In an interesting session opening the second day of Healthcare Estates 2022, four scientists and academics discussed hospital ventilation – including some of the key learnings for hospital engineers in the wake of COVID-19. They focused especially on improving infection resilience in the hospital environment, and tackling poorly ventilated spaces. HEJ editor, Jonathan Baillie, reports on an address by one of the four – Professor Cath Noakes of the University of Leeds – one of the UK’s leading experts on healthcare ventilation.
The ‘Engineering’-themed session began with Pete Sellars welcoming IHEEM’s new President, Alison Ryan, who had only taken over the Presidency from Paul Fenton at the previous day’s IHEEM AGM, to the stage. The first female President in IHEEM’s 79-year history, Alison Ryan briefly (see also separate report, pages 35- 38) shared some of her thoughts on her key priorities and goals in the role over the next two years, before chairing a thoughtprovoking conference session
She explained: “This session is focused on how we can improve infection resilience in the hospital environment, and tackle poorly ventilated spaces. It links well with current NHSE / NHSI plans to produce new guidance for the sector on healthcare refurbishment schemes.” She continued: “We have four key speakers in all – two professors and two doctors – here, with us, Professor Cath Noakes from the University of Leeds, two online speakers – Professor Peter Guthrie and Dr Sean Fitzgerald, both from the University of Cambridge, and, again in person here, Dr. Elaine CloutmanGreen, from Great Ormond Street Hospital NHS Foundation Trust.”
Chartered Mechanical Engineer with background in fluid dynamics
Welcoming the first of the four, Professor Cath Noakes, Alison Ryan explained that the Professor is a Chartered Mechanical Engineer with a background in fluid dynamics. She said: “Cath Noakes is Professor of Environmental Engineering for Buildings in the School of Civil Engineering at the University of Leeds, and leads research into ventilation, indoor air quality, and infection control in the built environment. During the pandemic she co-chaired the Environment and Modelling sub-group of SAGE, focusing on the science underpinning environmental transmission of COVID.”
Prof. Noakes began her presentation – titled ‘Enabling infection-resilient healthcare environments’ – by focusing on some of the key recent learnings on airborne transmission of bacteria and viruses in the healthcare environment, and some potential strategies for reducing such transmission, and thus the associated risks to patients, staff, and visitors. She said: “There’s nothing new in this; the environment always matters, it matters for infection control. Go back to Florence Nightingale, and she worked out – without all our modern techniques available to her, of course – that if you space your beds out, provide sufficient space, heat the room adequately, have good high ceilings, natural light, opening windows, and cross-ventilation – then you’ll reduce infection rates on your wards.
Air quality matters for many reasons
“Move forward 150 years, and we now know much more. Air quality matters for the things we see most obviously – COVID has highlighted respiratory infections – but we also know it matters for a whole raft of hospital-acquired infections, whether this applies to vulnerable patients exposed to opportunistic pathogens, such as people with cystic fibrosis, or whether it’s MRSA, C. difficile, or norovirus. All these have been associated with aerosol dissemination and environmental contamination.” Among the many sources which could put pathogens into a hospital’s air were the patients, staff, and visitors, but also the environment. Prof. Noakes said: “We know things get re-suspended when you make a bed; we know that with water systems, there’s an air / water interface. We get aerosolisation from showers, and dispersion from drains, and then, in some circumstances – particularly with vulnerable patients – the outdoor air brings pathogens in.”
Guidance and standards
Turning to standards on ventilation and air quality, Prof. Noakes noted that the new HTM 03-01: Specialised Ventilation for Healthcare Premises, had introduced stronger requirements around inspection and audit, and promoted the establishment of Ventilation Safety Groups in hospitals. She said: “We know, however, that we have a challenge. Most of our hospitals are not brand new, we have a fairly limited resource, and must therefore adapt the buildings we’ve got.” She continued: “We know we have specified ventilation for some healthcare spaces. This table (she slowed a slide featuring a table from HTM 03-01, parts A and B, 2021 update) suggests what these ventilation rates should be for a ward – six air changes / hour, but how many wards actually comply? I suspect it’s pretty hit and miss. Most of our standards also focus on the spaces traditionally considered as risky, but what about our waiting rooms, staff rooms, and corridors, and all those other spaces people interact within in a hospital?
A ‘double challenge’
“Alison (Ryan) has already touched on the Net Zero challenge,” Prof. Noakes continued, “and this is where we have a double challenge – because we know we must reduce our energy use, and that buildings account for about 10% of the total national health carbon footprint. Healthcare buildings make a sizeable contribution to our overall emissions, and ventilation is one of the key elements that comes under scrutiny.” There was then ‘the challenge of COVID’. Prof. Noakes said: “COVID changed our thinking. Suddenly, instead of airborne risk being confined to being a very distinct thing, it’s everywhere.
