Simulation of Aerosol Dispersion During Medical Examinations

The main route of transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) virus is airborne. The objective of this study is to analyze the aerosol dispersion and potential exposure to medical staff within a typical medical examination room during classical airway procedures. The multiphase simulation of the aerosol particles in the airflow is based on a Lagrangian-Eulerian approach. All simulation cases with surgical mask show partially but significantly reduced maximum dispersion distances of the aerosol particles compared to the cases without a surgical mask. The simulations have shown that medical examiners are exposed to a large amount of aerosol particles, especially during procedures such as laryngoscopy where the examiner's head is directly in front of the patient's face. However, exposure can be drastically reduced if the patient wears a mask which is possible for most of the procedures studied, such as otoscopy, sonography, or anamnesis. Copyright © 2022 by ASME.

Acoustic analysis of professional singing masks

Wearing face coverings became one essential tool in order to prohibit virus transmission during the COVID-19 pandemic. In comparison to speaking and breathing, singing emits a much higher amount of aerosol particles. Therefore, there are situations in which singers can perform or rehearse only if they are using protective masks. However, such masks have a more or less adverse effect not only on the singer's comfort and tightness of the mask but also on the radiated sound. For this reason, the spectral filtering and directivity of masks designed specifically for professional singing was measured. The tests were performed with a head phantom. Over most of the spectrum, attenuation is observed, although amplification happens at some low frequency bands for different mask types and directions. Especially singing masks with a plastic face shield showed partial amplification of up to +10 dB below a frequency of 2 kHz, while only slight significant attenuation and no amplification (minimal acoustic loss) were seen for woven fabric masks. Above 2.5 kHz, the transparent masks showed the greatest sound attenuation up to -30 dB, while woven fabric masks produced an overall lower sound attenuation of up to -5 dB. In addition at low frequencies, the sound was amplified or attenuated equally in all directions for masks with a stiff plastic face shield. At higher frequencies, the attenuation is higher to the frontal than to the backward direction.

Clinical characterization of respiratory large droplet production during common airway procedures using high-speed imaging.

During the COVID-19 pandemic, a significant number of healthcare workers have been infected with SARS-CoV-2. However, there remains little knowledge regarding large droplet dissemination during airway management procedures in real life settings. 12 different airway management procedures were investigated during routine clinical care. A high-speed video camera (1000 frames/second) was for imaging. Quantitative droplet characteristics as size, distance traveled, and velocity were computed. Droplets were detected in 8/12 procedures. The droplet trajectories could be divided into two distinctive patterns (type 1/2). Type 1 represented a ballistic trajectory with higher speed large droplets whereas type 2 represented a random trajectory of slower particles that persisted longer in air. The use of tracheal cannula filters reduced the amount of droplets. Respiratory droplet patterns generated during airway management procedures follow two distinctive trajectories based on the influence of aerodynamic forces. Speaking and coughing produce more droplets than non-invasive ventilation therapy confirming these behaviors as exposure risks. Even large droplets may exhibit patterns resembling the fluid dynamics smaller airborne aerosols that follow the airflow convectively and may place the healthcare provider at risk.