(Fri, 26 Mar 2010 12:30:00 +0000)
# 4462
For decades the assumption by just about everyone – from OSHA to the CDC, to medical professionals – has been that surgical facemasks did little to protect the wearer. Surgical masks were designed to contain the wearer’s germs and protect those around them, not the other way around.
If you wanted to protect yourself against respiratory viruses, you needed to wear a properly fitted N-95 (or better) respirator.
N-95 Respirator Surgical Facemask
Using an N-95 respirator is problematic on a number of fronts, however.
- They are uncomfortable to wear for long periods of time.
- They saturate with exhaled moisture relatively quickly, and must be changed out every couple of hours.
- The must be fit tested for each wearer
- The are 10 times more expensive than surgical masks.
- And our national supply of N-95s is totally inadequate to supply Health Care Workers during a prolonged pandemic wave.
Despite these limitations, many HCWs (Health Care Workers) have demanded that they be afforded the extra protection of N95 respirators when dealing with pandemic flu cases.
Indeed, the CDC’s pandemic infection control guidelines (updated March 10th) continue to recommend:
For the purposes of this document, close contact is defined as working within 6 feet of the patient or entering into a small enclosed airspace shared with the patient (e.g., average patient room):
Respiratory Protection –
Recommendation: CDC continues to recommend the use of respiratory protection that is at least as protective as a fit-tested disposable N95 respirator for healthcare personnel who are in close contact with patients with suspected or confirmed 2009 H1N1 influenza. This recommendation applies uniquely to the special circumstances of the current 2009 H1N1 pandemic during the fall and winter of 2009-2010 and CDC will continue to revisit its guidance as new information becomes available, within this season if necessary.
Masks and respirators, the CDC stresses, are the last line of defense in a health care facility. And they make allowances for supply problems as well, saying that respirators may be prioritized for higher risk aerosol producing procedures.
The CDC’s stance, however, isn’t universally accepted or followed. These are recommendations, after all, not mandates.
Many hospitals have opted to use surgical masks as a matter of routine, except when performing aerosol producing procedures. And this has caused no small amount of controversy in the healthcare profession.
In a major turnaround, over the past few months we’ve seen a series of studies that suggest that surgical masks may be `non-inferior’ to N95 masks, or that they provide a similar level of protection as the more expensive respirator.
Most of these are observational studies, and as such, may be open to some criticism. Health care workers do not work, and live, in a vacuum. Controlling (or quantifying) the effects of non-patient (community) exposure to respiratory viruses becomes a real challenge.
Today we’ve another such study, that suggests that inexpensive facemasks may be more effective than previously thought in protecting against the H1N1 virus.
First the press release, then a link to the study.
The effectiveness of ordinary surgical masks as opposed to respirators in protecting health care workers against the 2009 H1N1 influenza virus has been the subject of debate. An observational study published in the April 1, 2010 issue of Clinical Infectious Diseases, available online, suggests that surgical masks are just as effective as respirators in this regard.
Researchers analyzed the incidence of H1N1 among health care workers from April through August of 2009 at Tan Tock Seng Hospital in Singapore. A small percentage tested positive for H1N1 during this period. None had cared for any patients with H1N1 or worked in H1N1 screening areas of the emergency room. In all cases, transmission was believed to have occurred outside of patient care, when health care workers were in contact with roommates, the general public, and other sources.
From June 19 to July 21, health care workers at the hospital wore N95 respirators in the emergency room and an H1N1 isolation area. From July 22 to Aug. 31, surgical masks were used by workers in these areas. The incidence of H1N1 among workers remained low during both periods. Although the study was observational, the findings suggest that surgical masks and respirators did not differ in their effectiveness in preventing hospital staff from acquiring H1N1.
“What is more important than using high-filtration or respirator masks for known or suspected cases is to have a uniform policy, such as using surgical masks, when in close contact with all patients,” said study author Brenda Sze Peng Ang, MD, of the Tan Tock Seng Hospital in Singapore. “This way, health care workers are protected from getting infected by patients not initially thought to have H1N1.”
Here is the link to the journal article, with a few choice excerpts. If you are in the Health Care field, you will probably want to read this in its entirety.
DOI: 10.1086/651159
BRIEF REPORT
Brenda Ang,Bee Fong Poh, Mar Kyaw Win, and Angela Chow
There is ongoing debate about the efficacy of surgical masks versus N95 respirators for protection against pandemic novel swine‐origin influenza A (H1N1)–2009. Our hospital, which is designated to manage outbreaks of emerging infection, has robust surveillance systems to detect infection in staff. The incidence of pandemic H1N1‐2009 remained low in staff with use of surgical masks.
<SNIP>
Discussion. Although this is an observational study, nonetheless our findings show that surgical masks and N95 respirators do not appear to differ in efficacy in the prevention of the acquisition of pH1N1 by staff. Our findings also highlight the importance of a robust HCW surveillance system for the detection of nosocomial transmission of pathogens, including novel pathogens.
<SNIP>
Conclusion. Our surveillance systems were effective in detecting infection among HCWs. None of the HCWs who cared for pH1N1 patients acquired infection from them. Those HCWs who did acquire pH1N1 appeared to have been infected from community exposure or in social settings with colleagues. The incidence of pH1N1 remained low in exposed staff, even when staff used surgical masks.
We are still some ways off from having a complete understanding of the relative efficacy of surgical masks vs. N95 respirators.
Definitive answers are notoriously hard to come by.
We were, in retrospect, very lucky that H1N1 proved to have a lower R0 (reproductive number) than originally feared. That limited transmission. H1N1 also produced lower than expected mortality rates.
Again, a stroke of luck.
Had this been a highly lethal H5 avian virus, or even a SARS-like virus, the clamor for the greater perceived protection afforded by N95 masks would have been overwhelming.
And our supply would have been exhausted in a matter of weeks.
So it would indeed be good news if surgical masks turn out to be equally protective against respiratory viruses as are fit-tested N95 respirators.
They are cheaper, easier to wear, and in far more abundant supply.
But for that to be accepted by HCWs – particularly in the face of a dangerous pathogen – more convincing studies are going to be needed. Decades of practice and teaching are not easily swept aside.
Hopefully we’ll get better answers to all this before the next pandemic arrives.
