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Ahmed T, Rawat MS, Ferro AR, Mofakham AA, Helenbrook BT, Ahmadi G, Senarathna D, Mondal S, Brown D, Erath BD. Characterizing respiratory aerosol emissions during sustained phonation. JOURNAL OF EXPOSURE SCIENCE & ENVIRONMENTAL EPIDEMIOLOGY 2022; 32:689-696. [PMID: 35351959 PMCID: PMC8963400 DOI: 10.1038/s41370-022-00430-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 03/11/2022] [Accepted: 03/15/2022] [Indexed: 06/10/2023]
Abstract
OBJECTIVE To elucidate the role of phonation frequency (i.e., pitch) and intensity of speech on respiratory aerosol emissions during sustained phonations. METHODS Respiratory aerosol emissions are measured in 40 (24 males and 16 females) healthy, non-trained singers phonating the phoneme /a/ at seven specific frequencies at varying vocal intensity levels. RESULTS Increasing frequency of phonation was positively correlated with particle production (r = 0.28, p < 0.001). Particle production rate was also positively correlated (r = 0.37, p < 0.001) with the vocal intensity of phonation, confirming previously reported findings. The primary mode (particle diameter ~0.6 μm) and width of the particle number size distribution were independent of frequency and vocal intensity. Regression models of the particle production rate using frequency, vocal intensity, and the individual subject as predictor variables only produced goodness of fit of adjusted R2 = 40% (p < 0.001). Finally, it is proposed that superemitters be defined as statistical outliers, which resulted in the identification of one superemitter in the sample of 40 participants. SIGNIFICANCE The results suggest there remain unexplored effects (e.g., biomechanical, environmental, behavioral, etc.) that contribute to the high variability in respiratory particle production rates, which ranged from 0.2 particles/s to 142 particles/s across all trials. This is evidenced as well by changes in the distribution of participant particle production that transitions to a more bimodal distribution (second mode at particle diameter ~2 μm) at higher frequencies and vocal intensity levels.
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Affiliation(s)
- Tanvir Ahmed
- Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY, 13699, USA
| | - Mahender Singh Rawat
- Department of Civil and Environmental Engineering, Clarkson University, Potsdam, NY, 13699, USA
| | - Andrea R Ferro
- Department of Civil and Environmental Engineering, Clarkson University, Potsdam, NY, 13699, USA
| | - Amir A Mofakham
- Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY, 13699, USA
| | - Brian T Helenbrook
- Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY, 13699, USA
| | - Goodarz Ahmadi
- Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY, 13699, USA
| | | | - Sumona Mondal
- Department of Mathematics, Clarkson University, Potsdam, NY, 13699, USA
| | - Deborah Brown
- Joint Educational Programs, Trudeau Institute, Saranac Lake, NY, 12983, USA
| | - Byron D Erath
- Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY, 13699, USA.
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Stettler MEJ, Nishida RT, de Oliveira PM, Mesquita LCC, Johnson TJ, Galea ER, Grandison A, Ewer J, Carruthers D, Sykes D, Kumar P, Avital E, Obeysekara AIB, Doorly D, Hardalupas Y, Green DC, Coldrick S, Parker S, Boies AM. Source terms for benchmarking models of SARS-CoV-2 transmission via aerosols and droplets. ROYAL SOCIETY OPEN SCIENCE 2022. [PMID: 35592762 DOI: 10.6084/m9.figshare.c.5958950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
There is ongoing and rapid advancement in approaches to modelling the fate of exhaled particles in different environments relevant to disease transmission. It is important that models are verified by comparison with each other using a common set of input parameters to ensure that model differences can be interpreted in terms of model physics rather than unspecified differences in model input parameters. In this paper, we define parameters necessary for such benchmarking of models of airborne particles exhaled by humans and transported in the environment during breathing and speaking.
