ABSTRACT
Dental services are yet to return to a semblance of normality owing to the fear and uncertainty associated with the possible airborne transmission of diseases. The present study aims to investigate the impacts of environmental conditions [changes in ventilation location, ventilation rate, and relative humidity (RH)] and variations in dental patient's breathing rate on droplet transmission during dental service. Computational fluid dynamics simulation was performed based on our previous experimental study during ultrasonic scaling. The impacts of different factors were numerically analyzed by the final fate and proportion of emitted droplets in the dental surgery environment. The results revealed that about 85% of droplets deposited near the dental treatment region, where the patient's torso, face, and floor (dental chair) accounted for around 63%, 11%, and 8.5%, respectively. The change in the ventilation location had a small impact on the deposition of larger droplets (> 60 mu m), and a spatial region with high droplet mass concentration would be presented near the dental professional. The change in the ventilation rate from 5 to 8 ACH led to a 1.5% increment in the fraction of escaped droplets. 50% RH in dental environments was recommended to prevent droplets' fast evaporation and potential mold. Variations in the patient's breathing rate had little effect on the final fate and proportion of emitted droplets. Overall, environmental factors are suggested to maintain 50% RH and larger ACH in dental surgery environments. The findings can give policymakers insights into the role of environmental factors on infection control.
ABSTRACT
Aim: To evaluate the effect of decontamination and reuse on N95 masks. Background(s): The coronavirus disease (COVID-19) pandemic has strained the global availability of masks. Such shortage represents a threat to healthcare workers (HCWs). Mask reprocessing and reuse may alleviate the shortage. Many laboratory studies have proven the effectiveness and feasibility of decontaminating N95 masks. However, very few had HCWs wearing them between cycles of decontamination. Our study evaluated mask integrity (assessed by qualitative mask fitting [QMF], as well as technical measures like bacterial filtration efficacy [BFE]) through five cycles of decontamination using four different modalities - steam, moist heat (MH), UV-C irradiation (UVCI), and hydrogen peroxide vaporization (HPV). Method(s): Each study cycle involved a HCW wearing a N95 mask for two hours, followed by the assigned decontamination process, and then a QMF. This was repeated for a maximum of 5 cycles, as long as the wearer passed QMF. 40 HCWs were recruited for each of the four decontamination modalities. The technical measures of mask integrity assessed were: BFE, Particulate Filtration Efficiency (PFE), Pressure Drop and Splash Resistance. Result(s): 60.6% (HPV) to 77.5% (MH) of the masks passed five cycles of wear and decontamination, as assessed by the wearers passing QMF all five times. MH-decontaminated masks retained all technical measures of integrity through all 5 cycles. HPV reduced masks' BFE after the fourth cycle while UVCI tended to increase the Pressure Drop. Conclusion(s): The results suggest that MH is a promising method for decontaminating N95 masks without compromising fit and integrity. [Figure presented] [Table presented]Copyright © 2023 Southern Society for Clinical Investigation.
ABSTRACT
The outbreak of the COVID-19 pandemic in Singapore has resulted in the adoption of home-based learning (similar to remote or distance learning' worldwide) due to periodic school closures in Singapore. The media and academia have diverse views on the effectiveness of this alternative mode of education. This study draws data from teachers' interviews and students' focus group discussions of an ongoing large-scale baseline study on mother tongue education to reveal teachers' and students' perceptions of home-based learning. Findings showed that the participating teachers generally mimicked physical lessons online during home-based learning, and they faced difficulties in monitoring students' tasks online. Though students enjoyed the freedom of doing their learning tasks at their own pace, they were concerned with the lack of teachers' support and the social-emotional support from peers. With the feedback and reflections from teachers and students, it was observed that despite the availability of technology and online infrastructure, teachers need readiness for transiting between physical teaching and online instruction, whereas students need readiness for self-directed learning. From students' feedback, it was also noted that parents need readiness for educational technology and support for their children. To better prepare teachers, students, and parents for home-based learning, it is recommended that the developers provide more dedicated resources that take into consideration the different characteristics (e.g. orthography) of each language subject. Parents should also assume a greater role in monitoring their children's learning on behalf of the teachers for better effect in home-based learning.
