增加吸气时间对腹腔镜手术患者气体交换和呼吸力学的影响

目的 探讨延长吸气时间即反比通气对腹腔镜手术患者气体交换的影响.方法 择期腹腔镜下妇科手术患者75例,按照随机数字表法分为3组：传统的吸呼比1∶2组,吸呼比1∶1组,吸呼比2∶1组,每组各25例.潮气量设定为6～7ml/kg,吸呼比在气腹开始时进行调整.于下列时间点测定动脉血气：麻醉诱导后15min（T1）,CO2气腹开始后25min（T2）,50min（T3）时,并计算相应时间点氧合指数（PaO2/FiO2）和生理无效腔（VD/VT）;记录相应时点呼吸力学和血流动力学指标.结果 1∶2组T2、T3时点PaO2/FiO2较T1时有所下降（P＜0.05）,而1∶1组和2∶1组PaO2/FiO2无显著下降.3组PaCO2在T2、T3时点均明显增加,但T3时,2∶1组PaCO2比1∶1组和1∶2组低（P＜0.05）.与1∶2组比较,T2、T3时点,1∶1组和2∶1组VD/VT显著降低（P＜0.05）.气腹开始后所有组气道峰压和气道平台压均升高;与1∶2组相应时点比较,1∶1组和2∶1组T2、T3时点Pplat上升（P＜0.05）;T2和T3时,1∶1组和2∶1组的吸气峰流量较在T1时明显降低.手术开始后呼吸系统静态和动态顺应性降低,但组间无统计学差异（P＞0.05）.结论 腹腔镜手术时延长吸气时间有助于改善氧合.与常规吸呼比比较,延长吸气时间不增加气道峰压或气道平台压且能加快CO2的排出,反比通气可促进气体交换和改善呼吸功能.

Effects of Prolonged Inspiratory Time on Gas Exchange in Patients Undergoing Gynaecologic Laparoscopic Surgery

Objective To investigate the effects of prolonged inspiratory time via inspiratory to expiratory ratio（I/E） adjustment on gas exchange in patients undergoing gynaecologic laparoscopic surgery. Methods Seventyfive patients undergoing gynaecologic laparoscopie surgery were randomly assigned to one of four groups： conventional inspiratory -to -expiratory （I： E） ratio（ Group 1：2） , I： E ratio of 1 ： 1 （ Group 1 ： 1 ） and 2：1 （ Group 2：1 ）. Tidal volume was set to 6ml/kg, and I： E ratio was adjusted at the onset of pneumoperitoneurn. Arterial blood gas analysis with measurements of partial pres - sure of arterial oxygen/fraction of inspired oxygen （ PaO2/FiO2 ） , and physiologic dead space - to - tidal volume ratio （ VD/VT ） was performed 15 rain after anaesthetic induction （Tl ） , and 25 （ T2 ）. Results PaOJFiO2 at T2and T3 in Groups 1：1 and 2：1 were higher than Group 1： 2. The partial pressure of arterial carbon dioxide at T3 in Group 2：1 was lower than the other groups,though it was elevated in three groups. The VD/VT at T2and T3 were lower in Groups 1：1 and 2：1 than Group l：2. There was no statistical significane about respiratory system static compliance and dynamic compliance among three groups. Ppeak and Ppalt were increased in three groups,however, Groups 1：1 and 2：1 had higher plateau pressure at T2 and T3 than in group 1 ： 2. Conclusions The results implied that increased inspriatory time confered better CO2 elimination without elevating the peak or plateau airway pressure compared with conventional I： E ratio. A prolonged inspiratory time demonstrated a beneficial effect on gas exchange and respiratory mechanics in patients undergoing laparoseopie surgery in the Trendelenburg position.