Particle Deposition in a Cast of Human Tracheobronchial Airways

Abstract

Regional particle deposition efficiency and deposition patterns were studied experimentally in a human airway replica made from an adult cadaver. The replica includes the oral cavity, pharynx, larynx, trachea, and four generations of bronchi. This study reports deposition results in the tracheobronchial (TB) region. Nine different sizes of monodispersed, polystyrene latex fluorescent particles in the size range of 0.93-30 µm were delivered into the lung cast with the flow rates of 15, 30, and 60 l min −1 . Deposition in the TB region appeared to increase with the increasing flow rate and particle size. Comparison of deposition data obtained from physical casts showed agreement with results obtained from realistic airway replicas that included the larynx. Deposition data obtained from idealized airway models or replicas showed lower deposition efficiency. We also compared experimental data with theoretical models based on a simplified bend and bifurcation model. A deposition equation derived from these models was used in a lung dosimetry model for inhaled particles, and we demonstrated that there was general agreement with theoretical models. However, the agreement was not consistent over the large range of Stokes number. The deposition efficiency was found as a function of the Stokes number, bifurcation angle, and the diameters of parent and daughter tubes. An empirical model was developed for the particle deposition efficiency in the TB region based on the experimental data. This model, combined with the oral deposition model developed previously, can be used to predict the particle deposition for inertial effects with improved accuracy.

Micro-particle deposition and lobar distribution of mass flow in human upper respiratory tract model

“…Thus, multiple Stokes numbers and theoretical lines were applied to comparing the deposition efficiencies in this generation (Figure 3(b)). In the first generation, our simulated results are lower than the experimental data [7,18], but have high agreement with the empirical model developed from experimental measurement by Zhou et al [7] η=1-exp(-5.39·α·Stk), α=0.75. In the second generation, the simulated deposition efficiencies of two parts (G21 and G22) show high agreement with the experimental data and empirical model η=1-exp(-5.39·α·Stk 1.34 ), where α is 1.326 and 0.695 for the G21 and G22 respectively.…”

“…Previous particle deposition investigations in the oropharyngeal airway have used realistic replicas from cadavers [1], idealized oral models [2] and idealized mouth-throat models [3,4]. In TB airway studies, the effective methods *Corresponding author (email: zhanglz@nankai.edu.cn) include theoretical predictions on symmetrical bifurcation [5], experimental measurements on realistic replicas [6][7][8], Monte Carlo stochastic simulations [9,10] and computational fluid dynamics (CFD) determinate simulations [11,12].…”

“…The particle deposition efficiency of the TB airways is defined as the ratio of number of deposited particles in one region to the number of those entering this region. The Stokes number in the TB airways is defined as St=ρ p d 2 p U/(18μD) [7], where U 0 is mean velocity through the parent tube, and D 0 is the diameter of the parent tube. Figure 2 shows the comparison of the simulated deposition fraction in the oropharynx region with the experimental data [1] and numerical results [2], under three inspiratory flow rates (15 L/min, 30 L/min, 60 L/min).…”

Evolution of PM2.5 Measurements and Standards in the U.S. and Future Perspectives for China

“…Inhalation and lung deposition estimates served as part of the basis toward selecting the PM 2.5 and PM 10 size fractions for regulation. Inhalation properties have also been measured experimentally using casts of human airways (Gurman et al, 1984a, b;Zhou and Cheng, 2005) and simulated by computational fluid dynamics (CFD) models (Rostami, 2009), showing the same general patterns as those of Fig. 2.…”

Research of transport and deposition of aerosol in human airway replica

“…A lot of them were devoted to nasal deposition, but also tracheobronchial deposition was investigated on models to 4 th generation of branching. Work of Gurman et al [11], Zhou et al [28] and Cheng et al [4] could be used as an example. Local deposition is influenced by five basic deposition mechanisms: Interception, inertial impaction, gravitational sedimentation, diffusion and electrostatic precipitation.…”