Microbial contamination of powered air purifying respirators (PAPR) used by healthcare staff during the COVID-19 pandemic: an in situ microbiological study

8-hour performance of loose-fitting powered air-purifying respirators in simulated hospital and coal mine environments

Loose-fitting powered air-purifying respirators (LF-PAPRs) are increasingly used in hospitals and coal mines because of their high comfort and protection level, but the utilization faces the challenges of 8-hr continuous high protection requirements in the hospital environment and the coupling effects of high temperature, high humidity, high dust concentration in coal mines. Based on the self-developed powered air-purifying respirator simulation test system, this study explores the 8-hr changes of supplied airflow, the relative air pressure inside the inlet covering (ΔP), and total inward leakage (TIL) of four models of LF-PAPRs in simulated hospital and coal mine environments. Results show that: (1) In a simulated hospital environment, all four LF-PAPRs showed filter cartridge blockage within 5 ∼ 6 hr of continuous operation; while in the simulated coal mine, three models of LF-PAPRs showed filter cartridge blockage within 3 hr. (2) In both the hospital and coal mine environments, there are cases where the supplied airflow of LF-PAPRs dropped below 170 L/min within 3 hr. (3) In a simulated hospital environment, the ΔP of all LF-PAPRs maintained positive within 5-6 hr; while in the simulated coal mine, the ΔP of two LF-PAPRs, respectively, appeared negative after 1 hr and 1.6 hr operation. (4) The maximum TIL of the tested LF-PAPRs, respectively ranged from 0.5-0.9% and 1.4-3% in simulated hospital and coal mine environments. (5) In both hospital and coal mine environments, the supplied airflow and ΔP of each LF-PAPR showed a decreasing trend with increasing test duration, while the TIL significantly increased with testing time. (6) The supplied airflow, ΔP, and TIL of each LF-PAPR in the simulated hospital environment performed better than those in the coal mine. This study evaluated the performance of PAPR under the most severe operating conditions, and respirator performance may differ under in-situ conditions.

Powered air-purifying respirator (PAPR) disinfection and risk of surface damage from hydrogen peroxide and quaternary ammonium chloride-based disinfectants

Reusable Powered Air Purifying Respirators (PAPRs) have been increasingly used as an alternative to disposable masks or respirators for healthcare workers needing protection from respiratory droplets containing respiratory viruses, but little information is available concerning how well PAPRs resist damage from repeat disinfection over their lifetime. This study tested parts from four PAPRs against four commercially available hydrogen peroxide and quaternary ammonium chloride disinfectants by immersion for 28 days to simulate prolonged exposure. Risk of surface damage was assessed through color change, mass change, and visual observation of damage. Minimal risk of damage was found for three of the disinfectants tested and for the fourth disinfectant, a risk of surface damage to a small number of parts. Exposure to tap water caused similar damage in many cases. The study demonstrated that risk of surface damage varied by part and disinfectant, indicating that some disinfectants are more likely to be compatible against the wide range of materials and parts in a commercial PAPR and other disinfectants may show varying compatibility, with more risk to certain materials or parts.

Surgical helmets can be converted into efficient disinfectable powered air-purifying respirators

BACKGROUND

Filtering facepiece respirators often fail to provide sufficient protection due to a poor fit. Powered air-purifying respirators (PAPRs) are not designed for healthcare personnel, and are challenging to disinfect. Surgical helmets (SH) are available in many United States hospitals but do not provide respiratory protection. Several modifications to SH have been suggested, but none are sufficiently compliant with safety and efficiency standards. The purpose of this investigation was the development of a filter adaptor, which converts SHs into efficient, safe, and disinfectable PAPRs.

METHODS

Four critical features were investigated close to regulatory requirements: total inward leakage of particles, CO₂ concentrations, intra-helmet differential pressure, and automated disinfection.

RESULTS

The average total inward leakage in the 2 independent tests were 0.005% and 0.01%. CO₂ concentrations were lower than in the original SH. The modification generates a positive differential pressure. The filter's performance was not compromised after 50 cycles in a sterilization machine.

DISCUSSION

The modified SH provides several hundred times better protection than FFP-3 masks.

CONCLUSIONS

Surgical helmets can be modified into safe, efficient, and disinfectable PAPRs, suitable for HCP and the operating room in particular. They can play a role in the preparedness for upcoming events requiring efficient respiratory protection.

Fit-testing of respiratory protective equipment in the UK during the initial response to the COVID-19 pandemic

Background

Public Health England guidance stipulates the use of filtering facepiece (FFP3) masks for healthcare workers engaged in aerosol-generating procedures. Mask fit-testing of respiratory protective equipment is essential to protect healthcare workers from aerosolized particles.

Aim

To analyse the outcome of mask fit-testing across National Health Service (NHS) hospitals in the UK during the first wave of the coronavirus disease 2019 (COVID-19) pandemic.

Methods

Using the Freedom of Information Act, 137 NHS hospitals were approached on May 26^th, 2020 by an independent researcher to provide data on the outcome of fit-testing at each site.

Findings

Ninety-six hospitals responded to the request between May 26^th, 2020 to October 29^th, 2020. There was a total of 86 mask types used across 56 hospitals, 13 of which were used in at least 10% of these hospitals; the most frequently used was the FFP3M1863, used by 92.86% of hospitals. Overall fit-testing pass rates were provided by 32 hospitals with mean pass rate of 80.74%. The most successful masks, in terms of fit-test failure rates, were the Alpha Solway 3030V and the Alpha Solway S–3V (both reporting mean fit-test failures of 2%). Male- and female-specific pass and failure rates were provided by seven hospitals. Across the seven hospitals, 20.1% of men tested failed the fit-test for all masks used, whereas 19.9% of women tested failed the fit-test for all masks used. Failure rates were significantly higher in staff from Black, Asian, and Minority Ethnic (BAME) backgrounds 644/2507 (25.69%) across four hospitals.

Conclusion

Twenty percent of healthcare workers tested during the first response to the pandemic failed fit-testing for masks. A small sample revealed that this was most prominent in staff from BAME backgrounds.