An assessment of outpatient clinic room ventilation systems and possible relationship to disease transmission

The Wells-Riley model revisited: Randomness, heterogeneity, and transient behaviours

The Wells-Riley model has been widely used to estimate airborne infection risk, typically from a deterministic point of view (i.e., focusing on the average number of infections) or in terms of a per capita probability of infection. Some of its main limitations relate to considering well-mixed air, steady-state concentration of pathogen in the air, a particular amount of time for the indoor interaction, and that all individuals are homogeneous and behave equally. Here, we revisit the Wells-Riley model, providing a mathematical formalism for its stochastic version, where the number of infected individuals follows a Binomial distribution. Then, we extend the Wells-Riley methodology to consider transient behaviours, randomness, and population heterogeneity. In particular, we provide analytical solutions for the number of infections and the per capita probability of infection when: (i) susceptible individuals remain in the room after the infector leaves, (ii) the duration of the indoor interaction is random/unknown, and (iii) infectors have heterogeneous quanta production rates (or the quanta production rate of the infector is random/unknown). We illustrate the applicability of our new formulations through two case studies: infection risk due to an infectious healthcare worker (HCW) visiting a patient, and exposure during lunch for uncertain meal times in different dining settings. Our results highlight that infection risk to a susceptible who remains in the space after the infector leaves can be nonnegligible, and highlight the importance of incorporating uncertainty in the duration of the indoor interaction and the infectivity of the infector when estimating risk.

The influence of physical environment on health care-associated infections: A literature review

BACKGROUND

Health care-associated infections (HAIs) are a common issue in health care settings, caused by environmental microorganisms, leading to health risks and financial strain. Despite efforts to reduce HAIs, the role of the physical environment in reducing HAIs is not fully understood. This literature review aimed to identify physical environment variables contributing to HAIs.

METHODS

A literature search was conducted in scientific databases between 2016 and 2022 using keywords associated with infections and physical environment variables. After screening retrieved articles for eligibility, the articles were analyzed for relevant environmental and infection variables.

RESULTS

Out of 145, 27 articles were identified. The findings were grouped into 8 categories, including layout design, surfaces, behavior, lighting, Internet of Things, materials, airflow, and air quality, with sub-themes in each group.

CONCLUSIONS

The physical environment in health care facilities plays a crucial role in reducing and preventing the spread of HAIs. Proper design and construction of health care buildings, including ventilation and air conditioning systems, help prevent infection spread between functional areas. Antimicrobial materials, cleaning and disinfection protocols, and personal hygiene practices, such as hand hygiene, are key factors in infection control. The positioning of hand hygiene stations is also essential to improve compliance among health care professionals.

Evolution of the Push-2-Spin Fat Graft Processing Device: Enhancing Efficiency and Reducing Risk of Contamination

Background

Small-volume fat graft efficiency is a critical determinant of the cost and material effectiveness of aesthetic fat grafting in the clinical space. Recent development of devices, such as the Push-2-Spin (P2S) system (Pittsburgh, PA), has improved upon the process by yielding a rapid, handheld, multi-use system to minimize operative time and mess.

Objectives

In this study, the authors describe further technical innovations on the P2S prototype that improve operative ease of use, time, and safety.

Methods

Abdominoplasty samples were obtained as discarded tissue. Lipoaspirate was collected utilizing a 3.0 mm liposuction cannula and processed through centrifugation (Coleman technique), gauze (telfa) rolling, mesh straining, the tabletop P2S device (prototype), or the P2S handheld (P2S-H) device. Operative processing time, spin time, oil fraction, stromal vascular fraction (SVF) yield and viability, and adipocyte viability were assessed to compare the efficacy and viability of each device/technique. Blood agar smears of lipoaspirate were performed to assess for risk of contamination.

Results

The P2S-H device outperformed its prior iteration in rotary and processing speed and was significantly faster than each other technique assessed. Furthermore, the use of an inline system offered significant advantages over open-air techniques in terms of resistance to contamination. Serial use characteristics were assessed; under these conditions, oil yield as well as adipocyte and SVF number and viability was similar between all techniques.

Conclusions

The technical advancements to the P2S system which enable single-unit, handheld operation significantly improve operative time and minimize space requirements. This operative quality of life improvement comes at no cost to the efficacy of oil extraction, cellular yield, or cell viability.

Level of Evidence 3

Compliance with Medication amongst Persons with Diabetes Mellitus during the COVID-19 Pandemic, Kerala, India: A Cross Sectional Study

Compliance with medication in persons with diabetes mellitus (DM) has been a challenge during the COVID-19 pandemic, leading to poor glycemic control and higher risk of complications. In the state of Kerala, India, 20−25% of adults have DM. Our cross-sectional study aimed to assess medication compliance and factors associated with poor compliance in DM persons attending selected primary care government facilities in Kerala during the COVID-19 pandemic. Persons registered with DM for >6 months were consecutively interviewed between August and September 2021. Poor compliance was defined as answering “No” to one or more of three questions related to access and intake of medication two weeks prior to and the day before the interview. Factors independently associated with poor compliance were assessed using adjusted prevalence ratios (aPr) and 95% confidence intervals. Of the 560 DM persons included, 209 (37%) exhibited poor compliance. Factors associated with poor compliance were age 19−45 years (aPr 1.4, 1.1−1.9); inability to be blood glucose tested during the COVID-19 pandemic (aPr 3.6, 2.9−4.3); not having COVID-19 (aPr 1.4, 1.0−1.9); and being double vaccinated against COVID-19 (aPr 1.4, 1.1−2.0). Focused attention must be paid to these groups to improve medication compliance and prevent DM complications and severe COVID-19-related disease.

Infection prevention and control considerations regarding ventilation in acute hospitals

Infection prevention and control team members (IPCTM) are often intimidated by aspects of ventilation as they relate to healthcare, because they consider them technical and outside their area of comfort and expertise. However, engineers, estates departments and planners need IPCTM input to ensure appropriate design and use. The main areas of importance centre on the operating theatre, the provision of air-controlled ventilated isolation rooms, and how to respond to major outbreaks/pandemics. Concentrating on basic principles of infection prevention and control, developing relationships with key departments and individuals, and applying best practice to these and other areas as they arise, are of great value. Some background, information and suggestions are provided for IPCTM with a view to providing simple practical advice in these areas.

Ventilation in worker dormitories and its impact on the spread of respiratory droplets

Most of the COVID-19 cases in Singapore have primarily come from foreign worker dormitories. This people group is especially vulnerable partly because of behavioural habits, but the built environment they live in also plays a significant role. These dormitories are typically densely populated, so the living conditions are cramped. The short lease given to most dormitories also means the design does not typically focus on environmental performance, like good natural ventilation. This paper seeks to understand how these dormitories' design affects natural ventilation and, subsequently, the spread of the COVID-19 particles by looking at two existing worker dorms in Singapore. Findings show that some rooms are poorly orientated against the prevailing wind directions, so there is dominant stagnant air in these rooms, leading to respiratory droplets' long residence times. These particles can hover in the air for 10 min and more. Interventions like increased bed distance and removing upper deck beds only showed limited ventilation improvements in some rooms. Comparatively, internal wind scoops' strategic placement was more effective at directing wind towards more stagnant zones. Large canyon aspect ratios were also effective at removing particles from higher elevations.