Indian Journal of Burns

: 2020  |  Volume : 28  |  Issue : 1  |  Page : 113--114

Ward ventilation in a burn unit: Food for thought

Veena K Singh, Sarsij Sharma, Ansarul Haq, Neeraj Kumar 
 Department of Burns and Plastic Surgery, All India Institute of Medical Sciences, Patna, Bihar, India

Correspondence Address:
Dr. Veena K Singh
Department of Burns and Plastic Surgery, 5th Floor, OPD Block, All India Institute of Medical Sciences, Phulwarisharif, Patna - 801 505, Bihar

How to cite this article:
Singh VK, Sharma S, Haq A, Kumar N. Ward ventilation in a burn unit: Food for thought.Indian J Burns 2020;28:113-114

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Singh VK, Sharma S, Haq A, Kumar N. Ward ventilation in a burn unit: Food for thought. Indian J Burns [serial online] 2020 [cited 2021 Jul 26 ];28:113-114
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The physical design of a burn unit is an essential component of burn infection control strategy. The design should support the concept of zoning and ventilation standards in acute care areas. Although a plethora of guidelines on the ventilation of health-care facilities such as operating theaters, isolation rooms, and intensive care units have been published, guidelines regarding the ventilation of general ward spaces and patient rooms are much sparser. While designing the burn unit, much focus is on the interpretation of building codes and regulations rather than addressing fundamental issues regarding the clinical role of ward ventilation. Ward ventilation is generally specified in terms of patient comfort and cost-effectiveness and is perceived as having little impact on transmission of hospital-acquired infections.[1] However, studies have shown that ward ventilation plays an important role in controlling the spread of even if general view is that most nosocomial infections are transmitted by contact route.[2]

Ventilation strategy is driven by issues such as comfort, economy, and severity of infection. Ventilation can be natural or mechanical. Natural ventilation utilizes a 100% fresh air system having advantages of low running cost implications and avoidance of recirculation of airborne pathogens. The major disadvantage is that it cannot be used in areas with climatic extremes and in larger health-care facilities (internal spaces >6 m from a façade) where mechanical ventilation generally will be required. Mechanical ventilation system depends on air change rate, patient density, and particulate size. The greater the ventilation airflow rate, the lower the contaminant concentration level in the room air. The greater the air change rate, the shorter the average residence time of bioaerosol particles. However, only quoting air change rates takes no account of patient density. In reality, as ward occupancy levels increase (and so the number of nursing staff and visitors), bioaerosol production within the space also increases. Ventilation strategy should consider the effect of airflow direction on bioaerosol concentration generated within a ward space.

Ventilation strategy can be dilution of displacement type.[3] Dilution ventilation strategy relies on good air mixing within the room space and is achieved by supplying clean filtered air in through diffusers in the ceiling and extracting contaminated air out through grills also located in the ceiling. Displacement ventilation systems rely on the buoyancy effects caused when cool air is supplied at low level and is warmed when coming into contact with room occupants. Displacement ventilation generally reduces particle deposition on surfaces but greatly increases the number of particles suspended in the room air. The findings from studies on displacement ventilation suggest that this ventilation method may not be well suited to general ward spaces and that dilution ventilation can better control the spread of infection in general ward spaces.

To conclude, ventilation system designers should use computational fluid dynamics study and other simulation tools to evaluate the ventilation strategy in burn wards. This will help in drafting future guidelines regarding the minimum ventilation rates required in ward to prevent cross infection. For example, United States guidelines for ward ventilation state that air supplied to patients in general wards is first prefiltered (minimum efficiency reporting value [MERV]: 7, 30% dust spot efficiency) and then filtered to a MERV 14 or 15 standard (90%–95% dust spot efficiency) before delivery to the ward space. This standard of filtration ensures 85%–95% arrestance efficiency for 0.3–1.0 mm particles and 90% efficiency for 1.0 mm particles. Given that skin squama are generally 4–25 mm in size, this level of filtration ensures that the air supplied to the ward space is relatively clean, despite the fact that a large proportion of this air may be recirculated.[4]

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