New Research Shows Alarming Risk of COVID-19 From Aerosols to Healthcare Workers

Analysis shows that coughing, deep breathing, and screaming produce more than 100 times greater amounts of aerosols than oxygen therapies, potentially increasing the risk for front-line workers wearing only surgical masks.

New research published in Anesthesia (a journal of the Association of Anesthetists) disputes the guideline that special aerosol precautions are only necessary when using oxygen therapies for COVID-19 patients, and raises concerns about the safety of staff and patients in hospital wards, if so. not protected against infectious aerosols.

The study was designed to investigate whether oxygen therapies used for patients with severe COVID-19 produce large amounts of tiny respiratory particles called aerosols that can transmit viruses and bypass routine precautions used in hospital wards. The study found that these oxygen therapies do not produce excessive amounts of aerosols and, in fact, reduce aerosols, suggesting that these therapies could be made widely available.

The study also found that breathing activities such as coughing and deep breathing are an important source of aerosol particles, and this could potentially expose health workers to an increased risk of infection. Importantly, the authors clarify that in this study 10 healthy volunteers were used to produce the measured aerosols, not patients infected with SARS-CoV-2.

The study authors, including Dr. Nick Wilson (Royal Infirmary of Edinburgh, NHS Lothian, Scotland), Prof Euan Tovey (University of Sydney), Prof Guy Marks (University of New South Wales, Sydney) and Prof Tim Cook (Royal United Hospitals Bath NHS Foundation Trust, Bath, UK) say their findings may partially explain why staff working in wards wearing only surgical masks have about two to three times more infections and hospitalizations than those who work in the ICU, where the more complete is personal protective equipment such as N95 / FFP3 breathing masks are used.

The researchers built a new room with extremely clean air that contained 10 healthy volunteers. They breathed into a large cone and the researchers collected the particles that were exhaled and used a specialized machine called an ‘optical particle counter’ to measure the number and size of the particles. In contrast to previous studies, the researchers collected almost all exhaled particles and this allowed a clear comparison between the amounts of aerosols generated by respiratory activities and oxygen therapies.

First, the volunteers performed respiratory activities, including breathing, talking, screaming, coughing, and exercising, designed to mimic the respiratory activity of patients with respiratory infections such as COVID-19. This showed that increased respiratory activity (such as coughing and deep breathing), which is common in patients with COVID-19, increases the aerosol by more than 100 times.

The volunteers then repeated the experiments while receiving oxygen therapies commonly used in hospital patients with severe COVID-19, first the delivery of high-flow oxygen into the nose (high-flow nasal oxygen) and then oxygen delivered under pressure through a close-fitting face mask. (non-invasive ventilation). Aerosol counts were not increased and during increased respiratory activities and were even decreased.

There is much debate about the role of respiratory particles in guidelines to prevent transmission of COVID-19. Larger particles (greater than 1 / 200th of a millimeter) are traditionally called ‘droplets’ and are expected to travel only 1-2 meters from an infected patient before falling to the ground. Aerosols are smaller particles (less than 1 / 200th of a millimeter) and float in the air for extended periods, spread further, can accumulate in poorly ventilated areas, can be inhaled deep into the lungs and bypass loose-fitting face masks. Many current guidelines are designed to protect against droplets and infection spread by aerosols is only considered a risk if caused by medical therapies. In this new study, the volunteers produced up to 100 times more aerosol particles with activities such as coughing than during the oxygen therapy treatment.

This challenges current guidelines that state that medical personnel caring for patients with COVID-19 who are coughing and have breathing difficulties only need PPE that protects against the larger droplets. “Drop Protection” includes surgical masks but does not prevent aerosol particles from passing around the edges of the masks and being inhaled. N95 / FFP3 respirators that are tight-fitting and filter better, block more aerosols, but guidelines currently only recommend them for personnel caring for patients receiving advanced oxygen therapies.

Dr. Nick Wilson, lead author of the study, explains, “More than 90% of the total number of particles produced by both activities and therapies were the smaller aerosols. Aerosols are important because they can travel long distances in the air, avoid loose-fitting surgical face masks, and can be inhaled deep into the lungs. This raises concerns about the safety of people around patients with COVID-19. “

Prof Euan Tovey says: “The coughing and labored breathing that is common in patients with COVID-19 produces far more droplets and aerosols than are produced by patients treated with oxygen therapies. Surgical face masks do not provide adequate protection against aerosols and personnel safety can only be increased by more widespread use of specialized close-fitting respirators (N95 or FFP3 masks) and increased indoor ventilation. Since the respiratory therapies have not significantly increased aerosols, these treatments should be made widely available to patients with COVID-19 who need them. “

Prof Guy Marks says: “The study also has consequences outside hospitals. The generation of both droplets and especially aerosols through daily respiratory activities reinforces the importance of maintaining social distance, excellent ventilation in buildings and transportation, being outdoors where possible and the use of effective masks to protect against both virus and virus inhalation. to reduce the amount of virus. they disperse on the exhale. “

Prof Tim Cook concludes, “Our findings strongly support the re-evaluation of guidelines to better protect hospital personnel, patients and all those on the front lines dealing with people who have or are suspected of having COVID-19. “

Reference: “The effect of respiratory activity, non-invasive respiratory support, and face masks on aerosol generation and its relevance to COVID-19” by NM Wilson, GB Marks, A. Eckhardt, AM Clarke, FP Young, FL Garden, W. Stewart, TM Cook and ER Tovey, Mar 30, 2021, Anesthesia.
DOI: 10.1111 / anae.15475