Protection levels of N95-level respirator substitutes proposed during the COVID-19 pandemic: safety concerns and quantitative evaluation procedures

OBJECTIVE

The COVID-19 pandemic has precipitated widespread shortages of filtering facepiece respirators (FFRs) and the creation and sharing of proposed substitutes (novel designs, repurposed materials) with limited testing against regulatory standards. We aimed to categorically test the efficacy and fit of potential N95 respirator substitutes using protocols that can be replicated in university laboratories.

SETTING

Academic medical centre with occupational health-supervised fit testing along with laboratory studies.

PARTICIPANTS

Seven adult volunteers who passed quantitative fit testing for small-sized (n=2) and regular-sized (n=5) commercial N95 respirators.

METHODS

Five open-source potential N95 respirator substitutes were evaluated and compared with commercial National Institute for Occupational Safety and Health (NIOSH)-approved N95 respirators as controls. Fit testing using the 7-minute standardised Occupational Safety and Health Administration fit test was performed. In addition, protocols that can be performed in university laboratories for materials testing (filtration efficiency, air resistance and fluid resistance) were developed to evaluate alternate filtration materials.

RESULTS

Among five open-source, improvised substitutes evaluated in this study, only one (which included a commercial elastomeric mask and commercial HEPA filter) passed a standard quantitative fit test. The four alternative materials evaluated for filtration efficiency (67%-89%) failed to meet the 95% threshold at a face velocity (7.6 cm/s) equivalent to that of a NIOSH particle filtration test for the control N95 FFR. In addition, for all but one material, the small surface area of two 3D-printed substitutes resulted in air resistance that was above the maximum in the NIOSH standard.

CONCLUSIONS

Testing protocols such as those described here are essential to evaluate proposed improvised respiratory protection substitutes, and our testing platform could be replicated by teams with similar cross-disciplinary research capacity. Healthcare professionals should be cautious of claims associated with improvised respirators when suggested as FFR substitutes.

The incidences of positive Kleihauer-Betke test in low-risk pregnancies and maternal trauma patients

OBJECTIVE

This study was undertaken to determine the incidence of positive Kleihauer-Betke (KB) tests in low-risk, third trimester patients and compare them with historical "control" patients who received KB tests for maternal trauma evaluations.

STUDY DESIGN

Institution Review Board approval was obtained. KB tests were performed on 100 low-risk gravid women at the time of their routine glucose challenge tests after informed consent. All specimens were analyzed for fetal hemoglobin using the Clayton modification. Patients with identified risk factors for placental abruption were excluded. A retrospective chart review was performed on 583 historical control patients from 1998 to 2001 who had undergone maternal trauma evaluations, of which 151 had a KB test at comparable gestations. Demographic data from medical records were reviewed and compared. Data were analyzed with 2-sided Student t test, Mann-Whitney rank sum, and chi(2) tests, as indicated.

RESULTS

Of the low-risk women 5 of 98 (5.1%) had a positive KB test, whereas 4 of 151 (2.6%) trauma patients had a positive test (P=.31). None of these positive results were associated with a clinical abruption or fetal distress. One low-risk patient with sickle cell trait had a 40 mL KB result.

CONCLUSION

The incidence of a positive KB test in low-risk pregnancies does not differ from maternal trauma patients. Therefore, the presence of a positive KB test alone does not necessarily indicate pathologic fetal-maternal hemorrhage in patients with trauma.