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 Although condemned as outdated by health ministers in recent years, many remain in use.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 Although condemned as outdated by health ministers in recent years, many remain in use.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

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

Airflow Simulation and Measurement of Brake Wear Particle Emissions with a Novel Test Rig

Particle emissions generated by the braking systems of road vehicles represents a significant non-exhaust contributor. Fine particles such as these are transported through airborne routes. They are known to adversely affect human health and currently there are no policies in place to regulate them. Before this issue can be addressed, it is important to characterise brake wear debris which is the purpose of this study. A newly-developed test rig consisting of a closed but ventilated enclosure surrounds a brake dynamometer equipped with a cast iron rotor. A sampling probe was made in accordance with the isokinetic principles in order to withdraw a representative aerosol sample from the outlet duct. Measurements of real-time particulate numbers and mass distributions are recorded using a Dekati ELPI®+ unit and the brake materials were tested under drag-braking conditions. Prior to measurements, Computational Fluid Dynamics (CFD) simulations were performed to investigate the most suitable sampling points used in the experiments. Preliminary experimental results show that there is a noticeable increase in particle numbers, compared to background levels, with a corresponding change in the mass distribution; coarser particles become more prominent during these braking events. These results provide confidence in the performance of the test rig and its ability to measure airborne brake wear debris in order to compare emissions from various friction pairs

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

Aerodynamic Drag Reduction of Emergency Response Vehicles

This paper presents the first experimental and computational investigation into the aerodynamics of emergency response vehicles and focusses on reducing the additional drag that results from the customary practice of adding light-bars onto the vehicles’ roofs. A series of wind tunnel experiments demonstrate the significant increase in drag that results from the light bars and show these can be minimized by reducing the flow separation caused by them. Simple potential improvements in the aerodynamic design of the light bars are investigated by combining Computational Fluid Dynamics (CFD) with Design of Experiments and metamodelling methods. An aerofoil-based roof design concept is shown to reduce the overall aerodynamic drag by up to 20% and an analysis of its effect on overall fuel consumption indicates that it offers a significant opportunity for improving the fuel economy and reducing emissions from emergency response vehicles. These benefits are now being realised by the UK’s ambulance service

Optimizing upper-room UVGI systems for infection risk and energy

The effectiveness of UV-C irradiation at inactivating airborne pathogens is well proven, and the technology is already advocated for control of some respiratory diseases such as Tuberculosis. UV-C air disinfection is also commonly promoted as an energy efficient way of reducing infection risk in comparison to increasing ventilation. However determining how and where to apply UVGI devices for the greatest benefit is still poorly understood. This paper focuses on upper-room UVGI systems, where microorganism inactivation is accomplished by passing contaminated room air through an open UV field above the heads of occupants. Multi-zone models are developed to assess the potential impact of a UVGI installation across a series of inter-connected spaces such as a hospital ward; this may comprise rooms for one or more patients that are all connected to a common zone that may be a corridor or may act as a communal space, housing fore xample the nurses station. Simulation of dose couples the ventilation, air mixing and upper-zone average field to explore factors influencing device coverage. A first-order decay model of UV inactivation is coupled with the room air model to simulate patient room and whole-ward level disinfection under different mixing and UV field conditions. Steady-state computation of quanta concentrations are applied to the Wells-Riley equation to predict likely infection rates. Simulation of a hypothetical ward demonstrates the relative benefits of different system options for susceptible patients co-located with an infectious source or in nearby rooms. In each case energy requirements are also calculated and compared to achieving the same level of risk through improved ventilation. A design of experiment technique is applied to sample the design space and explore the most effective system design for a given scenario. Devices are seen to be most effective where they are located close to the infectious source. However, results show that when the location of the infectious source is not known,locating devices in patient rooms is likely to be more effective than installing them in connecting corridor or communal zones

Computational fluid dynamics modelling and optimisation of an upper-room ultraviolet germicidal irradiation system in a naturally ventilated hospital ward

Ultraviolet germicidal irradiation (UVGI) has been shown to be an effective technology for reducing the airborne bioburden in indoor environments and is already advocated as a potential infection control measure for healthcare settings. However, much of the understanding of UVGI performance is based on experimental studies or numerical simulation in mechanically ventilated environments. This study considers the application of an upper-room UVGI system in a naturally ventilated multi-bed hospital ward. A computational fluid dynamics model is used to simulate a Nightingale-type hospital ward with wind-driven cross-ventilation and three wall-mounted UVGI fixtures. A parametric study considering 50 different fixture configurations and three ventilation rates was carried out using a design of experiments approach. Each configuration was assessed by calculating the UV dose distribution over the ward and at each bed. Results show that dose is influenced by the location of the fixtures and the ventilation regime. Thermal effects are likely to be important at low ventilation rates and may reduce UV effectiveness. A metamodel-based numerical optimisation was applied at a ventilation rate of 6 air changes per hour. In this case, the optimum result is achieved when UVGI fixtures are mounted on the leeward wall at their lowest mounting height

Measurement of ventilation and airborne infection risk in large naturally ventilated hospital wards

Airborne pathogens pose a significant threat to human health and this is especially the case in hospital environments which house patients with weakened immune systems. Good ventilation design can reduce risk, however quantifying ventilation performance and its influence on infection risk is difficult, particularly for large naturally ventilated environments with multiple openings. This study applies a pulse-injection gas tracer method to assess potential infection risk and local ventilation rates in a naturally-ventilated environment. Experiments conducted in a 200 m3 cross-ventilated Nightingale ward show that local external wind speeds in the range 1–4 m/s lead to indoor ventilation rates of between 3.4 and 6.5 air changes per hour (ACH). Natural ventilation is shown to be effective in open wards with an even distribution of potential airborne infection risk throughout patient locations. Comparison with a partitioned ward highlighted the potential for protecting neighbouring patients with physical partitions between beds, however, higher tracer concentrations are present in both the vicinity and downstream of the source. Closing the windows to represent winter conditions dramatically increases infection risk, with relative exposure to the tracer increased fourfold compared to the scenarios with the windows open. Extract fans are shown to alleviate this problem suggesting that a hybrid approach utilising the respective strengths of natural and mechanical ventilation may offer the best year-round solution in this and similar settings