Posted on 10/13/2009 8:34:13 AM PDT by neverdem
New Study Evaluates Surgical Masks Vs. N95 Respirators For Preventing Influenza Among Health Care Workers
Surgical masks appear to be no worse than, and nearly as effective as N95 respirators in preventing influenza in health care workers, according to a study released early online today by JAMA. The study was posted online ahead of print because of its public health implications. It will be published in the November 4 issue of JAMA.
Influenza is the most important cause of medically attended acute respiratory illness worldwide and the authors write there is heightened concern this year because of the influenza pandemic due to the H1N1 virus. "Data about the effectiveness of the surgical mask compared with the N95 respirator for protecting health care workers against influenza are sparse," the authors provide as background information in the article. "Given the likelihood that N95 respirators will be in short supply during a pandemic and not available in many countries, knowing the effectiveness of the surgical mask is of public health importance."
Mark Loeb, M.D., M.Sc., from McMaster University, Hamilton, Ontario, Canada, and colleagues conducted a randomized controlled trial of 446 nurses in eight Ontario hospitals to compare the surgical mask with the N95 respirator in protecting health care workers against influenza. The nurses were randomized into two groups: 225 were assigned to receive surgical masks and 221 were assigned to receive the fitted N95 respirator which they were to wear when caring for patients with febrile (fever) respiratory illness. The primary outcome of the study was laboratory-confirmed influenza. Effectiveness of the surgical mask was assessed as non-inferiority of the surgical mask compared with the N95 respirator.
Between September 23, 2008 and December 8, 2008, "influenza infection occurred in 50 nurses (23.6 percent) in the surgical mask group and in 48 (22.9 percent) in the N95 respirator group (absolute risk difference -0.73 percent)," indicating non-inferiority of the surgical mask the authors report. Even among those nurses who had an increased level of the circulating pandemic 2009 H1N1 influenza strain, non-inferiority was demonstrated between the surgical mask group and the N95 respirator group for the 2009 influenza A(H1N1).
"Our data show that the incidence of laboratory-confirmed influenza was similar in nurses wearing the surgical mask and those wearing the N95 respirator. Surgical masks had an estimated efficacy within 1 percent of N95 respirators," the authors write. "That is, surgical masks appeared to be no worse, within a prespecified margin, than N95 respirators in preventing influenza."
In conclusion the authors state: "Our findings apply to routine care in the health care setting. They should not be generalized to settings where there is a high risk for aerosolization, such as intubation or bronchoscopy, where use of an N95 respirator would be prudent. In routine health care settings, particularly where the availability of N95 respirators is limited, surgical masks appear to be non-inferior to N95 respirators for protecting health care workers against influenza."
FReebie: "Vaccination status was similar: 68 participants (30.2%) in the surgical mask group and 62 (28.1%) in the N95 respirator group had received 2008-2009 trivalent inactivated influenza vaccine."
It is critical to look at the external factors involved.
To start with, a recent study showed that the ideal temperature for influenza to be transmitted by coughing and sneezing is 40F and low humidity. As the temperature and humidity increase, the virus becomes much more dependent on contact contamination, mostly by hand to object to hand, or direct person to person.
Second, air circulation is key. The worst situation would be a small area, with recirculated air via air conditioning. This would give the virus several opportunities to infect the same person. By increasing the size of the room and the volume of air, the situation is improved. But the best bet is to open a window, as air exchange happens faster than with air conditioning, fresh air coming in, and contaminated air leaving.
External viral enemies include other substances in the air that destroy viruses when they meet, the amount of UV light shining through the air, and those factors which affect with droplets of moisture that contain the virus.
Bigger study involving 2000 subjects demonstrated that N95 masks were beneficial but surgical masks did not provide significant protection.
http://www.cidrap.umn.edu/cidrap/content/influenza/swineflu/news/sep1709respir-jw.html
Thanks for the link.
The worst situation would be a small area, with recirculated air via air conditioning.
________
Like the back of an ambulance, yes. That’s why my flu patients get masks too. Or a non-rebreather, but none have needed O2.
Study provides clue to surviving Swine Flu
JAMA has a total of 6 FReebies about flu.
The New England Journal of Medicine(NEJM) has their H1N1 Information Center. I checked a few NEJM articles. All were FReebies.
Swine Flu Causes Lung Failure in Healthy Young People (Update1) Bloomberg.com
I’m not sure about H1N1, but typically with other flu, if there is going to be respiratory distress, it sets in at about day 5 of symptoms.
Recently, they discovered an unexpected mitigating factor, that opens the door to a bunch of unknown other ones: arsenic. It somehow inhibits the novel pathogen recognition for some time, and then, when the novel pathogen is recognized, the immune system overreacts.
Typically, this effect would occur with long term, low level exposure to arsenic. City drinking water is carefully monitored for arsenic, and has a very low EPA acceptable level, but well water around the US varies considerably, with some having very high levels. The other big source is arsenic-copper anti-termite wood preservative, which is 90% of the arsenic typically found above ground in most of the US.
I’m not sure about H1N1, but typically with other flu, if there is going to be respiratory distress, it sets in at about day 5 of symptoms.
Recently, they discovered an unexpected mitigating factor, that opens the door to a bunch of unknown other ones: arsenic. It somehow inhibits the novel pathogen recognition for some time, and then, when the novel pathogen is recognized, the immune system overreacts.
Typically, this effect would occur with long term, low level exposure to arsenic. City drinking water is carefully monitored for arsenic, and has a very low EPA acceptable level, but well water around the US varies considerably, with some having very high levels. The other big source is arsenic-copper anti-termite wood preservative, which is 90% of the arsenic typically found above ground in most of the US.
Also, Keep up with other H1N1 update stories on this thread: H1N1 flu victim collapsed on way to hospital [Latest H1N1 updates downthread] thanks to DvdMom and others.
Thanks for the ping!
Don't use this treated wood around gardens with vegetables you plan to eat. The arsenic can be contained in the vegetables.
You’re welcome, Alamo-Girl!
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