Although airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been recognized, the condition of ventilation for its occurrence is still being debated. We analyzed ...a coronavirus disease 2019 (COVID-19) outbreak involving three families in a restaurant in Guangzhou, China, assessed the possibility of airborne transmission, and characterized the associated environmental conditions. We collected epidemiological data, obtained a full video recording and seating records from the restaurant, and measured the dispersion of a warm tracer gas as a surrogate for exhaled droplets from the index case. Computer simulations were performed to simulate the spread of fine exhaled droplets. We compared the in-room location of subsequently infected cases and spread of the simulated virus-laden aerosol tracer. The ventilation rate was measured using the tracer gas concentration decay method. This outbreak involved ten infected persons in three families (A, B, C). All ten persons ate lunch at three neighboring tables at the same restaurant on January 24, 2020. None of the restaurant staff or the 68 patrons at the other 15 tables became infected. During this occasion, the measured ventilation rate was 0.9 L/s per person. No close contact or fomite contact was identified, aside from back-to-back sitting in some cases. Analysis of the airflow dynamics indicates that the infection distribution is consistent with a spread pattern representative of long-range transmission of exhaled virus-laden aerosols. Airborne transmission of the SARS-CoV-2 virus is possible in crowded space with a ventilation rate of 1 L/s per person.
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•This outbreak involved ten infected persons in three families.•Full video recording at time of infection allows restoration of the scene.•Time-averaged ventilation rates were only 0.9 L/s per person in the restaurant.•Insufficient ventilation played a role in this outbreak of COVID-19.
Non-invasive ventilation (NIV) has become a common treatment for acute and chronic respiratory failure. In comparison with conventional invasive mechanical ventilation, NIV has the advantages of ...reducing patient discomfort, procedural complications, and mortality. However, NIV is associated with frequent uncomfortable or even life-threatening adverse effects, and patients should be thoroughly screened beforehand to reduce potential severe complications. We performed a detailed review of the relevant medical literature for NIV complications. All major NIV complications are potentially life-threatening and can occur in any patient, but are strongly correlated with the degree of pulmonary and cardiovascular involvement. Minor complications can be related to specific structural features of NIV interfaces or to variable airflow patterns. This extensive review of the literature shows that careful selection of patients and interfaces, proper setting of ventilator modalities, and close monitoring of patients from the start can greatly reduce NIV complications.
During the 2020 COVID‐19 pandemic, an outbreak occurred following attendance of a symptomatic index case at a weekly rehearsal on 10 March of the Skagit Valley Chorale (SVC). After that rehearsal, 53 ...members of the SVC among 61 in attendance were confirmed or strongly suspected to have contracted COVID‐19 and two died. Transmission by the aerosol route is likely; it appears unlikely that either fomite or ballistic droplet transmission could explain a substantial fraction of the cases. It is vital to identify features of cases such as this to better understand the factors that promote superspreading events. Based on a conditional assumption that transmission during this outbreak was dominated by inhalation of respiratory aerosol generated by one index case, we use the available evidence to infer the emission rate of aerosol infectious quanta. We explore how the risk of infection would vary with several influential factors: ventilation rate, duration of event, and deposition onto surfaces. The results indicate a best‐estimate emission rate of 970 ± 390 quanta/h. Infection risk would be reduced by a factor of two by increasing the aerosol loss rate to 5 h−1 and shortening the event duration from 2.5 to 1 h.
To achieve gas exchange goals and mitigate lung injury, infants who fail with conventional ventilation (CV) are generally switched to high-frequency oscillatory ventilation (HFOV). Although preferred ...in many neonatal intensive care units (NICUs), research on this type of rescue HFOV has not been reported recently.
An online registry database for a multicenter, prospective study was set to evaluate factors affecting the response of newborn infants to rescue HFOV treatment. The study population consisted of 372 infants with CV failure after at least 4 hours of treatment in 23 participating NICUs. Patients were grouped according to their final outcome as survived (Group S) or as died or received extracorporeal membrane oxygenation (ECMO) (Group D/E). Patients' demographic characteristics and underlying diseases in addition to their ventilator settings, arterial blood gas (ABG) analysis results at 0, 1, 4, and 24 hours, type of device, ventilation duration, and complications were compared between groups.
