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1.
Indoor Air ; 32(3): e13012, 2022 03.
Article in English | MEDLINE | ID: covidwho-1752577

ABSTRACT

In this study, the risk of infection from SARS-CoV-2 Delta variant of passengers sharing a car cabin with an infected subject for a 30-min journey is estimated through an integrated approach combining a recently developed predictive emission-to-risk approach and a validated CFD numerical model numerically solved using the open-source OpenFOAM software. Different scenarios were investigated to evaluate the effect of the infected subject position within the car cabin, the airflow rate of the HVAC system, the HVAC ventilation mode, and the expiratory activity (breathing vs. speaking). The numerical simulations here performed reveal that the risk of infection is strongly influenced by several key parameters: As an example, under the same ventilation mode and emitting scenario, the risk of infection ranges from zero to roughly 50% as a function of the HVAC flow rate. The results obtained also demonstrate that (i) simplified zero-dimensional approaches limit proper evaluation of the risk in such confined spaces, conversely, (ii) CFD approaches are needed to investigate the complex fluid dynamics in similar indoor environments, and, thus, (iii) the risk of infection in indoor environments characterized by fixed seats can be in principle controlled by properly designing the flow patterns of the environment.


Subject(s)
COVID-19 , Automobiles , COVID-19/etiology , Computer Simulation , Humans , Hydrodynamics , SARS-CoV-2
2.
Sci Total Environ ; 826: 154143, 2022 Jun 20.
Article in English | MEDLINE | ID: covidwho-1706852

ABSTRACT

This work describes a modelling approach to SARS-CoV-2 dispersion based on experiments. The main goal is the development of an application integrated in Ansys Fluent to enable computational fluid dynamics (CFD) users to set up, in a relatively short time, complex simulations of virion-laden droplet dispersion for calculating the probability of SARS-CoV-2 infection in real life scenarios. The software application, referred to as TU Delft COVID-app, includes the modelling of human expiratory activities, unsteady and turbulent convection, droplet evaporation and thermal coupling. Data describing human expiratory activities have been obtained from selected studies involving measurements of the expelled droplets and the air flow during coughing, sneezing and breathing. Particle Image Velocimetry (PIV) measurements of the transient air flow expelled by a person while reciting a speech have been conducted with and without a surgical mask. The instantaneous velocity fields from PIV are used to determine the velocity flow rates used in the numerical simulations, while the average velocity fields are used for validation. Furthermore, the effect of surgical masks and N95 respirators on particle filtration and the probability of SARS-CoV-2 infection from a dose-response model have also been implemented in the application. Finally, the work includes a case-study of SARS-CoV-2 infection risk analysis during a conversation across a dining/meeting table that demonstrates the capability of the newly developed application.


Subject(s)
COVID-19 , Mobile Applications , Humans , Hydrodynamics , Masks , Risk Assessment , SARS-CoV-2
3.
Transl Vis Sci Technol ; 11(2): 2, 2022 Feb 01.
Article in English | MEDLINE | ID: covidwho-1677467

ABSTRACT

PURPOSE: The purpose of this study was to investigate the mechanism of potential droplet formation in response to air puff deformation with two noncontact tonometers (NCTs). METHODS: Twenty healthy volunteers were examined using two NCTs, Ocular Response Analyzer and Corvis ST, and two contact tonometers, iCare and Tono-Pen. High-speed videos of the tear film response were captured with at spatial resolution of 20 microns/pixel at 2400 fps. Droplet size, droplet velocity, distance between air puff impact location, and the tear meniscus-lid margin were characterized. RESULTS: One subject was excluded due to technical issues. Droplets were detected only in tests with instilled eye drop. Videos showed the tear film rolls away from the apex while remaining adherent to the ocular surface due to the tendency of the fluid to remain attached to a solid surface explained by the Coanda effect. Twelve out of 38 videos with an eye drop administration showed droplet formation. Only one resulted in droplets with predominantly forward motion, which had the shortest distance between air puff impact location and lower meniscus. This distance on average was 5.9 ± 1.1 mm. The average droplet size was 500 ± 200 µm. CONCLUSIONS: Results indicate no droplet formation under typical clinical setting. Hence, standard clinical use of NCT tests is not expected to cause droplets. NCT testing with eye drop administration showed droplet formation at the inferior eyelid boundary, which acts as a barrier and interrupts tear flow. TRANSLATIONAL RELEVANCE: Study of tear film interaction with NCT air puff shows that these tonometers are not expected to cause droplet formation in standard use and that if external drops are required, both eyelids should be held if patients need assistance to maintain open eyes to avoid droplets with predominantly forward motion.


