key: cord-0016228-f3y47az4
authors: Kao, Chia-Lung; Hong, Ming-Yuan; Chi, Chih-Hsien
title: Highlighting the Concepts of Local Exhaust Ventilation in Negative-Pressure Rooms
date: 2021-03-22
journal: Ann Emerg Med
DOI: 10.1016/j.annemergmed.2020.12.002
sha: 46706eef7bab7e41cdccc363a4d62b1112e298c6
doc_id: 16228
cord_uid: f3y47az4

nan

To the Editor: We think the letter by Braude and Femling 1 pointed out that negative-pressure rooms are not absolutely safe for health care professionals. The authors briefly mention that negative pressure and air exchanges will not make the room much safer owing to aerosolized particles that are generated continuously.

Among patients with suspected or confirmed coronavirus disease 2019, some may develop respiratory distress and critical illness, and aerosol-generating procedures, including intubation or chest compression, may be needed immediately. Negative-pressure isolation rooms are recommended and should be used for these patients, who may be undergoing aerosol-generating procedures. 2 Under such procedures, personal protective equipment is essential to health care providers. 1 Local exhaust ventilation can aid in capturing aerosolized particles at the source rapidly as they are produced. Such ventilation has been reported to effectively reduce the concentration of local harmful substances and has been used in industry widely. 3 Clinical studies also reveal that the concentration of surgical smoke can be reduced by local exhaust ventilation. 4 Local exhaust ventilation, a component of a negativepressure room that allows gas extraction, reduces physician exposure to airborne particles by capturing the contagious droplets or aerosol at the source. The negativepressure room is mainly modulated by a gas inlet and outlet to create a negative-pressure environment. At present, the negative-pressure room mainly focuses on the ventilation function. Making good use of local exhaust ventilation can greatly reduce the local concentration and reduce the risk of airborne transmission while patients are being treated.

We emphasize the importance of local exhaust ventilation in a negative-pressure room. In our simulation, we used a nebulizer to generate aerosolized particles from a manikin in a negative-pressure room. We found that if the patient's head was placed close to the air outlet, the number of aerosolized particles directly captured by the air outlet was increased, which resulted in the rapid removal of aerosolized particles (Figure 1 , Video E1, available online at http://www.annemergmed.com). Under such circumstances, the gas extraction system captures the particles from the source and therefore reduces the concentration of aerosolized particles to which health care workers are exposed. Although it is not possible to completely remove the aerosol, and the health care providers still need to wear protective equipment, we believe that local exhaust ventilation can greatly reduce the risk of medical staff contamination. Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The authors have stated that no such relationships exist. Figure 1 . The use of local exhaust ventilation effectively captured aerosolized particles directly from the source. In our simulation of aerosolized particles generated by a nebulizer, we found that if the head of the manikin was placed close to the air outlet of the gas extraction system, the number of aerosolized particles directly captured by the air outlet was increased, which resulted in the rapid removal of aerosolized particles.

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