|Ahead of print publication
The aerosol box
Amjad Maniar1, Balavenkatasubramanian Jagannathan2
1 Department of Anesthesia, Axon Anesthesia Associates, People Tree Hospital, Bangalore, Karnataka, India
2 Department of Anesthesia, Ganga Hospital and Research Centre, Coimbatore, Tamil Nadu, India
|Date of Submission||22-May-2020|
|Date of Acceptance||01-Jun-2020|
|Date of Web Publication||31-Jul-2020|
People Tree Hospital, #2, Tumkur Road, Goraguntepalya, Bangalore - 560022, Karnataka
Source of Support: None, Conflict of Interest: None
Despite being scientifically unproven, aerosol boxes have quickly risen in popularity during the COVID-19 pandemic. They have been created in various shapes and sizes, as well as materials across the world. Aerosol boxes offer a transparent barrier between the patient and the healthcare personnel, during intubation and may prove to be useful when prescribed protection equipment such as masks and eyewear are unavailable. In this article, we undertake a brief overview of aerosol boxes in current practice.
Keywords: Aerosol box, COVID-19, intubation
In early 2020, the rapid spread of the Coronavirus Disease 2019 (COVID-19)pandemic put anesthesiologists at the forefront. The sudden surge of patients brought about an unanticipated shortage in protective equipment needed to shield healthcare workers (HCWs) during intubations from a highly contagious virus. Several innovations were born as an immediate requirement to tackle the problem. One of these is the aerosol box that has become popular within the anesthesia community.
The aerosol box was first described by Dr. Hsein Yung Lai from Taiwan. The device was suggested as an additional barrier of protection during intubation, where exposure of HCWs to the virus in the form of aerosols is high. Dr. Lai described the dimensions of the box and suggested the materials with which it could be created. The aerosol box is an uncomplicated device and a basic version can be built with simple materials and tools.
In the past few months, several variations and improvements of the device have appeared. Many of these variants have been built from materials ranging from simple cardboard boxes and plastic wraps to complex thermoplastics. The concept is to simply provide a physical barrier between a highly infectious patient and HCWs. Information discussed in this article will be restricted to boxes made out of hard material [Figure 1] and [Figure 2].
| Features Incorporated in Aerosol Boxes|| |
Aerosol boxes are containment units to prevent splash of droplets and aerosols while intubating. Canelli et al. simulated a forceful cough with fluorescent dye and concluded that aerosols are better contained when using a box.
After placing the patient supine, the box is placed over the patient's head. Two circular holes that have been cut into one wall of the box are used for access. The healthcare worker's hands are inserted through these holes to intubate while he/she looks through the clear box. Some boxes have additional holes (three or four) so that an assistant can help in giving cricoid pressure if required.
Other boxes have additional smaller holes made to provide oxygen or suction. The concept of creating negative pressure within the box has been proposed. In the author's experience, this is difficult to do so as it requires high levels of vacuum to be connected to the box to create a pressure differential. This is unlikely to be available in the hospital setup. Moderate levels of vacuum (up to −200 mm Hg) are likely to enable fine aerosol clearance within the box. The generation of aerosols and particle activity is complex and varied.
There have also been reports on social media forums where certain boxes have been fashioned to suction aerosols via standalone suction pumps through High Efficiency Particulate Air (HEPA) filters. These are unique designs that may remain exclusive to centers with adequate resources. Some boxes are equipped to accommodate bougies and bronchoscopes.
Currently, the ideal materials used to build these boxes have been Polymethyl methacrylate (acrylic) and Polycarbonate. Both materials are clear thermoplastics. The advantages and disadvantages of both materials are listed in the [Table 1].
Drawbacks of Using an Aerosol Box
Aerosol boxes presently are within an unchartered territory in anesthesia practice. A recent article stated that usage of such units may increase the intubation time, as well as cause damage to protective equipment worn by the anesthesiologist. The article further stated that critically ill COVID-19 patients may be unable to tolerate the increase in time to intubation.
- Currently there is no scientific evidence that using an aerosol box prevents infection by respiratory pathogens. However, it is reasonable to assume that the box may provide protection similar to that expected with a face shield or goggles. The aerosol box should not be used as a substitute to recommended protective equipment like an N95 mask, gowns etc.