Subject(s)
Hydrodynamics , Lacerations , Humans , Intraocular Pressure , Manometry , Ophthalmic Solutions , Tonometry, Ocular
4.
Med Eng Phys ; 92: 71-79, 2021 06.
Article in English | MEDLINE | ID: covidwho-1452333

ABSTRACT

The comprehension of the fluid flow in the upper airways is of paramount importance when treating patients under clinical conditions that demand mechanical ventilation. Barotrauma and overdistension are related to undesirable pressures and might be responsible for morbidity and mortality. In the current work we use computational fluid dynamics to investigate the pressure field in the upper respiratory airways. We performed a set of simulations varying the volumetric flow rate of mechanical ventilators and we have shown that the pressure profile can be calculated by means of the volumetric flow rate in accordance with a mathematical expression given by Pav=aV˙2, where Pav is the average pressure at selected sections of the upper airways and V˙ is the volumetric flow rate. Numerical findings provide evidence that the constant a varies with the location of the plane in the upper airways. We also show that some particular diameters of endotracheal tubes (ETT) must be used with care for a given range of volumetric flow rates. Overall, we document an important relationship among pressure, volumetric flow rate and selected internal diameters from ETT.


Subject(s)
Intubation, Intratracheal , Ventilators, Mechanical , Humans , Hydrodynamics , Respiration, Artificial , Respiratory System
5.
Interv Neuroradiol ; 26(5): 557-565, 2020 Oct.
Article in English | MEDLINE | ID: covidwho-1455862

ABSTRACT

BACKGROUND: The Low-profile Visualized Intraluminal Support device (LVIS) has been successfully used to treat cerebral aneurysm, and the push-pull technique has been used clinically to compact the stent across aneurysm orifice. Our aim was to exhibit the hemodynamic effect of the compacted LVIS stent. METHODS: Two patient-specific aneurysm models were constructed from three-dimensional angiographic images. The uniform LVIS stent, compacted LVIS and Pipeline Embolization Device (PED) with or without coil embolization were virtually deployed into aneurysm models to perform hemodynamic analysis. Intra-aneurysmal flow parameters were calculated to assess hemodynamic differences among different models. RESULTS: The compacted LVIS had the highest metal coverage across the aneurysm orifice (case 1, 46.37%; case 2, 67.01%). However, the PED achieved the highest pore density (case 1, 19.56 pores/mm2; case 2, 18.07 pores/mm2). The compacted LVIS produced a much higher intra-aneurysmal flow reduction than the uniform LVIS. The PED showed a higher intra-aneurysmal flow reduction than the compacted LVIS in case 1, but the results were comparable in case 2. After stent placement, the intra-aneurysmal flow was further reduced as subsequent coil embolization. The compacted LVIS stent with coils produced a similar reduction in intra-aneurysmal flow to that of the PED. CONCLUSIONS: The combined characteristics of stent metal coverage and pore density should be considered when assessing the flow diversion effects of stents. More intra-aneurysmal flow reductions could be introduced by compacted LVIS stent than the uniform one. Compared with PED, compacted LVIS stent may exhibit a flow-diverting effect comparable to that of the PED.


Subject(s)
Embolization, Therapeutic/methods , Intracranial Aneurysm/therapy , Stents , Subarachnoid Hemorrhage/therapy , Angiography, Digital Subtraction , Cerebral Angiography , Computer Simulation , Hemodynamics , Humans , Hydrodynamics , Imaging, Three-Dimensional , Intracranial Aneurysm/diagnostic imaging , Magnetic Resonance Angiography , Prosthesis Design , Subarachnoid Hemorrhage/diagnostic imaging
6.
PLoS One ; 16(5): e0251817, 2021.
Article in English | MEDLINE | ID: covidwho-1388915

