scholarly journals Association of infected probability of COVID-19 with ventilation rates in confined spaces: a Wells-Riley equation based investigation

2020 ◽  
Author(s):  
Hui Dai ◽  
Bin Zhao
Keyword(s):  
Ventilation Rate ◽  
Generation Rate ◽  
Reproductive Number ◽  
Ventilation Mode ◽  
Airborne Transmission ◽  
Transmitted Infection ◽  
Aircraft Cabins ◽  
Confined Spaces ◽  
Ventilation Rates ◽  
Normal Ventilation

AbstractBackgroundA growing number of epidemiological cases are proving the possibility of airborne transmission of coronavirus disease 2019 (COVID-19). Ensuring adequate ventilation rate is essential to reduce the risk of infection in confined spaces.MethodsWe obtained the quantum generation rate by a COVID-19 infector with a reproductive number based fitting approach, and then estimated the association between infected probability and ventilation rate with the Wells-Riley equation.ResultsThe estimated quantum generation rate of COVID-19 is 14-48 /h. To ensure infected probabolity less than 1%, ventilation rate lareger than common values (100-350 m3/h and 1200-4000 m3/h for 15 minutes and 3 hours exposure, respectively) is required. If both the infector and susceptibles wear masks, the ventilation rate ensuring less than 1% infected probability is reduced to 50-180 m3/h and 600-2000 m3/h correspondingly, which is easier to be achieved by normal ventilation mode applied in some typical scenarios, including offices, classrooms, buses and aircraft cabins.InterpretationThe risk of potential airborne transmission in confined spaces cannot be ignored. Strict preventive measures that have been widely adopted should be effective in reducing the risk of airborne transmitted infection.

scholarly journals Estimating ventilation rates in rooms with varying occupancy levels: Relevance for reducing transmission risk of airborne pathogens

PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0253096
Author(s):  
Arminder K. Deol ◽  
Danny Scarponi ◽  
Peter Beckwith ◽  
Tom A. Yates ◽  
Aaron S. Karat ◽  
...  
Keyword(s):  
Linear Regression ◽  
Ventilation Rate ◽  
Equation Model ◽  
Transmission Risk ◽  
Linear Regression Method ◽  
Simple Linear Regression ◽  
Airborne Transmission ◽  
Steady State Method ◽  
The Absolute ◽  
Ventilation Rates

Background In light of the role that airborne transmission plays in the spread of SARS-CoV-2, as well as the ongoing high global mortality from well-known airborne diseases such as tuberculosis and measles, there is an urgent need for practical ways of identifying congregate spaces where low ventilation levels contribute to high transmission risk. Poorly ventilated clinic spaces in particular may be high risk, due to the presence of both infectious and susceptible people. While relatively simple approaches to estimating ventilation rates exist, the approaches most frequently used in epidemiology cannot be used where occupancy varies, and so cannot be reliably applied in many of the types of spaces where they are most needed. Methods The aim of this study was to demonstrate the use of a non-steady state method to estimate the absolute ventilation rate, which can be applied in rooms where occupancy levels vary. We used data from a room in a primary healthcare clinic in a high TB and HIV prevalence setting, comprising indoor and outdoor carbon dioxide measurements and head counts (by age), taken over time. Two approaches were compared: approach 1 using a simple linear regression model and approach 2 using an ordinary differential equation model. Results The absolute ventilation rate, Q, using approach 1 was 2407 l/s [95% CI: 1632–3181] and Q from approach 2 was 2743 l/s [95% CI: 2139–4429]. Conclusions We demonstrate two methods that can be used to estimate ventilation rate in busy congregate settings, such as clinic waiting rooms. Both approaches produced comparable results, however the simple linear regression method has the advantage of not requiring room volume measurements. These methods can be used to identify poorly-ventilated spaces, allowing measures to be taken to reduce the airborne transmission of pathogens such as Mycobacterium tuberculosis, measles, and SARS-CoV-2.

scholarly journals Proposing Alternative Solutions to Enhance Natural Ventilation Rates in Residential Buildings in the Cfa Climate Zone of Rasht

2021 ◽  
Vol 13 (2) ◽  
pp. 679
Author(s):  
Roya Aeinehvand ◽  
Amiraslan Darvish ◽  
Abdollah Baghaei Daemei ◽  
Shima Barati ◽  
Asma Jamali ◽  
...  
Keyword(s):  
Natural Ventilation ◽  
Residential Buildings ◽  
Residential Building ◽  
Ventilation Rate ◽  
Humid Climate ◽  
The Sustainable Development ◽  
Passive Strategies ◽  
Development Goals ◽  
Ventilation Rates ◽  
Ventilation Systems

