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Using stem cells as treatment for Acute Respiratory Distress Syndrome (ARDS) and Chronic Obstructive Pulmonary Disease (COPD) is a technique of rising interest. High concentrations of stem cells in the area of interest are vital, to enhance the effect of this therapy. The authors of this work try to achieve those concentrations by spraying a high concentrated solution of stem cells into the human airway using bronchoscopes equipped with nozzles, specifically designed for this purpose. Flexible coaxial nozzles mounted to a catheter have been developed and tested in earlier studies.
Since the general concept of coaxial atomization in cell spray applications has been proven in earlier studies, this work evaluates the effect of nozzle geometry on atomization characteristics such as spray angle as well as droplet sizes and velocities. In detail, the diameter of the inner annular exit for the liquid phase can be varied as well as the diameter of the annular exit of the gas phase. Additionally, the thickness of the wall between liquid and gas phase is also adjustable. Hence, different exit velocities of both the gas and liquid phase can be achieved allowing a wide range of atomization conditions. Investigations are carried out by a microscope high-speed visualization system including adapted post processing allowing the determination of the spray characteristics mentioned earlier.
Furthermore, the survival rates and concentrations of stem cells are measured along the radius of the spray cone. These factors are of interest, since the goal of atomization in human airways is defined by transporting as many intact cells as possible with maximum penetration length. Survival rates and cell concentrations are measured by phase contrast microscopy before and after the atomization process.
