How much better is respirator fit testing compared with fit checking?
Started by Philipp Du Cros on 23 Jun 2009
Dear Colleagues,
In the WHO Guidelines for the Prevention of tuberculosis in health care facilities in resource limited settings it mentions that "Should time and resources permit (financial and staff), a respirator (fit) testing program should be incorporated into the IC plan."
In trying to decide the relative benefit of respirator fit testing over simple fit checking for a program that is already attending to the administrative and environmental controls, I was wondering whether there were any studies that correlated individual fit checking with formal fit testing results (i.e any idea of sensitivity/specificity of fit checking)?
Also have there been any attempts to look at whether the respirator fit test procedure could be simplified (i.e. can you achieve the same results with testing 3 manoeuvres versus 6-7)?
Thanks for any information.
Philipp du Cros
Medecins Sans Frontieres
Attached resource: Respirator nose clips drawing
Keywords: Fit test, Personal Respiratory Protection, fit check
Paul A. Jensen, PhD, PE, CIH
Dear Phillip:
The following excerpts are from the preamble to the US Occupational Safety and health Administration (OSHA) legislation for respiratory protection (Title 42, Code of Federal Regulations, Part 1910.134):
"User seal check is defined as 'an action conducted by the respirator user to determine if the respirator is properly seated to the face.' Such a check is performed by the user each time the respirator is donned or adjusted to ensure that the tight-fitting respirator is properly seated on the user's face, i.e., that the proper seal has been achieved. Several commenters recommended that OSHA add the definition for 'fit check' from the ANSI Z88.2-1992 standard to replace the term 'facepiece seal check' that was used in Appendix B of the proposal (Exs. 54-208, 54-218, 54-219, 54-410, 54-424). The term 'fit check' has proven confusing to those respirator users who do not realize that a daily fit check is not a substitute for an annual fit test. The AIHA (Ex. 54-208)
recommended that OSHA add a statement to Appendix B to the effect that: 'Fit checks are not substitutes for qualitative or quantitative fit tests,' and OSHA has done so in this final standard. Because OSHA believes that the similarity between the terms 'fit check' and 'fit
test' is responsible for this confusion, OSHA has used the term 'user seal check' rather than 'fit check' in the final standard. The definition of 'user seal check' derives from the ANSI Z88.2-1992 standard's definition for 'fit check,' except that the word 'action' has been substituted for 'test' to avoid any possible confusion among respirator users."
"Similarly, although a negative or positive pressure user seal check is important to ensure proper donning and adjustment of the respirator each time it is put on, it is not a substitute for the selection of an adequately fitting respirator through fit testing. Most respirator fit testing is preceded by a user seal check, but experience with respirator fit testing has shown that some individuals who pass this user seal check with what they think is an adequately fitting facepiece subsequently fail their fit test due to poor respirator fit. As John Hale of Respirator Support Services (Ex. 54-5) stated, 'Yes, there is
some information to be obtained about gross facepiece-to-face leakage by performing these checks. But, there are no performance criteria, there is no known correlation between the result of this check and respirator fit or performance * * * .'"
Bottom line . . .
1. There are limited quality and independent data to support the efficacy of user seal checks (also known as fit checks).
2. Your priorities are correct. First, institute administrative and managerial controls. Then, institute environmental controls. One problem with environmental controls is that there are thousands (literally) of salespersons out there selling junk equipment, with no chance of significantly reducing airborne TB concentration in the room. If the risk cannot be controlled, institute respiratory protection.
One problem with respiratory protection is that there are thousands (literally) salespersons out there selling junk respirators, with no chance of significantly reducing the airborne TB concentration breathed in by the wearer. Without out fit testing, or at least researching well-fitting respirators, the protection afforded by wearing a respirator is a big unknown.
I will upload four articles of interest (the first deals with user seal checks, the middle two show that not all respirators are created equal, and the last one addresses your second comment):
1. Derrick JL, YF Chan, CD Gomersall, SF Lui. Predictive value of the user seal check in determining half-face respirator fit. Journal of Hospital Infection (2005) 59, 152-155.
http://www.ghdonline.org/ic/resource/predictive-value-of-the-user-seal-check-in-determi/
2. Coffey CC, RB Lawrence, DL Campbell, Z Zhuang, CA Calvert, PA Jensen. Fitting Characteristics of Eighteen N95 Filtering-Facepiece Respirators. Journal of Occupational and Environmental Hygiene (2004) 1:262-271.
http://www.ghdonline.org/ic/resource/fitting-characteristics-of-eighteen-n95-filtering-/
3. Lawrence RB, MG Duling, CA Calvert, CC Coffey. Comparison of Performance of Three Different Types of Respiratory Protection Devices. Journal of Occupational and Environmental Hygiene (2006) 3: 465-474.
http://www.ghdonline.org/ic/resource/comparison-of-performance-of-three-different-types/
4. Campbell DL, CC Coffey, PA Jensen, Z Zhuang. Reducing Respirator Fit Test Errors: A Multi-Donning Approach. Journal of Occupational and Environmental Hygiene (2005) 2: 391-399.
http://www.ghdonline.org/ic/resource/reducing-respirator-fit-test-errors-a-multi-donnin/
Finally, what have others experienced with the user seal check vs. fit testing?
