Qualitative fit test outcomes for N95 filtering facepiece respirators in health care workers

Development of a rapid, multi-organisational, multi-modal assessment of a newly available disposable respirator

BACKGROUND

A rapid large-scale evaluation of a newly available duckbill style P2/N95 respirator, the Care Essentials (CE) MSK-003, was required to determine its suitability for deployment into the Victorian healthcare service. The aims of this study were to assess the feasibility of establishing a rapid, multi-organisational and multi-modal evaluation of the respirator, and to investigate whether this respirator would meet the needs of healthcare workers.

METHODS

The evaluation was a collaboration among three healthcare organisations - two tertiary hospitals in metropolitan Melbourne and a rural-based hospital. Participants were healthcare workers undertaking their routine fit tests. They were required to complete quantitative fit testing and a usability assessment survey on the CE MSK-003 respirator. The a priori performance criteria were set as fit test pass rate of >70%, plus satisfactory subjective overall comfort and performance assessments, defined as a rating of adequate, good, or very good in >90% of the cohort.

RESULTS

A total of 1070 participants completed the multi-modal assessment within a month. Seventy-eight percent of participants passed their quantitative fit test. Over 90% of survey respondents reported that the CE MSK-003 was adequate, good or very good in terms of its overall comfort and performance assessments.

CONCLUSION

We demonstrated that a multi-modal evaluation of a new respirator can be rapidly conducted with a high level of participation in a controlled, consistent manner across multiple organisations. The evaluation results of the CE MSK-003 respirator exceeded our predetermined (a priori) minimal criteria, making it suitable for broad distribution to healthcare organisations.

Incidence of Fit Test Failure During N95 Respirator Reuse and Extended Use

Importance

The COVID-19 pandemic resulted in a widespread acute shortage of N95 respirators, prompting the Centers for Disease Control and Prevention to develop guidelines for extended use and limited reuse of N95s for health care workers (HCWs). While HCWs followed these guidelines to conserve N95s, evidence from clinical settings regarding the safety of reuse and extended use is limited.

Objective

To measure the incidence of fit test failure during N95 reuse and compare the incidence between N95 types.

Design, Setting, and Participants

This prospective cohort study, conducted from April 2, 2021, to July 15, 2022, at 6 US emergency departments (EDs), included HCWs who practiced N95 reuse for more than half of their clinical shift. Those who were unwilling to wear an N95 for most of their shift, repeatedly failed baseline fit testing, were pregnant, or had facial hair or jewelry that interfered with the N95 face seal were excluded.

Exposures

Wearing the same N95 for more than half of each clinical shift and for up to 5 consecutive shifts. Participants chose an N95 model available at their institution; models were categorized into 3 types: dome (3M 1860R, 1860S, and 8210), trifold (3M 1870+ and 9205+), and duckbill (Halyard 46727, 46767, and 46827). Participants underwent 2 rounds of testing using a different mask of the same type for each round.

Main Outcomes and Measures

The primary outcome was Occupational Safety and Health Administration-approved qualitative fit test failure. Trained coordinators conducted fit tests after clinical shifts and recorded pass or fail based on participants tasting a bitter solution.

Results

A total of 412 HCWs and 824 N95s were fit tested at baseline; 21 N95s (2.5%) were withdrawn. Participants' median age was 34.5 years (IQR, 29.5-41.8 years); 252 (61.2%) were female, and 205 (49.8%) were physicians. The overall cumulative incidence of fit failure after 1 shift was 38.7% (95% CI, 35.4%-42.1%), which differed by N95 type: dome, 25.8% (95% CI, 21.2%-30.6%); duckbill, 28.3% (95% CI, 22.2%-34.7%); and trifold, 61.3% (95% CI, 55.3%-67.3%). The risk of fit failure was significantly higher for trifold than dome N95s (adjusted hazard ratio, 1.75; 95% CI, 1.46-2.10).

Conclusions and Relevance

In this cohort study of ED HCWs practicing N95 reuse, fit failure occurred in 38.7% of masks after 1 shift. Trifold N95s had higher incidence of fit failure compared with dome N95s. These results may inform pandemic preparedness, specifically policies related to N95 selection and reuse practices.