Assessing the Physiological Relevance of Cough Simulators for Respiratory Droplet Dispersion.

Various breathing and cough simulators have been used to model respiratory droplet dispersion and viral droplets, in particular for SARS-CoV-2 modeling. However, limited data are available comparing these cough simulations to physiological breathing and coughing. In this study, three different cough simulators (Teleflex Mucosal Atomization Device Nasal (MAD Nasal), a spray gun, and GloGermTM MIST) that have been used in the literature were studied to assess their physiologic relevance. Droplet size, velocity, dispersion, and force generated by the simulators were measured. Droplet size was measured with scanning electron microscopy (SEM). Slow-motion videography was used to 3D reconstruct and measure the velocity of each simulated cough. A force-sensitive resistor was used to measure the force of each simulated cough. The average size of droplets from each cough simulator was 176 to 220 µm. MAD Nasal, the spray gun, and GloGermTM MIST traveled 0.38 m, 0.89 m, and 1.62 m respectively. The average velocities for the MAD Nasal, spray gun, and GloGermTM MIST were 1.57 m/s, 2.60 m/s, and 9.27 m/s respectively, and all yielded a force of <0.5 Newtons. GloGermTM MIST and the spray gun most closely resemble physiological coughs and breathing respectively. In conclusion, none of the simulators tested accurately modeled all physiologic characteristics (droplet size, 3-D dispersion velocity, and force) of a cough, while there were various strengths and weaknesses of each method. One should take this into account when performing simulations with these devices.

Assessment of Respiratory Droplet Transmission During the Ophthalmic Slit-Lamp Exam: A Particle Tracking Analysis.

PURPOSE: The global COVID-19 pandemic has resulted in a renewed focus on the importance of personal protective equipment (PPE) and other interventions to decrease spread of infectious diseases. Although several ophthalmology organizations have released guidance on appropriate PPE for surgical procedures and ophthalmology clinics, there is limited experimental evidence that demonstrates the efficacy of various interventions that have been suggested. In this study, we evaluated high-risk aspects of the slit-lamp exam and the effect of various PPE interventions, specifically the use of a surgical mask and a slit-lamp shield. DESIGN: Experimental simulation study. METHODS: This was a single-center study in a patient simulation population. This study examined the presence of particles in the air near or on a slit-lamp, a simulated slit-lamp examiner, or a simulated patient using a fluorescent surrogate of respiratory droplets. RESULTS: Simulated coughing without a mask or slit-lamp shield resulted in widespread dispersion of fluorescent droplets during the model slit-lamp examination. Coughing with a mask resulted in the most significant decrease in droplets; however, particles still escaped from the top of the mask. Coughing with the slit-lamp shield alone blocked most of forward particle dispersion; however, significant distributions of respiratory droplets were found on the slit-lamp joystick and table. Coughing with both a mask and slit-lamp shield resulted in the least dispersion to the simulated examiner and the simulated patient. Scanning electron microscopy demonstrated particle sizes of 3-100 µm. CONCLUSIONS: Masking had the greatest effect in limiting spread of respiratory droplets, whereas slit-lamp shields and gloves also contributed to limiting exposure to droplets from SARS-CoV-2 during slit-lamp examination.