目的：　研究急性呼吸窘迫综合征(ARDS)及急性肺损伤(ALI)时肺内分流(Qs/Qt)、肺泡死腔(VDalv)、气体交换及呼吸力学的改变。方法：　对麻醉后机械通气的10只幼猪给予持续静脉注射大肠杆菌内毒素,诱导ARDS/ALI的发生,并进行 180min的实验观察。测定了平均肺动脉压(MPAP)、心输出量(CO)、呼吸系统顺应性(Crs)、潮气末CO2 分压(ET CO2 )、一口气CO2 测定(SBT CO2 )、PaO2及PaCO2,并计算出心脏指数(CI)、Qs/Qt、VDalv及ET CO2 /PaCO2。结果：　大肠杆菌内毒素诱发ARDS/ALI后10min,MPAP开始升高,30min达高峰后略有下降,维持较高水平至 180min;Qs/Qt于90min达高峰;VDalv增加并持续180min,而CI,Crs,PaO2,ET CO2/PaCO2 降低(P<0.05)。结论：　Qs/Qt,VDalv ,血流动力学,呼吸力学及血气分析的综合测定,对ARDS/ALI早期诊断及了解其病理生理变化具有重要临床价值。

OBJECTIVE: To investigate the changes of pulmonary shunt fraction (Qs/Qt), alveolar dead space (V Dalv), gas exchange and respiratory mechanics in the septic acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). METHODS: Ten anaesthetized and ventilated young pigs were given an infusion of endotoxin for an experimental observation of 180 min to induce ARDS/ALI. The mean pulmonary artery pressure (MPAP), cardiac output (CO), respiratory compliance (Crs), end tidal CO2 (ET CO2), and single breath test for CO2 (SBT CO2), PaO2 and PaCO2 were recorded. Cardiac index (CI), Qs/Qt, V Dalv and ET CO2/PaCO2 were calculated. RESULTS: Endotoxin induced ARDS/ALI decreased in CI, Crs, PaO2, ET CO2/PaCO2, and increased in MPAP, Qs/Qt, V Dalv (P<0.05). CONCLUSIONS: Qs/Qt and V Dalv in combination with haemodynamics, respiratory mechanics and arterial blood gases are of great clinical importance in the diagnosis of ARDS/ALI and analysis of pathophysiological events.