Safety Evaluation Of Different Ventilation Modes On Mild Obstructive Ventilation Dysfunction In Elderly Patients Underwent Laparoscopic Cholecystectomy

Objective:To compare the ventilation effect and the safety with pressure-controlled ventilation（PCV）and volume-controlled ventilation（VCV）and PCV or VCV combined low PEEP（5cm H₂O）during laparoscopic cholecystectomy（LC）in elderly patients with mild obstructive ventilation dysfunction.Methods:This study is divided into two phases,The first stage:100 cases of patients with pre-existent mild obstructive ventilatory dysfunction in elderly,aged 65 to 75 yr,ASA physical statusâ…¡-â…¢,with body mass index of 18.5²3.9 kg/m²,undergoing elective LC,were randomly divided into two groups（n=50 each）:PCV group（group P）and VCV group（group V）.Fresh gas flow was set at 2 L/min,fraction of inspired oxygen（Fi O₂）60%,V_T at 8¹2ml/kg,I∶E at 1∶2,Ventilatory frequency at 12¹6bpm,P_ETCO₂ was maintained at 35⁴5 mm Hg in both groups,airway peak pressure（Ppeak）,airway plateau pressure（Pplat）,dynamic lung compliance（Cdyn）and inspiratory resistance（Raw）and P_ETCO₂ were measured at 5 min after intubation（before pneumoperitoneum）（T₁）,30 min after pneumoperitoneum（T₂）,10 min after the end of pneumoperitoneum（T₃）,And take the radial artery and central venous blood samples for blood gas analysis,oxygenation index（Pa O₂/Fi O₂）,respiratory index（RI）,physiologic dead space fraction（V_D/V_T）and the pulmonary shunt fraction（Qs/Qt）were calculated.Extubation time and 2 hours after extubation associated complications were recorded.The second stage:By analyzing the result of the first stage of the optimum ventilation mode（PCV）.100 cases of patients with pre-existent mild obstructive ventilatory dysfunction in elderly undergoing elective LC,were randomly divided into two groups（n=50 each）:PCV group（group P0）and PCV+PEEP group（group PP）.Fresh gas flow were set at 2 L/min,inhaled oxygen concentration（Fi O₂）60%,set the inspiratory pressure make the VT for 8¹2ml/kg,I∶E=1∶2,F=12¹6 bpm,In group P1,PEEP at 0cm H₂O;In group PP,PEEP at 5cm H₂O,P_ETCO₂ was maintained at 35⁴5 mm Hg.P_ETCO₂,airway peak pressure（Ppeak）,airway plateau pressure（Pplat）and dynamic lung compliance（Cdyn）,were measured at 5 min after intubation（T₁）,30 min after pneumoperitoneum（T₂）,10 min after the end of pneumoperitoneum（T₃）,And take the radial artery and central venous blood samples for blood gas analysis,calculating oxygenation index（Pa O₂/Fi O₂）,dead space ventilation rate（V_D/V_T）and pulmonary shunt fraction（Qs/Qt）.Extubation time,Steward’s score≥4 time and 2 hours after extubation associated complications were recorded.Results:Compared with group V,Ppeak,Pplat and Raw,RI,V_D/V_T and Qs/Qt were decreased at T_1-3,and Cdyn and Pa O₂/Fi O₂ were increased at T_1-3,and the incidence of hypoxemia was decreased within 2 h after extubation was statistically significant difference in group P（P<0.05）.There were no statistically significant difference in extubation time,the recovery time and the incidence of hypercapnia between the two groups（P>0.05）.Compared with group P0,PP group T_1-3 Ppeak and Pplat increaseddecreased（P<0.05）;There were no statistically significant difference in extubation time and the steward’s score≥4 time（P>0.05）,the incidence of hypoxemia and hypercapnia incidence was deceased in group PP（P<0.05）.Conclusion:Compared with VCV,PCV and PCV+PEEP（5cm H₂O）can better improve the ventilatory efficacy in elderly patients with pre-existent ventilation dysfunction undergoing LC during general anesthesia.While PCV+PEEP（5cm H₂O）has advantages of PCV and PEEP ventilation mode for improving pulmonary compliance and oxygenation index and lower pulmonary shunt fraction,But the best airway pressure range still further research.