A Computational Study of UV disinfection performance within a naturally ventilated hospital ward

The airborne transmission of pathogens including tuberculosis and influenza pose a significant threat to human health. This is especially the case in healthcare settings such as hospital wards which inevitably contain a high concentration of viruses and bacteria. These have the potential to infect both patients with weakened immune systems and healthcare workers. In order to reduce the infection risk, improvements in hospital ward design and the application of disinfection systems can offer significant benefits. One such strategy, upper-room Ultraviolet Germicidal Irradiation (UVGI), relies on a collimated irradiance field which works in conjunction with ventilation patterns to disinfect the air. The focus of this study is to predict the UVGI system performance within a naturally ventilated hospital ward, for a range of ambient conditions using Computational Fluid Dynamics (CFD). A computer model of an open-plan six-bed Nightingale-style hospital ward was generated based on the dimensions of a former hospital building situated in Bradford, UK. With a total volume of 200 m3, natural ventilation is supplied through three casement windows and a further three openings on the leeward side ensure steady cross-ventilation. Boundary conditions are based on experimental measurements of the ventilation rate which were determined using a tracer technique. An experimentally-determined irradiance field is included in the model and stored as a fixed-value scalar field. A total of fifty steady-state CFD simulations show that disinfection performance depends on the ventilation rate, the degree of mixing present and the position of the UVGI fixture within the ward. The results underline the potential performance gains from UVGI installations and how they could be integrated within existing healthcare facilities as an infection control measure

Functional recovery of a resilient hospital type

Four adaptation options for ‘Nightingale’-type hospital ward buildings devised with practising clinicians are presented and evaluated. The adaptations recover functionality in an archaic ward configuration by delivering care to current UK National Health Service (NHS) models whilst preserving resilience to summer overheating. The investigation builds on recent work that demonstrates the significant resilience to heatwaves enjoyed by such traditionally constructed communal dormitories, the dominant UK hospital type between the late 1850s and 1939. Nightingale wards are potentially well-ventilated naturally, with good dilution of airborne pathogens. Although condemned as outdated by health ministers in recent years, many remain in use. As financial retrenchment suggests economical, creative refurbishment of hospitals will be required rather than new-build and replacement, the authors argue for health estates’ strategies that place value on resilience in a changing climate. Proposed adaptation options are investigated to assess resulting internal airflows and patient exposure to airborne pathogens. Options are costed and payback periods calculated to the standard public sector methodology. The proposed adaptations save time and cost over new-build equivalents. Selection of the most appropriate option is dependent on the characteristics of the patient cohort and care required.Four adaptation options for ‘Nightingale’-type hospital ward buildings devised with practising clinicians are presented and evaluated. The adaptations recover functionality in an archaic ward configuration by delivering care to current UK National Health Service (NHS) models whilst preserving resilience to summer overheating. The investigation builds on recent work that demonstrates the significant resilience to heatwaves enjoyed by such traditionally constructed communal dormitories, the dominant UK hospital type between the late 1850s and 1939. Nightingale wards are potentially well-ventilated naturally, with good dilution of airborne pathogens. Although condemned as outdated by health ministers in recent years, many remain in use. As financial retrenchment suggests economical, creative refurbishment of hospitals will be required rather than new-build and replacement, the authors argue for health estates’ strategies that place value on resilience in a changing climate. Proposed adaptation options are investigated to assess resulting internal airflows and patient exposure to airborne pathogens. Options are costed and payback periods calculated to the standard public sector methodology. The proposed adaptations save time and cost over new-build equivalents. Selection of the most appropriate option is dependent on the characteristics of the patient cohort and care required.This is the final published version distributed under a Creative Commons Attribution License 2.0, which can also be viewed on the publisher's website at: http://www.tandfonline.com/doi/full/10.1080/09613218.2014.926605#.U8ZFv_ldXH

Relationship between healthcare worker surface contacts, care type and hand hygiene: an observational study in a single-bed hospital ward

This study quantifies the relationship between hand hygiene and the frequency with which healthcare workers (HCWs) touch surfaces in patient rooms. Surface contacts and hand hygiene were recorded in a single-bed UK hospital ward for six care types. Surface contacts often formed non-random patterns, but hygiene before or after patient contact depends significantly on care type (P=0.001). The likelihood of hygiene correlated with the number of surface contacts (95% confidence interval 1.1–5.8, P=0.002), but not with time spent in the room. This highlights that a potential subconscious need for hand hygiene may have developed in HCWs, which may support and help focus future hygiene education programmes

Simulating Pathogen Transport within a Naturally Ventilated Hospital Ward

Understanding how airborne pathogens are transported through hospital wards is essential for determining the infection risk to patients and healthcare workers. This study utilizes Computational Fluid Dynamics (CFD) simulations to explore pathogen transport within a six-bed Nightingale hospital ward. Grid independence of a ward model was addressed using the Grid Convergence Index (GCI) from solutions obtained using three fully-structured grids. Pathogens were simulated using source terms in conjunction with a scalar transport equation and a RANS turbulence model. Errors were found to be less than 4% in the prediction of air velocities but an average of 13% was seen in the scalar field. A parametric study into the pathogen release point illustrated that its distribution is strongly influenced by the local velocity field and the degree of mixing present

Profitability assessment of PV rooftop implementation for prosumer under net metering scheme in Indonesia

