Gravitational deposition in a rhythmically expanding and contracting alveolus
Gravitational deposition in a rhythmically expanding and contracting alveolus
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DOI：
10.1152/japplphysiol.00770.2002
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发表时间：
2003-08-01
影响因子：
3.3
通讯作者：
Tsuda, A
中科院分区：
文献类型：
--
作者：
Haber, S;Yitzhak, D;Tsuda, A
在之前的模拟中，我们的实验室证明了有节奏地扩张和收缩肺泡引起的流动是高度复杂的（Haber S, Butler JP, Brenner H, Emanuel I, and Tsuda a， J流体力学405:243 - 268,2000）。基于这些早期的发现，我们假设肺泡内气溶胶的轨迹和沉积与先前的预测有很大的不同。为了验证这一假设，模拟了细颗粒（直径0.5 - 2.5 μ m）在上述肺泡流场中移动并同时受到重力场影响的轨迹。结果表明，肺泡壁运动是决定气溶胶在肺泡内沉积增强的关键因素。特别是，直径0.5- 1 μ m的颗粒对详细的肺泡流动结构（如再循环流动）很敏感，因为它们经历了重力诱导的对流混合和沉积。因此，每个肺泡内的沉积浓度是不均匀的，肺泡入口环附近的密度优先较高，这与生理观察结果一致。沿腺泡树的沉积模式也不均匀，在腺泡代的前半期沉积较多。这是由于肺泡扩张和收缩导致的近端腺泡沉积增强和腺泡树下方气相中剩余颗粒数量减少的综合作用的结果。我们认为肺泡的周期性扩张和收缩运动在决定肺腺泡的重力沉积中起重要作用。
In a previous simulation, our laboratory demonstrated that the flow induced by a rhythmically expanding and contracting alveolus is highly complex (Haber S, Butler JP, Brenner H, Emanuel I, and Tsuda A, J Fluid Mech 405: 243 - 268, 2000). Based on these earlier findings, we hypothesize that the trajectories and deposition of aerosols inside the alveoli differ substantially from those previously predicted. To test this hypothesis, trajectories of fine particles (0.5 - 2.5 mum in diameter) moving in the foregoing alveolar flow field and simultaneously subjected to the gravity field were simulated. The results show that alveolar wall motion is crucial in determining the enhancement of aerosol deposition inside the alveoli. In particular, 0.5- to 1-mum-diameter particles are sensitive to the detailed alveolar flow structure (e.g., recirculating flow), as they undergo gravity-induced convective mixing and deposition. Accordingly, deposition concentrations within each alveolus are nonuniform, with preferentially higher densities near the alveolar entrance ring, consistent with physiological observations. Deposition patterns along the acinar tree are also nonuniform, with higher deposition in the first half of the acinar generations. This is a result of the combined effects of enhanced alveolar deposition in the proximal region of the acinus due to alveoli expansion and contraction and reduction in the number of particles remaining in the gas phase down the acinar tree. We conclude that the cyclically expanding and contracting motion of alveoli plays an important role in determining gravitational deposition in the pulmonary acinus.