Many of the audience would, she believed, have been involved in creating isolation rooms, surge spaces, and cohort spaces, and in trying to convert operating theatres, during the pandemic. She said: “Our new problem is that instead of transmission being most likely from seriously ill people, the biggest transmission risk seems to be from those at the beginning of their infection. We also have risks in spaces like staff rooms, which we previously thought of as safe.” The pandemic had also highlighted issues around ‘design gaps’. The Professor elaborated. “For example, does a positive pressure operating theatre pose a risk for people outside it? We don’t know some of this.”
Showing a graph from the pandemic’s ‘first wave’, she said she wanted to highlight the proportion of hospital-acquired COVID cases as a percentage of all such cases. This had increased, and was now running at 25 to 30%, ‘if not higher’. “Compare that with any other hospital-acquired infection,” she said, “and it’s a shockingly high number.”
Conventional thinking on infection control
Reiterating that COVID had ‘changed how we think about things’, Prof. Noakes said: “Go back to conventional infection control thinking, and we have the idea that disease is transmitted by droplets. You’re close to somebody, it’s about big things that come out of people’s mouths; you don’t think about ventilation mattering, and airborne transmission was always thought of as something rare, containable, and ‘specialist’. For example, with tuberculosis we would put patients in an isolation room.” COVID had changed all that, because suddenly everything is airborne. “In fact,” Prof. Noakes explained, “the droplets are not all big ones. They are aerosols that stay in the air, and are simply a bit more concentrated when you are close to somebody.”
Not only could they be transported quite readily, but transmission could ‘happen everywhere’. ‘Thinking about the complexity of this’, Prof. Noakes said that – ‘as with nearly every other respiratory virus’ – COVID-19 had a human source. Expanding on this, she said: “We breathe out droplets, most of which are aerosols of different sizes. They evaporate, and move through the air; to what extent depends on the individual’s activity and location. There’s a wide-ranging distribution of particles carrying the virus. They get transported into the air, and deposit onto surfaces, but the significance of this depends on different pathogens.
Inhaling droplets
“Then,” she continued, “people can get exposed. Get close to somebody, and you inhale more of those short-range aerosols. We can get large droplets that can have direct deposition, but these are not that likely to hit you. We then have deposition onto surfaces, and people potentially touching things.” How important this was depended both on the environment, and the duration of exposure. Inhalation exposure was, the speaker stressed, key, and pathogens can be transported more readily in air. The Professor noted: “It’s complex. We’ve got fluid dynamics, chemistry, and microbiology to consider here, plus – really importantly – human characteristics, because while we can do all the physics to the nth degree, people then come along and mess it all up. We all breathe out particles when we are not even thinking about it. Some people, of course, breathe out more than others. We don’t know why. We do know, however, that we breathe out more when we are louder – when we sing, shout, or cough.” There were, however, ‘big ranges’ in the number of particles exhaled and inhaled by different individuals, which made interpreting the associated data difficult.
Showing a graph of a log scale, she said: “The graph basically tells us that the majority of particles we breathe out are actually really small – typically under 10 microns in diameter. The smallest humanvisible particle is about 40 microns, so we can’t actually see much of what we breathe out – what we traditionally term droplets. Some of these very small particles contain virus, which is considerably harder to measure.”
US measuring system
The speaker explained that a group of US scientists had a special instrument which could measure viral RNA if an individual put their head into a ‘cone’ and, for example, breathed, or sang into it. She said: “Surprisingly, the scientists with this device typically see up to five times more of the viral RNA in the smallest aerosols than in the bigger droplets. This tells us the small things matter, and the same evidence comes for ‘flu. You also see big variations, although people wearing a mask do emit less into the environment – fairly simple physics really.”
Particles containing, for example, a virus, sometimes deposited on surfaces. Prof. Noakes said: “The graph on the left is comparing what might end up on people’s hands from touching surfaces in a single room versus a multi-bed room, where in fact you do you get more on your hands. Although not ‘rocket science’, it highlights that anything dispersed into the air is more readily dispersed onto surfaces close to other patients, and that while you might not think that a surface is contaminated, it will be.”
