Transparent 23-generation airway model for experimental investigation of aerosol flow and deposition within the human respiratory tract

A novel transparent airway model is presented, that simulates the geometry and airflow along all 23 bifurcation units of a representative pathway. The model is intended for the development of new aerosol/droplet based therapeutic techniques. The model is realized in fused quartz and thus allows the application of different optical measurement techniques for the analysis of aerosol propagation and deposition on microscopic level. In addition, it enables separate adjustment of the flow conditions for each individual bifurcation unit of the lung and therefore offers the possibility to simulate specific human breathing characteristic. The model can be rotated in two spatial directions to vary the local relevance of sedimentation for aerosol deposition. In this first study, the suitability of the model concept is investigated and evaluated by analyzing a predefined droplet aerosol during its propagation along the airway. A water aerosol is generated using a commercially available medical nebulizer and is actively inhaled by the lung model. Droplets within the airway are characterized in flight with regard to their mean size, velocity, and concentration as function of generation number and breathing characteristics using high-speed transmitted light microscopy. The present combination of measurement methodology and aerosol characteristics allows a quantitative analysis of the propagation of micro droplets up to the 10th generation of the respiratory tract. The data indicate that up to the 6th generation the droplets on average follow the respiratory flow almost with no slip and are deposited further downstream. The results underline the importance of airway models with a sufficiently high number of generations.

Automated summary

A novel transparent airway model is presented for the development of new aerosol-based therapeutic techniques, allowing for analysis of aerosol propagation and deposition. The model enables adjustment of flow conditions for each bifurcation unit of the lung and offers the possibility to simulate specific human breathing characteristics. Experimental results show that the model can simulate human respiratory features and quantitatively analyze aerosol deposition.