International healthcare ventilation strategies

One of the challenges for every country – which is handled differently across the globe – is the requirement for ventilation. On the face of it, there should be no disagreement between countries as to appropriate ventilation strategies as we all face the same airborne infections, and movement of air molecules in Chicago is much the same as in Addis Ababa. So, why the differing approaches?

Firstly, we know that ventilation matters in the control of airborne infectious disease (as well as allergens, contaminants, aerosolised particles, and droplets). We also know that filtration matters, as does pressure relationships, airflow distribution, air quantities, and temperature and humidity control. What we do not know is how much of any of these things matter, and in what combinations they matter. This lack of basic science necessarily throws us into the area of conjecture and hypothesis, and, as a result, other factors begin to matter. Secondly, healthcare ventilation

requirements generally attempt to address at least three sets of constraints at the same time, and in relation to each other. Healthcare ventilation standards intend

to provide for the comfort of patients, staff, and visitors (itself a daunting task given the generally inert, lightly clothed patients and the active, fully dressed care- givers). These ventilation standards must also prevent dangerous (or irritating or allergic) airborne substances that could affect anybody entering a space, whether these substances come from within or from outside the facility. Finally, these standards must provide

heightened protection where patients are unusually vulnerable, generally through compromised immune systems (burn units, oncology wards) or through bodily openings (surgery, procedure). Not only does each of these requirements have blurred boundaries, but when taken together, their uncertainties multiply. Regulations, however, by their very nature, tend to be black and white and prescriptive, which requires a one-size fits all solution. In a world where one size never fits all, and one size inevitably is too much for some situations and not enough for others, these kinds of standards engender waste. This matters, because facilities around the world are striving towards a poorly-


defined ‘global standard’ which all too often starts with the presumption that more is better. This paper argues that ventilation standards around the world are generally a function of local clinical operations, historical accident, and relative level of societal resource. What is required is for the world’s hospital engineers to work together to learn what matters under what conditions, and at what costs. To this end the IFHE is launching a programme to collect data that will help to better determine what factors really matter, and how much of them in what combination matter enough.

Chain of infection Infection preventionists think in terms of a chain of infection. For infection to occur, the following must be present: l Infectious agent (sufficient virulence)

l Reservoir (sufficient amplification)

l Portal of exit l Transmission (in sufficient quantity for sufficient time)

l Portal of entry l Susceptible host.

For ventilation systems in healthcare to be able to have an impact they may either affect: l Reservoir – the ability of the pathogen to amplify to sufficient quantity (temperature, humidity)

l Exit Portal – the ability of pathogens or other dangerous particles to enter a space, or to leave their reservoir into the air stream (filtration, ventilation, air changes); and

l Transmission – the ability of the pathogen to cross an air

space from the exit portal to the entry portal of a susceptible host.

Ventilation systems are only one intervention that can affect these factors. Others include room cleaning (to eliminate pathogens from ‘reservoirs’ that can be borne into the air), facility maintenance (to prevent the introduction of new reservoirs of pathogens and to ensure effectiveness of available engineered systems), community (drawing community boundaries appropriately) level of pathogens of and other dangerous particles, and operational procedures within the facility that segregate infectious and vulnerable people. Each of these factors, and many others will have an impact on the other factors, and on the overall risk of infection.

Walt Vernon Walt Vernon is the CEO of Mazzetti.

He has worked in the area of healthcare sustainability for decades, including the development of the Green Guide for Healthcare, the American Hospital

Association’s Sustainability Roadmap, and the World Health Organization’s book, Health in the Green Economy.

Alex Arnold

Alex Arnold is a Mechanical and Plumbing Engineer at Mazzetti, he has four years of design, construction, and

commissioning experience and is a professional engineer (PE) in California.

Christopher Lash

Christopher Lash is a Mechanical Engineer at Mazzetti, designing and managing the integration of MEP systems

to support a wide range of industries including Healthcare facilities. He has experience in design and construction of air and water systems for healthcare facilities and is a professional engineer (PE) in California and Colorado.


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