterial blood oxygenation,reduce intrapulmonary shunt and decrease the incidence of complications in patients undergoing video-assist thoracoscopic lobectomy during one-lung ventilation.