Today, renewable resources and the crucial role of passive strategies in energy efficiency in the building sector toward the sustainable development goals are more indispensable than ever. Natural ventilation has traditionally been considered as one of the most fundamental techniques to decrease energy usage by building dwellers and designers. The main purpose of the present study is to enhance the natural ventilation rates in an existing six-story residential building situated in the humid climate of Rasht during the summertime. On this basis, two types of ventilation systems, the Double-Skin Facade Twin Face System (DSF-TFS) and Single-Sided Wind Tower (SSWT), were simulated through DesignBuilder version 4.5. Then, two types of additional ventilation systems were proposed in order to accelerate the airflow, including four-sided as well as multi-opening wind towers. The wind foldable directions were at about 45 degrees (northwest to southeast). The simulation results show that SSWT could have a better performance than the aforementioned systems by about 38%. Therefore, the multi-opening system was able to enhance the ventilation rate by approximately 10% during the summertime.

Research on Dead-End Tunneling Ventilation Control System

2012 ◽  
Vol 516-517 ◽  
pp. 1188-1191
Author(s):  
Shu Fang Wang ◽  
Zhi Yong Yang ◽  
Ming Hai Li
Keyword(s):  
Concentration Distribution ◽  
Experimental System ◽  
Ventilation Mode ◽  
Smoke Emission ◽  
Control Rules ◽  
Dead End ◽  
Co Concentration ◽  
Simulation Results ◽  
Speed Adjustment ◽  
Normal Ventilation

On the basis of analysis of ventilation requirement and CO concentration distribution character in dead-end tunneling, this paper designed the ventilation equipment layout. Furthermore, a control strategy which includes normal ventilation mode and gun smoke discharging mode is established. In view of expert experience and numerical simulation results dead-end tunneling, fuzzy control is adopted to deal with this problem. Control rules principle is described in detail. Applying direct torque speed adjustment mode, an experimental system is designed and implemented. Partial experimental results show that gun smoke emission process is fast in order to increase efficiency, while normal ventilation mode is adjustable air flow for energy conservation.

Abstract 264: Automatic Detection of Ventilations Using the Thoracic Impedance Signal During Lucas Chest Compressions

Circulation ◽  
2019 ◽  
Vol 140 (Suppl_2) ◽  
Author(s):  
Xabier Jaureguibeitia ◽  
Unai Irusta ◽  
Elisabete Aramendi ◽  
Pamela Owens ◽  
Henry E Wang ◽  
...  
Keyword(s):  
Cardiac Arrest ◽  
Minute Ventilation ◽  
Lung Ventilation ◽  
Detection Algorithm ◽  
Ventilation Rate ◽  
Thoracic Impedance ◽  
Chest Compressions ◽  
Signal Processing Algorithm ◽  
Ventilation Rates ◽  
Mechanical Cpr

Introduction: Resuscitation from out-of-cardiac arrest (OHCA) requires control of both chest compressions and lung ventilation. There are few effective methods for detecting ventilations during cardiopulmonary resuscitation. Thoracic impedance (TI) is sensitive to changes in lung air volumes and may allow detection of ventilations but has not been tested with concurrent mechanical chest compressions. Hypothesis: It is possible to automatically detect and characterize ventilations from TI changes during mechanical chest compressions. Methods: A cohort of 420 OHCA cases (27 survivors to hospital discharge) were enrolled in the Dallas-Fort Worth Center for Resuscitation Research cardiac arrest registry. These patients were treated with the LUCAS-2 CPR device and had concurrent TI and capnogram recordings from MRx (Philips, Andover, MA) monitor-defibrillators. We developed a signal processing algorithm to suppress chest compression artifacts from the TI signal, allowing identification of ventilations. We used the capnogram as gold standard for delivered ventilations. We determined the accuracy of the algorithm for detecting capnogram-indicated ventilations, calculating sensitivity, the proportion of true ventilations detected in the TI, and positive predictive value (PPV), the proportion of true ventilations within the detections. We calculated per minute ventilation rate and mean TI amplitude, as surrogate for tidal volume. Statistical differences between survivors and non-survivors were assessed using the Mann-Whitney test. Results: We studied 4331 minutes of TI during CPR. There were a median of 10 (IQR 6-14) ventilations per min and 52 (30-81) ventilations per patient. Sensitivity of TI was 95.9% (95% CI, 74.5-100), and PPV was 95.8% (95% CI, 80.0-100). The median ventilation rates for survivors and non-survivors were 7.75 (5.37-9.91) min -1 and 5.64 (4.46-7.15) min -1 (p<10 -3 ), and the median TI amplitudes were 1.33 (1.03-1.75) Ω and 1.14 (0.77-1.66) Ω (p=0.095). Conclusions: An accurate automatic TI ventilation detection algorithm was demonstrated during mechanical CPR. The relation between ventilation rate during mechanical CPR and survival was significant, but it was not for impedance amplitude.

