We look at the latest evidence which shows how ventilation can have a positive impact on the control of pathogens in healthcare environments
Ventilation is becoming an increasingly-crucial tool to enable hospitals to protect patients and staff from the spread of potentially-harmful pathogens
Infection prevention and control (IPC) is vital in healthcare settings, and never more so than during the recent COVID-19 pandemic.
Covering everything from personal protective equipment (PPE) and training, to signposting, cleaning regimes, and decontamination; effective IPC is critical to ensuring the health of staff, visitors and patients.
And, since the outbreak of Coronavirus, hospitals are, on the whole, approaching IPC in five key ways:
But many of these approaches depend on human factors – people remembering to wear PPE, to change it after each patient contact, and to wear the correct type of PPE for any given task, for example.
This makes the third category – engineering controls – absolutely key as engineering controls do not rely on human activity in the same way in order to be effective.
And, of these, ventilation and airflow, is increasingly important.
Since Coronavirus was first identified earlier this year, research has pointed to the most-likely form of transmission being via aerosol-based routes and droplets carried in exhaled breath.
Hospitals need to consider where they are ventilating and what impact this has on a particular space
Speaking last month as part of the virtual Healthcare Estates Conference, Professor Cath Noakes from the School of Civil Engineering at the University of Leeds revealed that, while there is very little data from real-world medical settings, evidence from community settings shows the highest risk is probably within indoor environments and over short ranges.
As well as droplets settling on surfaces, and the virus transmitting directly between people during physical contact; there is also evidence of airborne transmission of COVID-19, particularly in poorly-ventilated spaces.
And, considering people are at their most contagious when they are largely asymptomatic, it is becoming increasingly important to consider ventilation of these spaces.
“We knew very little and have learnt a lot very quickly,” said Professor Noakes.
Current research has pointed to the risk being greater over shorter distances (less than 2m) and when face to face.
Singing or talking loudly, or when exercising, for example, have also been found to increase the risk of transmission significantly and are more likely to be associated with airborne transmission.
And studies show that, unlike tuberculosis, which may be exhaled by an infectious person in a similar way to COVID-19; Coronavirus does not need to get into a person’s lungs, instead infecting people via receptors in the nose and mouth.
“When airborne, aerosol particles in the air need drag force to keep them up and gravity to bring them down,” said Professor Noakes.
“But air velocity in a room is known to impact on this and various-sized particles can remain in the air for a significant amount of time, often travelling quite far from their original source.”
If a space is well ventilated you can’t completely contain the virus, but the ventilation will dilute the virus and the risks are technically lower
This is where ventilation can have a dramatic impact.
“If a space is well ventilated you can’t completely contain the virus, but the ventilation will dilute the virus and the risks are technically lower,” said Professor Noakes.
Professor Cath Noakes is leading research into ventilation, indoor air quality and infection control in the built environment
This is reflected in the Federation of European Heating, Ventilation and Air Conditioning Association’s recently-updated REHVA COVID-19 Guidance Document, which cites ventilation as the principal engineering control to help control infection, thus giving further weight to the vital role ventilation plays in the COVID-19 response effort.
It states that in hospitals with an optimal 12 air changes per hour (ACH) ventilation rate, aerosol transmission is mostly eliminated. But, in poorly-ventilated spaces, it may be dominant.
Professor Noakes adds: “We are seeing that when the ventilation rate is, say, 1-3 litres per second, per person, in a room, the risks really shoot up; but once you get to five, or ideally 10 l/s/person, it controls it in the majority of cases.”
But, she warned, that in a hospital context it is not the obvious patient wards that will be most affected as these tend to be better ventilated.
Instead, estates and facilities managers and IPC teams need to also consider smaller, more-relaxed environments such as staff restrooms, waiting areas, corridors and treatment rooms.
“Hospitals need to consider where they are ventilating and what impact this has on a particular space,” Professor Noakes said.
Ventilation systems are complex solutions and their impact depends on the type of technology and, critically, how it is deployed.
Growing in popularity is germicidal UV, which works by destroying the DNA of micro-organisms with lamps that emit UV-C irradiation.
This technology comes in many forms: from small portable consumer devices which can be ordered over the internet; to installed versions, which are part of the building services and are more sophisticated.
It’s about using our engineering skills and experience rather than just buying the latest thing we are presented with
But their impact depends on the number of UV lamps, their intensity, and their location, as well as other factors.
There are also Upper Room UV systems which are installed above head height.
These are harder to install effectively, but the results of research into their use shows they may offer greater ventilation while using less energy than other methods.
In addition, UV robots are available for decontamination, but these cannot be used in occupied rooms, so are less attractive to facilities managers in the current climate.
“It is well worth considering UV as a solution in spaces with lower ventilation rates” said Professor Noakes.
“But it has got to be the right size and rate for the room.
“And that is where we need the technical performance engineering community to help us.”
She adds: “I’m a bit cautious as there is a vast array of technology available and some are safe, but some are inefficient and some are dangerous and there is currently little guidance and regulation on their use.
“It’s about using our engineering skills and experience rather than just buying the latest thing we are presented with.”
