Small Changes Make a Big Difference in the Fit of N95 Respirators

Abstract

Background

In anticipation of future pandemics, N95 respirators (1870, 3M) have been stockpiled locally and nationally. Recently, small design changes were implemented (1870+, 3M) and manufacture of the 1870 mask has ceased. It is unknown what effect these design changes have on respirator fit and therefore the implication for use of respirators from both local and national stockpiles. OSHA regulations require healthcare providers (HCP) to use the same respirator with which they were fit tested.

Methods

We conducted a quality improvement project, to investigate equivalence between 1870 and 1870+ respirators. Given minor design changes in the 1870+ N95, we hypothesized that the 1870 and 1870+ respirators would be interchangeable, thus eliminating the need to re-fit test HCPs in the event a pandemic and need for the use of stockpiled respirators. Employees presenting to the Occupational Health Dept for employment or annual respirator fit testing were tested with both the 1870 and 1870+ N95. To compensate for subject fatigue, we alternated which respirator was fit-tested first. We collected de-identified gender, height and weight data as well as pass-fail rates. McNemar’s test was used to compare results for both respirators. Data were stratified by gender, BMI and combined gender/BMI.

Results

112 personnel (73 women, 39 men) were tested. Mean BMI = 26.5 (Women 27.1; Men 25.5). There were 16 (14%) failures for the 1870+ and 3 (2.7%) failures for 1870 model. One person failed both respirators. Personnel tested were 7.5 times as likely to fail the 1870+ vs. the 1870 (95% CI 1.74–67.6, P = 0.0036). After stratification by gender, women were 5.5 times as likely to fail the 1870+ N95 (95% CI 1.2–51, P = 0.027), however this was not evident for men (P = 0.25). Fifty-eight participants had BMI between 18 and 25 and 54 had BMI >25. Those with high BMI were more likely to fail fit test for 1870+ N95 (OR 9, 95% CI 1.25-394.5, P = 0.027). After stratifying by both BMI and gender, only women with BMI>25 persisted at risk for failure (OR 8, 95% CI 1.07–354; P = 0.045)

Conclusion

A high rate of N95 fit test failure was seen with the 1870+ respirator, driven by high failure rates in women with BMI >25. We were not able to show equivalence between 1870 and 1870+ respirators. Small changes in N95 design can have large effects on respirator fit and function and impact both pandemic readiness and hospital practices.

Disclosures

M. E. Rupp, 3M: Grant Investigator and Scientific Advisor, Research grant, Research support and Salary

Author notes

Session: 55. HAI: Occupational Health

Thursday, October 5, 2017: 12:30 PM