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Affiliation(s)
- Marc E J Stettler
- Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK
| | - Robert T Nishida
- Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2G8
| | | | - Léo C C Mesquita
- Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK
| | - Tyler J Johnson
- Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK
| | - Edwin R Galea
- Fire Safety Engineering Group, University of Greenwich, London SE10 9LS, UK
| | - Angus Grandison
- Fire Safety Engineering Group, University of Greenwich, London SE10 9LS, UK
| | - John Ewer
- Fire Safety Engineering Group, University of Greenwich, London SE10 9LS, UK
| | - David Carruthers
- Cambridge Environmental Research Consultants Ltd, 3 Kings Parade, Cambridge CB2 1SJ, UK
| | | | - Prashant Kumar
- Global Centre for Clean Air Research (GCARE), Department of Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, UK
| | - Eldad Avital
- School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK
| | - Asiri I B Obeysekara
- Applied Modelling and Computation Group, Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK
| | - Denis Doorly
- Department of Aeronautics, Imperial College London, London SW7 2AZ, UK
| | - Yannis Hardalupas
- Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK
| | - David C Green
- MRC Centre for Environment and Health, Environmental Research Group, Imperial College London, Michael Uren Biomedical Engineering Hub, London, W12 OBZ, UK
- NIHR HPRU in Environmental Exposures and Health, Imperial College London, Michael Uren Biomedical Engineering Hub, London, W12 OBZ, UK
| | - Simon Coldrick
- Health and Safety Executive, Harpur Hill, Buxton, Derbyshire SK17 9JN UK
| | - Simon Parker
- Defence Science and Technology Laboratory, Porton Down, Salisbury SP4 0JQ, UK
| | - Adam M Boies
- Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK
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3
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Stettler MEJ, Nishida RT, de Oliveira PM, Mesquita LCC, Johnson TJ, Galea ER, Grandison A, Ewer J, Carruthers D, Sykes D, Kumar P, Avital E, Obeysekara AIB, Doorly D, Hardalupas Y, Green DC, Coldrick S, Parker S, Boies AM. Source terms for benchmarking models of SARS-CoV-2 transmission via aerosols and droplets. ROYAL SOCIETY OPEN SCIENCE 2022; 9:212022. [PMID: 35592762 PMCID: PMC9066307 DOI: 10.1098/rsos.212022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 04/13/2022] [Indexed: 05/03/2023]
Abstract
There is ongoing and rapid advancement in approaches to modelling the fate of exhaled particles in different environments relevant to disease transmission. It is important that models are verified by comparison with each other using a common set of input parameters to ensure that model differences can be interpreted in terms of model physics rather than unspecified differences in model input parameters. In this paper, we define parameters necessary for such benchmarking of models of airborne particles exhaled by humans and transported in the environment during breathing and speaking.
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Affiliation(s)
- Marc E. J. Stettler
- Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK
| | - Robert T. Nishida
- Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2G8
| | | | - Léo C. C. Mesquita
- Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK
| | - Tyler J. Johnson
- Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK
| | - Edwin R. Galea
- Fire Safety Engineering Group, University of Greenwich, London SE10 9LS, UK
| | - Angus Grandison
- Fire Safety Engineering Group, University of Greenwich, London SE10 9LS, UK
| | - John Ewer
- Fire Safety Engineering Group, University of Greenwich, London SE10 9LS, UK
| | - David Carruthers
- Cambridge Environmental Research Consultants Ltd, 3 Kings Parade, Cambridge CB2 1SJ, UK
| | | | - Prashant Kumar
- Global Centre for Clean Air Research (GCARE), Department of Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, UK
| | - Eldad Avital
- School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK
| | - Asiri I. B. Obeysekara
- Applied Modelling and Computation Group, Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK
| | - Denis Doorly
- Department of Aeronautics, Imperial College London, London SW7 2AZ, UK
| | - Yannis Hardalupas
- Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK
| | - David C. Green
- MRC Centre for Environment and Health, Environmental Research Group, Imperial College London, Michael Uren Biomedical Engineering Hub, London, W12 OBZ, UK
- NIHR HPRU in Environmental Exposures and Health, Imperial College London, Michael Uren Biomedical Engineering Hub, London, W12 OBZ, UK
