不同潮气量机械通气对复苏犬肺泡表面活性物质的影响

Effect of mechanical ventilation with different tidal volumes on pulmonary surfactant in dogs duringcardiopulmonary resuscitation

目的观察不同潮气量（Vt）机械通气对室颤犬复苏后肺泡表面活性物质的影响，探讨心肺复苏的机械通气策略。方法选用健康成年犬24只，体质量（15±2）妇，雌雄不拘，随机（随机数字法）分为3组：对照组（A组）、低Vt组（B组）和高Vt组（C组）。对照组仅进行麻醉和气管插管；其余2组经右心室导管诱发室颤制作心搏骤停模型，复苏时分别以不同潮气量（低Vt组：6ml／kg；高Vt组：20ml／kg）机械通气6h，观察开始复苏前及机械通气后不同时间点犬动脉血气的变化；比较各组犬复苏成功率及72h存活情况；采用高效液相色谱法（HPLC）检测肺泡灌洗液中磷脂酰胆碱含量；测定肺组织湿干质量比（W／D）及肺组织病理学改变评分。结果（1）复苏开始时B、C两组犬pH显著降低，PaO2下降，PaCO2上升，与基础值比较差异具有统计学意义（P〈0．05），复苏后pH、PaO2均升高；C组ROSC2h后，PaCO2较B组下降差异具有统计学意义（P〈0．05），ROSC6h后，B组与C组比较HCO3-差异具有统计学意义（P〈0．05）；（2）与B组比较，C组磷脂酰胆碱含量减少（P〈0．05），肺组织W／D比值增加（P〈0．05），病理损伤形态学积分升高（P〈0．01）。结论低潮气量机械通气减少肺泡表面活性物质的丢失，减轻复苏后肺损伤，可作为复苏及复苏后一种保护性通气策略。

Objective To observe the effects of mechanical ventilation with different tidal volumes （Vt） on the pulmonary surfactant in dogs during cardiopulmonary resuscitation （CPR） and discuss the strategy of mechanical ventilation for CPR. Methods A total of 24 healthy, adult and mongrel canines were randomly （random number） divided into three groups, namely control group （A） , low Vt group （B） and high Vt group （C）. Canines without ventricular fibrillation in group A were not supported with mechanical ventilation, while canines in group B and group C were induced to get ventricular fibrillation （VF） with pacing catheter inserted through right external carotid vein into the right ventricle. CPR was initiated with mechanical ventilation with different Vt for 6 hours after ventricular fibrillation. The Vt set in group B was 6 ml/kg body weight and Vt set in group C was 20 ml/kg body weight. The arterial blood gas analyses were tested in different intervals. The levels of phosphatidylchline in bronchia alveolus lavage fluid （BALF） was assayed with high performance liquid chromatography （HPLC）. The ratio of wet and dry weight and the morphological change scores of lung tissue were calculated. Results After ventricularfibrillation, pH, PaO2 in both groups B and C decreased and PaCO2 increased in comparison with those before VF （ P 〈 0. 05）, while pH, PaO2 and PaCO2 were improved after mechanical ventilation. These was statistical difference in PaCO2 between group B and group C 2 h after mechanical ventilation （ P 〈 0. 05 ）. There was difference in HCO3 - between group B and group C 6 h after ROSC. The rate of successful restoration of spontaneous circulation （ROSC） and the 72 h survival rate were 75% and 50% respectively in group B, and 62. 5% and 40% respectively in group C. There were no statistically different between two groups （P 〉 0. 05 ）. The levels of phosphatidylchline in BALF of group B and C greatly decreased compared with the group A （All P 〈 0. 01 ）, while phosphatidylcholine detected in the group C decreased much more than that in the group B （P 〈0. 01 ）. The W/D ratio and morphological change scores in the group C were higher than those in the group B （ P 〈 O. O1 ）. Conclusion Low tidal volume ventilation can reduce the loss of pulmonary surfactant and mitigate pulmonary injury. Therefore it may be a protective ventilation strategy after resuscitation.