全麻中低潮气量机械通气对病人肺泡不张发生的影响

目的 探讨全麻中低潮气量（VT）机械通气对病人肺泡不张发生的影响。方法 择期全麻下行开颅手术病人16例。ASAⅠ级或Ⅱ级，心功能Ⅰ级或Ⅱ级，年龄20-50岁，随机分为2组，每组8例，常规VT（10 ml／kg）组（TV组）和低VT（6 ml／kg）组（LV组）。分别于气管插管后10 min和手术结束后10min采用移动CT行全肺扫描，计算膈上1 cm层面肺不张面积和百分比，同时行动脉血气分析，记录动脉血二氧化碳分压（PaCO2），并计算肺泡．动脉血氧分压差P（A-a），O2]、氧合指数（PaO2／FiO2）及呼吸指数（RI）。结果 气管插管后10 min和手术结束后10 min时2组病人肺泡不张的发生率、面积、百分比、P（A-a）O2、PaCO2、PaO2／FiO2及RI组内、组间差异均无统计学意义（P〉0．05）。结论 低VT （6 ml／kg）机械通气不增加全麻下开颅手术病人肺泡不张的发生。

Does atelectasis increase in patients ventilated with low tidal volume during general anesthesia?

Objective To determine whether atelectasis increases in patients ventilated with low tidal volume during general anesthesia. Methods Sixteen ASA I or II patients aged 20-50 yr undergoing elective intracranial operation under general anesthesia were randomly allocated to one of 2 groups ( n = 8 each) : group A traditional tidal volume (VT = 10 ml/kg ) and group B low tidal volume (VT = 6 ml/kg ) . All patients were intubated and mechanically ventilated (FiO2 = 100% , I:E = 1 -2, PEEP = 0). PETCO2 was maintained at 38-42 mm Hg by adjusting respiratory rate. ECG, SpO2 and PET CO2 were continuously monitored. Arterial blood samples were taken at 10 min after tracheal intubation and 10 min after the end of operation. PaO2 and PaCO2 were measured and PaO2/FiO2, P(A-a) O2 and respiratory index P(A-a) O2/PaO2 ] were calculated. Atelectasis was detected by CT scanning at 10 min after tracheal intubation and 10 min after the end of operation. CT scanning at the end of expiration can distinguish atelectatic lung tissue from normally ventilated and over-/under- ventilated lung tissue. The atelectatic lung area can be estimated.Results The two groups were comparable with respect to M/F sex ratio, age, body weight, duration of operation and the amount of fluid infused. There was no significant difference in atelectasis area and blood gas parameters after tracheal intubation and the end of operation between the two groups. Conclusion Mechanical ventilation with low tidal volume over a prolong surgery does not increase atelectasis in patients as compared with mechanical ventilation with traditional tidal volume.