key: cord-0777255-1wcva9dz
authors: Bryant, Jason; Tobias, Joseph D.
title: Enclosure with augmented airflow to decrease risk of exposure to aerosolized pathogens including coronavirus during endotracheal intubation. Can the reduction in aerosolized particles be quantified?
date: 2020-05-28
journal: Paediatr Anaesth
DOI: 10.1111/pan.13934
sha: 7cdf3046696aaf8bd48811d450f20599a4250171
doc_id: 777255
cord_uid: 1wcva9dz

As the pandemic of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2 or COVID‐19) has impacted hospital routines in recent weeks, recommendations to reduce health care worker infections are being developed. We report preliminary experience with the efficacy of an enclosure with augmented airflow to decrease the risk of exposure to aerosolized pathogens during airway management including endotracheal intubation. A particle generator was used to test the efficacy of the reduction of aerosolized particles by measuring their concentration within the enclosure and in the environment. No reductionin the concentration of aerosolized particles was noted with the enclosure flap open, whether the interior suction was on or off. However, with the enclosure closed and no augmented air flow (suction off), the particle concentration decreased to 1.2% of baseline. The concentration decreased even further, to 0.8% of baseline with the enclosure closed with augmented airflow (suction on). Aerosolized particulate contamination in the operating room can be decreased using a clear plastic enclosure with minimal openings and augmented airflow. This may serve to decrease the exposure of healthcare providers to aerosolized pathogens.

The recent coronavirus pandemic has increased awareness of the need for techniques to limit transmission of infectious agents during anesthetic care. 1 Healthcare workers are at particular risk during procedures with exposure to aerosolized particulate matter, including tracheal intubation. 2 The primary modes of viral transmission included contact with contaminated environmental surfaces and aerosolization. 3 During anesthetic care, the potential for aerosol transmission is high during airway manipulation including bag-valve-mask ventilation, direct laryngoscopy, endotracheal intubation, and tracheal extubation. [4] [5] [6] Although the use of personal protective equipment (PPE) reduces the transmission of infectious agents from a patient to the healthcare provider, other techniques to limit aerosolization and the use of barriers to protect against contamination of infectious agents into the environment may also be helpful. [7] [8] [9] However, none of these maneuvers have been quantitatively tested for a reduction in aerosolized particles. To reduce aerosolized particles in the operating room during endotracheal intubation and tracheal extubation, we propose using a clear plastic enclosure with limited openings and augmented airflow evacuation. We describe a novel device, made from routinely available equipment and items in the operating room and demonstrate its efficacy in limiting aerosolization during simulated bag-valvemask ventilation and airway management.

Measurement of aerosolized particle concentration did not involve human subjects and therefore according to hospital guidelines for clinical research, Institutional Review Board approval was not necessary.A stainless steel tube was used to hold a plastic enclosure with limited openings and augmented airflow evacuation away from the patient's face and torso to allow adequate room for bag-valve-mask ventilation, endotracheal intubation, and tracheal extubation. (Figure 1 

The results during the six conditions in 1000 particles per cubic centimeter are shown in table 1 . The greatest reduction in particles was with the enclosure closed using augmented airflow with suction which resulted in a decrease to 0.8% of baseline. The highest concentrations were noted when the flap was open. With the front flap open, the equilibrium of particles inside and outside the tent was the same with or without augmented airflow evacuation

Endotracheal intubation hasbeen associated with the highest risk of exposureto aerosolized particles and the risk of health care worker contamination given the proximity of the health care provider to the patient's airway. 1 With routinely available and relatively inexpensive equipment, we were able to fashion an enclosure which may decrease a healthcare worker's exposure to aerosolized particulate matter and pathogens during airway management.Thisreport also provides a description of how to use a standard particle generator to evaluate barrier devices. This technique can be used in future studies to evaluate the effectiveness of such devices.

We acknowledge that this simulation study conducted in a laboratory has limitations as it The high concentration of particles in the enclosure is due to the small volume of air in the enclosure and the high rate of particle generation. The usual ambient concentration used for fit testing of respirators is between 15 to 25 x 10 3 and the concentration in the enclosure was over ten Accepted Article times this number. 10 This high concentration was noted both inside and outside the enclosure when the flap was open. This differs from the clinical scenario, as after the patient's trachea is intubated and connected to the anesthesia circuit, there would be a cessation of particles released from the patient and the concentration would decline over time.

The time required for the ambient concentration of potential pathogens to decrease to an acceptable level after endotracheal intubation may vary based on air circulation within the enclosure. However, the front to the enclosure can be kept closed during and after airway management to allow the concentration of aerosolized particles to decrease thereby allowing surgery to proceed immediately. Care also would be necessary when removing the enclosure to not contaminate oneselfand or the room with the contained aerosolized particle or secretions that may have been deposited on the inside of the enclosure. Additional studies are needed to measure particle concentration during the act of endotracheal intubation as well as after removal of the enclosure. It may also be useful to compare this technique with other protective measures such as endotracheal intubation in a negative pressure room, or in rooms with laminar flow and high air movement (>60 air changes/hour). A specific protocol for removing the enclosure would be helpful in decreasing the risk of exposure of health care workers. This would require further study regarding the time required for areduction in the aerosolized particles after airway procedures.

As the device does not remove all risk of contact with aerosolized pathogens, use of this enclosure does not allow for decreased vigilance or changes in recommendations for use personal protective equipment and negative pressure or laminar high air movement rooms. However,it may decrease the number of aerosolized particles that anesthesia providers and other operating room staff are exposed to during endotracheal intubation and extubation. Furthermore, the plastic drape will provide additional protection during coughing and forceful expulsion of particles but care must be taken to decrease coughing and forceful breathing upon extubation. 11 This study did not study the efficacy of this device in transmission of aerosolized pathogens or changes in clinical safety for healthcare workers. Further investigations in the clinical setting are warranted to address these limitations. 

This article is protected by copyright. All rights reserved Six conditions:

Severe acute respiratory syndrome and coronavirus

Aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review

Perioperative COVID-19 defense, An evidence-based approach for optimization of infection control and operating room management

Lessons learned: protection of healthcare workers from infectious disease risks

A review of the risks and disease transmission associated with aerosol generating medical procedures

Protecting health care workers from SARS and other respiratory pathogens: a review of the infection control literature

Anaesthesia and SARS

Clear plastic drapes may be effective at limiting aerosolization and droplet spray during extubation: implications for COVID-19

Barrier enclosure during endotracheal intubation

Assessment of respirator fit capability test criteria for full-facepiece air-purifying respirators

Medications to reduce emergence coughing after general anaesthesia with tracheal intubation: a systematic review and network meta-analysis

Accepted Article 1. Enclosure closed, no augmented air flow (suction off) 2. Enclosure closed, augmented airflow (suction on) 3. Enclosure closed with arms inserted

Enclosure closed with arms inserted, augmented airflow (suction on) 5. Enclosure flap facing the provider open, no augmented air flow (suction off) 6. Enclosure flap facing the provider open

This article is protected by copyright. All rights reserved