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Tracheal intubation and extubation may not produce enough aerosols to warrant being designated as procedures associated with high risk for transmission of SARS-CoV-2, researchers say.
The researchers’ sampling of particle sizes in operating rooms calls into question the extreme infection protocols that have been mandated in many hospitals since the outbreak of COVID-19.
“Our findings are quite striking in that we don’t see aerosol generated to a significant level,” said Tony Pickering, MBChB, PhD, a professor of neuroscience and anestheisa at the University of Bristol in the United Kingdom.
The study was published in Anaesthesia.
Experts, however, are split on whether the data are sufficient to change safety protocols.
Aerosolized Droplets Monitored
Droplets greater than 20 µm in diameter appear to be the primary route by which SARS-CoV-2 is transmitted, but there is some evidence that smaller particles may also play a role. Aerosolized particles, which these authors say are “typically considered to be <20 µm in diameter and particularly those of < 5 µm,” might travel long distances, linger in the air, and potentially transit the length of the respiratory tract.
The World Health Organization and many national public health authorities have recommended that physicians who perform aerosol-generating procedures wear airborne-precaution personal protection equipment (PPE), including a fitted face piece (FFP3 or N95), a long-sleeved, fluid-resistant gown, gloves, and eye protection.
Many jurisdictions around the world, including in the United Kingdom and the United States, have designated tracheal intubation and extubation as aerosol-generating procedures.
Earlier retrospective and cohort studies of SARS-CoV-1 suggested that healthcare workers who perform intubation had an increased risk for infection from that virus. However, these data fall short of closing the case, Pickering and colleagues argue.
To investigate aerosolized particle generation during these procedures, the researchers used an optical particle sizer (TSI Inc) that could detect particles from 300 nm to 10 μm in diameter by laser optical scattering.
They sampled the air in an operating room with ultraclean, laminar flow ventilation, high-efficiency particular air filtration, and an air supply rate of 1200 m3/sec.
With this ventilation system, monitoring detected a background particle count of 0.4 particles per liter of air when the operating room was empty, and 3.4 particles per liter when the operating room was in use but no aerosol-generating procedure was underway.
The researchers then connected a sampling funnel through a tube to the optical particle sizer and positioned the funnel half a meter from the patients’ heads. They then carried out 19 intubations and 14 extubations. They found that a volitional cough in this setting sprayed an average of 732 (SD, 418) particles per liter of air.
Tracheal intubation, including face‐mask ventilation, produced almost no aerosolized particles (an average concentration of 1.4; SD, 1.4) per liter. The difference in concentration compared to a cough was highly significant (P < .0001).
Tracheal extubation produced an average detectable aerosol concentration of 21 particles per liter