正、负压通气对离体兔肺血流动力学和氧合效果的影响

Effects of positive/negative pressure ventilation on the lung haemodynamics and oxygeration of isolated perfused rabbit lungs

目的 :运用离体兔肺灌流模型 (IPL )比较正、负压两种通气对肺循环血流动力学及通气效果的影响。方法 :建立 18只肺负压通气 (NPV )的 IPL模型 ,控制灌流液流量 (133.33m l/ m in)不变 ,在相同的潮气量及呼气末跨肺压下 ,对 12只 IPL更换为正压通气 (PPV ) ,2 0 min后重新进行 NPV。在两种通气下 ,测定灌流压力 (Pa)、回流压力(Pv)、气道压力 (Paw)、肺重量 (L Wt)等指标并连续同步描记。检测灌流液血氧分压 (Po2 )值。另 6例 IPL一直行NPV.结果 :PPV可使 Pa、肺血管阻力增高 ,L Wt下降。 PPV吸气时 Pa增加 ,Pv下降 ,L Wt略有上升 ;NPV吸气时 Pa,Pv均下降 ,L Wt显着增加。 NPV时血氧增加幅度高于 PPV。结论 :本实验条件下 PPV导致肺血管阻力增加 ;NPV的氧合效果优于

AIM: To evaluate the effects of positive/negative pressure ventilation on pulmonary hemodynamic and oxygenation under the same tidal volume and end-expiratory transpulmonary pressure of isolated perfused rabbit lungs. METHODS: 12 isolated perfused rabbit lung(IPL) models were set up at a constant perfusion flow (133.3 ml/min) and given negative pressure ventilation (NPV). Ventilation mood was changed into positive pressure ventilation (PPV) progressively under the same tidal volume and end-expiratory transpulmonary pressure (residual volume). 20 min later, ventilation mood was changed back to NPV. The changes in perfusion pressure(Pa) and venous pressure(Pv), airway pressure(Paw) and lung weight of IPL(LWt) were measured and monitored simultaneously and continuously on the recorder. Besides, the perfusate underwent blood gas analysis. 6 additional IPLs, which were similarly treated but not changed into PPV served as the control. RESULTS: PPV increased the perfusion pressure and pulmonary vascular resistance and decreased the lung weight. Under PPV, Pa rose, Pv went down, and LWt increased slightly at the inhaling phase. However, when NPV was given, both the perfusion and venous pressures went down, and lung weight increased significantly at the inspiratory phase. The partial pressure of oxygen in perfusate increased much more significantly under NPV than under PPV. CONCLUSION:Positive pressure in the airway affected alveolus vessels, and caused an increase in the pulmonary vascular resistance and the oxygenation of NPV might be better than that of PPV.