ABSTRACT

The transmission of SARS-CoV-2 through contact with contaminated surfaces or objects is an important form of transmissibility. Thus, in this study, we evaluated the performance of a disinfection chamber designed for instantaneous dispersion of the biocidal agent solution, in order to characterize a new device that can be used to protect individuals by reducing the transmissibility of the disease through contaminated surfaces. We proposed the necessary adjustments in the configuration to improve the dispersion on surfaces and the effectiveness of the developed equipment. Computational Fluid Dynamics (CFD) simulations of the present technology with a chamber having six nebulizer nozzles were performed and validated through qualitative and quantitative comparisons, and experimental tests were conducted using the method Water-Sensitive Paper (WSP), with an exposure to the biocidal agent for 10 and 30 s. After evaluation, a new passage procedure for the chamber with six nozzles and a new configuration of the disinfection chamber were proposed. In the chamber with six nozzles, a deficiency was identified in its central region, where the suspended droplet concentration was close to zero. However, with the new passage procedure, there was a significant increase in wettability of the surface. With the proposition of the chamber with 12 nozzles, the suspended droplet concentration in different regions increased, with an average increase of 266%. The experimental results of the new configuration proved that there was an increase in wettability at all times of exposure, and it was more significant for an exposure of 30 s. Additionally, even in different passage procedures, there were no significant differences in the results for an exposure of 10 s, thereby showing the effectiveness of the new configuration or improved spraying and wettability by the biocidal agent, as well as in minimizing the impact caused by human factor in the performance of the disinfection technology.


Subject(s)
COVID-19/epidemiology , Decontamination/methods , Disinfection/methods , SARS-CoV-2/drug effects , COVID-19/metabolism , COVID-19/transmission , COVID-19/virology , Decontamination/instrumentation , Disinfectants/analysis , Disinfection/instrumentation , Humans , Hydrodynamics , Models, Theoretical , Pandemics , SARS-CoV-2/isolation & purification
7.
Int J Med Sci ; 18(10): 2102-2108, 2021.
Article in English | MEDLINE | ID: covidwho-1389721

ABSTRACT

Introduction: SARS-CoV-2 is a respiratory virus supposed to enter the organism through aerosol or fomite transmission to the nose, eyes and oropharynx. It is responsible for various clinical symptoms, including hyposmia and other neurological ones. Current literature suggests the olfactory mucosa as a port of entry to the CNS, but how the virus reaches the olfactory groove is still unknown. Because the first neurological symptoms of invasion (hyposmia) do not correspond to first signs of infection, the hypothesis of direct contact through airborne droplets during primary infection and therefore during inspiration is not plausible. The aim of this study is to evaluate if a secondary spread to the olfactory groove in a retrograde manner during expiration could be more probable. Methods: Four three-dimensional virtual models were obtained from actual CT scans and used to simulate expiratory droplets. The volume mesh consists of 25 million of cells, the simulated condition is a steady expiration, driving a flow rate of 270 ml/s, for a duration of 0.6 seconds. The droplet diameter is of 5 µm. Results: The analysis of the simulations shows the virus to have a high probability to be deployed in the rhinopharynx, on the tail of medium and upper turbinates. The possibility for droplets to access the olfactory mucosa during the expiratory phase is lower than other nasal areas, but consistent. Discussion: The data obtained from these simulations demonstrates the virus can be deployed in the olfactory groove during expiration. Even if the total amount in a single act is scarce, it must be considered it is repeated tens of thousands of times a day, and the source of contamination continuously acts on a timescale of several days. The present results also imply CNS penetration of SARS-CoV-2 through olfactory mucosa might be considered a complication and, consequently, prevention strategies should be considered in diseased patients.


Subject(s)
Olfactory Mucosa/virology , SARS-CoV-2/pathogenicity , Biomechanical Phenomena , Computer Simulation , Host-Pathogen Interactions/physiology , Humans , Hydrodynamics , Olfactory Mucosa/diagnostic imaging
8.
Curr Opin Virol ; 50: 103-109, 2021 10.
Article in English | MEDLINE | ID: covidwho-1370468

ABSTRACT

The COVID-19 pandemic has highlighted a need for improved frameworks for drug discovery, repurposing, clinical trial design and therapy optimization and personalization. Mechanistic computational models can play an important role in developing these frameworks. We discuss how mechanistic models, which consider viral entry, replication in target cells, viral spread in the body, immune response, and the complex factors involved in tissue and organ damage and recovery, can clarify the mechanisms of humoral and cellular immune responses to the virus, viral distribution and replication in tissues, the origins of pathogenesis and patient-to-patient heterogeneity in responses. These models are already improving our understanding of the mechanisms of action of antivirals and immune modulators. We discuss how closer collaboration between the experimentalists, clinicians and modelers could result in more predictive models which may guide therapies for viral infections, improving survival and leading to faster and more complete recovery.


