Wei Jianjian, Tang Julian W, Borojeni Azadeh A T, Yin Shi, Martin Andrew, Finlay Warren H, Li Yuguo
Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
Department of Medical Microbiology & Immunology, University of Alberta, Edmonton, Canada.
Build Environ. 2016 Feb 15;97:40-47. doi: 10.1016/j.buildenv.2015.12.011. Epub 2015 Dec 15.
To estimate the fraction of the exhaled airflow that is re-inhaled during normal nasal breathing, experiments were carried out in a water tank with an anatomically accurate respiratory tract model of a 4-year-old child. The velocity of respiratory flow was scaled using similarity laws between air and water. Breath simulation was performed via a computer-controlled piston-cylinder system. Food-dye visualization allows a qualitative analysis of the re-inhaled fraction of this exhaled flow. For the quantitative analysis, neutrally buoyant particles were added to the water medium, and illuminated by the laser which illuminates the whole breathing region of the respiratory model, such that the trajectory and quantity of the re-inhaled particles can be recorded and counted. The experimental results in the pediatric airway replica show that a negligible fraction (<0.06%) of the exhaled airflow is re-inhaled during normal nasal breathing in the absence of the rising thermal plume. The artificial plume generated by a heated aluminium brick at the tank bottom increases the re-inhalation ratio by 4 times under the investigated case (albeit still at a very low value of 0.15%). Our results thus reveal that during normal nasal breathing in the present pediatric subject, the vast majority of human exhaled airflow escapes from the inhalation zone and is not re-inhaled.
为了估算正常鼻腔呼吸过程中重新吸入的呼出气流比例，研究人员在水箱中使用一个解剖结构精确的4岁儿童呼吸道模型进行了实验。呼吸气流速度根据空气与水之间的相似定律进行缩放。通过计算机控制的活塞 - 气缸系统进行呼吸模拟。食用色素可视化可对呼出气流的重新吸入比例进行定性分析。为了进行定量分析，向水介质中添加了中性浮力颗粒，并由照亮呼吸模型整个呼吸区域的激光进行照射，以便记录和计数重新吸入颗粒的轨迹和数量。儿科气道复制品的实验结果表明，在没有上升热羽流的情况下，正常鼻腔呼吸过程中呼出气流的重新吸入比例可忽略不计（<0.06%）。在水箱底部由加热铝块产生的人工羽流在研究案例中使重新吸入比例增加了4倍（尽管仍处于非常低的0.15%的值）。因此，我们的结果表明，在当前儿科受试者的正常鼻腔呼吸过程中，绝大多数呼出气流从吸入区域逸出，不会被重新吸入。
