key: cord-0921516-3xecvsij
authors: Tsui, Ban C.H.; Deng, Aaron; Lin, Carole; Okonski, Fabian; Pan, Stephanie
title: Droplet evacuating strategy for simulated coughing during aerosol generating procedures in COVID-19 patients
date: 2020-06-11
journal: Br J Anaesth
DOI: 10.1016/j.bja.2020.06.009
sha: d2463318003c5f33e12df2b8e6cda1bacda08ca1
doc_id: 921516
cord_uid: 3xecvsij

nan

Editor -We read with interest the correspondences by Cubillos and colleagues 1 and Yong & Chen 2 describing two different barrier enclosure designs designed to reduce the risk of aerosolized SARS-CoV-2 exposure in healthcare providers performing aerosol-generating medical procedures. Gould and colleagues 3 questioned the merit of these enclosures that increased the difficulty in managing the airway and lacked any mechanism to safely remove or clean the barrier enclosures without dispersing high concentrations of aerosolized SARS-CoV-2 virus.

Based on industrial local exhaust ventilation systems that effectively evacuate hazardous particulate matter away from workers in occupations such as surgery 4 , a similar evacuation system was recently described. 5 A commercially available, disposable adult size oxygen face tent was repurposed and connected to suction to form an aerosol evacuation system. This aerosol evacuation system showed qualitative effectiveness in removing a continuous stream of visible aerosolized saline droplets generated during simulated passive breathing. However, tracheal extubation is a different challenge for healthcare providers as coughing occurs in ~ 40% 6 of patients undergoing extubation.

We therefore sampled surrounding air particle concentrations in both simulated passive In the absence of the negative airflow tent, aerosolized saline was released into the surrounding environment as expected ( Figure) . With active suction and the face tent in the forehead position during passive breathing, the PM 2.5 remained near ambient levels. However, considerable spikes in PM 2.5 that rapidly subsided were seen during the cough scenario. These spikes may be due to the direction and speed of the airflow from coughing that overwhelmed the suction capacity at the tested suction distance away from the mouth with the negative airflow tent on the forehead. In contrast, when the negative airflow tent was placed below the chin during the cough scenario, no spikes in PM 2.5 were encountered and PM 2.5 levels remained at baseline. These results suggest the importance of minimising coughing on induction when the negative airflow tent is on the forehead. The negative airflow tent should also be positioned below the chin for extubation to capture aerosols generated by coughs more effectively.

Furthermore, the negative airflow tent on the forehead may be uncomfortable for an awake patient and at risk for manual dislodgement by a semiconscious patient.

The adaptability of negative airflow tent positioning allows for flexibility during various aerosol-generating procedures such as tracheal intubation and extubation. The negative airflow tent is comprised of a transparent soft plastic material with a behind-the-neck strap for a secure fit that allows quick adjustments to accommodate mask ventilation and intubation without hindering performance. The negative airflow tent can also be advanced inferiorly to act as an additional physical barrier to prevent "forceful droplets" from reaching the healthcare provider. 9

This evacuation system is an improved alternative to static barrier enclosures to enhance the safety of healthcare providers performing aerosol-generating procedures without compromising patient care. Personal protective equipment (PPE) should remain the main defense during the COVID-19 pandemic. 3 With the threat of a potential second wave of infection as the world reopens, 10 any additional protective measures should not be overlooked. However, such measures should not trade off patient safety or create further exposure risks to healthcare providers after use.

The authors have no conflicts to declare.

Stimulation illustration and aerosol measurement. The negative airflow face tent evacuation system was placed on an airway manikin in two positions, on the forehead and below the chin. A forceful cough was simulated using an aerosol nebulizer while simultaneously emptying a resuscitator bag. The face tent was attached to a high-efficiency smoke evacuation system which, when turned on, evacuated the visible aerosol into the face tent and away from the simulated health care provider (see video). (Top) Different negative airflow tent positions for aerosol-generating medical procedures (AGMP). (Bottom) Results of particle concentration (µg m -3 ) measurements of particulate matter with diameter size < 2.5 µm (PM 2.5 ).

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