小潮气量加低水平呼气末正压通气对腹腔镜手术患者呼吸力学及肺氧合功能的影响

目的探讨小潮气量加低水平呼气末正压（positive end-expiratory pressure,PEEP）机械通气对肺功能正常患者人工气腹期间呼吸力学及肺氧合功能的影响。方法 2009年8月~2010年4月,45例ASAⅠ~Ⅱ级,择期全麻下行腹腔镜手术患者,随机均分为3组,每组15例。麻醉诱导维持用药相同,气管插管后行机械通气,气腹前3组通气参数均设定为潮气量（VT）8 ml/kg,呼吸频率（RR）12次/min,吸呼比（I∶E）=1∶2。气腹后通气参数设定分别为：Ⅰ组VT=6 ml/kg,RR=18次/min,PEEP=5 cm H2O;Ⅱ组VT=10 ml/kg,RR=10次/min,PEEP=0;Ⅲ组（对照组）同气腹前。分别在气管插管后（T0）,手术开始（T1）,气腹5 min（T2）,气腹30 min（T3）,气腹60 min（T4）,拔气管导管前15 min（T5）,拔气管导管后20 min（T6）监测脉搏血氧饱和度（SpO2）、呼气末CO2分压（PETCO2）、气道峰压（Ppeak）、平均气道压（Pmean）,并计算肺动态顺应性（Cdyn）。分别在T0,T3,T4,T6时点抽取动脉血监测血气,并根据动脉血氧分压（PaO2）、动脉血CO2分压（PaCO2）、吸入氧浓度（FiO2）等计算氧合指数、呼吸指数、肺泡动脉血氧分压差（A-aDO2）。结果 3组各时点平均动脉压及心率、PaO2组间比较差异无显著性（P〉0.05）。与T0时相比,Ppeak气腹后升高（P〈0.05）,Ⅱ、Ⅲ组更明显;Pmean气腹后也升高（P〈0.05）,Ⅰ组最明显;Cdyn气腹后明显降低（P〈0.05）,Ⅱ组最明显;PETCO2明显升高（P〈0.05）,Ⅰ组更明显;气腹后pH值明显降低（P〈0.05）,Ⅰ组最明显;Ⅰ、Ⅲ组PaCO2气腹后明显升高（P〈0.05）,Ⅱ组无明显变化（P〉0.05）。与机械通气时（T0、T3、T4）相比,3组A-aDO2拔管后（T6）明显降低（P〈0.05）,Ⅰ组更明显;氧合指数拔管后（T6）明显降低（P〈0.05）,3组组间差异无显著性（P〉0.05）;呼吸指数拔管后明显降低,Ⅰ组最明显（P〈0.05）。结论小潮气量机械通气加低水平呼气末正压可以有效降低术中气道压,改善肺顺应性,增加肺通气效率,可以安全地应用于腹腔镜手术呼吸管理中。

Effects of Low Tidal Volume Combined with Low Level of Positive End-expiratory Pressure on Respiratory Mechanics and Alveolar Oxygenation in Patients Undergoing Laparoscopic Surgery

Objective To investigate the effect of lower tidal volume（VT） combined with low level of positive end-expiratory pressure on lung compliance and oxygenation function in patients undergoing laparoscopic surgery. Methods Forty-five ASA class Ⅰ or Ⅱ patients scheduled to undergo an elective laparoscopic surgery were randomly divided into 3 groups with 15 cases in each.All the patients received mechanical ventilation（MV） with a VT at 8 ml/kg,respiration rate（RR） at 12 bpm,and I∶E at 1∶2 after induction of anesthesia.Since pneumoperitoneum,group Ⅰ were assigned to MV with a lower VT at 6 ml/kg,PEEP 5 cmH2O,and RR 18 bpm;group Ⅱ were administered with a higher VT at 10 ml/kg,RR at 10 bpm and no PEEP;while group Ⅲ were treated as pre-pneumoperitoneum.In the three groups,we monitored the SpO2,PETCO2,Ppeak,Pmean,Cdyn at the beginning of the operation（T1）,and 5,30,and 60 minutes post-pneumoperitoneum（T2-T4）,and 15 minutes before and 20 minutes after the extubation（T5 and T6）.Meanwhile,at T0,T3,T4 and T6,oxygenation index（OI）,respiration index（RI）,Oxygen pressure difference between alveolar and arterial（A-aDO2） were calculated based on the measurements of PaO2,PaCO2,and FiO2. Results No marked difference was detected in the invasive arterial pressure,heart rate,and PaO2 among the three groups（P0.05）.Compared to T0,after pneumoperitoneum both Ppeak and Pmean increased significantly（P0.05,increase of Ppeak was even more markedly in groups Ⅱ and Ⅲ,while increase of Pmean was more remarkable in group Ⅰ）;Cdyn and pH value decreased significantly especially in group Ⅱ and group Ⅰ respectively（both P0.05）,PETCO2 was raised significantly especially in group Ⅰ（P0.05）;PaCO2 was not changed remarkably in group Ⅱ（P0.05） but increased significantly in groups Ⅰ and Ⅲ（P0.05）.Compared to T0,T3 and T4,A-aDO2 decreased significantly after extubation（T6） in all the groups,especially in group I;and both OI and RI decreased significantly at the three groups（P0.05;no significant difference among the groups in OI,P0.05;but group Ⅰ showed significantly bigger decrease in RI,P0.05）. Conclusions Low tidal volume combined with low level of positive end-expiratory pressure for MV can reduce airway peak pressure and pulmonary dynamic compliance during pneumoperitoneum and improve the alveolar oxygenation,and thus can be safely used in laparoscopic surgery.