# 4853
Long-time readers of this blog are aware of a number of conflicting studies that have come out in recent years regarding the relative efficacy of surgical masks and N95 respirators in protecting HCWs (Health Care Workers) against airborne infections.
For decades, the assumption was that only properly fitted N95 masks protected the wearer, and that surgical masks were worn by HCWs to protect the patient during invasive procedures.
N-95 Respirator Surgical Facemask
Last year, during the summer outbreak of pandemic H1N1, many hospitals citing shortages of N95 masks, opted to equip their nurses with surgical masks instead.
This went against the recommended infection control guidelines issued by the CDC at the time, but was supported by several major infectious disease professional organizations.
This resulted in numerous protests last fall by nurses and other care givers, as I reported in:
CNA/NNOC Plan Protest Over Inadequate H1N1 Protection
(Photo from CNA/NNOC Webpage)
Since then, we’ve seen several `semi-reassuring’ studies that suggested that surgical masks are acceptable protection.
In October the NEJM published a perspective article (see NEJM Perspective: Respiratory Protection For HCWs) based on the recent IOM evaluation of surgical masks vs. respirators, and reiterated the advice:
Until more data are available, the committee recommends that clinicians reach for the N95 respirator when confronting patients with influenza-like illnesses, particularly in enclosed spaces.
A few days later JAMA (Journal of the American Medical Association) published a study which reported that HCWs using surgical masks experienced `noninferior rates of laboratory-confirmed influenza’.
In March of this year, we saw the following study (see Study: Efficacy of Facemasks Vs. Respirators).
Study finds surgical masks provided effective protection of health-care workers against H1N1
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.
The evidence over the winter, it seemed, was largely supportive of the notion that surgical masks were adequate protection against influenza viruses.
So in June of this year, the CDC released revised infection control guidance proposals which relaxed their previous recommendations to the allowing of surgical masks for routine care, and reserving N95 masks for aerosol producing procedures (intubation, suctioning, etc).
CDC: Proposed Influenza Infection Control Guidance
To complicate matters, however - after these studies suggested that surgical masks are reasonably protective against influenza - we now get a new study that questions whether surgical masks or N95 respirators provide any substantial protection to the wearer at all.
No . . . I don’t make these things up. I just report on them.
The study appears in the September issue of the AJIC (American Journal of Infection Control), and is titled:
Quantifying exposure risk: Surgical masks and respirators
Keith T. Diaz, MD, Gerald C. Smaldone, MD, PhD
These researchers (using mannequins fitted with a variety of masks, and using radiolabeled wet aerosols) determined that wearing surgical masks and N95 masks without an airtight (Vaseline) seal provided little more protection than wearing no mask at all.
They did find that placing a surgical mask on an infected source (patient) could significantly reduce the spread of a virus to the environment.
Since only the abstract is freely available, it is helpful that the SurgiStrategies website has posted a summary of these findings.
A hat tip to Tetano on FluTrackers for passing along this link.
AJIC Releases New Study on Face Masks and H1N1
The authors of this review quote the researchers as stating the type of mask (N95 vs Surgical) “does not play a significant role in reducing exposure to the recipient unless a respirator is physically sealed to the face of the source."
While obviously not the last word on the subject, the issue of just how protective various types of masks are to the wearer has just gotten a bit more murky.
Obviously, we will await the next mask efficacy study with considerable interest. In the meantime, I guess I’d better check my supply of Vaseline.