- There are no standardized recommendations on the dimensions or design of the box. As a result, boxes of varying dimensions are being commercially sold. This poses a conundrum on whether the box can be used on patients with varying body habitus.
- Intubation inside a box creates limitations in space, range of movements of the hand as well as restrictions in the mobility of the patient's head. This can make the process of intubation more difficult. Use of assistive devices like bougies can be challenging to HCWs.
- The aerosol box is not an airtight unit. The ports where the hands enter have space that could, in theory allow aerosols to escape from the box. This has been addressed by allowing for gown sleeves, plastic cling wrap, or surgical gloves to seal the openings.
- Intubation is not the only aerosol-generating procedure that is performed. Suctioning, nasogastric tube placement, airway insertion, bronchoscopy, and tracheostomy can all cause exposure. Additionally, the placement of central lines or upper limb blocks can also bring the practitioner close to the patient. Most boxes are not conducive to this spectrum of interventions.
Other Potential Uses
Equal attention must be given to extubation where the possibility of aerosol generation may be far greater. Many practitioners also use the box during extubation. If the design and space permits, it can be even left undisturbed over the patient's head after intubation for the duration of the surgery or maintained in a sedated and ventilated patient in intensive care. This may be useful when frequent suctioning of secretions is required.
There is no consensus yet whether placing central lines or regional anesthesia blocks near the neck place the practitioner at risk. The use of other barriers like large impermeable sheets or hole towels may provide some degree of protection. Use of aerosol boxes for such procedures needs evaluation. If ergonomics permit, such devices may also assume a role during tracheostomy of COVID-19 patients.
After usage, it is assumed that these boxes may be contaminated and require stringent disinfection. There are several hospital-grade disinfection agents like Sodium hypochlorite, Hydrogen peroxide and Isopropyl alcohol which can be immediately sprayed on the inner and outer surfaces of the box in close vicinity to the usage area. A second round of spray can be done to ensure that decontamination is complete. The boxes can then be washed.
Acrylic and Polycarbonate both have a melting point of about 160°C. The material, therefore, is compatible with autoclaving, but this may not hold for the adhesion methods used in the construction of the box, which may weaken, melt, or bubble. Uneven expansion of the glued edges may also distort the shape of the box. Ethylene oxide sterilization and low-temperature plasma sterilization are other options which are dependent on the size of the box whether it will fit into these sterilization systems.
Aggressive wiping with abrasive textiles will create scratches on the surface which will cause the material to eventually lose its optical clarity. It is preferred to use a microfiber cloth to dry the surface after disinfection. It is imperative to check with the manufacturer on disinfection methods as well as the compatibility of the agents used.
| Discussion|| |
There is still a long way to go before these boxes become an accepted norm. Intubation is expected to be slightly more challenging and there appears to be a brief learning curve. Anesthesiology teams must be trained to follow a particular sequence or process for its usage and theatre staff must also be educated about its usage. Careful planning of the intubation is imperative. If the airway appears difficult, it is better to follow a carefully set plan rather than attempt to change the process midway. Intubations are best finished in the first attempt, and to do so, the correct equipment must be used and an experienced operator must be involved.
It remains to be seen if aerosol boxes continue to be used as a barrier against infective pathogens even after the pandemic fades. For this, the boxes will have to be optimized to suit our exact needs and will need to survive the test of robust clinical studies.
Financial support and sponsorship
Conflicts of interest
Both authors have served as consultants in the design and manufacture of aerosol boxes in their own individual capacity. The information in the article is a result of their experience in this process. Images depicted in this article include boxes that have been created by the authors.
| References|| |
Tseng J-Y, Lai H-Y. Protecting against COVID-19 aerosol infection during intubation. J Chin Med Assoc 2020;83:582.
Canelli R, Connor CW, Gonzalez M, Nozari A, Ortega R. Barrier enclosure during endotracheal intubation. N
Engl J Med 2020;382:1957-8.
Begley JL, Lavery KE, Nickson CP, Brewster DJ. The aerosol box for intubation in COVID-19 patients: An in-situ
simulation crossover study. Anaesthesia 2020 doi: 10.1111/anae. 15115.
[Figure 1], [Figure 2]