不同潮气量、通气时间对家兔呼吸机相关肺损伤模型的影响

目的 探索不同潮气量、通气时间对制作家兔呼吸机肺损伤模型的影响.方法 54只家兔随机分为3组：常规潮气量组（VT10组,VT10 ml/kg）、中潮气量组（VT20组,VT20 ml/kg） 、大潮气量组（VT40组,VT40 ml/kg）;各组内再根据通气时间分别分为2 h、4 h和6 h 3个亚组.监测通气过程中的动脉血气、肺机械力学和血流动力学变化,肺组织大体标本及HE染色观察肺损伤情况,测定肺湿干比、BALF蛋白浓度,计数BALF中有核细胞和中性粒细胞数目.结果 VT10组在各时间点PaO2/FiO2保持稳定,VT20和VT40两组PaO2/FiO2随通气时间延长有下降趋势,其中VT20组通气4 h、6 h后PaO2/FiO2均＜300 mmHg,VT40组通气后2 h、4 h、6 h的PaO2/FiO2值均＜300 mmHg.VT10组肺组织肉眼及光镜下未见明显的改变.VT20组随着通气时间延长,可见一定程度的肺损伤,至通气6 h时,大体标本肉眼可见散在出血点,而VT40组通气2 h后肺组织就出现轻度损伤改变,通气4 h损伤显著.各组家兔的肺湿干比、BALF蛋白含量、有核细胞总数及中性粒细胞计数均随通气时间延长而升高.结论以VT40 ml/kg通气4 h为成功复制呼吸机所致肺损伤家兔模型的最理想条件.

Influence of Different Tidal Volumes and Duration of Ventilation on Ventilator-associated Lung Injury in Rabbits

Objective To explore the influence of different tidal volumes and duration of ventilation on ventila- tor-associated lung injury in rabbits during the model establishment. Methods A total of 54 rabbits were randomly divid- ed into three groups： the regular tidal volume group （group VT10, VT 10 ml/kg） , the medium tidal~ volume group （group VT20, VT20 ml/kg） and the largest tidal volume group （group VT40, VT40 ml/ kg） ; each group was divided into 3 subgroups according to duration of ventilation for 2 h, 4 h and 6 h. Arterial blood gas, and changes of pneumal me- chanical force and hemodynamic parameters during ventilation were monitored. Samples of pneumal tissue and HE stain were made to detect pulmonary injury and wet/dry ratio. Bronchoalveolar lavage fluid （BALF） was collected for measure- ment of protein concentration, and nucleated cells and neutral cells were counted. Results The PaO2/FiO2 in group VT10 at each time point was stable, PaO2/FiO2 had a downward trend in group VT20 and VT40 with extended aeration, in which the PaO2/FiO2 was less than 300 mmHg after ventilation for 4 h and 6 h in group VT20, and for 2 h, 4 h and 6 h in group VT40, PaO2/FiO2 of 〈 300 mmHg. The pneumal tissue had not obvious change in group VT10 observed by the naked eye and under light microscope. A certain degree of pulmonary injury could be found in group VT20 with ex- tended aeration time, and scattered bleeding points could be found in samples by naked eyes after ventilation for 6 h, while the mild pulmonary tissue damage appeared in group VT40 after ventilation for 2 h, and significant injury appeared after ventilation for 4 h. Pneumal wet/dry ratio, BALF protein level, total nucleated cells and neutral ceils count of rab- bits in all groups were higher with the prolonged duration of ventilation was lengthened. Conclusion The best way of replicating typical ventilator-induced model of pulmonary injury in rabbits is VT40 ml/kg ventilation for 4 h.