Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis

Given the wealth of published data on the efficiency of N95 FFRs and surgical masks resulting from various extensive experimental studies, it is surprising to learn that the investigators of this paper found no evidence that N95 respirators offer better protection compared to surgical masks. Our testing conducted with health care workers showed a clear difference. I would echo Dr. Lantos' comment "the absence of proof is not the proof of absence." Of course, more has to be done to improve the N95 FFRs, especially though improving the faceseal, but the health care community should be aware of a very low (if any) efficiency of surgical masks against aerosol particles while N95 have demonstrated significantly higher protection.

Conflict of Interest:

None declared

Further to Ms. Haslam-Stroud's comments, Justice Campbell also emphasized the Precautionary Principle which is still, 13 years later, all too much lacking; as most recently evidenced by the inadequate protection of nurses against Ebola in the USA. Both the SARS Commission and the later CSA Z94.4-11 standard clearly indicate the need for a Respiratory Safety Officer, which most hospitals still do not have, and the standard also utilizes "control banding", which if followed, would immediately exclude the use of surgical masks in infectious clinical settings. Both the premise and the conclusions of the meta-analysis are not in keeping with the Precautionary Principle. The meta-analysis reviewed the wrong studies; poorly conducted clinical studies instead of peer-reviewed scientific ones in areas such as occupational hygiene, biosafety, aerosol physics, and respiratory protection.

Conflict of Interest:

None declared

In the SARS Commission report, "Spring of Fear," Justice Archie Campbell wrote, "There were two solitudes: infection control and worker safety....infection control failed to protect nurses..."

To the detriment of health-care workers and their patients across Ontario, this divide between the two solitudes has been permitted to persist.

The opening sentence in this CMAJ paper's abstract reveals infection control's continuing failure to understand fundamental worker protection. It talks about determining what "...facial protection should be used by health-care workers to prevent transmission of acute respiratory infection." Then it goes on to explain the research into the comparative protective abilities between an approved N95 respirator and a surgical mask, which isn't recognized anywhere in science-based standards as a form of respiratory protection.

If the researchers wanted to look at facial protection they should have examined visors, goggles and hoods, etc., not an N95, which while worn on the face, and which may provide a limited physical barrier, is not designed as facial protection.

On the other hand, if respiratory protection is the question, then yes, the N95, widely used in health-care, is an appropriate starting point. It is the lowest, scientifically and legally acceptable form of personal equipment for protecting workers from inhaling harmful particles. But why compare them to surgical masks? While also worn on the face, surgical masks were never designed, tested or approved to protect the wearer. Their function is to prevent the wearer from expelling contaminants, e.g. onto a patient or a sterile field.

The conclusion, as confounding to me as the faulty starting point of this research, is that the lowest form of respirator, the N95, doesn't appear to work in health-care settings. If valid, that means we need to determine why not and focus on solutions like fit-testing, education, training and even developing an ergonomic design better suited to health care. It cannot mean we take away real respirators from health-care workers.

Despite this, the authors seem to want to waste more time on building randomized control trials to compare respiratory protective capability between the N95, a respirator they say doesn't work, and the surgical mask, something that isn't even a respirator. One really has to ask what ethics board would ever approve sending a control group of healthy workers into a room contaminated with airborne disease wearing surgical masks, which are not actual respirators. Furthermore, what would be the point?

A true respiratory protection program, as outlined in Canadian Standards Association standard Z94.4-11, should be a key component of a comprehensive infection control program that controls risk to health-care workers and their patients. In accordance with the hierarchy of controls, personal protective equipment (PPE) like a respirator is the last line of defence against a hazard, and the responsible action when you've proven PPE doesn't do the job is to find out why and correct it, not remove the last thing standing between a worker and harm.

If a particular gown allows fluid penetration when dealing with bodily fluids, do you take it off and abandon protection altogether? Or do you look for something that will better protect the worker? When facing the risk of exposure to an inhalable contaminant, there is no legal or ethical foundation for reverting to absolutely no respiratory protection, which is what a surgical mask represents.

I frankly do not agree that anyone has proven N95s can't work in health care. With proper training, reinforcement, staffing and other support (all components of a legally required respiratory protection program, none of which were controlled for in the cited studies) N95s have a proven track record. In limited situations they can be very effective in protecting respiratory tracts of wearers, as evinced in their use in British Columbia where SARS was stopped in its tracks, and in tuberculosis treatment around the world.

No one knows better than front-line nurses that the N95 is not a perfect fit for health-care settings and can be very uncomfortable to use. But nurses and other health-care workers deserve to be protected. As we face a future laden with all kinds of potential threats from natural emerging diseases and bioterrorism, wouldn't our limited time and resources be better spent focusing our research and response efforts on developing respirators that will better protect health care workers?

Linda Haslam-Stroud, RN, President, Ontario Nurses' Association

Conflict of Interest:

None declared