Subject(s)
COVID-19/drug therapy , Computer Simulation , SARS-CoV-2 , COVID-19/immunology , Humans , Hydrodynamics , Intersectoral Collaboration
9.
Rev Sci Instrum ; 92(7): 074101, 2021 Jul 01.
Article in English | MEDLINE | ID: covidwho-1338585

ABSTRACT

A fluid mechanics model of inhaled air gases, nitrogen (N2) and oxygen (O2) gases, and exhaled gas components (CO2 and water vapor particles) through a facial mask (membrane) to shield the COVID-19 virus is established. The model was developed based on several gas flux contributions that normally take place through membranes. Semiempirical solutions of the mathematical model were predicted for the N95 facial mask accounting on several parameters, such as a range of porosity size (i.e., 1-30 nm), void fraction (i.e., 10-3%-0.3%), and thickness of the membrane (i.e., 10-40 µm) in comparison to the size of the COVID-19 virus. A unitless number (Nr) was introduced for the first time to describe semiempirical solutions of O2, N2, and CO2 gases through the porous membrane. An optimum Nr of expressing the flow of the inhaled air gases, O2 and N2, through the porous membrane was determined (NO2 = NN2 = -4.4) when an N95 facial mask of specifications of a = 20 nm, l = 30 µm, and ε = 30% was used as a personal protection equipment (PPE). The concept of the optimum number Nr can be standardized not only for testing commercially available facial masks as PPEs but also for designing new masks for protecting humans from the COVID-19 virus.


Subject(s)
COVID-19/prevention & control , Masks , SARS-CoV-2 , Biomechanical Phenomena , Carbon Dioxide , Equipment Design , Exhalation , Gases , Humans , Hydrodynamics , Inhalation , Mathematical Concepts , Membranes, Artificial , Models, Theoretical , N95 Respirators , Nitrogen , Oxygen , Personal Protective Equipment , Porosity , Steam
10.
Sci Rep ; 11(1): 15429, 2021 07 29.
Article in English | MEDLINE | ID: covidwho-1333985

ABSTRACT

Evidences are escalating on the diverse neurological-disorders and asymptomatic cardiovascular-diseases associated with COVID-19 pandemic due to the Sanal-flow-choking. Herein, we established the proof of the concept of nanoscale Sanal-flow-choking in real-world fluid-flow systems using a closed-form-analytical-model. This mathematical-model is capable of predicting exactly the 3D-boundary-layer-blockage factor of nanoscale diabatic-fluid-flow systems (flow involves the transfer of heat) at the Sanal-flow-choking condition. As the pressure of the diabatic nanofluid and/or non-continuum-flows rises, average-mean-free-path diminishes and thus, the Knudsen-number lowers heading to a zero-slip wall-boundary condition with the compressible-viscous-flow regime in the nanoscale-tubes leading to Sanal-flow-choking due to the sonic-fluid-throat effect. At the Sanal-flow-choking condition the total-to-static pressure ratio (ie., systolic-to-diastolic pressure ratio) is a unique function of the heat-capacity-ratio of the real-world flows. The innovation of the nanoscale Sanal-flow-choking model is established herein through the entropy relation, as it satisfies all the conservation-laws of nature. The physical insight of the boundary-layer-blockage persuaded nanoscale Sanal-flow-choking in diabatic flows presented in this article sheds light on finding solutions to numerous unresolved scientific problems in physical, chemical and biological sciences carried forward over the centuries because the mathematical-model describing the phenomenon of Sanal-flow-choking is a unique scientific-language of the real-world-fluid flows. The 3D-boundary-layer-blockage factors presented herein for various gases are universal-benchmark-data for performing high-fidelity in silico, in vitro and in vivo experiments in nanotubes.