In recent months researchers from University Hospitals of Leicester NHS Trust in the UK and Turku University of Applied Sciences in Finland have also examined the risk faced by healthcare workers treating patients with viruses and how different forms of ventilation can protect them.
Our study suggests that some forms of ventilation, particularly local downward ventilation, can be efficient in managing the risks
Under different ventilation, distance, and PPE settings, laboratory experiments were carried out using a breathing thermal manequin as the patient and computer simulation to assess contaminated and supply airflow.
Commissioned by the Institution of Occupational Safety and Health (IOSH), the study found that, if the healthcare worker is leaning over a patient lying on a bed in an isolation room – for example to check blood pressure, pulse rate, or temperature – the air the patient breathes out flows directly towards them.
In a room with mixing ventilation, this means their exposure level rises by up to six times, significantly increasing their chance of infection.
But one form of ventilation, called local downward ventilation, can reduce this exposure to one third of the exposure found with a general mixing ventilation solution, the researchers found.
However, as Professor Noakes warned, consideration has to be given into how this is designed and where it is placed to minimise discomfort for patients, for example from draughts.
The report adds that the position of the exhaust is important as this can capture air only from a short distance and can’t control room airflows generally.
In this study, the most-effective exhaust positions were in the wall behind the patient bed or in the lighting panel above and behind the patient.
Mary Ogungbeje, occupational safety and health research manager at IOSH, said: “This important research highlights the risks that healthcare workers face when they are treating patients infected with airborne viruses, as well as how these risks can be managed.
“Many people working in healthcare have to come into contact with patients who are infected with contagious viruses, so it is crucial that effective systems are in place to protect them.
“Our study suggests that some forms of ventilation, particularly local downward ventilation, can be efficient in managing the risks, together with the use of personal protective equipment.
“We hope, therefore, that further research will be conducted to build on these findings and help protect many healthcare workers from being exposed to viruses and potentially becoming ill.”
Dr Julian Tang, a consultant virologist at the University Hospitals of Leicester NHS Trust and an honorary associate professor at the University of Leicester, adds: “The most-effective form of control is the ventilation engineering level of control.
The research has shown that there are certain types of ventilation that can benefit healthcare workers better without being detrimental to the patient
“That means that we have to try and improve the amount of clean air in the environment compared to the amount of contaminated air.
“The research has shown that there are certain types of ventilation – beyond just different speed and volume of ventilation – that can benefit healthcare workers better without being detrimental to the patient.
“And this report has tried to highlight those particular designs to show that if you are going to build a new hospital with new isolation rooms, these sorts of design are what you might want to follow.
“Obviously it’s difficult to modify existing isolation rooms to these new findings, and some existing facilities will be easier to modify than others; but if you know what the optimal ventilation design and strategy is, you can work towards it.”
Speaking to BBH Paul Lucas, managing director of Artic, which provides HVAC maintenance services to NHS trusts across the country, said: “In order to keep ventilated spaces as clean as possible, systems should be set to full fresh air provision, which will act to remove stale and potentially-virus-laden air with cleaner external air.
Hospitals have a genuine need for HVAC that cannot be ignored, especially since the rise in global warming is increasing the temperatures of summer months and the pandemic has raised a need for cleaner air in acute hospital environments
“If this is coupled with higher-than-normal air-change rates, fresh air ventilation to meet with health and safety regulations is maintained while ensuring, as much as possible, that the internal environment extracts any potentially-contaminated air before it can cause any harm.”
Artic predicts an increase in the use of AI-driven HVAC systems which can help to improve performance and reduce energy use
And he said working environments are set to change in light of the pandemic.
“Hospitals have a genuine need for HVAC that cannot be ignored, especially since the rise in global warming is increasing the temperatures of summer months and the pandemic has raised a need for cleaner air in acute hospital environments,” he added.
“Air conditioning provides comfort to patients, improving recovery times and leading to a shorter stay in hospital.
“And overheating is a serious issue within hospitals which would be made exponentially worse without air conditioning.
“HVAC systems help to maintain a germ-free environment that contributes to the wellbeing of patients and helps prevent the spread of diseases.”
But as medical equipment is often sensitive to temperature and humidity levels, HVAC systems are needed that allow staff to modify temperatures as needed.
And that can be addressed with modern AI-driven solutions.
Lucas said: “NHS facilities managers should measure and monitor the effectiveness of their heating and cooling systems.
AI-driven HVAC systems are integrated with smart sensors that monitor the conditions in the building and make real-time adjustments to ensure that indoor environment quality is maintained efficiently
“In some cases, Artificial Intelligence (AI) is being integrated into HVAC systems to improve their performance and reduce their impact on the environment.
“AI-driven HVAC systems are integrated with smart sensors that monitor the conditions in the building and make real-time adjustments to ensure that indoor environment quality is maintained efficiently.
“It would be extremely challenging for a facilities manager to monitor building conditions, take in and assess all the received data, and then to make these operational adjustment decisions.
“It would take a team of engineers working 24/7 to achieve what AI can do in minutes.”