| | - Simon Coldrick
- Health and Safety Executive, Harpur Hill, Buxton, Derbyshire SK17 9JN UK
| | - Simon Parker
- Defence Science and Technology Laboratory, Porton Down, Salisbury SP4 0JQ, UK
| | - Adam M. Boies
- Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK
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Vlaskin MS. Review of air disinfection approaches and proposal for thermal inactivation of airborne viruses as a life-style and an instrument to fight pandemics. APPLIED THERMAL ENGINEERING 2022; 202:117855. [PMID: 34867067 PMCID: PMC8628600 DOI: 10.1016/j.applthermaleng.2021.117855] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 10/20/2021] [Accepted: 11/24/2021] [Indexed: 05/02/2023]
Abstract
COVID-19 (Coronavirus Disease 2019) pandemic highlighted the importance of air biosecurity because SARS-CoV-2 is mainly transmitted from person to person via airborne droplets. Preventing infectious droplets from entering the body is one of the best ways to protect against infection. This paper reviews the transmission patterns of airborne pathogens and air disinfection methods. A particular emphasis is put on studies devoted to the thermal inactivation of viruses. These reviews reveal that air heat treatment has not been seriously considered as a possible air disinfection approach. Simple calculations show that the energy input required for thermal disinfection of human's air daily consumption is almost the same as for daily water consumption (by heat treatment from room temperature to 100 °C). Moreover, it is possible to organize a continuous heat recovery from the air already heated during disinfection to the inlet air, thus significantly increasing the energy efficiency. Therefore, I propose a solution for the thermal inactivation of airborne pathogens based on air heating and its subsequent cooling in a heat exchanger with heat recovery. Such a solution could be used to create mobile personal and stationary indoor air disinfectors, as well as heating, ventilation, and air conditioning systems. Thermal disinfection of air to breathe might one day be part of people's daily life like thermal disinfection of drinking water. Aside from limiting infectious disease transmission, thermal inactivation might be the basis for developing inhaled vaccines using thermally inactivated whole pathogens.
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Affiliation(s)
- Mikhail S Vlaskin
- Joint Institute for High Temperatures of the Russian Academy of Sciences, 13/2 Izhorskaya St, Moscow 125412, Russia
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5
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Fabregat A, Gisbert F, Vernet A, Ferré JA, Mittal K, Dutta S, Pallarès J. Direct numerical simulation of turbulent dispersion of evaporative aerosol clouds produced by an intense expiratory event. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:033329. [PMID: 33897242 PMCID: PMC8060975 DOI: 10.1063/5.0045416] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 02/19/2021] [Indexed: 05/04/2023]
Abstract
Airborne particles are a major route for transmission of COVID-19 and many other infectious diseases. When a person talks, sings, coughs, or sneezes, nasal and throat secretions are spewed into the air. After a short initial fragmentation stage, the expelled material is mostly composed of spherical particles of different sizes. While the dynamics of the largest droplets are dominated by gravitational effects, the smaller aerosol particles, mostly transported by means of hydrodynamic drag, form clouds that can remain afloat for long times. In subsaturated air environments, the dependence of pathogen-laden particle dispersion on their size is complicated due to evaporation of the aqueous fraction. Particle dynamics can significantly change when ambient conditions favor rapid evaporation rates that result in a transition from buoyancy-to-drag dominated dispersion regimes. To investigate the effect of particle size and evaporation on pathogen-laden cloud evolution, a direct numerical simulation of a mild cough was coupled with an evaporative Lagrangian particle advection model. The results suggest that while the dispersion of cough particles in the tails of the size distribution are unlikely to be disrupted by evaporative effects, preferential aerosol diameters (30-40 μm) may exhibit significant increases in the residence time and horizontal range under typical ambient conditions. Using estimations of the viral concentration in the spewed fluid and the number of ejected particles in a typical respiratory event, we obtained a map of viral load per volume of air at the end of the cough and the number of virus copies per inhalation in the emitter vicinity.
