Unsteady Mass Transport During Liquid Ventilation

液体通气的方法是一种非常有前途的救生替代品，人工通气，特别是在严重形式的急性呼吸窘迫综合征（ARDS），其中传统的通气方法失败。然而，由于缺乏对气体交换过程的详细了解和临床经验，液体通气方法尚未在临床常规中使用。 为了评估通气/灌注比，获得关于溶解气体分别通过全氟化碳（PFC）和支气管树的转运行为的知识是非常重要的。只有这样，呼吸参数（频率，潮气量）才能最佳地设置。只有进入气道前的气体浓度以及肺泡和血液气体浓度是已知的或可以测量的。在本研究项目的范围内，将研究溶解氧和二氧化碳通过人体上气道模型的运输。在此，将应用带PFC的液体通气。对于调查，新的方法，如使用氧敏感示踪粒子在PFC中的氧浓度的光学测量。颗粒将均匀分布在肺模型中。由于激发粒子的氧猝灭而导致的荧光强度的差异在照相机系统的帮助下以光学方式测量。除了采集氧气浓度分布外，还需要分别分析速度和质量流量分布。只有这样，才能评估溶解气体的输送机制。根据液体通气期间的典型呼吸参数（潮气量、呼吸频率）和PCF的低运动粘度，上气道直到第6代都以湍流为特征。这不同于层流占主导地位的传统通风的边界条件。因此，可以预期不同的质量传输途径。这将通过粒子图像测速（PIV）测量进行研究。

The method of liquid ventilation is a very promising alternative of life saving, artificial ventilation, especially at severe forms of the Acute Respiratory Distress syndrome (ARDS), where conventional ventilation methods fail. Nevertheless, due to a lack of detailed knowledge about the gas exchange processes and little clinical experience, the method of liquid ventilation has not been used in clinical routine, yet. In order to evaluate the ventilation/perfusion ratio, it is of high importance to gain knowledge about the dissolved gas transport behavior through the perfluorocarbon (PFC) and the bronchial tree, respectively. Only this way, the breathing parameters (frequency, tidal volume) can be set up optimally. Only the gas concentrations before entering the airways as well as the alveolar and blood gas concentrations are known or can be measured.Within the scope of this research project, the transport of dissolved oxygen and carbon dioxide through a model of the upper human airways will be investigated. Here, liquid ventilation with PFC will be applied. For the investigations, novel methods such as the optical measurement of the oxygen concentration by using oxygen sensitive tracer particles in PFC are applied. The particles will be distributed homogeneously in the lung model. Differences in fluorescence intensity due to oxygen quenching of the excited particles are measured optically with the help of a camera system. Besides gathering the oxygen concentration distribution it is necessary to analyze the velocity and mass flow distribution of the , respectively. Only this way the transport of mechanisms of dissolved gas can be evaluated. According to the typical breathing parameters (tidal volume, breathing frequency) during liquid ventilation and the low kinematic viscosity of PCF the upper airways down to the 6th generation are characterized by turbulent flow. This differs from the boundary conditions of conventional ventilation where laminar flow predominates. Consequently, different pathways of mass transport can be expected. This will be investigated by Particle Image Velocimetry (PIV) measurements.