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背景:临床已经证实,长时间(36～48h)吸入高浓度氧后可引起不可逆性氧毒性肺损伤。50%以内的低浓度吸氧是否能减少肺损伤中的潜在氧毒性?目的:观察家犬气管插管后连续纯氧通气7h肺超微结构的变化。设计:随机对照动物实验。单位:青岛大学医学院附属医院麻醉科。材料:选用20只健康成年杂种犬,雌性6只,雄性14只,体质量15～16kg,由青岛大学医学院附属医院动物实验中心提供。BIRD8400STi呼吸机系美国鸟牌器械公司生产,HP-M102A多功能监护仪系美国惠普公司生产。方法:实验于1999-07/2000-01在青岛大学医学院附属医院动物实验中心完成。①实验干预:按照性别将将实验犬分为纯氧机械通气组和34%氧浓度机械通气组,每组雌性3只,雄性7只。实验犬麻醉后,纯氧机械通气组设定吸入氧体积分数为1,34%氧浓度机械通气组设定吸入氧体积分数为0.34,通气时间均为7h。②实验评估:监测气管插管后1,3,5,7h平均动脉压、心率,采用Ohmeda5250RGM麻醉气体监测仪监测吸入氧浓度、呼气末二氧化碳分压、呼吸频率及呼吸道峰压;采用投射电子显微镜观察机械通气7h后各组右肺下叶超微结构变化。主要观察指标:实验犬血流动力学参数观察、肺组织超微结构改变观察。结果:20只犬均进入结果分析。①血流动力学参数观察:各时间点平均动脉压、呼气末二氧化碳分压、呼吸道峰压及心率差异无显著性(P>0.05)。②肺组织超微结构改变观察:纯氧机械通气组50%标本线粒体肿胀、排列紊乱,基质变浅,出现透明区,双层膜变薄,60%标本肺泡隔间质水肿,50%标本多形核白细胞血管内聚集或游出血管外现象;34%氧浓度机械通气组90%线粒体双层膜较完整,基质致密呈细颗粒状;10%标本可观察到Ⅰ型肺上皮细胞有吞饮增强、破坏及内皮细胞吞饮增强;20%标本肺泡隔间质水肿;未见到多形核白细胞血管内聚集或游出血管外现象及Ⅱ型肺泡上皮板层小体排空。结论:纯氧通气7h后观察到的肺超微结构损伤较多,吸入氧体积分数为0.34则相对较少,建议长时间气管插管通气时,宜降低吸入氧浓度,尽可能减少潜在的氧毒性肺损伤。
Background: It has been clinically proven that long time (36 ~ 48h) inhalation of high concentration of oxygen can cause irreversible oxygen toxicity of lung injury. Low concentration of oxygen within 50% can reduce the potential oxygen toxicity in lung injury? Objective: To observe the changes of lung ultrastructure in continuous pure oxygen ventilation 7 h after tracheal intubation in dogs. Design: Randomized controlled animal experiments. Unit: Affiliated Hospital of Qingdao University Medical College. MATERIALS: Twenty healthy adult mongrel dogs, 6 females and 14 males, weighing 15-16 kg were selected and provided by Animal Experimental Center, Affiliated Hospital of Qingdao University Medical College. BIRD8400STi breathing machine is the United States bird equipment company, HP-M102A multi-function monitor produced by the United States Hewlett-Packard. METHODS: The experiment was performed at Animal Experimental Center, Affiliated Hospital of Qingdao University Medical College from July 1999 to January 2000. ① Experimental intervention: The experimental dogs were divided into pure oxygen mechanical ventilation group and 34% oxygen concentration mechanical ventilation group according to their gender, 3 female and 7 male. Experimental dogs anesthesia, pure oxygen mechanical ventilation group set the inspired oxygen concentration of 1,34% oxygen concentration mechanical ventilation group set the inspired oxygen volume fraction of 0.34, ventilation time was 7h. ② Experimental evaluation: mean arterial pressure and heart rate were monitored at 1, 3, 5 and 7 hours after tracheal intubation. The inspired oxygen concentration, end-tidal carbon dioxide partial pressure, respiratory rate and respiratory peak pressure were monitored by Ohmeda5250RGM anesthetic gas monitor. The ultrastructural changes of the right lower lobe in each group were observed after 7 hours of mechanical ventilation by microscope. MAIN OUTCOME MEASURES: Hemodynamic parameters were observed in experimental dogs, ultrastructural changes of lung tissue were observed. Results: All 20 dogs were involved in the result analysis. ① hemodynamic parameters observed: mean arterial pressure at each time point, end-tidal carbon dioxide partial pressure, peak airway pressure and heart rate difference was not significant (P> 0.05). ② Observation of ultrastructural changes in lung tissue: In pure oxygen mechanical ventilation group, 50% of specimens had swollen mitochondria, disordered arrangement, shallow matrix, clear area, thinning of bilayer membrane, 60% alveolar septum edema and 50% Nucleated leukocytes gathered in the blood vessels or swimming out of extravascular phenomenon; mechanical ventilation group 34% oxygen concentration of 90% mitochondrial bilayer membrane more complete, dense matrix was fine granular; 10% specimens observed type I lung epithelial cells have swallowing drink Enhancement, destruction and endothelial cell swallowing enhanced; 20% alveolar septal edema; no evidence of polymorphonuclear leukocyte aggregation or out of extravascular phenomena and type II alveolar epithelial lamellar body emptying. CONCLUSIONS: The ultrastructural damage of lungs observed after pure oxygen ventilation for 7h is more, and the volume of inhaled oxygen is 0.34, which is relatively less. It is suggested that the inhaled oxygen concentration should be decreased when the tracheal intubation is prolonged for a long time to reduce the potential oxygen Toxic lung injury.