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Optimizing twin sampling tube stabilization improves quantitative fit test results for flat-fold duckbill filtering
Daryl Lindsay Williams1, Benjamin Kave2, Charles Bodas2
1Royal Melbourne Hospital, Parkville, Australia; University of Melbourne, Parkville, Victoria, Australia.
Introduction:
When performing quantitative fit testing (QNFT) on filtering facepiece respirators using an ambient aerosol technique, a twin sampling tube is connected between the condensation nuclei count machine and the probed respirator. To achieve high quality and repeatable QNFT results, robust sampling tube stabilization is required.
Methods:
In this prospective randomized crossover study, conducted in December 2021 to February 2022, we compared the commonly used hand-hold technique with the manufacturer-recommended lanyard technique in stabilizing the sampling tube during QNFT on a Halyard N95 respirator. Outcomes included QNFT pass rates, overall and individual fit factors, and concordance between the two techniques.
Results:
A total of 228 out of 316 participants (72.2%) passed the QNFT with the hand-hold technique, compared to the lanyard technique (166/316, 52%, P < .001). The most significant drop in the fit factors with the lanyard technique occurred during head movement side-to-side and up-and-down. The concordance between the 2 techniques was fair (Kappa coefficient = 0.39).
Conclusion:
Our study demonstrates that the method of sampling tube stabilization during QNFT has a significant impact on fit test pass rates, with a potential for false negative fit tests due to inadequate tube stabilization. Further research is required to examine the generalizability of these results to other respirators and fit testing apparatuses.
