'Protective' box a potential infection risk to healthcare workers

The ‘protective’ equipment that could be exposing healthcare workers to COVID-19.

An Australian study has shown that aerosol boxes designed to protect healthcare workers from COVID-19 can actually increase their exposure to airborne particles that carry the virus.

Aerosol-generating procedures are thought to increase healthcare providers’ risk of infection. Tracheal intubation is considered one of the highest-risk aerosol-generating procedures due to direct exposure to the airway and potential patient coughing during induction. Frontline anaesthetic, emergency and intensive care teams are most at risk. This situation has created a race to manufacture aerosol-containment devices, including improvised protection strategies for use during tracheal intubation.

Aerosol boxes have been promoted by multiple worldwide news organisations in print, on television, online and across social media as a quick and simple solution to help protect frontline workers during high-risk procedures, but have been produced outside normal regulatory frameworks without being clinically tested or validated for effectiveness and safety.

The authors of the study published in Anaesthesia include Drs Peter Chan, Joanna Simpson and colleagues from the Intensive Care and Anaesthesia Specialists at Eastern Health, Melbourne, Victoria, Australia.

“The consequences of promotion of such untested devices include either a false sense of security using these devices, or paradoxical increase in healthcare workers exposure to COVID-19,” the authors wrote.

The study was conducted in a self-contained intensive care unit room at Box Hill Hospital, Melbourne, using seven adult volunteers (four male, three female), who took turns in random order acting as the patient or the doctor (the person performing the intubation).

The study simulated exposure of the doctor to airborne particles sized 0.3–5.0 µm using five aerosol-containment methods (aerosol box; sealed box with and without suction; vertical drape; and horizontal drape) compared with no intervention. As each of the seven volunteers did all six trials (the five interventions plus no intervention), the study generated 42 sets of results.

The study tested aerosol-containment strategies, including vertical and horizontal draping.

To simulate aerosolisation, the patient volunteer held a bottle of fluid just under their mouth, and coughed every 30 seconds. Over five minutes, particle detection devices were used to count different-sized particles and assess particle spread.

Compared with no device use, the aerosol box showed an increase in airborne particle exposure of all sizes over five minutes. Assuming that COVID-19 particles act in the same way as the fluid used in this simulation, the results of this study suggest that this aerosol box was increasing exposure to COVID-19 particles, in some cases by a factor of five times or more.

“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,” the authors said.

“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.

“The race to generate sustainable equipment to protect healthcare workers during intubation procedures in patients with suspected or proven COVID-19, particularly in settings where PPE 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.

“Evidence for the safety and efficacy of these devices is lacking.”

The researchers concluded that the devices tested offered 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.”

Dr Chan added, “If this box were sold as a product, and therefore 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.”

Main image caption: Testing the aerosol box method.