Fast-track ventilation strategy to cater for pandemic patient isolation surges.

BACKGROUND: The shortage of isolation facilities in hospitals was highlighted during the severe acute respiratory syndrome (SARS) pandemic in 2003. Yet, as the nature and scale of future pandemics cannot be adequately estimated, it is difficult to justify construction of sufficient isolation facilities. A fast-track and cost-effective ventilation strategy for the retrofitting of existing general wards could help hospitals deal with patient surges. AIM: This article reviews the effectiveness of a fast-track, makeshift isolation approach employed during the SARS outbreak which involved installing simple window-mounted exhaust fans to create negative-pressure airflow in hospital general wards. METHODS: Computational fluid dynamics (CFD) was used to assess by simulation whether the approach adopted meets US Centers for Disease and Control and Prevention requirements for properly constructed isolation wards. FINDINGS: CFD simulation revealed that this makeshift approach could match the ventilation standards of isolation rooms. The approach was certainly effective as no secondary infections were reported in hospitals that used it during SARS. CONCLUSIONS: When there is a shortfall in isolation facilities to accommodate a surge in patients, the proposed ventilation set-up could be quickly and widely implemented by existing general wards.

Rethinking hospital general ward ventilation design using computational fluid dynamics.

Indoor ventilation with good air quality control minimises the spread of airborne respiratory and other infections in hospitals. This article considers the role of ventilation in preventing and controlling infection in hospital general wards and identifies a simple and cost-effective ventilation design capable of reducing the chances of cross-infection. Computational fluid dynamic (CFD) analysis is used to simulate and compare the removal of microbes using a number of different ventilation systems. Instead of the conventional corridor air return arrangement used in most general wards, air return is rearranged so that ventilation is controlled from inside the ward cubicle. In addition to boosting the air ventilation rate, the CFD results reveal that ventilation performance and the removal of microbes can be significantly improved. These improvements are capable of matching the standards maintained in a properly constructed isolation room, though at much lower cost. It is recommended that the newly identified ventilation parameters be widely adopted in the design of new hospital general wards to minimise cross-infection. The proposed ventilation system can also be retrofitted in existing hospital general wards with far less disruption and cost than a full-scale refurbishment.

Role of ventilation in airborne transmission of infectious agents in the built environment - a multidisciplinary systematic review.

There have been few recent studies demonstrating a definitive association between the transmission of airborne infections and the ventilation of buildings. The severe acute respiratory syndrome (SARS) epidemic in 2003 and current concerns about the risk of an avian influenza (H5N1) pandemic, have made a review of this area timely. We searched the major literature databases between 1960 and 2005, and then screened titles and abstracts, and finally selected 40 original studies based on a set of criteria. We established a review panel comprising medical and engineering experts in the fields of microbiology, medicine, epidemiology, indoor air quality, building ventilation, etc. Most panel members had experience with research into the 2003 SARS epidemic. The panel systematically assessed 40 original studies through both individual assessment and a 2-day face-to-face consensus meeting. Ten of 40 studies reviewed were considered to be conclusive with regard to the association between building ventilation and the transmission of airborne infection. There is strong and sufficient evidence to demonstrate the association between ventilation, air movements in buildings and the transmission/spread of infectious diseases such as measles, tuberculosis, chickenpox, influenza, smallpox and SARS. There is insufficient data to specify and quantify the minimum ventilation requirements in hospitals, schools, offices, homes and isolation rooms in relation to spread of infectious diseases via the airborne route. PRACTICAL IMPLICATION: The strong and sufficient evidence of the association between ventilation, the control of airflow direction in buildings, and the transmission and spread of infectious diseases supports the use of negatively pressurized isolation rooms for patients with these diseases in hospitals, in addition to the use of other engineering control methods. However, the lack of sufficient data on the specification and quantification of the minimum ventilation requirements in hospitals, schools and offices in relation to the spread of airborne infectious diseases, suggest the existence of a knowledge gap. Our study reveals a strong need for a multidisciplinary study in investigating disease outbreaks, and the impact of indoor air environments on the spread of airborne infectious diseases.