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Affiliation(s)
- Alexandre Fabregat
- Department d'Enginyeria Mecànica, Universitat Rovira i Virgili, Av. Països Catalans 26, Tarragona 43007, Spain
| | - Ferran Gisbert
- Department d'Enginyeria Mecànica, Universitat Rovira i Virgili, Av. Països Catalans 26, Tarragona 43007, Spain
| | - Anton Vernet
- Department d'Enginyeria Mecànica, Universitat Rovira i Virgili, Av. Països Catalans 26, Tarragona 43007, Spain
| | - Josep Anton Ferré
- Department d'Enginyeria Mecànica, Universitat Rovira i Virgili, Av. Països Catalans 26, Tarragona 43007, Spain
| | - Ketan Mittal
- Sidney Lu Mechanical Engineering Building, University of Illinois at Urbana-Champaign, 1206 W. Green St., MC 244, Urbana, Illinois 61801, USA
| | - Som Dutta
- Mechanical and Aerospace Engineering, Utah State University, 4130 Old Main Hill, Logan, Utah 84322-4130, USA
| | - Jordi Pallarès
- Department d'Enginyeria Mecànica, Universitat Rovira i Virgili, Av. Països Catalans 26, Tarragona 43007, Spain
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Abrupt Deterioration of COVID-19 Patients and Spreading of SARS COV-2 Virions in the Lungs. Ann Biomed Eng 2020; 48:2705-2706. [PMID: 33140243 PMCID: PMC7605482 DOI: 10.1007/s10439-020-02676-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 10/21/2020] [Indexed: 01/22/2023]
Abstract
A unique feature of COVID-19 interstitial pneumonia is an abrupt progression to respiratory failure. Our calculation shows that this abrupt deteriorate may be caused by a sudden shift in the spread of virus-laden bioaerosols through the airways to many different regions of the lungs from the initial site of infection.
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Host-to-host airborne transmission as a multiphase flow problem for science-based social distance guidelines. INTERNATIONAL JOURNAL OF MULTIPHASE FLOW 2020; 132. [PMCID: PMC7471834 DOI: 10.1016/j.ijmultiphaseflow.2020.103439] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The COVID-19 pandemic has strikingly demonstrated how important it is to develop fundamental knowledge related to the generation, transport and inhalation of pathogen-laden droplets and their subsequent possible fate as airborne particles, or aerosols, in the context of human to human transmission. It is also increasingly clear that airborne transmission is an important contributor to rapid spreading of the disease. In this paper, we discuss the processes of droplet generation by exhalation, their potential transformation into airborne particles by evaporation, transport over long distances by the exhaled puff and by ambient air turbulence, and their final inhalation by the receiving host as interconnected multiphase flow processes. A simple model for the time evolution of droplet/aerosol concentration is presented based on a theoretical analysis of the relevant physical processes. The modeling framework along with detailed experiments and simulations can be used to study a wide variety of scenarios involving breathing, talking, coughing and sneezing and in a number of environmental conditions, as humid or dry atmosphere, confined or open environment. Although a number of questions remain open on the physics of evaporation and coupling with persistence of the virus, it is clear that with a more reliable understanding of the underlying flow physics of virus transmission one can set the foundation for an improved methodology in designing case-specific social distancing and infection control guidelines.
