Fit-tested PPE and HEPA filtration are ‘best protection’ for healthcare workers, study finds


New research from Australia adds further evidence that more needs to be done to protect healthcare workers from the spread of aerosols.

HEPA filtration combined with a tested N95 mask and full PPE has been shown to provide nearly complete prevention of nasal contamination.

Despite triage efforts, health care facilities, including GPs and hospitals, have been sites of COVID-19 transmission.

In an effort to keep staff and patients safe, a number of voice GPs have advocated for greater support around access to personal protective equipment (PPE) and, more recently, guidance on the use of air filtration systems.

Now there is new research to support their calls.

Led by Monash University researchers, the results confirm that full PPE – including a fit-tested N95 mask – used in conjunction with a HEPA filtration system, provides the best protection for healthcare workers against exposure to viral aerosols.

The experimental study, which has not yet been peer-reviewed, used a nebulizer to pump bacteriophage PhiX174 into a sealed clinical room for 40 minutes, testing three scenarios:

  1. A medical professional in full PPE (surgical mask, gloves, gown and face shield)
  2. Healthcare worker in full PPE with tested N95 mask
  3. Healthcare worker in full PPE with tested N95 mask and HEPA filter system in room

In the first scenario, the results showed significant infiltration, with more than 200 virus particles detected in the nostrils, while the addition of a fit-tested N95 mask reduced infiltration slightly, with between 25 and 200 particles. viruses detected in the nostrils.

However, the third scenario, including both a tested N95 mask and a HEPA filter system that cleaned the room volume 13 times per hour, was found to provide nearly complete prevention, with 0 to 1 virus particles detected.

Lead author Dr Simon Joosten from the Monash University School of Clinical Sciences said the results clearly highlight that the standard PPE strategy is not suitable for preventing aerosol transmission.

“Air filtration and PPE work together,” he said. newsGP. “In this controlled setting, either used in isolation always results in significant contamination of the healthcare worker.

“It really gets to the heart of one of the lessons we’ve all learned from the pandemic, which is that you can’t really solve this problem with just one approach. PPE and air filtration are the two key pillars of this layered approach, and vaccination is obviously the third.

Although the results have not yet been released, senior management at Monash Health and Epworth Health took immediate action on the data by purchasing a number of HEPA filters for hospital wards to reduce risk.

“I haven’t done research that had such an impact so quickly; it’s been really rewarding and kinda crazy, to be honest,” Dr. Joosten said.

And while the research was presented for hospital settings, he says the results are “directly translatable” to general practice, with the study scenario based on a closed clinical room setup with no natural ventilation.

“So if you think of a room like a GP cabin that doesn’t have a window, maybe an air conditioner, that from a ventilation point of view is the worst case scenario,” Dr. Joosten.

“But even in the worst-case scenario with incredibly high viral loads, our data shows that the strategy of an air filter and adequate PPE can protect the healthcare worker.”

Queensland GP Dr Maria Boulton, who has been advocating for GPs and practice staff to have access to tested N95 masks for almost two years, said newsGP she was not surprised by the results.

“From the start of the pandemic, it made sense to me to provide healthcare workers with the best protection possible – protection against airborne particles,” said Dr Boulton.

“Thousands of coal miners are tested each year in New South Wales and Queensland and provided with N95 masks which allow them to be used when their work requires it.

“I’m disappointed we’re this far into the pandemic and GPs and GP staff can’t say the same…even though we’re on the front line and have cared for patients throughout the pandemic.”

One factor that has added to the challenge is the delay in recognizing the role of aerosol spread in the transmission of COVID-19, with the role only officially recognized by the Australian Infection Control Expert Group (ICEG ) in October 2020 and by the World Health Organization (WHO) in May 2021.

Dr Joosten says this has been a ‘painful lesson’ from the pandemic in Australia, which he attributes in large part to historical misconceptions about aerosol transmission of respiratory diseases dating back to the 19th century that have persisted to the present day. .

“In Australia, we spend 90% of our time indoors, but there are currently no regulatory controls over indoor air quality,” he said.

“It’s quite amazing and I think the regulatory gap probably stems from the same historical misconceptions and misunderstandings that respiratory disease is transmitted through stale indoor air.

‘[It’s] really set us back.

“If we had been very clear from the start that this is getting through the air we breathe, I think we could have acted more decisively and there would be less confusion about what is needed to protect. the people.”


In the absence of government support, some GPs have sourced their own HEPA filters. (Picture: provided)

In her own practice, Dr Boulton has taken steps to ensure all staff are tested and has invested in HEPA filters. She says that with COVID-19 transmission now widespread, the need to protect staff is even more pressing.

“We need to keep our GP staff working so we can continue caring for COVID patients in the community, care for the increasing number of patients with non-COVID presentations, and continue to deploy COVID vaccines,” he said. she declared.

But with most practices having no choice but to source privately, Dr Boulton says practices face the added challenge of competing with governments and wholesalers who have greater buying power, which which was a “long and costly” challenge.

“One of the N95 mask models that fits most of our staff is now impossible to find, [and] many of our suppliers are unable to deliver orders placed in December and have refunded us,” she said.

“That’s why I advocated for the government to use its logistics and purchasing power to resource general practice and facilitate fit testing. The same predictable problem plays out [out] with access to rapid antigen tests.

Dr. Joosten witnessed it first hand. Just a week after presenting the results of its research to Victoria’s Department of Health, the state government invested $190 million in the purchase of HEPA filters to equip classrooms.

Although PPE and filtration systems come at a cost, Dr. Joosten notes that these are much more practical options compared to rebuilding infrastructure around ventilation.

Dr Boulton agrees, but says practices need the support of all levels of government to be able to protect not just their staff, but also vulnerable patients.

“We need a long-term solution that will secure stocks of PPE for general Australian practice,” she said.

“GPs and GP staff are on the front line and continue to mobilize. Where would we be without them?’

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