Deposition of 0.5 to 2 Micron Aerosol in the Human Lung

描述(申请人提供)：存款金额较小(小于 2.5 mm)的颗粒物主要由以下机制支配： 沉积和扩散。我们最近在微重力条件下进行的研究 (Mg)环境已显示出显著程度的强化沉积 小颗粒，与现有的数值模型预测的相比 证词。这似乎很可能是由于之前下落不明的 对于人体肺内流动的不可逆性的影响(有效 提供增强的扩散)。这种强化的沉积意味着现有的 小颗粒(小于2.5毫米)的模型可能低估了暴露， 而这种增加的暴露发生在牙槽骨的敏感区域。 肺部。我们建议通过研究1)来研究增强的肺泡沉积 包含屏气的扩散对气溶胶扩散的贡献 在气雾剂试验中：2)肺内对流混合的增加导致 通过导致肺内流线的复杂混合的流动逆转； 3)1G时肺内对流混合增加 类似的研究使用了地面上最小的颗粒。为了研究这些 影响，我们建议测量吸入物的区域沉积和扩散 美国宇航局KC-135微重力装置中MG中0.5微米和2微米粒子的团注 研究飞机，地面上有0.5微米的颗粒。通过执行这些操作 在没有重力的情况下，我们将能够直接研究这些 效果没有混杂的影响，沉积，重力 进程。这种不受沉积影响的直接观测是 在地球实验室里是不可能的。有很多肺的证据 起病于小气道或肺泡，肺泡增多 通过增强扩散的沉积可能在长期MG之间提供联系 暴露和肺部疾病。这项研究的结果将允许现有的模型 区域内肺内气溶胶沉积有待改善，特别是 较小的颗粒(在0.5微米到1微米的范围内)。这样的信息 将为评估接触小剂量辐射提供一个大大改进的基础 在长时间的航天飞行和地球上都有吸入颗粒物。

DESCRIPTION (provided by the applicant): The deposition of small (less than 2.5Mm) particles in the human lung is governed primarily by the mechanisms of sedimentation and diffusion. Recent studies we performed in the microgravity (MG) environment have shown a significant degree of enhanced deposition of small particles, compared to that predicted by existing numerical models of deposition. It seems likely that this results from the previously unaccounted for effects of the non-reversibility of flows in the human lung (effectively providing enhanced diffusion). Such enhanced deposition means that existing models for small particles (less than 2.5 Mm) probably underestimate exposure, and that this increased exposure occurs in the sensitive alveolar regions of the lung. We propose to investigate enhanced alveolar deposition by studying 1) The contribution of diffusion to aerosol dispersion by inclusion of breathhold in aerosol bolus tests: 2) The increase in convective mixing in the lung caused by flow reversals that induces complex mixing of the streamlines in the lung; and 3) The increase in convective mixing in the lung in 1G by performing similar studies using the smallest particles on the ground. To study these effects, we propose to measure regional deposition and dispersion of inhaled boluses of 0.5 and 2 micron particles in MG in the NASA KC-135 Microgravity research Aircraft, and 0.5 micron particles on the ground. By performing these studies in the absence of gravity we will be able to directly study these effects without the confounding influence of sedimentation, a gravitational process. Such direct observations without the influence of sedimentation are not possible in the terrestrial laboratory. There is evidence for many lung diseases beginning in the small airways or alveoli, and increased alveolar deposition through enhanced diffusion may provide a link between long-term MG exposure and lung disease. The results of this study will allow existing models of regional intrapulmonary aerosol deposition to be improved, especially for the smaller particles (those in the range 0.5 to 1 micron). Such information will provide a much-improved basis for the assessment of exposure to small inhaled particles both in long duration spaceflight and on Earth.