Environmental Physics Department, Hungarian Academy of Sciences Centre for Energy Research, Budapest, Hungary.
Inhal Toxicol. 2013 Aug;25(10):593-605. doi: 10.3109/08958378.2013.815666.
For a correct assessment of health consequences of inhaled aerosols as a function of dose, whether for environmental, occupational or therapeutic agents, knowledge of their deposition distribution in the respiratory tract and subsequent clearance is important. The objective of this study is to model particle clearance at bronchial airway bifurcation level and to analyze the combined effect of deposition and clearance. For this purpose, a numerical model has been implemented. Air and mucus flow fields were computed in a model bronchial airway bifurcation. Inhaled particles with 1 and 10 µm aerodynamic diameters were tracked to determine deposition and clearance patterns. Simulation results revealed the existence of a slow clearance zone around the peak of the airway bifurcation causing delayed clearance of the particles depositing or entering here. Particles clearing up from the deeper airways and crossing the studied bifurcation do not accumulate in this zone, because of their tendency to avoid it. The average residence time of these particles was around 20 min independently of particle size (whether it is 1 or 10 µm). However, as a result of the superposition of deposition and clearance mechanisms, the final spatial distribution of particles deposited primarily in the target bifurcation is size dependent, because deposition is size specific. Although deposition density of particles deposited in the slow clearance area is one-two orders of magnitude higher than the average deposition density, these values are reduced by clearance by the factors of 4-7, depending on the particle size and the surface area of the selected slow clearance zone. In conclusion, although particle deposition is inhomogeneous, clearance can significantly decrease the degree of spatial non-uniformity of the particles. Therefore, for a correct assessment of doses at local levels, it is important to consider both deposition and clearance. Although future research may overwrite some of the model assumptions on the nature of mucus, the authors think that most of the current predictions will hold.
为了正确评估吸入气溶胶作为剂量函数的健康后果，无论是环境、职业还是治疗性制剂，了解它们在呼吸道中的沉积分布和随后的清除情况非常重要。本研究的目的是模拟支气管气道分叉处的颗粒清除，并分析沉积和清除的综合效应。为此，实现了一个数值模型。在支气管气道分叉模型中计算了空气和粘液流场。跟踪吸入的具有 1 和 10 µm 空气动力学直径的颗粒，以确定沉积和清除模式。模拟结果表明，在气道分叉的峰值周围存在一个缓慢清除区，导致颗粒的清除延迟，这些颗粒在这里沉积或进入。从更深的气道清除并穿过研究分叉的颗粒不会积聚在这个区域，因为它们有避免它的趋势。这些颗粒的平均停留时间约为 20 分钟，与颗粒大小无关（无论是 1 µm 还是 10 µm）。然而，由于沉积和清除机制的叠加，主要沉积在目标分叉处的颗粒的最终空间分布是尺寸依赖性的，因为沉积是尺寸特异性的。尽管沉积在缓慢清除区的颗粒的沉积密度比平均沉积密度高一到两个数量级，但由于清除，这些值减少了 4-7 倍，具体取决于颗粒大小和所选缓慢清除区的表面积。总之，尽管颗粒沉积不均匀，但清除可以显著降低颗粒空间不均匀性的程度。因此，为了正确评估局部水平的剂量，考虑沉积和清除非常重要。尽管未来的研究可能会改变模型对粘液性质的一些假设，但作者认为目前的大部分预测仍然成立。