Regards,
Paul J
4:46 PM, 23 Jun 2009 | Permalink
James Derrick
From our results (Predictive value of the user seal check in determining half-face respirator fit) I calculate:
Sensitivity 77%
Specificity 64%
PPV 0.83
NPV 0.56
The three respirators in our study were chosen because they were the most likely to fit our population (Chinese). Most of the respirators we tested, however, had pass rates of 10% or less. One popular respirator did not work even when it was stuck to the face of our subjects with adhesive tape. It is quite possible that you are using this respirator.
If you are using poor respirators, almost all people who pass based on a user seal check will not actually be protected. I would suggest that a first step would be to test a variety of respirators in your population and narrow your selection down to the ones which have the best pass rates.
In actual use, even a correctly fitting half face respirator will not provide much more than a 10 fold reduction in inhaled particle count. This is a fairly modest level of protection. A powered respirator gives a much higher level of protection, does not require fit testing and can be used by bearded subjects. For protection against a disease like TB, it may be simpler to buy a small number of powered respirators if you do not have the resources to engage in a large scale fit testing program.
All PPE (including powered respirators) require good training to be effective. The filtering facepiece respirators are particularly easy to misuse. If you test these respirators when they are worn improperly, they all fail miserably. The fit test is not intended to be a substitute for training, but at least it means that the staff have had some exposure to correct donning of the respirator.
5:33 AM, 1 Jul 2009 | Permalink
Grigory Volchenkov, MD
Qualitative fit test in our institution (200 staff members) shows that 98 - 100% of HCWs pass with 3M 9320 or 9322 respirators, about 95% pass with Russian FFP2 repirator Alina-P.
I think recommendation for HCW to use powered PPE in low or medium resource settings is not realistic. Most of administrators in our settings believe that use of filtering facepiece respirators is not affordable (which is not true according to our experience).
We also found that FFP3 3M 6000 series repirators can be less costly to use than disposal FFP2 3M 9322.
Dr. Grigory V. Volchenkov
Head Doctor
Vladimir Oblast TB Dispansery
Sudogodskoe shosse, 63
Vladimir 600023 RUSSIA
6:12 AM, 1 Jul 2009 | Permalink
James Derrick
Yes unfortunately the powered respirators are much more expensive.
We were informed by 3M in Hong Kong that the 9320 is the same respirator as the 9210, packaged for a different market. We used a different fit test method to Dr Volchenkov, so I would not want to be too dogmatic, but the difference between our results and his are certainly suggestive that there may be marked ethnic differences in fit rate between respirator models.
As well as the cost issue, our clinical impression was that the 3M 6000 series respirators had a higher fit rate than the filtering facepiece respirators. I cannot comment on other brands, as we did not have them available. These respirators still require staff training and fit testing. I believe that Ref 3 above discusses this.
6:40 PM, 5 Jul 2009 | Permalink
Paul A. Jensen, PhD, PE, CIH
Dear James et al.:
Yes, the 3M 92XX series are N95 respirators and the 3M 93XX series are FFP2 respirators . . . Essentially the same (they come off te same factory line). This statement may not be politically correct: Asian faces are flatter that European faces . . . Unless the nose clip is formed properly, the chances of a good fit are not good! I will try to sketch something for Sophie to upload** (thanks for the great support, Sophie!). I will also try to dscribe in words. For most folks with relatively flat faces or very small bridge of the nose, the best thing to try is to bend the nose clip as follows:
1. Find the center of the nose clip and make a "U" around one of your thumb tips.
2. Approximately 1 cm from the top of the "U" make a 90 degree bend out.
3. Do the same to the other side.
4. It should now look relatively flat with just a little "blip" for the nose.
5. Now see how well this fits around the nose.
6. With some practise, you will find that this will increase your pass rate.
7. The 3M 6000 series will probably fit a greater percentage.
8. Finally, I do not endorse/promote 3M or any other brand of respirator. They all have their good points (e.g., inherently well fitting when new, out-of-the-box) and bad points (e.g., those super-thin blue rubberbands that lose their elasticity quickly). Your mileage may vary!
** See the nose clips sketch here: http://www.ghdonline.org/ic/resource/respirator-nose-clips-drawing/
Regards,
Paul J
--------------------------
Sent from my BlackBerry . . . Please excuse my fumbling thumbs!
10:03 AM, 6 Jul 2009 | Permalink
S. Mehtar
Yes Paul
I agree. Do give us something to go help us.
Regards
Shaheen
Prof Shaheen Mehtar
MBBS, FRC Path (UK), FCPath (Micro) (SA), MD (Eng)
Chair IPC Africa Network
Head of Academic Unit for Infection Prevention and Control
Tygerberg Hospital & Stellenbosch Uni
PO Box 19063,
Tygerberg 7505, Cape Town
Visit our UIPC Website
http://www.sun.ac.za/uipc
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11:38 AM, 6 Jul 2009 | Permalink