PPE in conjunction with HEPA filters offers best protection: study

Full PPE, involving a fit-tested N95 mask, in conjunction with a HEPA filtration system is said to offer health workers in a hospital setting the best protection against virus aerosol exposure, according to a new study by Monash University.

The study used a live virus aerosol model that highlighted the standard PPE strategy that was developed with droplet transmission in mind is not geared to prevent aerosol transmission and may offer insufficient protection in a hospital environment.

The experimental study, led by Dr Simon Joosten, from the Monash University School of Clinical Sciences, used a nebuliser to pump bacteriophage PhiX174 into a sealed clinical room for 40 minutes testing three scenarios:

• A healthcare worker in full PPE — surgical mask, gloves, gown, face shield.
• A healthcare worker in full PPE — but with a fit-tested N95 mask.
• A healthcare worker in full PPE — with a fit-tested N95 mask and a HEPA filter system.
   

Virus exposure was then captured via skin swabs applied to the face, nostrils, forearms, neck and forehead.

Studying the interaction of virus aerosol and PPE, the research found significant infiltration in scenario one (over 200 virus particles detected in nostril), slightly less infiltration in scenario two (between 25 and 200 virus particles detected in nostrils) and almost complete prevention in scenario three (zero to 1 virus particle detected).

While the research is currently under peer review, the findings, when presented to hospital management at Monash Health and Epworth Health, resulted in immediate impact with Dr Joosten involved in helping both health services deploy HEPA filter technology on hospital wards caring for COVID-19 patients.

Dr Joosten said the findings demonstrate that standard PPE alone does not protect against infectious aerosol at high load.

“Among the most important protective measures are vaccination, personal protective equipment and ventilation. Here we show that personal protective equipment and ventilation interact to provide added protective benefit against virus-laden aerosol.”

Monash Health’s Chief Medical Officer, Professor Anjali Dhulia, said Dr Joosten’s previously published and most recent HEPA filter data research contributed to the deployment of HEPA filter technology at Monash Health.

Dr Lachlan Henderson, Group Chief Executive, Epworth HealthCare, said keeping patients, staff and doctors safe has been the priority throughout the pandemic.

“We have also regularly reviewed airflows at each of our hospitals. Dr Joosten’s virus aerosol research was critical in guiding our infection control team to deploy HEPA filter technology at Epworth as an added layer of protection,” Dr Henderson said.

Dr Joosten was recently awarded a $50,000 grant from the Epworth Medical Foundation and will advise on airflow management in the upgraded cancer ward at Epworth Freemasons.

Image credit: ©stock.adobe.com/au/amazing studio