Fiber Deposition in the Tracheobronchial Region: Experimental Measurements

Abstract

Fiber deposition efficiency in the tracheobronchial region was studied by using two human airway replicas. Carbon fibers with a monodisperse diameter of 3.66 μ were delivered into lung casts at the flow rates of 15, 45, and 60 L/min. Deposition efficiencies in each airway bifurcation were obtained individually. Even though the data shows large variability among the bifurcations within the same generation, there is a general trend for the data obtained in these two replicas. Our results show that fiber deposition for carbon fibers increases with the Stokes number, indicating that inertial impaction is the dominant mechanism. Also, fiber deposition in the tracheobronchial region is lower than that of spherical particles at a given Stokes number, and is similar to the deposition found in the nasal and oral airways as reported previously. This finding implies that it is easier for fibers to penetrate the upper respiratory tract and to reach the lower airways as compared to spherical particles. Our measurements are in general agreement with data obtained with asbestos fiber as reported in another study using a hollow airway replica. Our study appears to give a higher deposition efficiency than the results obtained using idealized single symmetrical bifurcation models. This demonstrates, again, the importance of using a realistic airway model, including larynx, to simulate the airway geometry and flow pattern of the human respiratory tract.