ABSTRACT
Numerous short-term exposure events in public spaces were reported during the COVID-19 pandemic, especially during the spread of Delta and Omicron. However, the currently used exposure risk assessment models and mitigation measures are mostly based on the assumption of steady-state and complete-mixing conditions. The present study investigates the dynamics of airborne transmission in short-term events when a steady state is not reached before the end of the events. Large-eddy simulation (LES) is performed to predict the airborne transmission in short-term events, and three representative physical distances between two occupants are examined. Both time-averaged and phase-averaged exposure indices are used to evaluate the exposure risk. The results present that the exposure index in the short-term events constantly varies over time, especially within the first 1/ACH (air changes per hour) hour of exposure between occupants in close proximity, posing high uncertainty to the spatial and temporal evolutions of the risk of cross-infection. The decoupling analysis of the direct and indirect airborne transmission routes indicates that the direct airborne transmission is the predominated route in short-term events. It suggests also that the general dilution ventilation has a relatively limited efficiency in mitigating the risk of direct airborne transmission, but determines largely the occurrence time of the indirect one. Given the randomness, discreteness, localization, and high-risk characteristics of direct airborne transmission, a localized method that has a direct interference on the respiratory flows would be better than dilution ventilation for short-term events, in terms of both efficiency and cost.
ABSTRACT
Introduction In the face of a rapidly advancing pandemic with uncertain pathophysiology, pop-up healthcare units, ad hoc teams and unpredictable personal protective equipment supply, it is difficult for healthcare institutions and front-line teams to invent and test robust and safe clinical care pathways for patients and clinicians. Conventional simulation-based education was not designed for the time-pressured and emergent needs of readiness in a pandemic. We used 'rapid cycle system improvement' to create a psychologically safe learning oasis in the midst of a pandemic. This oasis provided a context to build staff technical and teamwork capacity and improve clinical workflows simultaneously. Methods At the Department of Anaesthesia and Intensive Care in Prince of Wales Hospital, a tertiary institution, in situ simulations were carried out in the operating theatres and intensive care unit (ICU). The translational simulation design leveraged principles of psychological safety, rapid cycle deliberate practice, direct and vicarious learning to ready over 200 staff with 51 sessions and achieve iterative system improvement all within 7 days. Staff evaluations and system improvements were documented postsimulation. Results/Findings Staff in both operating theatres and ICU were significantly more comfortable and confident in managing patients with COVID-19 postsimulation. Teamwork, communication and collective ability to manage infectious cases were enhanced. Key system issues were also identified and improved. Discussion To develop readiness in the rapidly progressing COVID-19 pandemic, we demonstrated that 'rapid cycle system improvement' can efficiently help achieve three intertwined goals: (1) ready staff for new clinical processes, (2) build team competence and confidence and (3) improve workflows and procedures.
ABSTRACT
Viable aerosols in the airflow may increase the risk of occupants contracting diseases. Natural ventilation is common in buildings and is accompanied by re-entry airflow during the ventilation process. If the re-entry airflow contains toxic or infectious species, it may cause potential harm to residents. One of the Covid-19 outbreaks occurred in a public residential building at Luk Chuen House (LC-House) in Hong Kong. It is highly suspected that the outbreak of the disease is related to the re-entry airflow. The study attempts to explain and discuss possible causes of the outbreak. In order to understand the impact of airflow on the outbreak, a public residential building similar to LC-House was used in the study. Two measurements M - I and M - II with the same settings were conducted for a sampling unit in the corridor under low and strong wind conditions respectively. The sampling unit and the tracer gas carbon dioxide (CO2) were used to simulate the index unit and infectious contaminated airflow respectively. The CO2 concentrations of the unit and corridor were measured simultaneously. Two models of Traditional Single-zone model (TSZ-model) and New Dual-zone model (NDZ-model) were used in the analysis. By comparing the ACH values obtained from the two models, it is indicated that the re-entry airflow of the unit is related to the corridor wind speeds and this provides a reasonable explanation for the outbreak in LC-House, and believes that the results can help understand the recent frequent cluster outbreaks in other residential buildings.