Abstract P101: Comparison of Ventilation Rate Measured with Thoracic Bioimpedance and with Capnography during Out-of-Hospital Cardiopulmonary Resuscitation

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Ahamed H Idris ◽  
Sarah Beadle ◽  
Mohamud Daya ◽  
Dana Zive
Keyword(s):  
Cardiac Arrest ◽  
Ventilation Rate ◽  
Rater Agreement ◽  
Chest Compressions ◽  
Intra Class Correlation ◽  
Automated Software ◽  
Ventilation Rates ◽  
Patient File ◽  
Hospital Cardiac Arrest ◽  
Manual Review

Objective: To determine the ability of thoracic bioimpedance to measure ventilation rate during cardiac arrest and CPR. Methods: Philips MRx devices monitored 32 patients during out-of-hospital cardiac arrest and CPR. The devices recorded chest compressions with an accelerometer, continuous 1-lead EKG, thoracic bioimpedance, and continuous capnography. Of the 32 files, 4 were not used in this study because of incomplete recording. Two reviewers manually annotated ventilation waveforms independently using Laerdal QCPR software, which also automatically annotated ventilation through the bioimpedance channel. Reviewers manually measured ventilation rate (number of breaths/min) recorded with capnography for each 1 minute epoch, which were matched and compared with those measured through bioimpedance for each patient file (N = 28). A total of 585 1-minute epochs were measured and compared. We assessed intra-class correlation for 2 individual raters for ventilation rates measured with capnography and with annotated bioimpedance to establish inter-user reliability of measurements. Ventilation rate measured with capnography vs. bioimpedance was compared with simple regression. Results: The majority (60%) of ventilation rates measured with capnography and with automated software bioimpedance were within 2 breaths/min of each other. After manual annotation of the bioimpedance channel, 81% of 1-min epochs were within 2 breaths/min of rates measured with capnography. Ventilation rate measured with capnography had good correlation with bioimpedance (r = .82, p < .0001). Inter-rater agreement is estimated to be 0.96 for ventilation rate measured with capnography and 0.93 for rate measured with bioimpedance. Discussion: The software occasionally missed obvious ventilation waveforms and occasionally annotated waveforms obviously caused by chest compressions. Manual review and annotation improved the accuracy of ventilation rates measured with bioimpedance. Approximately 75% to 90% of recordings made with the Philips MRx device are expected to be useful for measurement. Conclusion: Ventilation rate measured with thoracic bioimpedance alone is acceptable using the Philips MRx device. Inter-rater agreement for measurements is excellent.

Ventilation of Wind-Permeable Clothed Cylinder Subject to Periodic Swinging Motion: Modeling and Experimentation

2008 ◽  
Vol 130 (9) ◽  
Author(s):  
N. Ghaddar ◽  
K. Ghali ◽  
B. Jreije
Keyword(s):  
Cotton Fabric ◽  
Current Model ◽  
Ventilation Rate ◽  
External Pressure ◽  
Motion Modeling ◽  
Tracer Gas ◽  
Wind Speeds ◽  
Air Speed ◽  
Local Thermal Comfort ◽  
Ventilation Rates

Abstract A theoretical and experimental study has been performed to determine the ventilation induced by swinging motion and external wind for a fabric-covered cylinder of finite length representing a limb. The estimated ventilation rates are important in determining local thermal comfort. A model is developed to estimate the external pressure distribution resulting from the relative wind around the swinging clothed cylinder. A mass balance equation of the microclimate air layer is reduced to a pressure equation assuming laminar flow in axial and angular directions and that the air layer is lumped in the radial direction. The ventilation model predicts the total renewal rate during the swinging cycle. A good agreement was found between the predicted ventilation rates at swinging frequencies between 40rpm and 60rpm and measured values from experiments conducted in a controlled environmental chamber (air velocity is less than 0.05m∕s) and in a low speed wind tunnel (for air speed between 2m∕s and 6m∕s) using the tracer gas method to measure the total ventilation rate induced by the swinging motion of a cylinder covered with a cotton fabric for both closed and open aperture cases. A parametric study using the current model is performed on a cotton fabric to study the effect of wind on ventilation rates for a nonmoving clothed limb at wind speeds ranging from 0.5m∕sto8m∕s, the effect of a swinging limb in stagnant air at frequencies up to 80rpm, and the combined effect of wind and swinging motion on the ventilation rate. For a nonmoving limb, ventilation rate increases with external wind. In the absence of wind, the ventilation rate increases with increased swinging frequency.