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8
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Dhand R, Li J. Coughs and Sneezes: Their Role in Transmission of Respiratory Viral Infections, Including SARS-CoV-2. Am J Respir Crit Care Med 2020; 202:651-659. [PMID: 32543913 PMCID: PMC7462404 DOI: 10.1164/rccm.202004-1263pp] [Citation(s) in RCA: 187] [Impact Index Per Article: 46.8] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Affiliation(s)
- Rajiv Dhand
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Tennessee Graduate School of Medicine, Knoxville, Tennessee; and
| | - Jie Li
- Division of Respiratory Care, Department of Cardiopulmonary Sciences, Rush University Medical Center, Chicago, Illinois
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9
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Seminara G, Carli B, Forni G, Fuzzi S, Mazzino A, Rinaldo A. Biological fluid dynamics of airborne COVID-19 infection. RENDICONTI LINCEI. SCIENZE FISICHE E NATURALI 2020; 31:505-537. [PMID: 32837713 PMCID: PMC7429142 DOI: 10.1007/s12210-020-00938-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 07/21/2020] [Indexed: 12/26/2022]
Abstract
ABSTRACT We review the state of knowledge on the bio-fluid dynamic mechanisms involved in the transmission of the infection from SARS-CoV-2. The relevance of the subject stems from the key role of airborne virus transmission by viral particles released by an infected person via coughing, sneezing, speaking or simply breathing. Speech droplets generated by asymptomatic disease carriers are also considered for their viral load and potential for infection. Proper understanding of the mechanics of the complex processes whereby the two-phase flow emitted by an infected individual disperses into the environment would allow us to infer from first principles the practical rules to be imposed on social distancing and on the use of facial and eye protection, which to date have been adopted on a rather empirical basis. These measures need compelling scientific validation. A deeper understanding of the relevant biological fluid dynamics would also allow us to evaluate the contrasting effects of natural or forced ventilation of environments on the transmission of contagion: the risk decreases as the viral load is diluted by mixing effects but contagion is potentially allowed to reach larger distances from the infected source. To that end, our survey supports the view that a formal assessment of a number of open problems is needed. They are outlined in the discussion. GRAPHIC ABSTRACT
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Affiliation(s)
- Giovanni Seminara
- Accademia Nazionale dei Lincei, Rome, Italy
- Università di Genova, Genoa, Italy
| | - Bruno Carli
- Accademia Nazionale dei Lincei, Rome, Italy
- Istituto di Fisica Applicata Nello Carrara (IFAC), Consiglio Nazionale Delle Ricerche, Sesto Fiorentino, Italy
| | | | - Sandro Fuzzi
- Istituto di Scienze dell’Atmosfera e del Clima (ISAC), Consiglio Nazionale Delle Ricerche, Rome, Italy
| | - Andrea Mazzino
- Dipartimento di Ingegneria Civile, Chimica e Ambientale (DICCA), Università di Genova, Genoa, Italy
- Istituto Nazionale di Fisica Nucleare, Via Dodecaneso 33, 16146 Genoa, Italy
| | - Andrea Rinaldo
- Accademia Nazionale dei Lincei, Rome, Italy
- Laboratory of Ecohydrology IEE/ENAC, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
- DICEA, Università di Padova, Padua, Italy
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Affiliation(s)
- Kimberly A Prather
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92037, USA.
| | - Chia C Wang
- Department of Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan 804, Republic of China
- Aerosol Science Research Center, National Sun Yat-Sen University, Kaohsiung, Taiwan 804, Republic of China
| | - Robert T Schooley
- Department of Medicine, Division of Infectious Diseases and Global Public Health, School of Medicine, University of California San Diego, La Jolla, CA 92093, USA
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A feasibility study into adenosine triphosphate measurement in exhaled breath condensate: a potential bedside method to monitor alveolar deformation. Purinergic Signal 2018; 14:215-221. [PMID: 29752619 PMCID: PMC6107466 DOI: 10.1007/s11302-018-9607-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 04/24/2018] [Indexed: 12/13/2022] Open
Abstract
Recent research suggested an important role for pulmonary extracellular adenosine triphosphate (ATP) in the development of ventilation-induced lung injury. This injury is induced by mechanical deformation of alveolar epithelial cells, which in turn release ATP to the extracellular space. Measuring extracellular ATP in exhaled breath condensate (EBC) may be a non-invasive biomarker for alveolar deformation. Here, we study the feasibility of bedside ATP measurement in EBC. We measured ATP levels in EBC in ten subjects before and after an exercise test, which increases respiratory parameters and alveolar deformation. EBC lactate concentrations were measured as a dilution marker. We found a significant increase in ATP levels in EBC (before 73 RLU [IQR 50–209] versus after 112 RLU [IQR 86–203]; p value 0.047), and the EBC ATP-to-EBC lactate ratio increased as well (p value 0.037). We present evidence that bedside measurement of ATP in EBC is feasible and that ATP levels in EBC increase after exercise. Future research should measure ATP levels in EBC during mechanical ventilation as a potential biomarker for alveolar deformation.
