State of the Globe: Aerosol Boxes in Intensive Care - A Boon or a Myth

The COVID-19 pandemic, originating from Wuhan, China, is the third recorded outbreak of a coronavirus which shook humanity and rapidly became a global concern. There were more than 200 million confirmed cases and more than 4.6 million people lost their lives globally between December 2019 and September 2021.^[1,2]

The very data suggests that this particular variant was not only highly contagious, spreading like wildfire but was also virulent enough to cause such a degree of catastrophe to the entire human race. The case fatality ratio varied as the disease progressed (being >20% at outset in Wuhan to almost <5% after a year in Wuhan, attributable to better understanding of the disease and improved care).^[3] Furthermore, the overall case fatality ratio varied with different countries (ranging from 2% to 10%).^[4] Thus, with such transmissibility and significantly high case fatality rate, the disease forced the authorities and the health-care systems all over the world to put forward plans to curb the spread and lessen the mortality in a hurry. Health-care workers were the frontline warriors and a WHO estimate showed that 80,000–180,000 health-care workers died because of the disease between January 2020 and May 2021.^[5]

Thus, the major challenge of the control of the pandemic was to save the frontline warriors from the deadly virus and make them secure in trying to save the patients (“save the saviours”). The entire global response team started measures to prevent aerosol spread, especially in high aerosol-generating procedures such as intubation, oral suctioning, and mask ventilation. One such out-of-the-box innovation was an “aerosol box,” designed to allow intubation with minimum contamination of the atmosphere and health-care workers. This became an instant hit as intubation was supposed to be a high-risk, aerosol-generating procedure, and the use of an aerosol box seemed an “obvious” boon. However, since its inception and multicentric use many studies unexpectedly gave contrasting results, making this hack to be rather a bittersweet pill and showing its intended benefit to be a myth.

The first documented aerosol box was designed by Dr. Lai Hsien-Yung, a Taiwanese Anesthesiologist in March 2020 and he unselfishly without patenting spread the design through Google.^[6] This led to immediate acclaim and widespread use along with cloning and variations in design with extra holes for assistants, adding surgical gloves, or silicone coverings to occlude holes, etc.^[6]

Rising COVID-19 cases, increasing hospitalizations, and intensive care unit admissions led to relative scarcity of health-care resources which was further aggravated by disease spread and ensuing morbidity and mortality among the medical fraternity. The advent of new, easily reproducible, “common sense” justifiable products was seen by one and all as a boon. In between the peak of the COVID disaster and the need of immediate control measures on May 1, 2020, the Food and Drug Administration (FDA) issued an Emergency Use Authorization for this new device – the aerosol box – and its derivatives (known as protective barrier enclosures), in the hope that these devices could provide “an extra layer of barrier protection in addition to personal protective equipment (PPE) when caring for or performing medical procedures on patients who are known or suspected to have COVID-19.”^[7]

The subsequent studies though showed reduction in contamination of predoffing PPE but they failed to estimate postdoffing exposure. In a study by Azhar et al., it was shown that any advantage given by an aerosol box can be offset by proper doffing of PPE and they further found out that the use of these boxes significantly increased intubation times and reduced intensivist’s mobility and visibility. The latter two disadvantages have been repeatedly proved in different studies from various sources.^[8]

In fact, in a review by Sorbello et al., where they analyzed more than 50 studies on the same topic, they found that the use of these barrier enclosure devices may have further disadvantages for the patient (such as the inability for an assistant to help leading to intubation failure, patient injuries, and delayed intubations leading to deteriorating hypoxia), for the intensivist (like more time to intubation causing more contamination of gloves and arms, further leading to secondary increased aerosolization during doffing, PPE breach due to apparatus, mirage-like security, etc.), and even for the support staff (bulky contaminated equipment to manage on and off the patient, difficult to disinfect and lack of sterilization standards, etc.). In fact, they went ahead and advised against using the said barrier devices or to be used only if there is no PPE protection for the intensivist.^[9]

The same findings were reiterated in another study which proved that these barrier devices increased rather than decreased the aerosol contamination of the incubator’s PPE and hence may be detrimental for the operator, giving him/her a false sense of security, thus becoming a poisoned chalice.^[10] This was followed by a narrative in the reputed journal “Anesthesia” which warned against the nonregulated use of these barrier devices.^[11]

As more and more evidence supported that aerosol boxes were not an efficient way to prevent contamination and there were many significant disadvantages adding on to them, the FDA withdrew the emergency use authorization of these boxes on August 20, 2020. As research continued, it became widely known that the use of these mechanical aerosol barrier devices led to more harmful effects than benefits to both patients and health-care workers. All these proved that the obvious advantages expected after the initial, well-intended use were actually a myth and use of such devices rather, paradoxically adds on to the already existing complexities associated with such aerosol-generating procedures.

Although in the classic form, this device’s benefits were proven to be a myth rather than a boon, it definitely led to further research and innovations on aerosol generation and their containment such as air shields, negative pressure barrier devices, use of video laryngoscopy rather than conventional laryngoscopy, clamping the tube after intubation and unclamping only after connected to the circuit, and advocating the use of muscle relaxants while intubating patients and re-emphasizing the level 3 recommendation of strict and sincere use of PPE during these procedures.