The Professor next showed a slide of a study focusing on a COVID-19 outbreak in Korea. This clearly demonstrated the significance of movement of air between spaces. Here a bathroom ventilation system was not functioning correctly – it was under positive rather than negative pressure, and thus pushing air from the bathroom into a central zone and ward spaces
Prevalence of natural ventilation
“So,” she said, “this is a complex picture. Lots of our hospitals are naturally ventilated, and we know they are hugely variable; it depends on what you do, and the wind.” Showing another chart demonstrating ‘Variation in natural ventilation’, she said: “So on the left, the red bars are when you’ve got the windows closed, and the dark blue bars when they are open; this is a Nightingale ward. Unsurprisingly,” she added, “this is a ‘leaky ward’ – you get a much higher exposure when you close the windows; about four times the amount when you close the windows to when they are open.”
Another chart showed measurements from a study of naturally ventilated wards in Peru. This highlighted the massive potential variability with natural ventilation, depending on the wind direction, whether the wind is blowing, and any temperature difference. Prof. Noakes said: “So, we know our buildings, and that we have a raft of different risk factors – environmental risk factors influence transmission, but so do human factors. While we can’t control them all, our buildings have a major impact in setting out the conditions, and influencing our interactions. The building design determines whether spaces are crowded, any pinch points, and whether people can distance a little bit more.
Human behaviour’s influence
“Given that buildings can’t manage all the behaviour, it’s key to recognise that while we can take this to a point with engineering, we then need the human behaviour factors and the rest of the infection and prevention control measures integrated together.” This led on to ‘some bigger questions’, which the two subsequent online speakers, Peter Guthrie and Shaun Fitzgerald, would discuss in more detail.
She explained to delegates: “We have carried out a big piece of work with the Royal Academy of Engineering over the past two years, following a request from the Government’s Chief Scientific Adviser, Sir Patrick Vallance, which drove questions following from the pandemic on how we can make our buildings more resilient.” The work had, she explained, resulted in the publication of detailed report, Infection Resilient Environments: Buildings that keep us healthy and safe. While the healthcare sector already knew more about the subject than many others, the team involved had wanted to look across all environments. Prof. Noakes said: “We reported in spring 2021 on immediate actions, because we were then still very much at the height of the pandemic. Phase 2, on which we reported in June 2022, focused much more on the longerterm strategic challenges with buildings, and those immediate things all focused on guidance, understanding, and incentives to improve buildings.”
Workshops held
The personnel involved had held many workshops, and asked participants: ‘What does infection resilience mean?’ The speaker elaborated: “What are the impacts if you have a lack of resilience? It isn’t just about just spread of infection. There is a whole raft of other factors that stem from it, around, for example, how people change their transport modes, whether they are off sick, lose confidence, and whether people’s productivity suffers.” There was thus a broad spectrum of factors to consider.
“Thinking about buildings,” Prof. Noakes continued, “and we have many competing priorities. One of the biggest tensions is health versus sustainability. However, what about other factors – such as outdoor air pollution, comfort, and security? The challenge with opening windows in most hospitals is that their opening is restricted for security and safety reasons.” For many buildings, the speaker noted, ‘even in healthcare’ – such as GP practices and dental surgeries, infection control had never been at the heart of the design; it had simply been an ‘add-on’.
Wide-ranging report
Against this backdrop, Prof. Noakes encouraged delegates to read the Infection Resilient Environments: Buildings that keep us healthy and safe report, which focuses on a wide range of factors around strategy, construction in use and retrofit, standards, regulation, commissioning, and leadership. Healthcare was ‘in some senses, ahead of the game here’, with applicable standards, regulations, and processes, to embed infection control within the engineering side. “However,” she asked, “are there issues around commissioning? Do we actually know – when somebody tells you their ward will deliver six air changes per hour, that it will do so? When did you last check?” While there was a raft of technologies to draw on to efficiently and safely ventilate healthcare spaces, how many of them met standards, and how confident could buyers be that they would perform ‘as sold’?
The speaker continued: “We also need to consider how we communicate – not just within the engineering community, but with the clinical frontline, who need to actually deliver some of this.” This took the presentation on to ‘How much do we know about our environments? The Professor said the answer was ‘probably a lot less than we think.’ Her key message here was that ‘every action we take has a consequence’. For example, ventilating all the required spaces ‘brilliantly’ not only had a consequence in terms of risk / benefit for different diseases, but putting everybody in a single room might address one problem, but bring a different one – in terms of some patients feeling isolated, as well as difficulties for patient observation.
Where does the knowledge lie?