HFOV as rescue treatment was successful in 58.1% of patients. Demographic and treatment parameters were not different between groups, except that infants in Group D/E had lower birthweight (BW) (1655 ± 1091 vs. 1858 ± 1027 g, p = 0.006), a higher initial FiO2 setting (83% vs. 72%, p < 0.001), and a higher rate of nitric oxide exposure (21.8% vs. 11.1%, p = 0.004) in comparison to infants who survived (Group S). The initial cut-offs for a successful response on ABG were defined as pH >7.065 (OR: 19.74, 95% CI 4.83-80.6, p < 0.001), HCO3 >16.35 mmol/L (OR: 1.06, 95% CI 1.01-1.1, p = 0.006), and lactate level <3.75 mmol/L (OR: 1.09%95 CI 1.01-1.16, p = 0.006). Rescue HFOV duration was associated with retinopathy of prematurity (p = 0.005) and moderate or severe chronic lung disease (p < 0.001), but not with patent ductus arteriosus or intraventricular hemorrhage, in survivors (p > 0.05).
Rescue HFOV as defined for this population was successful in more than half of the patients with CV failure. Although the response was not associated with gestational age, underlying disease, device used, or initial MV settings, it seemed to be more effective in patients with higher BW and those not requiring nitric oxide. Initial pH, HCO3, and lactate levels on ABG may be used as predictors of a response to rescue HFOV.
•A scale experimental model with hybrid ventilation was created.•Hybrid ventilation efficiencies with different mechanical exhaust velocities were analyzed.•A critical mechanical exhaust velocity in ...the hybrid ventilation was identified.•Ventilation efficiency and ventilation strategy of different modes of hybrid ventilation were investigated.
Hybrid ventilation is an effective means of minimizing ventilation energy and improving indoor environment. A scale experimental model with a heat source was created for hybrid buoyancy-driven natural ventilation with a mechanical exhaust system. The aim of this study is to examine the performance of hybrid ventilation in an industrial building. The temperature distributions and hybrid ventilation efficiencies with different mechanical exhaust velocities were analyzed. Results showed that the hybrid ventilation efficiency first increased and then decreased with the mechanical exhaust velocity. A critical mechanical exhaust velocity was identified and the hybrid ventilation efficiency reached maximum at the critical mechanical exhaust velocity. The critical mechanical exhaust velocity was 1.4 m/s at the heat flux of the heat source q = 200 W and 1.0 m/s at q = 500 W, and the corresponding ventilation efficiencies were 24.4 and 6.69, respectively. Four modes of hybrid ventilation were investigated, and ventilation strategies of different modes of hybrid ventilation were given. An excessive mechanical ventilation rate will cause consumption of ventilation energy to increase and may lead to short circuiting of airflow and a bad thermal environment. These results should prove helpful in designing of hybrid ventilation systems for industrial buildings.
The objective of this article is to review the scientific literature on airflow distribution systems and ventilation effectiveness to identify and assess the most suitable room air distribution ...methods for various spaces. In this study, different ventilation systems are classified according to specific requirements and assessment procedures. This study shows that eight ventilation methods have been employed in the built environment for different purposes and tasks. The investigation shows that numerous studies have been carried out on ventilation effectiveness but few studies have been done regarding other aspects of air distribution. Amongst existing types of ventilation systems, the performance of each ventilation methods varies from one case to another due to different usages of the ventilation system in a room and the different assessment indices used. This review shows that the assessment of ventilation effectiveness or efficiency should be determined according to each task of the ventilation system, such as removal of heat, removal of pollutant, supply fresh air to the breathing zone or protecting the occupant from cross infection. The analysis results form a basic framework regarding the application of airflow distribution for the benefit of designers, architects, engineers, installers and building owners.
•We review eight ventilation/airflow distribution methods regarding ventilation efficiency.•We find that five indices can be used to assess the performance of a ventilation system.•The review discovers that DV, PV, SV and POV have certain energy saving potentials from 20% to 75%.•POV has a potential to protect occupants from exposure to indoor contaminant.
ABSTRACT
Background and objective
Non‐invasive ventilation (NIV) is part of the standard of care for hypercapnic respiratory failure secondary to COPD, but may be poorly tolerated. Preliminary ...evidence suggests nasal high‐flow (NHF) therapy may improve hypercapnia in COPD and be well tolerated. We compared NHF and NIV in people with COPD and chronic hypercapnic respiratory failure.
