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

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 10⁻³ (0.1%) for smaller particles. Penetration values for particles in the 500 nm-5 μm range were below 10⁻² (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.

Characterization of RNase P holoenzymes from Methanococcus jannaschii and Methanothermobacter thermoautotrophicus

The partial purification and basic biochemical characterization of the RNase P holoenzymes of two species of methanogenic Archaea, Methanothermobacter thermoautotrophicus (previously Methanobacterium thermoautotrophicum strain deltaH) and Methanococcus jannaschii, are described. The properties of these enzymes, particularly buoyant density in Cs2SO4 and recent information about the subunit composition of the archaeal enzymes, suggest that RNase P enzymes in Archaea are much more alike than earlier studies in Sulfolobus acidocaldarius and Haloferax volcanii suggested.