Experimental Measurements Of Far Field Cough Airflows Produced By Healthy And Influenza-Infected Subjects

Dudalski, Nicholas; Mohamed, Ahmed S.; Savory, Eric; Mubareka, Samira

doi:10.25071/10315/35362

Cited by 4 publications

(15 citation statements)

References 8 publications

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“…OPSs are usually calibrated against polystyrene latex spheres, which differ in refractive properties from respiratory aerosols and droplets, which are typically multiphase and not just transparent. Only transparent droplets can be quantified reliably with the OPS technique 22 …”

Section: Discussionmentioning

confidence: 99%

“…Given the nature of their profession, it is crucial for otolaryngologists to generate high‐level evidence regarding aerosolization risk of their clinical and surgical procedures. Other modalities for the study of aerosols include microscopy, interferometric Mie imaging, aerodynamic particle sizing, scanning mobility particle spectrometry, and laser diffractometry 22 . Microscopy involves the introduction of dye into the mouth of a subject and collection of ejected materials on a celluloid slide, which can be examined under a microscope 23–25 .…”

Section: Discussionmentioning

confidence: 99%

“…Lastly, laser diffractometry uses a system of lasers in a 100‐mm‐long × 10‐mm‐diameter cylinder to measure light scattering from passing particles 31 . Of these modalities, interferometric Mie imaging and laser diffractometry provide more accurate data on aerosol counts and distribution patterns, as they do not rely on airborne materials to be drawn into a sampling unit 22 …”

Section: Discussionmentioning

confidence: 99%

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Is Office Laryngoscopy an Aerosol‐Generating Procedure?

et al. 2020

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Objectives/Hypothesis: The aims of this work were 1) to investigate whether office laryngoscopy is an aerosolgenerating procedure with an optical particle sizer (OPS) during clinical simulation on healthy volunteers, and 2) to critically discuss methods for assessment of aerosolizing potentials in invasive interventions. Study Design: Prospective quantification of aerosol and droplet generation during clinical simulation of rigid and flexible laryngoscopy. Methods: Two healthy volunteers were recruited to undergo both flexible and rigid laryngoscopy. An OPS was used to quantify aerosols and droplets generated for four positive controls relative to ambient particles (speech, breathing, /e/ phonation, and /ae/ phonation) and for five test interventions relative to breathing and phonation (flexible laryngoscopy, flexible laryngoscopy with humming, flexible laryngoscopy with /e/ phonation, rigid laryngoscopy, and rigid laryngoscopy with /ae/ phonation). Particle counts in mean diameter size range from 0.3 to >10 μm were measured with OPS placed at 12 cm from the subject's nose/mouth. Results: None of the laryngoscopy interventions (n = 10 each) generated aerosols above that produced by breathing or phonation. Breathing (n = 40, 1-3 μm, P = .016) and /ae/ phonation (n = 10, 1-3 μm, P = .022; 3-5 μm. P = .083; >5 μm, P = .012) were statistically significant producers of aerosols and droplets. Neither speech nor /e/ phonation (n = 10 each) were associated with statistically significant aerosols and droplet generation. Conclusions: Using OPS to detect droplets and aerosols, we found that office laryngoscopy is likely not an aerosolgenerating procedure. Despite its prior use in otolaryngological literature, an OPS has intrinsic limitations. Our study should be complemented with more sophisticated methods of droplet distribution measurement.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Is Office Laryngoscopy an Aerosol‐Generating Procedure?

et al. 2020

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“…The objectives of the present work are:To numerically investigate the characteristics of a human cough jet in a quiescent environment, such as the variation with time of the velocity field, streamwise jet penetration and maximum jet width. Two different turbulence modelling approaches, the URANS and LES, are used for comparison purposes; andTo validate the numerical results with the experimental data (Wei and Li, 2017; Dudalski et al , 2018; Mohamed, 2017). …”

Section: Introductionmentioning

confidence: 99%

“…To validate the numerical results with the experimental data (Wei and Li, 2017; Dudalski et al , 2018; Mohamed, 2017).…”

Section: Introductionmentioning

confidence: 99%

A numerical modelling investigation of the development of a human cough jet

Ali

Savory

et al. 2021

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PurposeThis study aims (1) to numerically investigate the characteristics of a human cough jet in a quiescent environment, such as the variation with time of the velocity field, streamwise jet penetration and maximum jet width. Two different turbulence modelling approaches, the unsteady Reynolds-averaged Navier–Stokes (URANS) and large eddy simulation (LES), are used for comparison purposes. (2) To validate the numerical results with the experimental data.Design/methodology/approachTwo different approaches, the URANS and LES, are used to simulate a human cough jet flow. The numerical results for the velocity magnitude contours and the spatial average of the two-dimensional velocity magnitude over the corresponding particle image velocimetry (PIV) field of view are compared with the relevant PIV measurements. Similarly, the numerical results for the streamwise velocity component at the hot-wire probe location are compared with the hot-wire anemometry (HWA) measurements. Furthermore, the numerical results for the streamwise jet penetration are compared with the data from the previous experimental work.FindingsBased on the comparison with the URANS approach and the experimental data, the LES approach can predict the temporal development of a human cough jet reasonably well. In addition, the maximum width of the cough jet is found to grow practically linearly with time in the far-field, interrupted-jet stage, while the corresponding axial distance from the mouth of the jet front increases with time in an approximately quadratic manner.Originality/valueCurrently, no numerical study of human cough flow has been conducted using the LES approach due to the following challenges: (1) the computational cost is much higher than that of the URANS approach; (2) it is difficult to specify the turbulent fluctuations at the mouth for the cough jet properly; (3) it is necessary to define the appropriate conditions for the droplets to obtain statistically valid results. Therefore, this work fills this research gap.

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The effect of body position while coughing on the airborne transmission of pathogens

et al. 2022

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Given the recent acceptance of the central role of airborne transmission for SARS-CoV-2, increased attention has been paid to the dispersion of respiratory droplets in different scenarios. Studies including numerical simulations have been conducted on methods for breaking the chains of transmission. Here, we present the first such study on the impact of body position while coughing on the dispersion of respiratory droplets. Four scenarios are examined, including normal standing, bending the head at different angles, coughing into the elbow in still air, and a gentle breeze from the front and behind. The model showed that an uncovered cough is dangerous and causes many droplets to enter the environment, posing a cross-contamination threat to the others. Droplets with an initial diameter smaller than 62.5 μm remain suspended in windless air for more than 3 min. In the presence of wind, these droplets move with the wind flow and may travel long distances greater than 3.5 m. The model showed that covering the mouth with the elbow while coughing is clearly the best strategy for reducing airborne transmission of exhaled pathogens. About 62% of the initial number of droplets deposit on the cougher's elbow immediately after the cough and have no chance of spreading through the air in both windless and windy conditions. Covering the cough in windless or light breeze conditions also causes the upward thermal plume around the body to expel many small droplets.

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Experimental Measurements Of Far Field Cough Airflows Produced By Healthy And Influenza-Infected Subjects

Cited by 4 publications

References 8 publications

Is Office Laryngoscopy an Aerosol‐Generating Procedure?

Is Office Laryngoscopy an Aerosol‐Generating Procedure?

A numerical modelling investigation of the development of a human cough jet

The effect of body position while coughing on the airborne transmission of pathogens

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