高频振荡通气对急性呼吸窘迫综合征肺局部气体分布的影响与呼吸机相关肺损伤机制研究

Acute respiratory distress syndrome (ARDS) is a devastating clinical syndrome which is characterized by diffuse heterogeneous lung injury. Mechanical ventilation is an essential component in supportive therapy of ARDS. Yet it has been associated with potential complications known as ventilator-induced lung injury (VILI), inadequate mechanical ventilation itself can further injure damaged lungs. Theoretically, high-frequency oscillatory ventilation (HFOV) is an optimal lung-protective strategy. However, the mechanism determining gas distribution of the lung in ARDS during HFOV remains unclear. An improved fundamental understanding of gas distribution in HFOV is essential in order to harness its potential to improve outcome in patients with ARDS.It is shown that transpulmonary pressure elucidates lung and chest wall mechanics and is used to guide ventilation strategy. In our previous study, we found that higher frequency HFOV decreased transpulmonary pressure and alleviated lung injury. In our current study, we investigated the effect of HFOV on local gas distribution in the lung with ARDS. Our study try to determine regional ventilation, perfusion, and compliance in animal ventilated with HFOV and conventional ventilation by using real-time EIT. Oxygenation hemodynomics and transpulmonary pressure were monitored during experiment . The purpose of this study was to provide novel ventilation strategies in ARDS by optimized HFOV, and develop a better understanding of the possible mechanisms on regional gas distribution.

机械通气是ARDS主要支持治疗手段，不当机械通气可导致和加重肺损伤。HFOV是ARDS保护性通气治疗措施之一，但HFOV对肺局部气体分布的影响和损伤机制尚不清，临床应用亟待优化，探索HFOV对ARDS肺气体分布是优化HFOV机械通气策略的关键。跨肺压是反映肺和胸廓机械力学机制的指标，可指导HFOV机械通气策略的优化设置。我们前期研究显示高频率HFOV可降低跨肺压，改善肺损伤。本研究通过ARDS动物模型，采用EIT实时监测肺局部通气血流变化，同时监测氧合，血流动力学等，记录食道压力和呼吸力学指标，评估HFOV在机械通气过程中改善气体分布不均一性中的作用、以及对动物模型呼吸力学机制、血流动力学等的影响。本研究力求采用新型床旁监测技术和动物实验为HFOV在ARDS的最佳机械策略实施提供理论依据。

急性呼吸窘迫综合征(Acute respiratory distress syndrome, ARDS)是临床常见呼吸衰竭类型，肺损伤的不均一性是其重要的病理生理特点。机械通气是其主要支持治疗手段，不当的机械通气可能导致或加重肺损伤的不均一性，造成呼吸机相关性肺损伤。因此，寻求合理的机械通气策略，进而改善ARDS患者预后是临床亟需解决的问题。高频振荡通气(High frequency oscillatory ventilation, HFOV)理论上是肺保护性的机械通气方式，但其对肺局部气体分布的影响及作用机制尚不明确。探索高频振荡 通气对ARDS肺内气体分布的影响是优化其机械通气方案的关键，对临床肺保护性通气策略的实施具有重要意义。. 本研究通过复制ARDS动物模型，采用电阻抗断层显像技术(Electrical impedance tomography, EIT)监测常频通气时呼气末正压递增过程中肺内气体分布，将EIT图像分为过度膨胀区、复张区、潮气通气区，实现了区域肺通气状态的量化。并进一步用EIT评估了复张肺组织及过度膨胀肺组织与氧合指数及肺顺应性之间的相关性。结果显示，随着呼气末正压的升高，氧合指数与复张肺组织均逐渐增加，并且两者之间具有很好的相关性。而过度膨胀区随着压力的升高也是增加的，但其与肺顺应性之间的无明显相关性。. 本研究还通过EIT监测高频振荡通气平均气道压递减过程中ARDS动物肺内气体分布，并同步监测血流动力学，呼吸力学和气体交换指标。结果显示，EIT指导下HFOV最佳肺内气体分布的平均气道压与氧合法的结果一致。而按照临床上目前常推荐按常规机械通气法设置HFOV平均气道压，即常频通气下平均气道压之上5cmH2O或按照圆桌会议专家公式初始设置为30cmH2O，并不能改善肺内气体分布，反而造成了部分肺泡的过度膨胀，加重了肺损伤的不均一性。因此，EIT指导下的平均气道压设置改善肺内气体分布及氧合，减轻肺损伤，有助于临床优化HFOV的通气方案，更好地实现肺保护性通气。