机械通气动态通气参数对ARDS犬肺组织病理学的影响

Effect of Dynamic Ventilatory Factors on Lung Histopathology in a Dog Model of Acute Respiratory Distress Syndrome

目的研究机械通气动态通气参数对急性呼吸窘迫综合征(ARDS)犬肺组织损伤的影响。方法取24条健康杂种犬,采用气管内盐酸吸入法建立ARDS模型后随机分为A、B、C、D 4组,并按下述方案进行机械通气。A组:小潮气量(6 mL/kg)、低吸气流速[6 mL/(kg.s)]、高通气频率(30次/min);B组:大潮气量(20 mL/kg)、高吸气流速[20 mL/(kg.s)]、高通气频率(30次/min);C组:大潮气量(20 mL/kg)、高吸气流速[17 mL/(kg.s)]、低通气频率(15次/min);D组:大潮气量(20 mL/kg)、低吸气流速[10 mL/(kg.s)]、低通气频率(15次/min)。机械通气4 h后处死动物,取出肺脏,观察肺脏外形,光镜下观察病理组织学形态,并进行DAD评分及高倍镜下中性粒细胞计数。结果光镜下可见B组肺泡壁结构模糊,肺泡壁塌陷,肺泡腔消失。病变区有大量的中性粒细胞浸润、蛋白液和红细胞渗出。肺组织病理DAD评分:B组为12.8±1.47,显著高于A组和D组(P<0.01),但与C组无明显差异(P>0.05)。结论大潮气量、高吸气流速、高通气频率机械通气可导致严重的肺损伤,降低通气频率,可适当的减轻这类损伤。在大潮气量的基础上,降低通气频率及吸气流速,对损伤的肺组织可起到一定的保护作用。

Objective To evaluate the effect of dynamic ventilatory factors on lung histopathology in a dog model of acute respiratory distress syndrome （ARDS）. Methods The ARDS dog model was duplicated by instillation hydrochloric acid. The dogs were divided into 4 groups： （1） low VT （6 mL/kg） at respiratory rate 30, low inspiratory flow 6 mL/（kg · s）. （2） large VT （20 mL/kg） at respiratory rate 30, high inspiratory flow 20 mL/（kg · s）. （3） large VT （20 mL/kg） at respiratory rate 15,high inspiratory flow 17 mL/（kg · s）. （4） large VT （20 mL/kg） at respiratory rate 15,low inspiratory flow 10 mL/（kg · s）. All the dogs were killed after 4 h ventilation. Physiology parameters, lung histopathological changes, DAD scores, and PMN counting were measured. Results Under light microscope, lung tissue appeared seriously pathological changes in group B. Alveolar wall was obscure and dent without cavity. There were the infiltration of inflammatory cells and proteins and red blood cells. Alveolar septum became thick. DAD scores in group B （12.8 ±1.47） was higher than that in groups A and D（P〈0.01）,there was no difference be- tween groups B and C（P〈0.05）. Conclusion Large volume ventilation with high inspiratory flow ,high respiratory rate could produce severe lung injury. Reduction of inspiratory flow and respiratory rate at large volume ventilation provides pulmonary protection.