Subject(s)
Fluid Shifts/physiology , Models, Theoretical , Nanotubes/chemistry , Rheology/methods , Algorithms , Biophysical Phenomena , COVID-19/physiopathology , Cardiovascular Physiological Phenomena , Cardiovascular System/physiopathology , Computational Biology/methods , Humans , Hydrodynamics , Physical Phenomena , SARS-CoV-2/isolation & purification
11.
Comput Biol Med ; 136: 104723, 2021 09.
Article in English | MEDLINE | ID: covidwho-1329739

ABSTRACT

BACKGROUND: Nitric oxide (NO) is important in respiratory physiology and airway defense. Although the paranasal sinuses are the major source of nasal NO, transport dynamics between the sinuses and nasal cavities are poorly understood. METHODS: Exhaled nasal NO tracings were measured in two non-asthmatic subjects (one with allergic rhinitis, one without) using NO analyzer connected via face mask. We subsequently performed computational fluid dynamics NO emission simulations based on individual CT scans and compared to the experimental data. RESULTS: Simulated exhaled NO tracings match well with experimental data (r > 0.84, p < 0.01) for both subjects, with measured peaks reaching 319.6 ppb in one subject (allergic-rhinitis), and 196.9 ppb in the other. The CFD simulation accurately captured the peak differences, even though the initial sinus NO concentration for both cases was set to the same 9000 ppb based on literature value. Further, the CFD simulation suggests that ethmoid sinuses contributed the most (>67%, other sinuses combined <33%) to total nasal NO emission in both cases and that diffusion contributes more than convective transport. By turning off diffusion (setting NO diffusivity to ~0), the NO emission peaks for both cases were reduced by >70%. CONCLUSION: Historically, nasal NO emissions were thought to be contributed mostly by the maxillary sinuses (the largest sinuses) and active air movement (convection). Here, we showed that the ethmoid sinuses and diffusive transport dominate the process. These findings may have a substantial impact on our view of nasal NO emission mechanisms and sinus physiopathology in general.


Subject(s)
Nitric Oxide , Paranasal Sinuses , Exhalation , Humans , Hydrodynamics , Maxillary Sinus , Nasal Cavity/diagnostic imaging , Paranasal Sinuses/diagnostic imaging
12.
Biosensors (Basel) ; 11(7)2021 Jul 07.
Article in English | MEDLINE | ID: covidwho-1323110

ABSTRACT

Optofluidic flow-through biosensors are being developed for single particle detection, particularly as a tool for pathogen diagnosis. The sensitivity of the biosensor chip depends on design parameters, illumination format (side vs. top), and flow configuration (parabolic, two- and three-dimensional hydrodynamic focused (2DHF and 3DHF)). We study the signal differences between various combinations of these design aspects. Our model is validated against a sample of physical devices. We find that side-illumination with 3DHF produces the strongest and consistent signal, but parabolic flow devices process a sample volume more quickly. Practical matters of optical alignment are also discussed, which may affect design choice.


Subject(s)
Biosensing Techniques/instrumentation , Lab-On-A-Chip Devices , Hydrodynamics , Microfluidic Analytical Techniques
13.
Annu Rev Biomed Eng ; 23: 547-577, 2021 07 13.
Article in English | MEDLINE | ID: covidwho-1307981

ABSTRACT

The host-to-host transmission of respiratory infectious diseases is fundamentally enabled by the interaction of pathogens with a variety of fluids (gas or liquid) that shape pathogen encapsulation and emission, transport and persistence in the environment, and new host invasion and infection. Deciphering the mechanisms and fluid properties that govern and promote these steps of pathogen transmission will enable better risk assessment and infection control strategies, and may reveal previously underappreciated ways in which the pathogens might actually adapt to or manipulate the physical and chemical characteristics of these carrier fluids to benefit their own transmission. In this article, I review our current understanding of the mechanisms shaping the fluid dynamics of respiratory infectious diseases.