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Wei J, Li Y. Airborne spread of infectious agents in the indoor environment. Am J Infect Control 2016; 44:S102-8. [PMID: 27590694 PMCID: PMC7115322 DOI: 10.1016/j.ajic.2016.06.003] [Citation(s) in RCA: 242] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 06/16/2016] [Indexed: 11/30/2022]
Abstract
BACKGROUND Since the 2003 severe acute respiratory syndrome epidemic, scientific exploration of infection control is no longer restricted to microbiologists or medical scientists. Many studies have reported on the release, transport, and exposure of expiratory droplets because of respiratory activities. This review focuses on the airborne spread of infectious agents from mucus to mucus in the indoor environment and their spread as governed by airflows in the respiratory system, around people, and in buildings at different transport stages. METHODS We critically review the literature on the release of respiratory droplets, their transport and dispersion in the indoor environment, and the ultimate exposure of a susceptible host, as influenced by airflows. RESULTS These droplets or droplet nuclei are transported by expired airflows, which are sometimes affected by the human body plume and use of a face mask, as well as room airflow. Room airflow is affected by human activities such as walking and door opening, and some droplets are eventually captured by a susceptible individual because of his or her inspired flows; such exposure can eventually lead to long-range spread of airborne pathogens. Direct exposure to the expired fine droplets or droplet nuclei results in short-range airborne transmission. Deposition of droplets and direct personal exposure to expired large droplets can lead to the fomite route and the droplet-borne route, respectively. CONCLUSIONS We have shown the opportunities for infection control at different stages of the spread. We propose that the short-range airborne route may be important in close contact, and its control may be achieved by face masks for the source patients and use of personalized ventilation. Our discussion of the effect of thermal stratification and expiratory delivery of droplets leads to the suggestion that displacement ventilation may not be applicable to hospital rooms where respiratory infection is a concern.
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Affiliation(s)
- Jianjian Wei
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong.
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13
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Abstract
The human body interacts with the environment in many different ways. The lungs interact with the external environment through breathing. The enormously large surface area of the lung with its extremely thin air-blood barrier is exposed to particles suspended in the inhaled air. The particle-lung interaction may cause deleterious effects on health if the inhaled pollutant aerosols are toxic. Conversely, this interaction can be beneficial for disease treatment if the inhaled particles are therapeutic aerosolized drugs. In either case, an accurate estimation of dose and sites of deposition in the respiratory tract is fundamental to understanding subsequent biological response, and the basic physics of particle motion and engineering knowledge needed to understand these subjects is the topic of this article. A large portion of this article deals with three fundamental areas necessary to the understanding of particle transport and deposition in the respiratory tract. These are: (i) the physical characteristics of particles, (ii) particle behavior in gas flow, and (iii) gas-flow patterns in the respiratory tract. Other areas, such as particle transport in the developing lung and in the diseased lung are also considered. The article concludes with a summary and a brief discussion of areas of future research.
