Particle dynamics and deposition in true-scale pulmonary acinar models

Abstract

Particle transport phenomena in the deep alveolated airways of the lungs (i.e. pulmonary acinus) govern deposition outcomes following inhalation of hazardous or pharmaceutical aerosols. Yet, there is still a dearth of experimental tools for resolving acinar particle dynamics and validating numerical simulations. Here, we present a true-scale experimental model of acinar structures consisting of bifurcating alveolated ducts that capture breathing-like wall motion and ensuing respiratory acinar flows. We study experimentally captured trajectories of inhaled polydispersed smoke particles (0.2 to 1 μm in diameter), demonstrating how intrinsic particle motion, i.e. gravity and diffusion, is crucial in determining dispersion and deposition of aerosols through a streamline crossing mechanism, a phenomenon paramount during flow reversal and locally within alveolar cavities. A simple conceptual framework is constructed for predicting the fate of inhaled particles near an alveolus by identifying capture and escape zones and considering how streamline crossing may shift particles between them. In addition, we examine the effect of particle size on detailed deposition patterns of monodispersed microspheres between 0.1–2 μm. Our experiments underline local modifications in the deposition patterns due to gravity for particles ≥0.5 μm compared to smaller particles, and show good agreement with corresponding numerical simulations.

Biomimetics of the pulmonary environment in vitro: A microfluidics perspective

“…2(b)] and alveolated airway trees spanning several bifurcating generations 41–43 [Fig. 2(c)] have begun to surface in an effort to replicate more faithfully the innate acinar morphology.…”

“…This discrepancy yields a low ratio of alveolar-to-ductal volume; 44 a limitation not necessarily critical in replicating the biological functions of the epithelial barrier and air-liquid interface (see Sec. IV) but important in evaluating realistic aerosol deposition patterns 41 . This latter point may be pertinent for cytotoxicity and dosimetry, or alternatively, in targeting therapeutic delivery 45,46 …”

“…In turn, the coupling between oscillatory shear flows in acinar ducts and the alveolar cavity openings leads to distinct flow configurations that are sensitive to the location of an alveolus along the acinar tree 65,70 . Using micro-particle image velocimetry ( μ PIV), measurements in microfluidic alveolated tree models 41,42 have revealed the existence of a range of complex recirculating (i.e., vortex) flows in alveoli, with a gradual crossover to more radial-like streamlines in the deeper acinar generations (Fig. 3).…”

Do nanoparticles provide a new opportunity for diagnosis of distal airspace disease?

“…The former is achieved by large nanoparticles, while the latter increases for small nanoparticles. 47,[86][87][88] Based on the analysis explained, the optimal particle size range for AiDA is 40-100 nm, but experiments and detailed model calculations, especially for diseased lungs, are necessary to confirm these theoretical predictions. …”

Numerical assessment of airflow and inhaled particles attributes in obstructed pulmonary system

“…Multi-scale computational models of the airways have been established by [19] to identify the pathophysiological mechanisms in asthma and COPD. An anatomically-inspired model of the lung acinus featuring a bifurcating tree of alveolated airways with moving walls has been developed [20], [21]. Moreover, the airflow characteristics of human airways between the 8 th and 14 th generations have been examined [22].…”