Abstract
Obtaining in vivo data of particle transport in the human lung is often difficult, if not impossible. Computational fluid dynamics (CFD) can provide detailed information on aerosol transport in realistic airway geometries. This paper provides a review of the key CFD studies of aerosol transport in the acinar region of the human lung. It also describes the first ever three-dimensional model of a single fully alveolated duct with moving boundaries allowing for the cyclic expansion and contraction that occurs during breathing. Studies of intra-acinar aerosol transport performed in models with stationary walls (SWs) showed that flow patterns were influenced by the geometric characteristics of the alveolar aperture, the presence of the alveolar septa contributed to the penetration of the particles into the lung periphery and there were large inhomogeneities in deposition patterns within the acinar structure. Recent studies have now used acinar models with moving walls. In these cases, particles penetrate the alveolar cavities not only as a result of sedimentation and diffusion but also as a result of convective transport, resulting in a much higher deposition prediction than that in SW models. Thus, models that fail to incorporate alveolar wall motions probably underestimate aerosol deposition in the acinar region of the lung.
Highlights
While it is widely accepted that fine particles can penetrate deep into the alveolar region of the lung, no technique allowing for accurate direct in vivo measurements is yet available
Harrington et al (2006) have developed the first three-dimensional model of a single bifurcation of alveolated ducts. All these studies showed that flow patterns were influenced by geometric characteristics, in particular at the level of the alveolar aperture, that the presence of the alveolar septa contributed to the penetration of the particles in the periphery of the lung, and that there were large inhomogeneities in deposition patterns within the acinar structure
This study focused on the effect of moving walls (MWs) boundaries on predicting aerosol deposition
Summary
While it is widely accepted that fine particles (smaller than 2.5 mm) can penetrate deep into the alveolar region of the lung, no technique allowing for accurate direct in vivo measurements is yet available. Harrington et al (2006) have developed the first three-dimensional model of a single bifurcation of alveolated ducts All these studies showed that flow patterns were influenced by geometric characteristics, in particular at the level of the alveolar aperture, that the presence of the alveolar septa contributed to the penetration of the particles in the periphery of the lung, and that there were large inhomogeneities in deposition patterns within the acinar structure. The paper provides a detailed review of previous key CFD studies of aerosol transport and deposition in the acinar region of the lung It describes the first ever three-dimensional model of a single fully alveolated duct with moving boundaries allowing for the simulation of the cyclic expansion and contraction that occurs during breathing. Predictions of aerosol deposition are compared with those obtained in a similar model with rigid walls
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