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Affiliation(s)
- Akira Tsuda
- Harvard School of Public Health, Boston, Massachusetts
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14
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Holmgren H, Gerth E, Ljungström E, Larsson P, Almstrand AC, Bake B, Olin AC. Effects of breath holding at low and high lung volumes on amount of exhaled particles. Respir Physiol Neurobiol 2012; 185:228-34. [PMID: 23123969 DOI: 10.1016/j.resp.2012.10.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2012] [Revised: 10/22/2012] [Accepted: 10/22/2012] [Indexed: 11/28/2022]
Abstract
Exhaled breath contains particles originating from the respiratory tract lining fluid. The particles are thought to be generated during inhalation, by reopening of airways closed in the preceding expiration. The aim here was to explore processes that control exhaled particle concentrations. The results show that 5 and 10s breath holding at residual volume increased the median concentration of particles in exhaled air by 63% and 110%, respectively, averaged over 10 subjects. An increasing number of closed airways, developing on a timescale of seconds explains this behaviour. Breath holds of 5, 10 and 20s at total lung capacity decreased the concentration to 63%, 45% and 28% respectively, of the directly exhaled concentration. The decrease in particle concentration after breath holding at total lung capacity is caused by gravitational settling in the alveoli and associated bronchioles. The geometry employed here when modelling the deposition is however not satisfactory and ways of improving the description are discussed.
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Affiliation(s)
- Helene Holmgren
- Environmental Inorganic Chemistry, Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
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15
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Greenwald R, Fitzpatrick AM, Gaston B, Marozkina NV, Erzurum S, Teague WG. Breath formate is a marker of airway S-nitrosothiol depletion in severe asthma. PLoS One 2010; 5:e11919. [PMID: 20689836 PMCID: PMC2912922 DOI: 10.1371/journal.pone.0011919] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Accepted: 07/07/2010] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Children with severe asthma have poor symptom control and elevated markers of airway oxidative and nitrosative stress. Paradoxically, they have decreased airway levels of S-nitrosothiols (SNOs), a class of endogenous airway smooth muscle relaxants. This deficiency results from increased activity of an enzyme that both reduces SNOs to ammonia and oxidizes formaldehyde to formic acid, a volatile carboxylic acid that is more easily detected in exhaled breath condensate (EBC) than SNOs. We therefore hypothesize that depletion of airway SNOs is related to asthma pathology, and breath formate concentration may be a proxy measure of SNO catabolism. METHODS AND FINDINGS We collected EBC samples from children and adolescents, including 38 with severe asthma, 46 with mild-to-moderate asthma and 16 healthy adolescent controls, and the concentration of ionic constituents was quantified using ion chromatography. The concentrations of EBC components with volatile conjugates were log-normally distributed. Formate was the principal ion that displayed a significant difference between asthma status classifications. The mean EBC formate concentration was 40% higher in samples collected from all asthmatics than from healthy controls (mean = 5.7 microM, mean+/-standard deviation = 3.1-10.3 microM vs. 4.0, 2.8-5.8 microM, p = 0.05). EBC formate was higher in severe asthmatics than in mild-to-moderate asthmatics (6.8, 3.7-12.3 microM vs. 4.9, 2.8-8.7 microM, p = 0.012). In addition, formate concentration was negatively correlated with methacholine PC(20) (r = -0.39, p = 0.002, asthmatics only), and positively correlated with the NO-derived ion nitrite (r = 0.46, p<0.0001) as well as with total serum IgE (r = 0.28, p = 0.016, asthmatics only). Furthermore, formate was not significantly correlated with other volatile organic acids nor with inhaled corticosteroid dose. CONCLUSIONS We conclude that EBC formate concentration is significantly higher in the breath of children with asthma than in those without asthma. In addition, amongst asthmatics, formate is elevated in the breath of those with severe asthma compared to those with mild-to-moderate asthma. We suggest that this difference is related to asthma pathology and may be a product of increased catabolism of endogenous S-nitrosothiols.
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Affiliation(s)
- Roby Greenwald
- Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, United States of America
| | - Anne M. Fitzpatrick
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Benjamin Gaston
- Department of Pediatrics, University of Virginia, Charlottesville, Virginia, United States of America
| | - Nadzeya V. Marozkina
- Department of Pediatrics, University of Virginia, Charlottesville, Virginia, United States of America
| | - Serpil Erzurum
- Department of Medicine and Pathobiology, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - W. Gerald Teague
- Department of Pediatrics, University of Virginia, Charlottesville, Virginia, United States of America
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