Three-Dimensional Numerical Analysis of Horizontal and Vertical Coalescence of Bubbles at Two Submerged Horizontal Orifices on the Wall

2019 ◽  
Author(s):  
Z. P. Li ◽  
L. Q. Sun ◽  
X. L. Yao ◽  
Y. Piao
Keyword(s):  
Numerical Simulation ◽  
Internal Pressure ◽  
Three Dimensional ◽  
Ventilation Rate ◽  
Smoothing Technique ◽  
Dimensional Model ◽  
Mesh Smoothing ◽  
Three Dimensional Model ◽  
Coalescence Time ◽  
Ventilation Rates

Abstract In the process of bubbling from two submerged adjacent orifices, bubbles coalescence becomes inevitable. But the study of the evolution and interaction of bubbles from submerged orifices is little, especially numerical simulation. In this paper, combined with mesh smoothing technique, mesh subdivision technique and the technique of axisymmetric coalescence and 3D coalescence, a three-dimensional model of bubbles coalescence at two submerged adjacent orifices on the wall is established by the boundary element method. Then, numerical simulations were carried out for horizontal and vertical coalescence before detachment. Finally, by changing the ventilation rate and the Froude number, the effects of different ventilation rates and buoyancy on the process of bubbles coalescence at two adjacent orifices were investigated. The results show that for horizontal coalescence, the effect of ventilation rate is more pronounced than buoyancy. As the ventilation rate increases or the influence of buoyancy is decreased, the amplitude of internal pressure fluctuation of the bubble decreases and the coalescence time decreases. For vertical coalescence, the effect of buoyancy is more pronounced than ventilation rate. With the influence of buoyancy is decreased, the vertical coalescence time is increased, the internal pressure of the bubble is decreased. The influence of ventilation rate is similar to that of horizontal coalescence.

Animal Experiments on the Effects of PEEP and Different Ventilation-Compression Ratios in Neonatal Cardiopulmonary Resuscitation

1985 ◽  
Vol 1 (S1) ◽  
pp. 214-215
Author(s):  
W. F. Dick ◽  
E. Traub ◽  
K. Engels ◽  
K. -H. Lindner
Keyword(s):  
Body Weight ◽  
Cardiac Arrest ◽  
Artificial Ventilation ◽  
Animal Experiments ◽  
Ventilation Rate ◽  
Positive End Expiratory Pressure ◽  
Cardiac Compression ◽  
Ventilation Rates ◽  
Average Body ◽  
Average Body Weight

The physiological range of respiratory rates and heart rates in neonates is approximately 40 per min and 120 per min, respectively, which yields a theoretical ventilation-compression ratio of 1:3ratherthan 1:5.Thirty-six anesthetized pigs with an average body weight of 4–5 kg were used in the study. After establishing a steady state by artificial ventilation with 100% oxygen, a cardiac arrest was induced by an intravenous injection of potassium chloride. Following the cardiac arrest, the animals were resuscitated with ventilation rates of 30 and 40 per min, respectively, while external cardiac compression was performed at rates between 60 and 160 per min. Randomly selected animals were resuscitated with ventilation-compression ratios of 1:2, 1:3 and 1:4 for 10 min each, 6 animals each were ventilated using a ventilation rate of 30 per min, 40 per min, or positive end-expiratory pressure.

Wind-Driven Natural Ventilation in an Areaway-Attached Basement with a Single-Sided Opening for Residential Purposes

2011 ◽  
Vol 383-390 ◽  
pp. 5344-5349
Author(s):  
Zhen Bu
Keyword(s):  
Natural Ventilation ◽  
Ventilation Rate ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Effective Ventilation ◽  
The Mean ◽  
Ventilation Rates ◽  
Les Model ◽  
Good Agreement

This paper discusses the sustainability of the areaway-attached basement concept with the attentions focused on wind-driven single-sided natural ventilation. First, numerical simulations were performed on an areaway-attached basement with a single-sided opening. Two CFD approaches: Reynolds averaged Navier-Stokes (RANS) and large-eddy simulation (LES) were used and compared with the previous experimental results of effective ventilation rate. A good agreement between the measurement and LES model was found and RANS model tends to underestimate the ventilation rates. Furthermore, Based on LES with the inflow turbulent fluctuations, the mean airflow patterns within and around the areaway-attached basement was investigated for different wind incidence angles to examine the influences of wind direction on ventilation performances.

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