Subject(s)
Communicable Diseases/physiopathology , Communicable Diseases/transmission , Hydrodynamics , Respiration Disorders/physiopathology , Aerosols , COVID-19/transmission , History, 19th Century , History, 20th Century , History, 21st Century , Humans , Infectious Disease Medicine/history , Physical Distancing , Respiratory System/physiopathology , Respiratory System/virology , Rheology , SARS-CoV-2 , Saliva , Ventilation
14.
Emerg Med J ; 38(9): 673-678, 2021 Sep.
Article in English | MEDLINE | ID: covidwho-1287247

ABSTRACT

AIM: Cardiopulmonary resuscitation (CPR) is an emergency procedure where interpersonal distance cannot be maintained. There are and will always be outbreaks of infection from airborne diseases. Our objective was to assess the potential risk of airborne virus transmission during CPR in open-air conditions. METHODS: We performed advanced high-fidelity three-dimensional modelling and simulations to predict airborne transmission during out-of-hospital hands-only CPR. The computational model considers complex fluid dynamics and heat transfer phenomena such as aerosol evaporation, breakup, coalescence, turbulence, and local interactions between the aerosol and the surrounding fluid. Furthermore, we incorporated the effects of the wind speed/direction, the air temperature and relative humidity on the transport of contaminated saliva particles emitted from a victim during a resuscitation process based on an Airborne Infection Risk (AIR) Index. RESULTS: The results reveal low-risk conditions that include wind direction and high relative humidity and temperature. High-risk situations include wind directed to the rescuer, low humidity and temperature. Combinations of other conditions have an intermediate AIR Index and risk for the rescue team. CONCLUSIONS: The fluid dynamics, simulation-based AIR Index provides a classification of the risk of contagion by victim's aerosol in the case of hands-only CPR considering environmental factors such as wind speed and direction, relative humidity and temperature. Therefore, we recommend that rescuers perform a quick assessment of their airborne infectious risk before starting CPR in the open air and positioning themselves to avoid wind directed to their faces.


Subject(s)
COVID-19/transmission , Cardiopulmonary Resuscitation/adverse effects , Models, Biological , Out-of-Hospital Cardiac Arrest/therapy , SARS-CoV-2/pathogenicity , Aerosols/adverse effects , COVID-19/complications , COVID-19/virology , Cardiopulmonary Resuscitation/standards , Computer Simulation , Guidelines as Topic , Humans , Humidity , Hydrodynamics , Out-of-Hospital Cardiac Arrest/complications , Personal Protective Equipment/standards , Risk Assessment/methods , Risk Assessment/statistics & numerical data , Temperature , Wind
15.
Comput Methods Programs Biomed ; 208: 106257, 2021 Sep.
Article in English | MEDLINE | ID: covidwho-1284010

ABSTRACT

OBJECTIVE: To evaluate the quantitative changes of respiratory functions for critically ill COVID-19 patients with mechanical ventilation, computational fluid dynamics (CFD) analysis was performed based on patient-specific three-dimensional airway geometry. METHODS: 37 cases of critically ill patients with COVID-19 admitted to the ICU of Huangshi Traditional Chinese Medicine Hospital from February 1st to March 20th, 2020 were retrospectively analyzed. 5 patients whose clinical data met the specific criteria were finally cataloged into death group (2 patients) and survival group (3 patients). The patient-specific three-dimensional airways were reconstructed from the central airways down to the 4th-5th bifurcation of the tracheobronchial tree. The volume changes of bronchi were calculated during the disease progression according to the comparison of two CT scans. Additionally, the changes of air flow resistance were analyzed using numerical simulation of CFD. RESULTS: Pearson correlation analysis demonstrated that there was negative correlation between the change of volume (ΔV) and the change of resistance (ΔR) for all COVID-19 patients (r=-0.7025). For total airway volume, an average decrease of -11.41±15.71% was observed in death group compared to an average increase of 1.86±10.80% in survival group (p=0.0232). For air flow through airways in lower lobe, the resistance increases for death group by 10.97±77.66% and decreases for survival group by -45.49±42.04% (p=0.0246). CONCLUSION: The variation of flow resistance in the airway could be used as a non-invasive functional evaluation for the prognosis and outcome of critically ill patients with COVID-19. The 'virtual' pulmonary function test by integrating follow-up CT scans with patient-derived CFD analysis could be a potentially powerful way in improving the efficiency of treatment for critically ill patients with COVID-19.


