Modeling of Aerosol Transport in Alveolated Airways

描述（由申请方提供）：本研究的长期目标是更好地了解吸入颗粒物（PM）在人肺中的命运。无论PM暴露是由大气污染、生物战、职业因素还是吸入性药物治疗引起的，这一点都很重要。越来越多的证据将空气中细颗粒物的存在与心肺疾病联系起来。这种PM非常值得关注，因为它可以深入到腺泡中。迄今为止，最现实的模型，人类腺泡由一个多分叉结构的二维肺泡管（AD）。在本研究中，我们将开发具有高度解剖现实性的儿童和成人肺的三维腺泡模型。第一种类型的模型将包括具有刚性壁的AD的单个分叉。第二种类型的模型将解决在呼吸期间肺泡壁运动的影响，并将形成多达四个连续分叉的真实结构。这将是迄今为止开发的最全面的腺泡模型。将模拟颗粒直径（dp）范围为0.005-5 μ m，流速范围从安静呼吸到适度运动的PM输送和沉积（DE）。当0.5<dp<5（m）时，DE主要由重力沉积作用引起，并主要受构造相对于重力矢量的方位的影响。当dp < 0.5（m）时，DE主要是由于布朗扩散，并受可供PM存款的肺泡表面的影响。将确定速度剖面、肺泡壁的节律运动和PM固有运动对整体对流混合的贡献。对流混合导致吸入的PM不可逆地转移到驻留空气中。因此，在正常呼气结束时，一些PM保持悬浮在远端气道中，并在下一次呼吸期间更深地渗透到肺中，最终沉积在肺中。拉伸和折叠的过程中，由于在肺中的流动的不可逆性，空气流线成为折叠回自己，也将被模拟，以确定它是否是负责额外的混合腺泡，并因此较高的DE比以前预测的。最后，数值预测将在人类受试者和简单的物理模型中获得的实验数据进行比较。这项研究的结果将提供一个链接的机制，即使是看似温和的PM暴露可能会导致或加剧肺部疾病，也将有助于更好地设计吸入药物的空间靶向。

DESCRIPTION (provided by applicant): The long-term objective of this study is to better understand the fate of inhaled particulate matter (PM) in the human lung. This is important whether PM exposure results from atmospheric pollution, biological warfare, and occupational factors or inhaled drug therapy. More and more evidence links the presence of fine PM in the air with cardiopulmonary diseases. This PM is of great concern because it can penetrate deep into the acinus. To date, the most realistic model of the human acinus consists of a multi-bifurcation structure of two-dimensional alveolated ducts (AD). In the present study we will develop three-dimensional acinar models of children and adult lung with a high degree of anatomical realism. A first type of model will consist of a single bifurcation of AD with rigid walls. A second type of model will address the effects of alveolar wall motions during breathing and will form a realistic structure of up to four successive bifurcations. This will be the most comprehensive acinar models yet developed. PM transport and deposition (DE) will be simulated for particle diameters (dp) ranging 0.005-5 (m and for flow rates ranging from quiet breathing to moderate exercise. For 0.5<dp<5 (m, DE is mainly due to gravitational sedimentation and is mainly affected by the structure orientation with respect to the gravity vector. For dp < 0.5 (m, DE is mainly due to Brownian diffusion and is affected by the alveolar surface available to PM to deposit. The contribution of velocity profiles, rhythmical motions of the alveolar walls and PM intrinsic motions to overall convective mixing will be determined. Convective mixing causes inhaled PM to be irreversibly transferred to the resident air. As a result, some PM remains in suspension in the distal airways at the end of a normal expiration and penetrates deeper in the lung during the next breath where it eventually deposits. The process of stretch and fold where, because of non-reversibility of flow in the lung, air streamlines become folded back on themselves, will also be simulated to determine whether it is responsible for additional mixing in the acinus, and consequently for higher DE than that previously predicted. Finally the numerical predictions will be compared to experimental data obtained in human subjects and in simple physical models. The results of this study will provide a link to the mechanisms by which even seemingly modest PM exposure can cause or exacerbate lung disease and will also help to better design spatial targeting of inhaled drugs.