Chhabra Sudhaker, Prasad Ajay K
Department of Mechanical Engineering, University of Delaware, Newark, DE 19716, USA.
J Biomech Eng. 2010 May;132(5):051010. doi: 10.1115/1.4001113.
The acinar region of the human lung comprises about 300x10(6) alveoli, which are responsible for gas exchange between the lung and the blood. As discussed in Part I (Chhabra and Prasad, "Flow and Particle Dispersion in a Pulmonary Alveolus-Part I: Velocity Measurements and Convective Particle Transport," ASME J. Biomech. Eng., 132, p. 051009), the deposition of aerosols in the acinar region can either be detrimental to gas exchange (as in the case of harmful particulate matter) or beneficial (as in the case of inhalable pharmaceuticals). We measured the flow field inside an in-vitro model of a single alveolus mounted on a bronchiole and calculated the transport and deposition of massless particles in Part I. This paper focuses on the transport and deposition of finite-sized particles ranging from 0.25 microm to 4 microm under the combined influence of flow-induced advection (computed from velocity maps obtained by particle image velocimetry) and gravitational settling. Particles were introduced during the first inhalation cycle and their trajectories and deposition statistics were calculated for subsequent cycles for three different particle sizes (0.25 microm, 1 microm, and 4 microm) and three alveolar orientations. The key outcome of the study is that particles <or=0.25 microm follow the fluid streamlines quite closely, whereas midsize particles (d(p)=1 microm) deviate to some extent from streamlines and exhibit complex trajectories. The motion of large particles >or=4 microm is dominated by gravitational settling and shows little effect of fluid advection. Additionally, small and midsize particles deposit at about two-thirds height in the alveolus irrespective of the gravitational orientation whereas the deposition of large particles is governed primarily by the orientation of the gravity vector.
人类肺部的腺泡区域包含约3亿个肺泡，这些肺泡负责肺与血液之间的气体交换。如第一部分所述（Chhabra和Prasad，“肺小泡内的流动与颗粒扩散——第一部分：速度测量与对流颗粒输运”，美国机械工程师协会《生物医学工程杂志》，第132卷，第051009页），气溶胶在腺泡区域的沉积可能对气体交换有害（如有害颗粒物的情况），也可能有益（如可吸入药物的情况）。在第一部分中，我们测量了安装在细支气管上的单个肺泡体外模型内的流场，并计算了无质量颗粒的输运和沉积。本文重点研究在流动诱导平流（根据粒子图像测速法获得的速度图计算）和重力沉降的联合影响下，尺寸范围从0.25微米到4微米的有限尺寸颗粒的输运和沉积。在第一次吸气循环期间引入颗粒，并针对后续循环计算三种不同粒径（0.25微米、1微米和4微米）和三种肺泡取向的颗粒轨迹和沉积统计数据。该研究的关键结果是，尺寸小于或等于0.25微米的颗粒相当紧密地跟随流体流线，而中等尺寸颗粒（d(p)=1微米）在一定程度上偏离流线并呈现复杂轨迹。尺寸大于或等于4微米的大颗粒的运动主要由重力沉降主导，流体平流的影响很小。此外，无论重力方向如何，小颗粒和中等尺寸颗粒都沉积在肺泡约三分之二高度处，而大颗粒的沉积主要由重力矢量的方向控制。
