Effects of positional changes on alveolar dynamics and respiratory mechanics in rats with and without acute lung injury.

肺保护性机械通气是现代麻醉和重症监护的标志，并且已经显示出显著降低肺健康和损伤患者的发病率和死亡率。除了使用低潮气量外，体位疗法也显示出有益的效果，呼吸阻力和顺应性以及血气分析常规用于床边，但只能提供有限的关于通气和灌注区域分布的信息。此外，诸如CT和MRI的成像方式提供了关于肺的整体结构的信息，但是关于健康肺和损伤肺中的肺泡动力学的知识有限。据推测，特别是在低压下受伤的肺中，重力依赖性区域的肺泡塌陷，但迄今为止这还不能通过任何成像方式来证明。本研究拟在健康肺和肺表面活性物质耗竭性急性肺损伤大鼠模型上，观察机械通气对肺泡组织结构和功能的影响。我们将在俯卧位和仰卧位对肺部的相同区域进行成像。根据重力位置，推测同一肺区域内的肺泡结构和动力学将发生变化。特别是在受伤的肺中，我们假设肺泡平均较小且部分充满液体，通气参数如气道和组织阻力和顺应性将与肺泡结构的成像同时测量并与它们相关联。结合肺泡动力学和肺弹性，我们希望能更好地了解机械通气时的生理和病理生理过程。我们的研究结果将有助于临床医生在床边更好地解释全球肺功能测量，并有助于更好地理解，并可能改善肺保护性机械通气策略，以进一步降低机械通气患者的发病率和死亡率。

Lung protective mechanical ventilation is a hallmark of modern anesthesia and intensive care and has been shown to significantly reduce morbidity and mortality in both, lung healthy and injured patients. Beside the use of low tidal volumes, positional therapy has been shown to be associated with beneficial effects.Respiratory resistance and compliance as well as blood gas analysis are routinely used at the bedside but provide only limited information about the regional distribution of ventilation and perfusion. Moreover, imaging modalities such as CT and MRI provide information about the global structure of the lung, but there is limited knowledge about the alveolar dynamic, neither in healthy nor in injured lungs. It is assumed that especially in injured lungs at low pressure, alveoli in gravitationally dependent areas collapse, but this could not be proven by any imaging modality so far. In this proposal, the effects of mechanical ventilation on the structure and function of alveolar tissue will be imaged in vivo in lung healthy and rats with surfactant depletion induced acute lung injury. We will image the same areas of the lung in both, prone and supine position. Presumable there will be changes in alveolar structure and dynamic within the same lung region based on the gravitationally position. Especially in the injured lung, we assume that alveoli will be on average smaller and partly liquid filled.Ventilation parameters such as airway and tissue resistance and compliance will be measured simultaneously with the imaging of alveolar structures and correlated to them. From the combination of alveolar dynamics and lung elasticity, we hope to gain a better understanding for the physiological and pathophysiological processes during mechanical ventilation. Our results will hopefully help the clinician at the bedside to better interpret global lung functional measurements and help to better understand and maybe improve lung protective mechanical ventilation strategies to further reduce morbidity and mortality of mechanically ventilated patients.