She continued: “And who knows most about the environment? The designers? The people who run your hospital? Also, do your frontline clinical team understand how their environment works – because they’re the people delivering the care?” ‘Short term’, the Professor said there was ‘a need to think a bit more about better understanding what we do’. Elaborating, she said: “How do our systems perform? Where are those weak points – technical and behavioural? A naturally ventilated space, for instance, relies on somebody to open the window. We need to consider where the dependencies are – if you change one thing, does it upset something else somewhere else?”
‘Beyond infection control’, healthcare planners, designers, and architects, needed to consider ‘how we tie in noise, comfort, and energy, etc’. “So,” Prof. Noakes said, “we need to think about how we maintain balanced systems, ensure that they operate properly, and, for example, that filters in a ventilation system are changed. What about particular guidance? Have you, for example, ever given guidance on how to open windows? It sounds simple, but we just assume that people know how and when to do it. Equally, when do you use the air-conditioning? Is it a good idea or not? How do we change things? Can we take temporary capacities, what are suitable local upgrades, and what can we add in? We may not be able to build a new building, but we could perhaps add in air cleaning and disinfection strategies? How do you select the best though?”
Modelling at Addenbrooke’s
Healthcare engineers already had good knowledge on simple things, such as that by changing the diffuser design, you got a better air mix in the room, and flushed out pathogens. Here Prof. Noakes mentioned some modelling focusing on ‘growing evidence around air cleaning technology’. Addenbrooke’s Hospital in Cambridge was, for instance, currently undertaking a major trial on this using combined HEPA and UV filters, to see if staff see a reduction in bioburden, and would hopefully be reporting on infection rates soon. Prof. Noakes said: “There is already some precedent data from Singapore, which shows that installing such filters can reduce Aspergillus infections.” Another ventilation technology well recognised by healthcare engineers was upper room UV, which employs UV light to disinfect pathogens in the environment. The Professor said: “It’s not suitable everywhere, and needs careful consideration in designing it in in the right place. I don’t know, currently, of any UK hospital which uses it, but it’s a wellestablished technology that works well.”
Use of Far-UV
There were also ‘some new technologies on the horizon’. She elaborated: “We’ve been working on some research on the use of Far-UV, which is much safer than conventional UV, and can have a spectacular impact on pathogens, but is not some ‘magic’ new technology. There is a whole raft of considerations around safety and practical implications etc. We should, though, be looking at where these new technologies are.”
Longer term, Professor Noakes said there was an imperative to think about how we embed ventilation and infection prevention and control together. She said: “It’s not a case of ‘Estates’ does ventilation, and ‘IPC’, everything else. We need learning between the two disciplines, and we need the importance of the air in healthcare facilities to be recognised; some still seem to see it by as a ‘niche’ thing. We also need to balance that risk across different aspects of patient care. I think there are lots of questions around technology. There’s some brilliant innovation out there, but how much do we need? How much ventilation and air cleaning are needed in different spaces? A really big question is whether natural ventilation is still appropriate – a really tough one? From an energy perspective,” she added, “it’s very hit and miss, while from the perspective of ensuring that the environment is appropriate, the same conundrum applies. Where should we use it, and how do we make sure it’s done well?
Challenges around Net Zero
“Equally,” the Professor said, “if we’re going to put in other technologies, where should we install them, should we apply them long term, and how do we ensure they are used correctly?” The speaker said she felt there was ‘a real challenge’ over infection control and Net Zero. She said: “This is probably the biggest challenge we’ve got now, because there’s a real risk that we hunker down this winter, seal everything up, and focus solely on trying not to spend money on energy. My worry is that this will have a massive set of health consequences, not just in hospitals, but also in homes, workplaces, and schools. And then,” Prof. Noakes said, ‘How do we learn the lessons?’ We don’t have resilient environments; we can’t just go back to where we were before. We have to move forward and be more resilient, because the next pandemic might be even worse, and there almost certainly will be another.
Potential for things to ‘go spectacularly wrong’
“We also know that when things go wrong in a healthcare setting, they can go spectacularly wrong,” the Professor said. “I think you probably all know of the hospitals in Scotland where there are official inquiries at the moment. It costs lives, and vast amounts of money.”
Coming to her presentation’s close, Professor Noakes said she wished to thank the many people she had worked with, adding: “Remember, there’s no magic bullet, and watch for the snake oil out there, because there is some. Finally,” she added, “for anybody who loves ventilation, we are going to launch World Ventilation Day on 8 November. So, for that day, plan your activities, run something online, tweet about it, put it on your social media, and use it as a day to celebrate everything that’s great about ventilation.” This brought the Professor’s presentation to a close, and she handed back to Pete Sellars to introduce the next speaker, Professor Peter Guthrie of the University of Cambridge.