Subject(s)
Airway Resistance , COVID-19 , Critical Illness , Humans , Hydrodynamics , Lung , Prognosis , Retrospective Studies , SARS-CoV-2
16.
Environ Res ; 199: 111361, 2021 08.
Article in English | MEDLINE | ID: covidwho-1240350

ABSTRACT

COVID-19 virus can replicate in the infected individual's larynx independently, which is different from other viruses that replicate in lungs only, e.g. SARS. It might contribute to the fast spread of COVID-19. However, there are few scientific reports about quantitative comparison of COVID-19 exposure dose (inhalation dose and adhesion dose) for the susceptible individual when the viruses were released from the larynx or lungs. In this paper, a typical numerical model was built based on a breathing human model with real respiratory tract. By using a computational fluid dynamics (CFD) method, two kinds of virus released sites in the infected individual's respiratory tract (larynx, lungs), seven kinds of particle sizes between 1 and 50 µm, three kinds of expiratory flow rates: calm (10 L/min), moderate (30 L/min) and intense (90 L/min) were used to compare the particle deposition proportion and escape proportion. The inhalation dose and the adhesion dose of the susceptible individual were quantified. The results showed that COVID-19 virus-containing droplets and aerosols might be released into the environment at higher proportions (39.1%-44.2%) than viruses that replicate in lungs only (15.3%-37.1%). The exposure doses (inhalation dose and adhesion dose) of the susceptible individual in different situations were discussed. The susceptible individual suffered a higher exposure dose when the viruses were released from the larynx rather than lungs (the difference for 1 µm particles was 1.2-2.2 times). This study provides a possible explanation for the higher transmission risk of COVID-19 virus compared to other viruses and some control advice of COVID-19 in typical indoor environments were also discussed.


Subject(s)
COVID-19 , Larynx , Aerosols , Humans , Hydrodynamics , SARS-CoV-2
17.
Otolaryngol Head Neck Surg ; 164(2): 285-293, 2021 02.
Article in English | MEDLINE | ID: covidwho-1140419

ABSTRACT

OBJECTIVE: To define the aerosol and droplet risks associated with endonasal drilling and to identify mitigation strategies. STUDY DESIGN: Simulation series with fluorescent 3-dimensional (3D) printed sinonasal models and deidentified cadaveric heads. SETTINGS: Dedicated surgical laboratory. SUBJECTS AND METHODS: Cadaveric specimens irrigated with fluorescent tracer and fluorescent 3D-printed models were drilled. A cascade impactor was used to collect aerosols and small droplets of various aerodynamic diameters under 15 µm. Large droplet generation was measured by evaluating the field for fluorescent debris. Aerosol plumes through the nares were generated via nebulizer, and mitigation measures, including suction and SPIWay devices, nasal sheaths, were evaluated regarding reduction of aerosol escape from the nose. RESULTS: The drilling of cadaveric specimens without flexible suction generated aerosols ≤3.30 µm, and drilling of 3D sinonasal models consistently produced aerosols ≤14.1 µm. Mitigation with SPIWay or diameter-restricted SPIWay produced same results. There was minimal field contamination in the cadaveric models, 0% to 2.77% field tarp area, regardless of drill burr type or drilling location; cutting burr drilling without suction in the 3D model yielded the worst contamination field (36.1%), followed by coarse diamond drilling without suction (19.4%). The simple placement of a flexible suction instrument in the nasal cavity or nasopharynx led to complete elimination of all aerosols ≤14.1 µm, as evaluated by a cascade impactor positioned immediately at the nares. CONCLUSION: Given the findings regarding aerosol risk reduction, we strongly recommend that physicians use a suction instrument in the nasal cavity or nasopharynx during endonasal surgery in the COVID-19 era.


Subject(s)
Aerosols , COVID-19/prevention & control , COVID-19/transmission , Infectious Disease Transmission, Patient-to-Professional/prevention & control , Nasal Surgical Procedures/adverse effects , Natural Orifice Endoscopic Surgery/adverse effects , Cadaver , Humans , Hydrodynamics , Intubation, Intratracheal , Models, Biological , Personal Protective Equipment , Printing, Three-Dimensional , Risk Assessment
18.
Environ Res ; 197: 110975, 2021 06.
Article in English | MEDLINE | ID: covidwho-1118425