Methods
Single‐blind randomized controlled two‐way cross‐over single‐centre trial was conducted in New Zealand. Twenty‐four participants with stable hypercapnic COPD received: NHF at 45 L/min and NIV at 15/4 cm H2O, each for 60 min with a 15‐min washout in between. The primary outcome was transcutaneous partial pressure of carbon dioxide (PtCO2) at 60 min, adjusted for baseline.
Results
NIV reduced the PtCO2 more than NHF (mean (SD) at 60 min by −5.3 (5.0) vs −2.5 (3.5) mm Hg; difference: −2.8 (−5.0 to −0.5) P = 0.021). Difference across all time points was −2.5 mm Hg (95% CI −4.5 to −0.5, P = 0.016). There was no significant difference in the proportion of participants with a reduction of PtCO2 ≥ 4 or ≥ 8 mm Hg. Participants rated NHF significantly better for ease of application, comfort and fit.
Conclusion
In stable COPD patients with chronic hypercapnia, NIV resulted in a greater reduction in PtCO2 compared with NHF, which was of uncertain clinical significance. NHF was better tolerated than NIV and may be a therapeutic option for some people with hypercapnic respiratory failure.Clinical Trial Registration: ACTRN12616001701415 at www.anzctr.org.au
See related Editorial
Non‐invasive ventilation (NIV) reduces transcutaneous partial pressure of carbon dioxide (PtCO2) more than nasal high‐flow (NHF) therapy in hypercapnic COPD, but NHF is better tolerated.
Today, invasive and non-invasive home mechanical ventilation have become a well-established treatment option. Consequently, in 2010, the German Respiratory Society (DGP) has leadingly published the ...guidelines on "Non-Invasive and Invasive Mechanical Ventilation for Treatment of Chronic Respiratory Failure." However, continuing technical evolutions, new scientific insights, and health care developments require an extensive revision of the guidelines. For this reason, the updated guidelines are now published. Thereby, the existing chapters, namely technical issues, organizational structures in Germany, qualification criteria, disease-specific recommendations including special features in pediatrics as well as ethical aspects and palliative care, have been updated according to the current literature and the health care developments in Germany. New chapters added to the guidelines include the topics of home mechanical ventilation in paraplegic patients and in those with failure of prolonged weaning. In the current guidelines, different societies as well as professional and expert associations have been involved when compared to the 2010 guidelines. Importantly, disease-specific aspects are now covered by the German Interdisciplinary Society of Home Mechanical Ventilation (DIGAB). In addition, societies and associations directly involved in the care of patients receiving home mechanical ventilation have been included in the current process. Importantly, associations responsible for decisions on costs in the health care system and patient organizations have now been involved.
Natural ventilation is considered a prerequisite for sustainable buildings and is therefore in line with current trends in the construction industry. The design of naturally ventilated buildings is ...more difficult and carries greater risk than those that are mechanically ventilated. A successful result relies increasingly on a good understanding of the abilities and limitations of the theoretical and experimental procedures that are used for design. There are two ways to naturally ventilate a building: wind driven ventilation and stack ventilation. The majority of buildings employing natural ventilation rely primarily on wind driven ventilation, but the most efficient design should implement both types. Natural Ventilation of Buildings: Theory, Measurement and Design comprehensively explains the fundamentals of the theory and measurement of natural ventilation, as well as the current state of knowledge and how this can be applied to design. The book also describes the theoretical and experimental techniques to the practical problems faced by designers. Particular attention is given to the limitations of the various techniques and the associated uncertainties. Key features: Comprehensive coverage of the theory and measurement of natural ventilation Detailed coverage of the relevance and application of theoretical and experimental techniques to design Highlighting of the strengths and weaknesses of techniques and their errors and uncertainties Comprehensive coverage of mathematical models, including CFD Two chapters dedicated to design procedures and another devoted to the basic principles of fluid mechanics that are relevant to ventilation This comprehensive account of the fundamentals for natural ventilation design will be invaluable to undergraduates and postgraduates who wish to gain an understanding of the topic for the purpose of research or design. The book should also provide a useful source of reference for more experienced industry practitioners.
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