Impact of Salivary Rheology on Expiratory Aerosol Formation in the Vocal Folds during Phonation

唾液流变学对发声期间声带呼气气溶胶形成的影响

• 批准号: 2311618
• 负责人: William Ristenpart
• 金额: $ 59万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-15 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2311618&HistoricalAwards=false
• 关键词: Impact; Salivary; Rheology; Expiratory; Aerosol

More people die from lower respiratory diseases, like influenza and COVID-19, than any other type of infectious disease. After much early confusion during the COVID-19 pandemic, the scientific consensus now is that many airborne diseases are spread via “aerosols,” which are very tiny droplets emitted by humans when they speak or otherwise exhale. These tiny droplets are much too small to see, but they are sufficiently large to carry viruses or other pathogens. Although it is believed that many tiny droplets are formed at the vocal cords during speech, to date no work has directly examined this hypothesis. In this research project, a trained medical doctor will insert a fiber optic camera through the nose of human study participants to provide the first direct video observations of the vocal cords during droplet formation. Simultaneous experiments by engineers will measure the overall rate of droplet emission, as well as the ‘viscosity’ or thickness of the saliva in each participant. The research will thus directly test the hypothesis that the rate of droplet emission responsible for air-borne disease transmission is directly related to the viscosity of the saliva in infected individuals.The droplet formation rate is hypothesized to be governed by a balance of elastic, capillary, and inertial effects in the saliva that lines the glottis, as characterized by the Deborah and Ohnesorge numbers. Each time the vocal folds move apart (up to hundreds of times per second), thin fluid filaments are stretched and eventually pinch apart, yielding satellite droplets that are caught in the expiratory airflow and ultimately exhaled into the surrounding environment. The research team includes an otolaryngologist with much experience visualizing patients’ vocal folds using a laryngoscope (which features a fiber optic cable inserted through the nose). A stroboscopy video system will be used to directly visualize and record the vocal folds in vivo of participants during vocalization at systematically varied loudness, while simultaneous measurements of the expiratory aerosol emission rate will be performed using an aerodynamic particle sizer. Saliva samples from each participant will be collected to measure the storage and loss moduli of the saliva with a double-gap geometry rheometer, and to measure the extensional viscosity and drop formation dynamics using capillary break-up rheometry in a liquid bridge geometry. The combination of these multiple data streams over a statistically significant number of different participants will inform complementary fluid mechanics modeling and provide unprecedented and fundamental insight into expiratory droplet formation, potentially providing a fluid mechanical explanation for why some individuals are super-emitters of expiratory aerosols.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

与其他任何类型的传染病相比，死于流感和新冠肺炎等下呼吸道疾病的人更多。在新冠肺炎大流行期间经历了很长时间的混乱之后，现在科学上的共识是，许多空气传播的疾病都是通过“气雾剂”传播的。“气雾剂”是人类说话或呼气时排放的非常微小的水滴。这些微小的液滴太小了，看不见，但它们足够大，可以携带病毒或其他病原体。尽管人们相信，在说话过程中，声带会形成许多微小的水滴，但到目前为止，还没有研究直接检验这一假设。在这项研究项目中，一名训练有素的医生将通过人体研究参与者的鼻子插入光纤摄像机，以提供在水滴形成过程中对声带的第一次直接视频观察。工程师同时进行的实验将测量每个参与者唾液的总体释放速度，以及唾液的“粘度”或厚度。因此，这项研究将直接检验这一假设，即导致空气传播疾病的飞沫排放速度与感染者唾液的粘度直接相关。根据Deborah和Ohnesorge数值的特征，飞沫的形成速度被认为是由声门内唾液中弹性、毛细和惯性效应的平衡控制的。每次声带分开(每秒高达数百次)，细小的液体细丝被拉伸，最终被掐断，产生卫星液滴，这些液滴被呼气气流捕获，最终被呼出进入周围环境。研究小组包括一位经验丰富的耳鼻喉科医生，他使用喉镜(其特点是通过鼻子插入光纤电缆)可视化患者的声带。将使用频闪视频系统在发声过程中以系统变化的响度直接可视化和记录参与者的声带，同时将使用空气动力学颗粒测量仪同时测量呼气气溶胶发射率。将收集每个参与者的唾液样本，以使用双间隙几何流变仪测量唾液的储存和损失模数，并使用液桥几何形状的毛细管破碎流变仪测量拉伸粘度和液滴形成动力学。在具有统计意义的不同参与者中，这些多个数据流的组合将为互补的流体力学建模提供信息，并提供对呼气微滴形成的前所未有和基本的洞察，潜在地为为什么一些人是呼气气溶胶的超级排放者提供流体力学解释。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。