Engineering Fluid Dynamics, University of Twente, Enschede, The Netherlands.
Department of Pulmonary Diseases/Home Mechanical Ventilation, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
Respiration. 2021;100(12):1196-1207. doi: 10.1159/000518735. Epub 2021 Sep 15.
Various forms of noninvasive respiratory support methods are used in the treatment of hypoxemic CO-VID-19 patients, but limited data are available about the corresponding respiratory droplet dispersion.
The aim of this study was to estimate the potential spread of infectious diseases for a broad selection of oxygen and respiratory support methods by revealing the therapy-induced aerodynamics and respiratory droplet dispersion.
The exhaled air-smoke plume from a 3D-printed upper airway geometry was visualized by recording light reflection during simulated spontaneous breathing, standard oxygen mask application, nasal high-flow therapy (NHFT), continuous positive airway pressure (CPAP), and bilevel positive airway pressure (BiPAP). The dispersion of 100 μm particles was estimated from the initial velocity of exhaled air and the theoretical terminal velocity.
Estimated droplet dispersion was 16 cm for unassisted breathing, 10 cm for Venturi masks, 13 cm for the nebulizer, and 14 cm for the nonrebreathing mask. Estimated droplet spread increased up to 34 cm in NHFT, 57 cm in BiPAP, and 69 cm in CPAP. A nonsurgical face mask over the NHFT interface reduced estimated droplet dispersion.
During NHFT and CPAP/BiPAP with vented masks, extensive jets with relatively high jet velocities were observed, indicating increased droplet spread and an increased risk of droplet-driven virus transmission. For the Venturi masks, a nonrebreathing mask, and a nebulizer, estimated jet velocities are comparable to unassisted breathing. Aerosols are transported unboundedly in all these unfiltered therapies. The adequate use of protective measures is of vital importance when using noninvasive unfiltered therapies in infectious respiratory diseases.
在治疗低氧血症 COVID-19 患者时，会使用各种形式的无创呼吸支持方法，但关于相应的呼吸飞沫传播的数据有限。
本研究旨在通过揭示治疗引起的空气动力学和呼吸飞沫传播，来估计广泛选择的氧气和呼吸支持方法的传染病传播潜力。
通过记录模拟自主呼吸、标准氧气面罩应用、鼻高流量治疗（NHFT）、持续气道正压通气（CPAP）和双水平气道正压通气（BiPAP）过程中呼出的空气烟雾羽流的光反射，来可视化 3D 打印上气道几何形状的呼出空气烟雾羽流。根据呼出空气的初始速度和理论终端速度来估计 100μm 颗粒的分散度。
未辅助呼吸时的估计飞沫分散度为 16cm，文丘里面罩为 10cm，雾化器为 13cm，无重复呼吸面罩为 14cm。在 NHFT 中，估计飞沫扩散增加到 34cm，在 BiPAP 中增加到 57cm，在 CPAP 中增加到 69cm。在 NHFT 界面上使用非手术面罩可减少估计的飞沫扩散。
在具有通风面罩的 NHFT 和 CPAP/BiPAP 期间，观察到具有相对较高射流速度的广泛射流，表明飞沫扩散增加，飞沫驱动的病毒传播风险增加。对于文丘里面罩、无重复呼吸面罩和雾化器，估计的射流速度与自主呼吸相当。在所有这些未经过滤的治疗中，气溶胶都无束缚地传输。在传染性呼吸道疾病中使用非侵入性未经过滤的治疗时，适当使用保护措施至关重要。
