Modeling of aerosol transmission of airborne pathogens in ICU rooms of COVID-19 patients with acute respiratory failure

Abstract

The COVID-19 pandemic has generated many concerns about cross-contamination risks, particularly in hospital settings and Intensive Care Units (ICU). Virus-laden aerosols produced by infected patients can propagate throughout ventilated rooms and put medical personnel entering them at risk. Experimental results found with a schlieren optical method have shown that the air flows generated by a cough and normal breathing were modified by the oxygenation technique used, especially when using High Flow Nasal Canulae, increasing the shedding of potentially infectious airborne particles. This study also uses a 3D Computational Fluid Dynamics model based on a Lattice Boltzmann Method to simulate the air flows as well as the movement of numerous airborne particles produced by a patient’s cough within an ICU room under negative pressure. The effects of different mitigation scenarii on the amount of aerosols potentially containing SARS-CoV-2 that are extracted through the ventilation system are investigated. Numerical results indicate that adequate bed orientation and additional air treatment unit positioning can increase by 40% the number of particles extracted and decrease by 25% the amount of particles deposited on surfaces 45s after shedding. This approach could help lay the grounds for a more comprehensive way to tackle contamination risks in hospitals, as the model can be seen as a proof of concept and be adapted to any room configuration.

Effects of surgical masks on aerosol dispersion in professional singing

“…After being expelled, these droplets follow ballistic trajectories and descend to the ground quickly [ 30 – 32 ]. For the investigation of the dispersion of expelled aerosol particles and droplets, qualitative, and quantitative flow visualization techniques as smoke visualization with bright light or laser light-sheet illumination, Particle Image Velocimetry [ 33 ] (PIV, with derivates as Particle Tracking Velocimetry) or Schlieren visualization [ 34 , 35 ] have been applied using mostly manikin models [ 35 , 36 ] or single human subjects [ 37 , 38 ].…”

Current approaches for preventing environment-associated contamination in healthcare facilities: a systematic literature review by open access database

“…Faced the increase in antibiotic-resistant pathogens, together with the emergence of new strains, Abraham et al (2021) [64] suggest the installation of copper surfaces in healthcare facilities, public transportation, public places, and food industries, considering that this material has continuing self-sanitising properties, working as a reducer or barrier to touch-transferred infections. HVAC systems [1-3, 13-15, 17-20, 22, 23, 25, 29, 30, 32, 33, 36, 37] HVAC systems play a key role in the risk of airborne infection [20] Importance of adequately positioning the patients (bed orientation) and the mobile air treatment units in the environment [20] Need to consider case by case when applying CFD simulation, since each room has its own parameters [1, 2, 13-22, 24, 26-29, 31, 33-37] Numerical (CFD) simulations and experiments can be used to visualise the airflow, the dispersion of aerosols generated by coughing, to visualise which areas are most susceptible to virus spread, to study and visualise the best arrangement and area of inlets and outlets of HVAC systems, and the best separation of spaces (partitions), among others [32] Possibility of using fluorescent tracer particles experiment to simulate airborne particle dispersion [2] Ventilation rate, inlet and outlet diffuser positions, and partitions between beds, among others, influence the airborne pathogen dispersion [23] Importance of modulate pressurization, direction of airflow, air exchange per hour, existence of air-handling systems with HEPA filters, UVC lighting, among others to reduce patient infection and exposure risk [17,25] According to ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers), indoor air quality is determined by the distribution of temperature, relative humidity, air velocity values, and pollution levels in the room environment. Ventilation type (central airconditioning system or non-central air conditioning system), increased visitor and doctors' activities, and cleaning sessions also interfere with indoor air quality [15] Necessity of increasing the rate of air change, decreasing recirculation of air, increasing the use of outdoor air and HEPA filters for disease and infection control [30] Indoor air temperature, relative humidity, indoor ventilation rate, air filtration system, differential pressure control, and mechanical strategies are related to patient medical outcomes [3] Necessity of increasing air supply and exhaust ventilation on toilets to avoid the fecal-oral transmission due to the droplets generated when flushing with the toilet lid open [27] The air exchange rate, the location of an infected patient, and the location of exhaust grilles in a ward influence the extent of the contamination.…”

3D modelling and simulation of the dispersion of droplets and drops carrying the SARS-CoV-2 virus in a railway transport coach

“…Again, the patients were represented in a very simplified way (as parallelepiped solids), thereby limiting the reliability of the computations. Crawford et al 32 were interested in the distribution of micrometric particles emitted during the coughing and breathing of patients placed in intensive care units and equipped with oxygenation devices. The study used Power Flow® CFD software which is based on the Lattice Boltzmann method to simulate the flow and on motion tracking of the droplets.…”