Teilprojekte

Trachea:

• Investigation of the Unsteady Mass Transport in the Tracheobronchial Tree Under Artificial Ventilation Conditions
  
  (Untersuchung des instationären Massentransports im Tracheobronchialbaum und der peripheren Lunge unter Manipulation der Tubusströmung und bei Hochfrequenz-Beatmung zur gezielten Homogenisierung der Ventilation)
  
  Brücker, Schröder, Simbruner, Rüdiger - Aachen, Innsbruck
  
  

  Aim of this joint research project between fluid dynamics and medicine is to develop new strategies for lung ventilation in order to homogenize or redistribute the air flow in the lung. This requires a deep physical understanding of unsteady mass transport in the bronchial tree. Detailed investigations of the time dependent three-dimensional flow field are carried out using experimental and numerical methods such as 3D Particle-Image Velocimetry and CFD. The experiments use a fully transparent in vitro model of the bronchial tree down to the sixth generation which offers a non-obstructed view into the internal flow in the branches. Special care is taken to fulfill realistic boundary conditions including ventilation devices such as endotracheal tubes, regional variations of compliance and simulating obstruction of different lung parts. The final goal is - based on the thoroughly physical understanding of mass transport under such conditions - to develop improved artificial ventilation. These studies are accompanied by in-vivo animal tests using the Electrical Impedance Tomography (EIT) as well as the radiographical illustration of the distribution of air using radiopaque tracers.

• Simulation of Transient Convective Flow Conditions within Dynamic Central Geometries of the Tracheobronchial Tree during Spontaneous Breathing
  
  (Simulation instationärer konvektiver Strömungsverhältnisse in sich dynamisch verändernden zentralen Geometrien des Tracheobronchialbaumes unter Spontanatmung)
  
  Kauczor, Meinzer, Thiele, Gust - Heidelberg, Berlin
  
  

  The dynamic changes of the convective inspiratory and expiratory flow conditions and their dependence from the dynamically changing cross-sectional areas and branching angles within the central airways are still unclear. Starting from the knowledge of the normal anatomy we will investigate the effects of diseases with substantial deformities of the tracheobronchial tree or an increased collapsibility during expiration by means of computational fluid dynamics. High resolution cross-sectional imaging, such as computed tomography (CT) and magnetic resonance imaging (MRI), will provide the geometrical information about the dynamic changes during the respiratory cycle to define the boundary conditions for the simulation. They will also serve to validate the results of the simulation. Imaging together with simulation will contribute to a better understanding of the actual flow conditions by information about the details of the geometries, modelling approaches as well as temporal and spatial resolution. Purpose of our investigations is to describe the functional significance of temporary and fixed pathological deformities of the central tracheobronchial tree in chronic obstructive pulmonary disease (COPD) and scoliosis in a quantitative fashion. This information is important for the general understanding of the diseases, the administration of inhaled therapies as well as the development of concepts for protective ventilation.

• Transient Interactions between Flow and Airway Walls in the Lower Respiratory Tract during Breathing and Ventilation and the Impact on Pulmonary Perfusion
  
  (Instationäre Strömungs-Atemwegswand-Wechselwirkungen im Bereich der unteren Atemwege unter Atmung und Beatmung und deren Einfluss auf die Lungenperfusion)
  
  Kauczor, Semmler, Gust, Wall - Heidelberg, Garching
  
  

  The distensibility of the airway walls and their interaction with gas flow within the smaller airways is essential for a basic understanding of the respiratory system. However, due to its complexity it is rarely understood. Purpose of this project is the development of a complex and coupled model for simulation for airways and flow on the basis of dynamic high resolution imaging. This model will be capable to account for transient flow conditions within the airways which might be anatomically normal, distorted or lack stability. Beyond factors such as the fluid lining, effects of surface tension, implications on the respiratory pump and pulmonary perfusion will be considered as well. High resolution cross-sectional imaging, such as computed tomography (CT) and magnetic resonance imaging (MRI), will provide the geometrical information while dedicated tagging and phase contrast sequences in MRI will demonstrate the dynamic changes during the respiratory cycle. Based on phantom and animal experiments of healthy and diseased lungs (acute respiratory distress syndrome = ARDS) novel insights into insufficiently understood mechanical effects of breathing and ventilation will be elucidated as well as analysed and interpreted to be used for protective ventilatory concepts of the future. Studies in patients will allow for simulation of the actual individual structural complexity and the effects of diseases such as emphysema and fibrosis, and finally allow to validate the results of the simulation.

• Optimisation of HFOV parameter settings: HFOV in the context of MRI: initial animal experience
  
  (Optimierung der "High-Frequency Oscillatory Ventilation" mittels strömungsmechanischer Methoden und Kontrastgas-gestützter Magnerresonanzthomographie)
  
  Schreiber, Wagner, David - Mainz, Göttingen
  
  

  Despite several decades of research into the principles and clinical application of high frequency oscillatory ventilation (HFOV) many issues remain unresolved, particularly regarding its use in adults. It has been theorized that optimization of HFOV modes would involve minimizing tidal volumes to reduce the risk of overdistension-injury and cyclical lung unit collapse. In fact, the very mechanical mechanisms of HFOV remain incompletely understood. To investigate optimal settings that maximize lung protection and gas exchange particularly in ARDS patients, an interdisciplinary approach of flow mechanics, MR imaging techniques and anethesiology is chosen in the project presented here. The project is based on both simulations of flow patterns within the bronchial tree as well as the visualization of alveolar stress and ventilation by MRI of contrast gases such as helium-3 and fluorinated gases. A basic premise for the project is the compatibility of MRI and HFOV equipment, i.e., the trouble-free functioning of all devices in the MRI context. Here we present initial results of the MRI of a wash-out of C4F8-gas during HFOV in a healthy pig. Fortunately, both our HFOV equipment proves MR-compatible, and the ventilation device does not substantially interfere with the MR-measurement through RF-radiation.