Aerosol boxes used to protect health workers during Covid-19 intubation have been found to “increase” exposure to airborne particles that carry the virus, a new study by specialists in Australia has found.
Using certain aerosol boxes (pictured above), of a similar type to those manufactured and used in UK hospitals, substantially increased airborne particle contamination compared with all other devices and when none was used.
“Evidence for the safety and efficacy of these devices is lacking”
Study authors explained that “spikes” of airborne particles were seen and coincided with patient coughing. They, therefore, believe the particles were “escaping from the arm access holes” in the boxes.
The research was carried out by Dr Peter Chan, Dr Joanna Simpson and colleagues, intensive care and anaesthesia specialists at Eastern Health in Melbourne. The full study was published in the journal Anaesthesia.
The authors flagged that the significant danger posed to frontline health workers exposed to coronavirus had created a “race” to manufacture aerosol containment devices, including improvised protection strategies and devices for use during tracheal intubation.
They warned that aerosol boxes had been promoted as a quick and simple solution to protecting frontline workers and also an example of private industries stepping up production to support staff – but warned that evidence to support such devices was “lacking”.
“The race to generate sustainable equipment to protect healthcare workers during tracheal intubation procedures in patients with suspected or proven Covid-19, particularly in settings where [personal protective equipment] supply is limited, has flooded the scientific community and social media with a variety of novel devices meant to contain potentially infectious aerosols produced by patients,” the study said.
“Evidence for the safety and efficacy of these devices is lacking,” it added.
“We were surprised to find airborne particle contamination of the doctor increased substantially”
According to study authors, there had also been increasing concerns from the medical community about the devices.
As part of their work, the researchers partnered with Ascent Vision Technologies, a Melbourne-based engineering company, to test the effectiveness of varying methods of aerosol containment, including the so-called aerosol box.
Carried out in a self-contained intensive care unit room at Box Hill Hospital in Melbourne, the study included four male and three female volunteers who took turns acting as the patient or the health professional performing the intubation.
The study simulated exposure of the health professional to airborne particles sized 0.3-5.0 microns, using five different aerosol containment methods, including, aerosol boxes, sealed box with and without suction, vertical drape, and horizontal drape, and also compared these with no intervention device.
To simulate aerosolisation, the patient volunteer held a bottle of fluid under their mouth and coughed every 30 seconds.
Over five minutes, detection devices were used to count different sized particles and assess particle spread and in total, 42 sets of results were generated.
Findings from the research showed that, compared with no device use, the aerosol box showed an increase in airborne particle exposure of all sizes over five minutes.
Based on the assumption that Covid-19 particles acted in the same way as the fluid used in the study, authors said the results suggest the aerosol box was in fact increasing exposure to virus particles to the health professional, and in some cases by a factor of five times or more.
“The use of any aerosol containment device has been eliminated from our intubation protocols”
Commenting on their findings, the authors said: “We were surprised to find airborne particle contamination of the doctor increased substantially using the aerosol box compared with all other devices and with no device use.
“Spikes of airborne particles were clearly seen, coinciding with patient coughing. We believe that these represent particles escaping from the arm access holes in the aerosol box,” they said.
The authors said they had demonstrated that “devices such as the aerosol box we tested – which is typical of designs used worldwide – confer minimal to no benefit in containing aerosols during an aerosol-generating procedure and may increase rather than decrease airborne particle exposure”.
“The use of any aerosol containment device has been eliminated from our intubation protocols until their safety can be properly established,” they added.
Meanwhile, Dr Chan went as far as to say that if such devices were sold and regulated, “it would likely need to be immediately recalled due to a potential infection risk to the healthcare worker”.
“Unfortunately, because these devices have been donated and are not regulated in any way, healthcare workers might be continuing to increase their exposure to Covid-19 while thinking they are protecting themselves,” he added.