Balásházy Imre, Hofmann Werner, Farkas Arpád, Madas Balázs G
Health and Environmental Physics Department, MTA KFKI Atomic Energy Research Institute, Budapest, Hungary.
Inhal Toxicol. 2008 Apr;20(6):611-21. doi: 10.1080/08958370801915291.
Particle transport and deposition within a model alveolus, represented by a rhythmically expanding and contracting hemisphere, was modeled by a three-dimensional analytical model for the time-dependent air velocity field as a superposition of uniform and radial flow components, satisfying both the mass and momentum conservation equations. Trajectories of particles entrained in the airflow were calculated by a numerical particle trajectory code to compute simultaneously deposition by inertial impaction, gravitational sedimentation, Brownian diffusion, and interception. Five different orientations of the orifice of the alveolus relative to the direction of gravity were selected. Deposition was calculated for particles from 1 nm to 10 microm, for 3 breathing conditions, and for 5 different entrance times relative to the onset of inspiration. For the analyzed cases, the spatial orientation of the orifice of an alveolus has practically no effect on deposition for particles below about 0.1 microm, where deposition is dominated by Brownian motion. Above about 1 microm, where deposition is governed primarily by gravitational settling, deposition can vary from 0 to 100%, depending on the spatial orientation, while deposition of particles 0.1-1 microm falls between these two extreme cases. Due to the isotropic nature of Brownian motion, deposition of the 10-nm particles is practically uniform for all spatial orientations. However, for larger particles, deposition can be quite inhomogeneous, consistent with the direction of gravity. While nearly all particles are exhaled during the successive expiration phase, there are a few cases where particles still leave the alveolus even after many breathing cycles.
通过一个三维分析模型对由有节奏地扩张和收缩的半球表示的模型肺泡内的颗粒传输和沉积进行建模，该模型用于随时间变化的空气速度场，作为均匀流和径向流分量的叠加，满足质量和动量守恒方程。通过数值颗粒轨迹代码计算气流中夹带的颗粒轨迹，以同时计算通过惯性碰撞、重力沉降、布朗扩散和拦截的沉积。选择了肺泡孔相对于重力方向的五种不同取向。计算了1纳米至10微米颗粒在三种呼吸条件下以及相对于吸气开始的五种不同进入时间的沉积情况。对于所分析的情况，肺泡孔的空间取向对于约0.1微米以下的颗粒的沉积几乎没有影响，在该粒径范围内沉积主要由布朗运动主导。在约1微米以上，沉积主要由重力沉降控制，沉积量可从0%到100%不等，具体取决于空间取向，而0.1 - 1微米颗粒的沉积则介于这两种极端情况之间。由于布朗运动的各向同性，10纳米颗粒在所有空间取向下的沉积实际上是均匀的。然而，对于较大的颗粒，沉积可能非常不均匀，与重力方向一致。虽然几乎所有颗粒在连续呼气阶段都会呼出，但在少数情况下，即使经过许多呼吸周期，颗粒仍会离开肺泡。
