Design and evaluation of a portable negative pressure hood with HEPA filtration to protect health care workers treating patients with transmissible respiratory infections

Abstract

Background: To mitigate potential exposure of healthcare workers (HCWs) to SARS-CoV-2 via aerosol routes, we have developed a portable hood which not only creates a barrier between HCW and patient, but also utilizes negative pressure with filtration of aerosols by a high-efficiency particulate air filter. Material and Methods: The hood has iris-port openings for access to the patient, and an opening large enough for a patient's head and upper torso. The top of the hood is a high-efficiency particulate air filter connected to a blower to apply negative pressure. We determined the aerosol penetration from outside to inside in laboratory experiments. Results: The penetration of particles from within the hood to the breathing zones of HCWs outside the hood was near 10 -4 (0.01%) in the 200-400 nm size range, and near 10 À3 (0.1%) for smaller particles. Penetration values for particles in the 500 nm-5 mm range were below 10 À2 (1%). Fluorometric analysis of deposited fluorescein particles on the personal protective equipment of an HCW revealed that negative pressure reduces particle deposition both outside and inside the hood. Conclusions: We find that negative pressure hoods can be effective controls to mitigate aerosol exposure to HCWs, while simultaneously allowing access to patients.

Containment of procedure-associated aerosols by an extractor tent: effect on nebulized drug particle dispersal

“…Particles retained within the tent fell within the size range of airborne particles of probable respiratory origin shown to contain SARS-CoV-2 RNA in clinical studies, and in particular those < 5 μm in diameter shown to carry the highest coronavirus titres [ 5 , 31 ]. Although this study was not conducted with infectious particles or human subjects, this suggests that the Demister 2000, like other portable isolation devices employing filtered extraction [ 32 ], would prevent the dispersal of respiratory viruses such as SARS-CoV-2 from aerosols generated from infected patients. By effectively expanding isolation capacity without building or structural alterations, these devices have potential to increase treatment capacity during respiratory pandemics whilst protecting healthcare staff and patients from infection.…”

A simple, effective enclosure with disposable coverings for inexpensive containment of aerosolized COVID viruses during tracheal intubation and extubation

“…18,19 These enclosures utilized a suction device to generate negative pressure and HEPA filters to help prevent the spread of aerosolized particles, with the openings either uncovered or covered with rubber septum. 18,19 Phu et al reported a 99% particle reduction in the 0.5 to 5 µm range, which is slightly higher than the 93-97% reduction reported here without suction. This is likely due to our particle measurements extending down to smaller sizes (to 0.01 µm), because these smaller particles can more easily escape the enclosure.…”

“…The copyright holder for this this version posted November 24, 2020. ; https://doi.org/10.1101/2020.11.23.20237255 doi: medRxiv preprint Several approaches have recently been developed to help protect healthcare providers during these procedures, including placing plastic barriers or hoods over the patient in an effort to contain produced aerosols. 16,18,19 A limitation is that the enclosure must have sizable openings in its side walls to allow the introduction of medical equipment and provide the healthcare worker's hands access to the patient. These holes have been found to funnel the aerosol that escapes from the enclosure.…”

Computational modelling of an aerosol extraction device for use in COVID-19 surgical tracheotomy

“…as simple as plastic sheeting Matava, Yu and Denning (2020) or rigid boxes), methods using enclosures combined with a degree of suction, (e.g. as described by Perella, Tabarra, Hataysal, Pournasr, and Renfrew (2021) and Phu et al (2020) ), and methods which may include some shield or barrier, but which primarily rely on capture of aerosol by suction. An example of the latter is decribed in the model study reported by Matava et al (2020) , in which the capture performance is studied for a conical nozzle placed 25–35 cm above the mouth of a mannikin.…”