AJIC Releases New Study on Face Masks and H1N1

[tetano]

New research may challenge common assumptions regarding use of face masks and respirators to prevent the spread of H1N1 viruses, according to a study in the Sept. issue of the American Journal of Infection Control.

The study concludes that having infected individuals wear basic surgical masks may do more to hinder the spread of H1N1 than having uninfected individuals wear more advanced respirators that do not fit properly.

The new research should prompt public health officials to rethink how best to control the spread of novel viruses during future pandemics.

Currently, the Centers for Disease Control (CDC) and Prevention recommend the use of N95 respirators (a mask that fits closely to the face) for protection from the 2009 H1N1virus. The recommendation is based on the assumption that these respirators efficiently filter airborne droplets that carry the virus, thus protecting the wearer from infected individuals.

However, Gerald C Smaldone, MD, PhD and Keith T. Diaz, MD, researchers at Stony Brook University Medical Center, conducted experiments that showed N95 respirators do not achieve the close fit to the face necessary to prevent airborne droplets from breaching the gap between the skin and the mask of uninfected individuals.

What?s more, the research shows that basic surgical masks worn by potentially infectious individuals may do a better job of preventing H1N1 spread by deflecting exhaled viruses away from those around them. ?For exhaled particles, our study demonstrates the value of manipulating the source rather than trying to simply protect the receiver," say the authors.

The researchers conclude that the assumed filtration property of any type of mask ?does not play a significant role in reducing exposure to the recipient unless a respirator is physically sealed to the face of the source." The authors note that sealing the mask to the face is a daunting task not easily achieved. The authors performed their research using mannequins in a chamber constructed to simulate air flow between two persons.

The authors conclude: ?Deflection of exhaled particles, such as can be achieved with a surgical mask worn at the source, achieves far greater levels of protection than an N95 respirator on the recipient."

http://www.surgistrategies.com/news/2010/08/ajic-releases-new-study-on-face-masks-and-h1n1.aspx

 

[gsgs]

Re: AJIC Releases New Study on Face Masks and H1N1

Mask-wearing and seasonal influenza vaccination are protective for respiratory infection in HCWs; the protective efficacy of medical masks is better than that of cotton yarn ones

http://www.ncbi.nlm.nih.gov/pubmed/21503394

 

[Laidback Al]

Re: AJIC Releases New Study on Face Masks and H1N1

AJIC: American Journal of Infection Control - September 2010 (Vol. 38, Issue 7, Pages 501-508, DOI: 10.1016/j.ajic.2010.06.002)

Quantifying exposure risk: Surgical masks and respirators

Keith T. Diaz, Gerald C. Smaldone

Background

The interaction between the source of respiratory infectious aerosols and the receiver has not been investigated. Using a bench model, we measured the effects of filtration and deflection achieved with surgical masks and N95 respirators.
Methods

We constructed a chamber designed to produce radiolabeled wet aerosols simulating contaminated particles exhaled during tidal breathing (source). Particles within the chamber were exposed to either 6 or 0 air exchanges/hr. Aerosols were defined by cascade impaction. Source aerosols were exhaled via a ventilated mannequin head suitable for mask protection. A similar ventilated head within the chamber assessed recipient exposure (receiver). A filter within the receiver quantified exposure. Two types of masks, an N95 respirator and surgical mask, were tested. Data were presented as percent of nebulized particles on the receiver filter (exposure) and simulated workplace protection factor (sWPF).
Results

In the presence of chamber air exchange, applying a mask on the source (primarily deflection) resulted in significant reduction in exposure to the receiver (sWPF170-320). Masks on receiver (filtration) did not significantly reduce exposure from that of no masks (sWPF1.37-2.21), except with a Vaseline seal (sWPF118). With 0 air exchanges/hr, only Vaseline seal was effective in reducing exposure (sWPF 16-101).
Conclusion

In a ventilated space, deflection of exhaled particles with a mask worn at the source achieved far greater levels of protection than any mask on the receiver. Mask filtration at source or receiver did not play a significant role in reducing exposure.


http://www.ajicjournal.org/article/S0196-6553(10)00597-3/abstract

 

[gsgs]

Re: AJIC Releases New Study on Face Masks and H1N1

what is a "vaseline seal" ?
searching ...

From the reviews that I have read about the positive pressure mask having a beard does not seem to be a problem because no seal is needed.

It depends how good of a seal you want. We use full face, positive pressure resperators on the fire dept. If anyone wearing them has any kind of facial hair, even just a 1 day haven't shaved, they have to use vaseline to make sure of the seal. It all depends on how well you want it to seal to your face. And that will depend on how find the dust is and the pressure and volume of air being delivered to the mask. In training with smoke bombs (non toxic smoke) we don't use vaseline to seal the mask. You can sometimes smell the smoke in the mask if you have facial hair. And we do not have cheap masks and are using bottled air, so smoke has to be from the smoke bomb, not poor filtering.