personal protective equipment (PPE) (4); however, more effective containment measures such as administrative and engineering controls (EC), have been surprisingly overlooked.
This omission can be secondary to the difficulty of setting negative-pressure rooms in due time, and at Hospital Universitario San Ignacio (Bogota, Colombia) in affiliation with Pontificia Universidad Javeriana, we faced this difficulty, and therefore we aimed to redesign the original "Aerosol box" (5) into a negative-pressure microenvironment ( Table 1) in an effort to produce an interim EC measure during the crisis.
Isolation: a clear plastic (1m x 1.5m) is hermetically attached through synthetic gutters. This plastic has a "t-shirt like" opening for the head of the patient to access the box and is resealable to decrease particle dispersion when removing the box. Six circular ports for arm access, each with a diameter of 15 cm, provide versatility for using this box in other settings where the arrangements of ventilators connections vary; moreover, when the box is not in use, sliding doors keep these ports sealed. Additionally, each port has external flanges to firmly attach disposable long-arm veterinary gloves and maintain the hermetic seal when working inside. There is an additional port at the bottom, with a small sliding door for the anaesthetic breathing circuit, that can be sealed when not in use.
Ventilation: A suction tube (Pressure: -150 mmHg) is taped inside, exhausting air to a closed canister with a hypochlorite solution located outside of the box. In compliance with NIOSH, this suction removes the hazard at the source and increases air exchange within the sealed acrylic box, decreasing the load of airborne contaminants even while removing the box.
Fluorescein Test: Using concentrated (orange) nebulized fluorescein (Bio Glow ™), we tested for leaks and aerosol dispersion within the box and with diluted liquid fluorescein (green), we tested for droplets spread under Cobalt-blue light. The clearance of the nebulized solution and evidence of orange particles within the suction tube attest for clearance of particles through negative pressure. Both tests demonstrated visual containment for aerosols and droplets (Figure 1 d, e, f).
Simulation scenarios: We performed multiple high fidelity simulated tracheal intubations using conventional laryngoscope (#3 Macintosh blade) and videolaryngoscope (King Vision ™ and Storz ™), we also performed several simulated extubations and scenarios requiring endotracheal tube disconnections from the anaesthesia breathing circuit (e.g. transport to ICU, head or neck surgery requiring removal of the box) to test for actions, such as the use of clamps for endotracheal tube or faster ways of resealing the head-opening to decrease aerosolization of enclosed particles when removing the box. We found simulation to be the cornerstone for anesthesiologists and other staff involved in airway management to accept and become more comfortable with the device, from these experiences we developed and improved checklists to ensure availability of tools within the aerosol box to reduce the number of times ports are opened during airway manipulation. Even though this was a challenging process due to time constraints and a feeling of changing rules, it was and still is, presented as an alternative for airway management; therefore the criteria of the specialist is not at stakes.
Surgical Scenarios. Once the simulation stage was completed, we started using the aerosol box with asymptomatic patients admitted for elective surgery and eventually for suspected and confirmed COVID-19 patients scheduled for emergent surgery.
Before entering the Operating Room we explain its use to the patient, and if agreed, we proceed to use it; when considered appropriate, the patient can be sedated to improve the tolerance and comfort within the box. We have found paramount to have adequate and continuous communication with the patient and the airway team during these circumstances to ensure the success and safety of the procedure.
We have been able to successfully perform endotracheal intubations with conventional laryngoscope and videolaryngoscopes, rescue face-mask ventilation, awake intubations for fullstomach and awake extubations, without a significant increase of time during these manoeuvres.
The surgical site determines the feasibility of leaving the box during the procedure; when the surgical procedure is below the upper thorax, such as during appendectomies, laparoscopic cholecystectomies, femoral or tibial osteosynthesis; it is feasible to leave the box in place during the surgery and avoid disconnecting the breathing circuit during the removal of the box. For head and neck surgeries, the use of the box as a barrier is balanced with the need for disconnecting the circuit during its removal.
Acknowledging that extubation presents a less controlled scenario for anesthesiologists, with a higher risk of exposing other staff and us to aerosols (lack of neuromuscular relaxation, cough reflex, spontaneous ventilation), we favour its use during extubation and during the subsequent recovery time, especially for symptomatic patients. We have found it useful during this time, because we have the possibility of suctioning airway secretions, deliver bronchodilators via a nebulizer and allow high-flow oxygen therapy for a short time while maintaining a closed environment within the box. Although we have not come across reintubation scenarios, they remain a possibility within the box, because the laryngoscope or videolaryngoscope, the face mask, the suction tube, and the wire remain inside the box; a quick opening of one port to introduce the new endotracheal tube can be foreseen as a flaw.
To this date it has not been used in patients with anticipated difficult airway, however using a videolaringoscope as described earlier is a possibility as well as other equipment required for intubation (e.g., laryngeal mask, intubation bougie, stylet, among others).
Other scenarios. These include intubations of suspected or confirmed COVID-19 patients in the intensive care unit (ICU), providing CPR for patients lying supine, and as a barrier for awake patients during regional anaesthesia. Recently, some pediatric ENT surgeons have started using it during high-risk AGP such as tonsillectomies, and while changing tracheostomy tubes, however, we acknowledge that they could benefit from other modifications in size and shape to fit their needs better during the procedure.
As we described earlier, this device was modified to provide an alternative for safer airway management during this COVID-19 crisis, and its use is up to the anesthesiologist's preference; the portability of this box allows its rapid removal in a non-anticipated difficult airway or in any situation that presents as a potential safety threat to the patient.
Use of fiberbronchoscope: from simulation scenarios, we observed that the box does not provide easy access for the fiberbronchoscope. Therefore, it has a limited value in case of an anticipated difficult airway that requires the use of fiberbronchoscope. A modification to the upper side of the box would be necessary to fit this purpose.
Time for preparing the box for an emergent surgery or intubation: It takes about 5 to 7 minutes to assemble it; therefore, we have a stock of boxes sealed and ready to be used.
Waste generation: Although the box is reusable, the other materials used to achieve isolation (e.g. gloves and plastic) are disposed of after their use, which is not environmentally friendly.
Nurses are in charge of these disposals and require minimal but highly relevant training in the removable of the plastics to avoid the risk of cross-infection. In the simulation lab, we teach our team how to assemble and dispose of the plastics adequately.
Changing the position of the patient: Several surgeries need to change the position of the patient.
Although some anesthesiologists have managed to maintain the box in place while changing the position of the patient (mainly lateral recumbent in thoracic surgery), it is a challenging manoeuvre. In some cases, it needs to be removed.
our local context, enhancing the barrier between healthcare workers and hazards such as droplets and aerosols (6), with a keen focus on limiting aerosols dispersion. We believed that this new device overcomes some limitations mentioned by other authors (7, 8) , and highlights the importance of allowing training time for staff involved with airway management. We also acknowledge that further studies are needed to evaluate which combination of PPE and EC provides the best control for minimizing contamination and infectious risks for HCW. This essential finding can assist in determining barriers and PPE to be used when reestablishing Operating Room workflow in many institutions. 