This study conducts an analysis of photovoltaic (PV) rooftop potential for domestic application in Indonesia. In this study, the potential solar energy is simulated by using IES VE software coupled with a Monte Carlo probabilistic approach to account for the variability of solar energy. Economic analysis is undertaken based on the calculated solar energy using an exceedance probability of 90%. The economic analysis is developed under the latest net metering scheme as regulated by Regulation of Minister of Energy and Mineral Resources in Indonesia. The study shows that despite a mismatch between the peak solar generation and the peak demand for power that rooftop PV is still cost effective. Using the latest net metering scheme, the costumer is benefiting from a PV rooftop investment despite the significant reduction of export energy price compared to the previous net metering regulation

Development of a numerical optimization approach to ventilation system design to control airborne contaminant dispersion and occupant comfort

Airflow, contaminant and temperature during heating and ventilation in a model room represented by a square cavity with inlet and outlet ports, has been studied. The aim of this work is concerned with the development and implementation of a practical and robust optimization scheme based on the combination of Genetic algorithm and response surface methodology (RSM) with the aim of assisting hospital ward designers and managers /operators to enhance infection control (i.e. reduce the risk of airborne transmission) without compromising patient comfort and environmental impact

The Influence of Street Canyon Design on Hospital Air Quality

This study considers air exchange between outdoor and indoor environments in the context of a hospital room with single-sided natural ventilation. Computational fluid dynamics (CFD) simulations are used to examine the trade-off between outdoor pollutant ingress and indoor contaminant dilution, and the influence of the street canyon design. Two street-canyon aspect ratios were investigated (Height/Width=0.5 and 1) with roof angles of zero and 26.6º. An open window was located on the on the leeward side connecting to an interior room. ANSYS Fluent 15 was used to model airflow in the indoor and outdoor spaces and employed a k-omega turbulence model. A tracer was released in the outdoor location between the buildings and concentrations determined inside the open window. A second tracer released inside the building was used to establish concentrations at the pedestrian level outside. Increasing canyon width reduced the residence time of the outdoor pollutant and reduces ingress. Flat roofs for both ratios drew the tracer to the leeward side of the building due to negative pressures. However, pitched roofs created more complex systems that reduced contaminant in the canyon due to unsteady vortices. Contaminants released inside the room result in proportionally higher concentrations outside for narrow canyons

An Effective Surrogate Tracer Technique for S. aureus Bioaerosols in a Mechanically Ventilated Hospital Room Replica Using Dilute Aqueous Lithium Chloride

Finding a non-pathogenic surrogate aerosol that represents the deposition of typical bioaerosols in healthcare settings is beneficial from the perspective of hospital facility testing, general infection control and outbreak analysis. This study considers aerosolization of dilute aqueous lithium chloride (LiCl) and sodium chloride (NaCl) solutions as surrogate tracers capable of representing Staphylococcus aureus bioaerosol deposition on surfaces in mechanically ventilated rooms. Tests were conducted in a biological test chamber set up as a replica hospital single patient room. Petri dishes on surfaces were used to collect the Li, Na and S. aureus aerosols separately after release. Biological samples were analyzed using cultivation techniques on solid media, and flame atomic absorption spectroscopy was used to measure Li and Na atom concentrations. Spatial deposition distribution of Li tracer correlated well with S. aureus aerosols (96% of pairs within a 95% confidence interval). In the patient hospital room replica, results show that the most contaminated areas were on surfaces 2 m away from the source. This indicates that the room’s airflow patterns play a significant role in bioaerosol transport. NaCl proved not to be sensitive to spatial deposition patterns. LiCl as a surrogate tracer for bioaerosol deposition was most reliable as it was robust to outliers, sensitive to spatial heterogeneity and found to require less replicates than the S. aureus counterpart to be in good spatial agreement with biological results

Testing of a downflow system for high risk infectious disease isolation rooms

Isolation room airflows for infectious diseases are designed to minimise the risk of transmission of airborne pathogens to those outside the room and to protect healthcare workers who tend to the patient. This study considers the risk in the vicinity of the patient and conducts an experimental investigation into a downflow ventilation design to evaluate whether it is capable of providing protection to a healthcare worker. Anemometry and smoke tests are conducted in a mock up room to assess influence of ventilation rate, extract design, heat loads and flow local to a healthcare worker. Results show a good downward flow can be established, but a fan speed capable of delivering 0.35m/s and central extract are required to create a uniform flow. Heat loads and a healthcare worker leaning over the bed both compromise downflow effectiveness; local flow acceleration and exhaust can mitigate to some extent

OCRL1 engages with the F-BAR protein pacsin 2 to promote biogenesis of membrane-trafficking intermediates

Mutation of the inositol 5-phosphatase OCRL1 causes Lowe syndrome and Dent-2 disease. Loss of OCRL1 function perturbs several cellular processes, including membrane traffic, but the underlying mechanisms remain poorly defined. Here we show that OCRL1 is part of the membrane-trafficking machinery operating at the trans-Golgi network (TGN)/endosome interface. OCRL1 interacts via IPIP27A with the F-BAR protein pacsin 2. OCRL1 and IPIP27A localize to mannose 6-phosphate receptor (MPR)–containing trafficking intermediates, and loss of either protein leads to defective MPR carrier biogenesis at the TGN and endosomes. OCRL1 5-phosphatase activity, which is membrane curvature sensitive, is stimulated by IPIP27A-mediated engagement of OCRL1 with pacsin 2 and promotes scission of MPR-containing carriers. Our data indicate a role for OCRL1, via IPIP27A, in regulating the formation of pacsin 2–dependent trafficking intermediates and reveal a mechanism for coupling PtdIns(4,5)P2 hydrolysis with carrier biogenesis on endomembranes