Aerosol containment devices may increase exposure to COVID-19

Novel devices developed to prevent aerosol exposure during the intubation of coronavirus disease 2019 (COVID-19) patients appear to bear no significant benefit to laryngoscopists, according to a new study. On the contrary, the use of such devices may even increase exposure.

“[N]ovel devices intended to protect the laryngoscopist require objective testing to ensure they are fit for purpose and do not result in increased airborne particle exposure,” researchers said.

The present study employed an in-situ simulation model to evaluate the degree exposure of the intubation technician to airborne particles sizes 0.3–5.0 µm in size, compared across five containment devices: aerosol box, sealed box with and without suction, vertical drapes, and horizontal drapes. Seven healthy volunteers (aged >18 years; 4 males) participated in the study, along with a volunteer laryngoscopist.

A one-way, Kruskal-Wallis analysis of variance revealed that over a 5-minute interval, there was a significant difference in the median airborne particle counts across the six trial scenarios, including the use of five containment devices and a no-device control. [Anaesthesia 2020;doi:10.1111/anae.15188]

Posthoc comparisons were then performed. Using the sealed box with active suction led to a significant drop in the counts of 0.3-, 0.5-, 1.0-, and 2.5-µm particles at all time periods after 30 seconds (p=0.003). No such effect was found for particles 5.0 µm in size. In comparison, sealed boxes without suction only reduced the counts of 2.5-µm particles relative to no device use, and only at the 300-second (p=0.004) and 360-second (p=0.007) time points.

Both the horizontal and vertical drapes presented no significant benefit or disadvantage to the no-device control across all particle sizes and time points.

Notably, using the aerosol box led to a significant spike the median particle count at 300 seconds. This was reported for particles of sizes 1 µm (p=0.002), 2.5 µm (p=0.008), and 5.0 µm (p=0.002). The researchers also noticed that aerosolized particles escaped from the arms of the aerosol box with every patient cough, leading to particle counts that were consistently higher than in all other devices tested.

“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 researchers said.

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

The present study has important limitations to consider, the researchers pointed out. These include its small size, in-situ simulation design, and the observed variability of particle sizes across the different devices. “This suggests that the level of laryngoscopist exposure is unpredictable and likely influenced by the aerosol containment device set-up and the volume, negative pressure generated from suction and frequency of patient coughing.”

“Further large-scale studies are needed to examine aerosol containment devices in this context, as well as others, such as tracheal extubation,” they said. “The use of any aerosol containment device has been eliminated from our intubation protocols until their safety can be properly established.”