Although liquid ventilation has been researched and studied for the last six decades, it did not achieve its expected optimal performance. Within this work, a deeper understanding of the fluid dynamics during liquid ventilation shall be gathered to extend the already available clinical knowledge about this ventilation strategy. In order to reach this goal, advanced optical flow measurement techniques are applied in different models of the human conductive airways to obtain global velocity fields, identifying prominent flow structures and to determine important dissolved oxygen transport paths. As the velocity measurements revealed, the evolving flow field is strongly dominated by secondary flow effects and is highly dependent on the local airway geometry. During the visualization experiments of the dissolved oxygen concentration fields, different transportation paths occur at inspirational and expirational flow. The initial concentration distribution can be linked to the underlying flow fields but decouples after the peak velocity phases. With higher flow rates/ tidal volumes, a more homogeneously distributed oxygen concentration can be reached.:List of Figures ....................................................................................... VII List of Tables ........................................................................................XIII Nomenclature ........................................................................................ XV 1 Introduction......................................................................................... 1 1.1 Motivation ........................................................................................1 1.2 Research objectives........................................................................... 3 1.3 Outline............................................................................................ 4 2 State of the art .................................................................................... 5 2.1 Liquid Ventilation............................................................................. 5 2.2 In vitro modeling.............................................................................. 8 2.3 Flow measurements ......................................................................... 11 2.4 Gas transport..................................................................................13 3 Flow field measurements ................................................................... 16 3.1 Hydrodynamic Model.......................................................................16 3.1.1 Lung replica ..........................................................................16 3.1.2 Flow parameter .....................................................................18 3.1.3 Limitations ...........................................................................22 3.2 Particle Tracking Velocimetry (PTV) ................................................24 3.2.1 Measurement principle ...........................................................24 3.2.2 Double-frame 2D-PTV ...........................................................25 3.2.3 Time-resolved 3D-PTV ..........................................................28 3.2.4 Phase-locked ensemble PTV ................................................... 31 3.3 Experimental set-up and measurement procedure ...............................33 3.3.1 Lung flow facility...................................................................33 3.3.2 2D-PTV configuration............................................................36 3.3.3 3D-PTV configuration............................................................36 3.4 Results & Discussion........................................................................38 3.4.1 Artificial lung........................................................................38 3.4.2 Realistic lung ........................................................................52 3.5 Conclusion ......................................................................................59 4 Oxygen transport ...............................................................................61 4.1 Hydrodynamic Model....................................................................... 61 4.1.1 Lung replica .......................................................................... 61 4.1.2 Flow parameter .....................................................................62 4.1.3 Limitations ...........................................................................65 4.2 Oxygen Sensitive Dye ......................................................................66 4.3 Experimental set-up......................................................................... 71 4.4 Results & Discussion........................................................................75 4.4.1 Constant flow rate .................................................................75 4.4.2 Oscillatory flow .....................................................................83 4.5 Conclusion ......................................................................................90 5 Summary............................................................................................ 92 6 Outlook .............................................................................................. 95 Bibliography ............................................................................................ 97 / Trotz intensiver Forschung in den letzten sechs Jahrzehnten, befindet sich die Flüssigkeitsbeatmung immernoch weit entfernt vom klinischen Alltag. Mit dieser Arbeit soll ein Beitrag geleistet werden, um das Wissen um die strömungsmechanischen Effekte während der Flüssigkeitsbeatmung zu vertiefen. Dazu werden verschiedene Modellexperimente durchgeführt, bei welchen moderne laseroptische Strömungsmessmethoden zum Einsatz kommen. Untersucht werden dabei unterschiedlich komplexe Geometrien der leitenden menschlichen Atemwege mit dem Ziel wesentliche Strömungsstrukturen, globale Geschwindigkeitsfelder und wichtige Transportwege des gelösten Sauerstoffs zu identifiziern. Die Geschwindigkeitsmessungen zeigen ein stark durch sekundäre Strömungseffekte dominiertes Geschwindigkeitsfeld, welches wesentlich von der lokalen Geometrie abhängig ist. Durch die qualitative und quantitative Erfassung der gelösten Sauerstoffkonzentrationsfelder können wichtige Transportwege aufgedeckt werden. Diese unterscheiden sich deutlich zwischen inspiratorischer und expiratorischer Strömungsrichtung. Die initialen Konzentrationsfelder stimmen mit den unterliegenden Geschwindigkeitsfeldern überein, unterscheiden sich ab der verzögernden Strömungsphase jedoch. Höhere Volumenströme/Tidalvolumen tragen dabei zu einer gleichmäßigeren Konzentrationsverteilung bei.:List of Figures ....................................................................................... VII List of Tables ........................................................................................XIII Nomenclature ........................................................................................ XV 1 Introduction......................................................................................... 1 1.1 Motivation ........................................................................................1 1.2 Research objectives........................................................................... 3 1.3 Outline............................................................................................ 4 2 State of the art .................................................................................... 5 2.1 Liquid Ventilation............................................................................. 5 2.2 In vitro modeling.............................................................................. 8 2.3 Flow measurements ......................................................................... 11 2.4 Gas transport..................................................................................13 3 Flow field measurements ................................................................... 16 3.1 Hydrodynamic Model.......................................................................16 3.1.1 Lung replica ..........................................................................16 3.1.2 Flow parameter .....................................................................18 3.1.3 Limitations ...........................................................................22 3.2 Particle Tracking Velocimetry (PTV) ................................................24 3.2.1 Measurement principle ...........................................................24 3.2.2 Double-frame 2D-PTV ...........................................................25 3.2.3 Time-resolved 3D-PTV ..........................................................28 3.2.4 Phase-locked ensemble PTV ................................................... 31 3.3 Experimental set-up and measurement procedure ...............................33 3.3.1 Lung flow facility...................................................................33 3.3.2 2D-PTV configuration............................................................36 3.3.3 3D-PTV configuration............................................................36 3.4 Results & Discussion........................................................................38 3.4.1 Artificial lung........................................................................38 3.4.2 Realistic lung ........................................................................52 3.5 Conclusion ......................................................................................59 4 Oxygen transport ...............................................................................61 4.1 Hydrodynamic Model....................................................................... 61 4.1.1 Lung replica .......................................................................... 61 4.1.2 Flow parameter .....................................................................62 4.1.3 Limitations ...........................................................................65 4.2 Oxygen Sensitive Dye ......................................................................66 4.3 Experimental set-up......................................................................... 71 4.4 Results & Discussion........................................................................75 4.4.1 Constant flow rate .................................................................75 4.4.2 Oscillatory flow .....................................................................83 4.5 Conclusion ......................................................................................90 5 Summary............................................................................................ 92 6 Outlook .............................................................................................. 95 Bibliography ............................................................................................ 97