ABSTRACT

The deposition phenomenon of microparticle and SAR-CoV-2 laced bioaerosol in human airways is studied by Taguchi methods and response surface methodology (RSM). The data used herein is obtained from simulations of airflow dynamics and deposition fractions of drug particle aerosols in the downstream airways of asthma patients using computational fluid dynamics (CFD) and discrete particle motion (DPM). Three main parameters, including airflow rate, drug dose, and particle size, affecting aerosol deposition in the lungs of asthma patients are examined. The highest deposition fraction (DF) is obtained at the flow rate of 45 L min-1, the drug dose of 200 µg·puff-1, and the particle diameter of 5 µm. The optimized combination of levels for the three parameters for maximum drug deposition is performed via the Taguchi method. The importance of the influencing factors rank as particle size > drug dose > flow rate. RSM reveals that the combination of 30 L min-1, 5 µm, 200 µg·puff- has the highest deposition fraction. In part, this research also studied the deposition of bioaerosols contaminated with the SAR-CoV-2 virus, and their lowest DF is 1.15%. The low DF of bioaerosols reduces the probability of the SAR-CoV-2 virus transmission.


Subject(s)
Hydrodynamics , Lung , Administration, Inhalation , Aerosols , Computer Simulation , Humans , Models, Biological , Particle Size
19.
Biomech Model Mechanobiol ; 20(3): 1087-1100, 2021 Jun.
Article in English | MEDLINE | ID: covidwho-1107829

ABSTRACT

It is essential to study the viral droplet's uptake in the human respiratory system to better control, prevent, and treat diseases. Micro-droplets can easily pass through ordinary respiratory masks. Therefore, the SARS-COV-2 transmit easily in conversation with a regular mask with 'silent spreaders' in the most physiological way of breathing through the nose, indoor and at rest condition. The results showed that the amount of deposited micro-droplets in the olfactory epithelium area is low. Also, due to receptors and long droplet residence time in this region, the possibility of absorption increases in the cribriform plate. This phenomenon eventually could lead to brain lesion damage and, in some cases, leads to stroke. In all inlet flow rates lower than 30 L/min inlet boundary conditions, the average percentage of viral contamination for upper respiratory tract is always less than 50% and more than 50% for the lungs. At 6L/min and 15L/min flow rates, the average percentage of lung contamination increases to more than 87%, which due to the presence of the Coronavirus receptor in the lungs, the involvement of the lungs increases significantly. This study's other achievements include the inverse relationship between droplets deposition efficiency in some parts of the upper airway, which have the most deformation in the tract. Also, the increased deformities per minute applied to the trachea and nasal cavity, which is 1.5 times more than usual, could lead to chest and head bothers.


Subject(s)
COVID-19/transmission , COVID-19/virology , Models, Biological , Respiratory System/virology , SARS-CoV-2 , Adult , Air Microbiology , Algorithms , Biomechanical Phenomena , Brain/diagnostic imaging , COVID-19/diagnostic imaging , Computer Simulation , Disease Transmission, Infectious/statistics & numerical data , Humans , Hydrodynamics , Imaging, Three-Dimensional , Inhalation , Male , Models, Anatomic , Nose/virology , Pandemics , Particle Size , Respiratory Rate , Respiratory System/anatomy & histology , Respiratory System/diagnostic imaging , SARS-CoV-2/isolation & purification , SARS-CoV-2/pathogenicity , Stroke/diagnostic imaging , Stroke/etiology , Tomography, X-Ray Computed
20.
Sci Rep ; 11(1): 4617, 2021 02 25.
Article in English | MEDLINE | ID: covidwho-1104549

ABSTRACT

The Covid-19 pandemic has focused attention on airborne transmission of viruses. Using realistic air flow simulation, we model droplet dispersion from coughing and study the transmission risk related to SARS-CoV-2. Although this model defines most airborne droplets as 8-16 µm in diameter, we infer that larger droplets of 32-40 µm in diameter may potentially be more infectious due to higher viral content. Use of face masks is therefore recommended for both personal and social protection. We found social distancing effective at reducing transmission potential across all droplet sizes. However, the presence of a human body 1 m away modifies the aerodynamics so that downstream droplet dispersion is enhanced, which has implications on safe distancing in queues. At 1 m distance, we found that an average of 0.55 viral copies is inhaled for a cough at median loading, scalable up to 340 copies at peak loading. Droplet evaporation results in significant reduction in droplet counts, but airborne transmission remains possible even under low humidity conditions.


Subject(s)
Air Microbiology , COVID-19/transmission , Cough/virology , SARS-CoV-2/physiology , Humans , Hydrodynamics , Masks , Models, Biological , Particle Size , Risk Assessment
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