Saha Sudipta, Manna Manish Kumar, Chakravarty Aranyak, Sarkar Sourav, Mukhopadhyay Achintya, Sen Swarnendu
School of Nuclear Studies and Application, Jadavpur University (Salt Lake campus), Kolkata 700106, India.
Department of Mechanical Engineering, Jadavpur University, Kolkata 700032, India.
Biomicrofluidics. 2024 Sep 17;18(5):054106. doi: 10.1063/5.0219332. eCollection 2024 Sep.
Bioaerosols produced within the respiratory system play an important role in respiratory disease transmission. These include infectious diseases such as common cold, influenza, tuberculosis, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among several others. It is, therefore, of immense interest to understand how bioaerosols are produced within the respiratory system. This has not been extensively investigated. The present study computationally investigates how bioaerosols are produced in a model respiratory tract due to hydrodynamic interactions between breathed air and a thin mucus layer, which lines the inner surface of the tract. It is observed that Kelvin-Helmholtz instability is established in the thin mucus layer due to associated fluid dynamics. This induces interfacial surface waves which fragment forming bioaerosols under certain conditions. A regime map is created-based on pertinent dimensionless parameters-to enable identification of such conditions. Analysis indicates that bioaerosols may be produced even under normal breathing conditions, contrary to expectations, depending on mucus rheology and thickness of the mucus layer. This is possible during medical conditions as well as during some treatment protocols. However, such bioaerosols are observed to be larger ( m) and are produced in less numbers ( ), as compared to those produced under coughing conditions. Treatment protocols and therapeutic strategies may be suitably devised based on these findings.
呼吸系统内产生的生物气溶胶在呼吸道疾病传播中起着重要作用。这些疾病包括普通感冒、流感、肺结核、严重急性呼吸综合征冠状病毒2（SARS-CoV-2）等多种传染病。因此，了解生物气溶胶在呼吸系统内如何产生极具意义。对此尚未进行广泛研究。本研究通过计算调查了在模型呼吸道中，由于呼出空气与覆盖呼吸道内表面的薄黏液层之间的流体动力学相互作用，生物气溶胶是如何产生的。研究发现，由于相关的流体动力学，在薄黏液层中会形成开尔文-亥姆霍兹不稳定性。这会引发界面表面波，在特定条件下这些表面波会破碎形成生物气溶胶。基于相关无量纲参数创建了一个状态图，以确定这些条件。分析表明，与预期相反，根据黏液流变学和黏液层厚度，即使在正常呼吸条件下也可能产生生物气溶胶。在医疗状况以及某些治疗方案期间都可能出现这种情况。然而，与咳嗽条件下产生的生物气溶胶相比，观察到此类生物气溶胶更大（ 微米）且数量更少（ ）。可根据这些发现适当制定治疗方案和治疗策略。
