Effects Of Different Ventilation Modes On Lung Ventilation In Patients Undergoing Laparoscopic Surgery In Trendelenburg Position

Objective To observe the effects of volume controlled ventilation（VCV）and pressure-controlled ventilation-volume guaranteed（PCV-VG）mode on lung ventilation during general anesthesia in patients undergoing laparoscopic surgery in Trendelenburg position.Methods sixty patients scheduled for elective laparoscopic gynecology surgery in Trendelenburg position,aged 40-65 years,ASA physical stutes I or II,with BMI between 18-30 kg/m²were randomly divided into Group V volume-controlled ventilation group and Group P pressure-controlled ventilation-volume guaranteed group,30 cases in each group.After entering the OR,a peripheral venous access was established,and BP,ECG,Sp O₂,and BIS were routinely monitored.The radial artery was punctured and placed under local anesthesia to monitor invasive arterial pressure.A EIT electrode strap was worn along the sixth intercostal space of the chest and connected to an EIT device（Switzerland;Swisstom）.Anesthesia induction:intravenous midazolam 0.02 mg/kg,sufentanil 0.4-0.6μg/kg,etomidate 0.3 mg/kg,rocuronium 0.8-1.0 mg/kg.Avance anesthesia machine（Datex-Ohmeda,USA）was used for controlled ventilation.After intubation,volume control ventilation mode（Group V）and pressure-controlled ventilation-volume guaranteed（Group P）mode were used in each group.Intraoperative ventilator parameter setting:tidal volume8ml/kg,respiratory rate 12-16 times/min,suction ratio 1:2,pressure limit set to 35cm H₂0,inhaled oxygen concentration 60%,flow rate 2 L/min,maintaining P_ETC0₂:35-45 mm Hg.Anesthesia maintenance:Intravenous infusion of propofol 4-8mg·kg^-1·h^-1,remifentanil 0.1-0.3μg·kg^-1·min^-1,cis-atracurium 0.1-0.2mg·kg^-1·h^-1,the dosage of propofol and remifentanil was adjusted to maintain the BIS value of 40-60.Hemodynamic stability was maintained during the operation,and vasoactive drugs were used if necessary.MAP,HR,the percentages of area in center of ventilation（Co V）,dependent silent spaces（DSS）and non-dependent silent spaces（NSS）were recorded at seven different time points:tracheal intubation 5min（T₁）,immediately after changing the position（T₂）,change the position 30min（T₃）,change the position 60min（T₄）,change the position 120min（T₅）,change the supine position（T₆）and VT,airway peak pressure(P_peak)were recorded from T₁to T₅.Blood gas analysis results were recorded at T₁,T₃,T₄and T₅.Record FEV1,FVC,MVV at 3days(T_3d)and 7 days(T_7d)after operation.Results There was no significant difference in general information in the two groups（P>0.05）.There was no significant differences in MAP,HR and VT between the two groups at different time points.Compared with the V group,the DSS of the P group was significantly decreased and the Co V of the P group was significantly increased from T₃to T₆（P<0.05）.The Pa O₂、OI of the P group was significantly increased at T₄and T₅（P<0.05）,and the Ppeak of the P group was significantly increased from T₃to T₅（P<0.05）.FEV1,FVC and MVV increased significantly in group P at T_3dand T_7d.Conclusion Compared with VCV,PCV-VG can significantly improve intraoperative lung ventilation and pulmonary oxygenation in patients undergoing laparoscopic surgery in Trendelenburg position.